Download bacteriology1 review 2016 AY

Bacteriology Review
Part I
Alyson Yee
5/4/16
Hints
• Lectures (slides, notes, recordings) are high yield
• Work on understanding the basic biology of each
bacterium and how that contributes to its
pathogenesis
• Practice questions on Chalk in with lectures
• Think about each answer choice
• Even if you get a question right, write out an explanation
of WHY and/or try to alter the stem to make the
statement true
Things to know
• About each bug:
• Classification (G+/-, shape)
• Clinical picture
• What makes this bug unique? Think protein virulence
factors or intracellular lifestyle, etc
• What about the biology helps explain the associated
disease?
• About treatment/prevention:
• Know if there are vaccines
• Know major Abx and resistance mechanisms
Basic Principles
Prokaryotes vs. Eukaryotes
• Bacteria:
• Lack membrane bound organelles (including ER,
nucleus)
• Have cell walls (exception : MTb)
• Have motility structures like flagella
• Can undergo horizontal gene transfer
• Can carry plasmids
• Have smaller ribosomes
Pathogens: Koch’s postulates
• Organism is regularly found in the lesions of the
disease (diseased, not healthy)
• The organism can be isolated in pure culture on
artificial media
• Inoculation of this culture produces a similar
disease in experimental animals
• The organism can be recovered from the lesions in
these reinfected animals
When might Koch’s postulates not
apply?
• No animal model (ex. Syphilis)
• Can’t be grown in culture
• Opportunistic pathogens (found in healthy
individuals but not disease-causing)
Peptidoglycan
• Backbone composed of
GlcNAc and MurNAc repeats
• Tetra or pentapeptide
substituent on each repeat
• Peptide bridges linking the
carboxylic acid of D-alanine to
an amino group of a
neighboring chain.
• Gram negatives use
diaminopimelic acid for their
NH2 group
• Gram positives use either
lysine or diaminopimelic acid
Peptidoglycan biosynthesis
1.
Water soluble nucleotide linked
precursor in cytoplasm
2.
Transfer from the nucleotide to a
membrane lipid (C55 AKA bactoprenol
AKA undecaprenol AKA lipid I)
3.
Addition of this building block to the
linear glycan chain (transglycosylation)
4.
Cross-linking to an adjacent chain
(transpeptidation)
Staining and Cell Shapes
Gram Stain
• Crystal violet is washed out of thin
peptidoglycan layer, cells only stain with
safranin -> pink cells = gram negative
• Crystal violet embeds deep into thick
peptidoglycan, not fully washed out ->
purple cells = gram positive
•
Some bacteria have a thick, waxy cell wall which is resistant to Gram staining
•
•
Mycobacteria, Nocardia, Cryptosporidium
Ziehl-Neelson stain: use heat and acid to drive lipid-soluble stain into cell wall
Shapes
•Spherical: coccus, cocci
• Staphylococcus, streptococcus
•Rod-shaped: bacillus, bacilli
• Bacillus and Clostridium spp.
•Comma shaped and spiral
• Vibrios, spirilla and spirochetes
Gram positive
envelope
Envelope structure of Gram-positive and
Gram-negative bacteria
Unique to Gram Positives
Wall teichoic acid = attached to cell wall, give structure
and resistance to antimicrobials
Lipoteichoic acid = attached to lipid membrane, give
division plane and anchor wall
LPXTG
motif
proteins
are
anchored
to the wall
by sortase
**Remember: Gram positive bacteria have a THICK cell wall
Unique to Gram Negatives
Lipopolysaccharide = LPS
 activates immune
response  Gram
negative sepsis
3 components:
1. O Antigen = variable
among different species,
seen by immune system
2. Core= sugar, common to
all Gram negatives
3. Lipid A= outer half of
outer membrane bilayer,
common to all Gram
negatives
Periplasm=
Space b/w outer and inner
membranes in Gram
negatives. Contains many
hydrolytic enzymes (βlactamases
Braun’s lipoprotein: links the
peptidoglycan (via diaminopimelic
acid) to the outer membrane. Allows
the firm attachment of the OM to the
cell envelope
**Remember: Gram negative bacteria have:
1) two membranes
2) a THIN cell wall
1) Which of the following statements concerning bacterial
envelope structure is not correct?
(A) Many Gram-positive bacteria elaborate both wall teichoic acid
and lipoteichoic acid
(B) Peptidoglycan is a constituent of the envelope of Gram-positive
and Gram-negative bacteria
(C) The outer membrane, an asymmetrical lipid bilayer containing
lipopolysaccharide, is found in Gram-negative bacteria but not in
Gram-positive bacteria
(D) Lipoproteins, containing thioether linked diacylglyceride, are
found in Gram-negative bacteria but not in Gram-positive bacteria
(E) Flagella, an envelope embedded rotary filament conferring
motility, are found in Gram-positive and in Gram-negative bacteria
1) Which of the following statements concerning bacterial
envelope structure is not correct?
(A) Many Gram-positive bacteria elaborate both wall teichoic acid
and lipoteichoic acid
(B) Peptidoglycan is a constituent of the envelope of Gram-positive
and Gram-negative bacteria
(C) The outer membrane, an asymmetrical lipid bilayer containing
lipopolysaccharide, is found in Gram-negative bacteria but not in
Gram-positive bacteria
(D) Lipoproteins, containing thioether linked diacylglyceride, are
found in Gram-negative bacteria but not in Gram-positive bacteria
(E) Flagella, an envelope embedded rotary filament conferring
motility, are found in Gram-positive and in Gram-negative bacteria
3) Which of the following statements concerning bacterial
envelope assembly is not correct?
A) Lipopolysaccharide synthesis begins in the bacterial
cytoplasm/cytoplasmic membrane and generates the lipid X
intermediate.
B) Peptidoglycan synthesis requires undecaprenol
(bactoprenol) as a lipid carrier
C) Surface proteins of Gram-negative bacteria are inserted
into the outer membrane, typically using a beta-barrel
structure
D) Sortases insert surface proteins into the lipid bilayer by
forming a linkage with glycolipids.
E) D-alanylation of wall teichoic acids proceeds via a
lipoteichoic acid intermediate.
3) Which of the following statements concerning bacterial
envelope assembly is not correct?
A) Lipopolysaccharide synthesis begins in the bacterial
cytoplasm/cytoplasmic membrane and generates the lipid X
intermediate.
B) Peptidoglycan synthesis requires undecaprenol
(bactoprenol) as a lipid carrier
C) Surface proteins of Gram-negative bacteria are inserted
into the outer membrane, typically using a beta-barrel
structure
D) Sortases insert surface proteins into the lipid bilayer by
forming a linkage with glycolipids.
E) D-alanylation of wall teichoic acids proceeds via a
lipoteichoic acid intermediate.
Pattern recognition receptors (PRRs) sense pathogen
associated microbial patterns (PAMPs)
PRRs
Location
PAMP
Adaptors
Effectors
Toll like receptors (TLRs)
TLR1
Surface
Triacylated lipopeptides
MyD88
IL-6, TNF-α
IL-6, TNF-α, IL-8, MCP-1,
RANTES
TLR2
Surface
Di/triacylated lipopeptides MyD88, TIRAP
TLR4
Surface
LPS
MyD88, TRIF, TIRAP, TRAM IL-6, TNF-α, IFNβ, IP-10
TLR5
Surface
Flagellin
MyD88
TNF-α
TLR6
Surface
Diacylated lipopeptides
MyD88, TIRAP
TNF-α, IL-6, IL-8, MCP-1,
RANTES
TLR11
Endosomes
Profilin, flagellin
MyD88
IL-12, TNF-α
TLR12
Endosomes
Profilin
MyD88
IL-12p40, IFN-α
TLR13
Endosomes
23s rRNA
MyD88
IL-6, IL-12p40
IPS1
IFN-β
Cytosolic DNA sensors
cGAS
Cytoplasm
AT rich dsDNA
STING
Cytoplasm
dsDNA, c-di-GMP, c-di-AMP STING
IFN-β, IP-10, IL-6, IL-1β
Cytosolic Nod factors and inflammasome
Nod2
Cytoplasm
muropeptides
ASC
IL-1β, IL-18
NAIP5/6
Cytoplasm
flagellin
ASC
IL-1β, IL-18
NAIP2
Cytoplasm
T3/4S substrates
ASC
IL-1β, IL-18
2) Which of the following statements concerning recognition of
bacterial invaders by the mammalian immune system is correct?
A) Nod signaling activates the inflammasome in mammalians cells
and can respond to the lipopolysaccharide of Gram-negative
bacteria.
B) Toll like receptors are positioned in the cytoplasm of mammalian
cells where they perceive lipoprotein and peptidoglycan signals
from bacterial invaders
C) cGAS is an enzyme that generates 2’-3’ cGAMP from DNA to
activate STING-mediated immune signaling of microbial invaders
D) Flagellin, a component of flagella, can only be recognized by the
NAIP2/NLRC4 inflammasome of mammalian cells, which activates
caspase 1 and IL-1beta production.
E) TLR4 recognizes the 23S rRNA of bacterial invaders
2) Which of the following statements concerning recognition of
bacterial invaders by the mammalian immune system is correct?
A) Nod signaling activates the inflammasome in mammalians cells
and can respond to the lipopolysaccharide of Gram-negative
bacteria.
B) Toll like receptors are positioned in the cytoplasm of mammalian
cells where they perceive lipoprotein and peptidoglycan signals
from bacterial invaders
C) cGAS is an enzyme that generates 2’-3’ cGAMP from DNA to
activate STING-mediated immune signaling of microbial invaders
D) Flagellin, a component of flagella, can only be recognized by the
NAIP2/NLRC4 inflammasome of mammalian cells, which activates
caspase 1 and IL-1beta production.
E) TLR4 recognizes the 23S rRNA of bacterial invaders
Gram positive Cocci:
Staphylococcus spp.
Streptococcus spp.
Pathogenic staphylococci
Trait
S. aureus
S. epidermidis
S. saprophyticus
Many Infections /
Intoxications
Positive
Opportunistic
Infections
Negative
Urinary Tract
Infections
Negative
Habitat
Skin & Nares
Skin
Colonies
Yellow (aureus)
White (albus)
Skin, Urinary
Tract
Often white
Catalase
Plus
Plus
Plus
Protein A /
Clumping F.
Mannitol
Plus
Negative
Negative
Plus
Negative
Plus
Novobiocin
Negative
Negative
Plus
Disease
Coagulase
Staphylococcus aureus
• CLASSIFICATION: G+ cocci in clusters
• CLINICAL: infections (skin, trauma-related, hematogenous,
nosocomial) and toxinoses (food poisoning, exfoliative
skin disease, Toxic shock)
• IMPORTANT PROTEINS: exoproteins: hemolysins,
hydrolases, exotoxins, surface protein A
• OTHER KEY CONCEPTS: Forms abscesses (sequestered
from immune system), Quorum sensing via agr locus
• DIAGNOSIS: culture, coagulase test
• TREATMENT: surgical drainage, Abx (vancomycin)
• RESISTANCE: B-lactamases, PBP2a, transposon-based
vancomycin resistance
Staphylococcal abscesses enable persistence
in host tissues
S. aureus diseases
• SSTIs:
• 30%/30%/30% stably/intermittently/not colonized
• >1 million per year, high recurrence
• Carbuncle, furunculosis, impetigo
• Invasive diseases:
• Following trauma or other disease
• Fasciitis, cellulitis, osteomyelitis
• Hematogenous:
• Leading cause of sepsis, lethal infectious disease
• Endocarditis, abscesses, septic arthritis
S. aureus toxinoses
• Food poisoning
• T cell superantigens
• SSSS
• Exfoliatin A and B
• Toxic shock
• tsst-1 or -2
S. aureus virulence factors
(There are a TON but these are the most famous)
Protein A
Ag-binding
Fc
Coagulase
Blocks Fc region
from binding
complement or
receptors for
phagocytosis,
tricks B cells
(super Ag)
Prothrombin +++ Thrombin
Fibrinogen
Alpha-hemolysin
Lysis
Other surface proteins:
IsdB: Fe acquisition
FnBP: binding to mucosa
Fibrin
Protein A blocks opsonization and phagocytosis as
well as the development of adaptive immunity
S. aureus treatment
Treating S. aureus is
difficult because it’s
so good at acquiring
resistance.
Vancomycin is used
a lot because of
MRSA, but VRSA
appearing now too
Penicillin resistance
Methicillin resistance
1. Betalactam is
sensed
2. Causes
production of
altered PBP
(PBP2a)
1. Beta-lactam is sensed
2. Causes production of
beta-lactamase
3. Beta-lactamase
hydrolyzes beta-lactam
3. Methicillin can’t block PBP2a
from building cell wall
S. aureus and MRSA diagnosis and therapy
• Surgical debridement/drainage of SSTI or deep seated abscess; removal
of infected foreign material
• Culture tissue or blood sample for S. aureus/MRSA isolation and antibiotic
resistance analysis
• Antibiotic treatment for S. aureus/MRSA begins without culture diagnosis
of the bacterial infection
• clindamycin (macrolide, inhibits protein synthesis)
• vancomycin (glycopeptide, inhibits cell wall synthesis)
• linezolid (oxazolidinones, inhibits protein synthesis)
• daptomycin (lipopeptide, unknown mechanism)
• trimethoprim-sulfomethazole (folic acid synthesis inhibition)
• S. aureus persisters, small colony variants that escape antibiotic killing,
occur frequently and cause recurrent disease while acquiring drugresistance.
4) Which of the following statements concerning immunity to S. aureus
infection is not correct?
A) Recurrent disease following antibiotic and surgical therapy of skin and
soft tissue infections (SSTI) occurs frequently (≤9%)
B) If left untreated, S. aureus infection culminates in an immunological
crisis and in the development of immune responses that protect against
subsequent infection.
C) As clinical trials for candidate vaccines and antibody therapeutics have
failed, an FDA licensed vaccine is currently not available.
D) Individuals who are colonized with S. aureus are more likely to acquire
S. aureus infections as compared to non-colonized individuals.
E) Risk factors for S. aureus infection includes indwelling catheters,
endotracheal intubation, medical implantation of foreign bodies, trauma,
surgical procedures, hemodialysis, immunosuppressive therapy, diabetes,
increased age and low birth weight.
4) Which of the following statements concerning immunity to S. aureus
infection is not correct?
A) Recurrent disease following antibiotic and surgical therapy of skin and
soft tissue infections (SSTI) occurs frequently (≤9%)
B) If left untreated, S. aureus infection culminates in an immunological
crisis and in the development of immune responses that protect against
subsequent infection.
C) As clinical trials for candidate vaccines and antibody therapeutics have
failed, an FDA licensed vaccine is currently not available.
D) Individuals who are colonized with S. aureus are more likely to acquire
S. aureus infections as compared to non-colonized individuals.
E) Risk factors for S. aureus infection includes indwelling catheters,
endotracheal intubation, medical implantation of foreign bodies, trauma,
surgical procedures, hemodialysis, immunosuppressive therapy, diabetes,
increased age and low birth weight.
5) Which of the following is not a suitable
therapeutic for MRSA infections?
A) oxacillin
B) clindamycin
C) daptomycin
D) linezolid
E) trimethoprim-sulfomethoxazole
5) Which of the following is not a suitable
therapeutic for MRSA infections?
A) oxacillin
B) clindamycin
C) daptomycin
D) linezolid
E) trimethoprim-sulfomethoxazole
• 6) Which of the following statements concerning S. aureus
virulence factors is correct?
• A) Coagulase is a protease that cleaves fibrinogen to form a fibrin
deposit.
• B) α-hemolysin (Hla) cleaves phospholipids to destabilize host cell
membranes including the membranes of red blood cells.
• C) von Willebrand Factor binding protein associates with von
Willebrand Factor to block the formation of a fibrin meshwork
during S. aureus bloodstream infections.
• D) Staphylococcal enterotoxins bind to the GSα subunit of
intestinal epithelial cells to synthesize the second messenger
cAMP.
• E) Protein A crosslinks B cell receptors (VH3 clan IgM) and triggers
proliferation of B lymphocytes.
• 6) Which of the following statements concerning S. aureus
virulence factors is correct?
• A) Coagulase is a protease that cleaves fibrinogen to form a fibrin
deposit.
• B) α-hemolysin (Hla) cleaves phospholipids to destabilize host cell
membranes including the membranes of red blood cells.
• C) von Willebrand Factor binding protein associates with von
Willebrand Factor to block the formation of a fibrin meshwork
during S. aureus bloodstream infections.
• D) Staphylococcal enterotoxins bind to the GSα subunit of
intestinal epithelial cells to synthesize the second messenger
cAMP.
• E) Protein A crosslinks B cell receptors (VH3 clan IgM) and
triggers proliferation of B lymphocytes.
Other Staph (coagulase -)
• Epidermidis
•
•
•
•
•
Opportunistic pathogen (nosocomial)
Common cause of sepsis, NEC in neonates
Highly resistant to antibiotics
Colonize human skin
Treatment: Vancomycin, remove catheter/valve/IV
• Saprophyticus
• UTI
• Second (only to E. coli) leading cause of UTI in sexually
active, young women
• Treatment: Penicillin, TMP-SMX (TrimethoprimSulfomethoxazole)
Streptococcus classification:
Two ways
Hemolysis: zone of clearance on
blood agar
• Alpha = green (reduced
hemoglobin) : S. pneumoniae,
Viridans group
• Beta = clear : S. pyogenes, S.
agalactiae
• Gamma = no hemolysis:
Viridans group
• Enterococci can be alpha, beta
or gamma
Lancefield: cell wall Ccarbohydrate
• Group A: S. pyogenes
• Group B: S. agalactiae
(Notice that these are both
beta-hemolytic)
**All are Gram positive cocci in chains, catalase negative**
Streptococci and their human diseases
GAS
β-hemolytic
S. pyogenes
GBS
GDS
β-hemolytic β-hemolytic
S. agalactiae E. faecalis
Viridans S.
α- or γ-hemol.
S. pneumoniae
α-hemolytic
Pharyngitis
Neonatal
meningitis
Endocarditis
(subacute)
Endocarditis
(Subacute)
Pneumonia
Scarlet fever
Puerperal
fever
UTI
Otitis media
Erysipelas,
Pyoderma
Nosocomial
infections
Sinusitis
Pneumonia
Peritonitis
Bacteremia
Sinusitis,
Otitis
Endocarditis
(subacute)
Toxinoses
Meningitis
Acute
rheumatic
fever*
Glomerulonephritis*
GAS = Streptococcus pyogenes
• Virulence factors
• M protein: critical determinant. Responsible for
resisting phagocytosis. Immunity to infection is M type
specific.
• Hyaluronic acid capsule resembles hyaluronic acid in
host (synovial fluid, joints) so hidden from immune
system
• Streptolysin O: pokes hole in mammalian cells (ASO is a
lab to indicate strep infection)
S. pyogenes diseases
• Infections
• Pharyngitis (strep throat)
• *the differential for pharyngitis is enormous. Understand findings for and
against strep.
• Diagnosis: culture (gold standard), rapid antigen-detection test (>95%
sensitivity)
• Skin infections (impetigo, cellulitis)
• Can progress to otitis media, abscesses, meningitis, pneumonia
• Toxigenic
• Scarlet fever: erythrogenic toxin (SpeA), centrifugal rash (trunk to
extremities), spares palms and soles, strawberry tongue
Erythrogenic toxin (SpeA)
• Structural gene is located on bacteriophage (T12 or other)
that lysogenizes GAS
• Secreted SpeA binds to the T cell receptor and crosslinks
with MHC class II receptor of antigen presenting cells
• Triggers T cell proliferation and cytokine storm
• Increases disease severity of GAS pharyngitis
• Formerly used to assess susceptibility by intradermal
injections with and without neutralizing antibody (Dick
test)
Post-infectious complications of S. pyogenes
• Acute rheumatic fever (assoc w/ strep throat): anti-strep Ab attack heart proteins.
High probability of RF if evidence of GAS infection and two major manifestations or
one major and two minor.
• Jones Criteria supporting evidence of antecedent GAS infection (positive throat culture or rapid
streptococcal antigen test), elevated or rising streptococcal antibody titer:
• Major Criteria
•
•
•
•
•
Carditis
Polyarthritis
Chorea
Erythema Marginatum
Subcutaneous nodules
• Minor criteria:
• Clinical findings:
•
•
•
Arthralgia
Fever
Elongated PR interval
• Laboratory findings
•
Elevated acute phase reactants (ESR, CRP)
• Acute glomerulonephritis (associated with skin infections): immune complexes
deposit in glomerulus. Causes hematuria, hypertension
Group B Strep: S. agalactiae
• Causative agent of neonatal meningitis & sepsis
• Give Penicillin/Amp to pregnant GBS + women
• Diagnosis: latex agglutination with antibodies
recognizing GBS group carbohydrate antigen or
CAMP test
• Classified by T pili serotypes
CAMP+
GBS
S. aureus (hlb+)
Group D Strep: Enterococcus faecalis
• Commensal of the human and animal gastrointestinal
tract
• Diseases: subacute bacterial endocarditis (SBE), UTIs,
biliary tract infections, nosocomial infections in
surgical, immunocompromised, cancer and transplant
patients
• Diagnosis: culture, antibody against group specific
carbohydrate, PCR, antibiotic susceptibility testing
• Most hospital E. faecalis isolates are HIGHLY resistant
to antibiotics even ampicillin and vancomycin (aka:
vancomycin-resistant enterococci (VRE)).
• Treatment: ampicillin, vancomycin + aminoglycosides,
linezolid, daptomycin
Viridans Group Strep
• This is a group. Not a species.
• Found on teeth, cause caries
• Prophylactic antibiotics (penicillin) for dental
patients with hx of heart valve disease
• Alpha hemolytic, optochin resistant
Strep pneumoniae = Pneumococcus
• No Lancefield group
• -hemolysis due to pneumolysin, optochin
sensitive
• Pneumonia
• Otitis media
• Sinusitis
• Bacteremia—found in 80% of meningitis
(adults/children), can cause subacute endocarditis
Symptoms & signs of pneumococcal
pneumonia
• Sudden onsets of chills, fever 40°C and malaise
• Cough, tachypnea, dyspnea and chest pain
• Bloody sputum
• Auscultation & percussion – loss of vesicular sound
(normal sound heard over the lung field), crackling,
loss of resonance, egophony (increased resonance)
• Day 5-10 of illness, crisis, sudden drop in fever and
improvement or fatal infection (development of
opsonizing antibodies)
• Pathology: phases of red and white (or grey)
hepatization.
Polysaccharide Capsule in Strep pneumo
• The single most important virulence factor
• antiphagocytic properties
• prevents complement deposition
• more than 100 serotypes
• Capsular “Opsonizing antibodies”  "lysis" after "crisis"
of pneumococcal pneumonia.
• 25 μg of capsular polysaccharides = vaccine against S.
pneumoniae Pneumovax/Prevnar
• Vaccine has led to serotype replacement
• 7) Which of the following statements concerning the Lancefield classification
of streptococcal species is not correct?
• A) Group A streptococci (GAS), also designated Streptococcus pyogenes, cause
pharyngitis in humans and can be detected in throat swab samples with a quick
test specific for the group A carbohydrate
• B) Group B streptococci (GBS), also designated Streptococcus agalactiae, cause
neonatal meningitis and can be detected in vaginal swab samples of pregnant
women 35-37 weeks of gestation.
• C) Group D streptococci, also designated Enterococcus faecalis, colonize the
intestinal tract and are able to cause nosocomial infections in cancer patients.
• D) Streptococcus pneumoniae is not subject to the Lancefield classification and
its C-polysaccharide is detected with the C-reactive protein in human plasma.
• E) Group (wall) carbohydrates are subject to antigenic variation, which is why
new Lancefield groups of streptococcal species are uncovered frequently.
• 7) Which of the following statements concerning the Lancefield classification
of streptococcal species is not correct?
• A) Group A streptococci (GAS), also designated Streptococcus pyogenes, cause
pharyngitis in humans and can be detected in throat swab samples with a quick
test specific for the group A carbohydrate
• B) Group B streptococci (GBS), also designated Streptococcus agalactiae, cause
neonatal meningitis and can be detected in vaginal swab samples of pregnant
women 35-37 weeks of gestation.
• C) Group D streptococci, also designated Enterococcus faecalis, colonize the
intestinal tract and are able to cause nosocomial infections in cancer patients.
• D) Streptococcus pneumoniae is not subject to the Lancefield classification and
its C-polysaccharide is detected with the C-reactive protein in human plasma.
• E) Group (wall) carbohydrates are subject to antigenic variation, which is why
new Lancefield groups of streptococcal species are uncovered frequently.
• 8) Which of the following statements concerning the
acute rheumatic fever (ARF) is not correct?
• A) Subcutaneous nodules and polyarthritis can be
manifestations of ARF.
• B) Fewer than 10,000 cases of ARF occur world-wide
each year, which is why the development of a
protective vaccine would not be economical.
• C) Myocarditis with Aschoff body lesions and heart
murmur can be a manifestation of ARF.
• D) ARF is associated with GAS (S. pyogenes) pharyngitis.
• E) Chorea Sydenham and Erythema marginatum can be
manifestations of ARF
• 8) Which of the following statements concerning the
acute rheumatic fever (ARF) is not correct?
• A) Subcutaneous nodules and polyarthritis can be
manifestations of ARF.
• B) Fewer than 10,000 cases of ARF occur world-wide
each year, which is why the development of a
protective vaccine would not be economical.
• C) Myocarditis with Aschoff body lesions and heart
murmur can be a manifestation of ARF.
• D) ARF is associated with GAS (S. pyogenes) pharyngitis.
• E) Chorea Sydenham and Erythema marginatum can be
manifestations of ARF
• 9) Which of the following statements concerning the prevention
of streptococcal diseases is not correct?
• A) Neonatal meningitis caused by GBS is prevented by vaccination
of pregnant women with capsular conjugate vaccine.
• B) Otitis media caused by Streptococcus pneumoniae is prevented
by immunization with capsular conjugate vaccine.
• C) The further development of acute rheumatic fever is prevented
with penicillin prophylaxis.
• D) Pneumococcal pneumonia is prevented with a 23-valent
capsular polysaccharide vaccine without polysaccharide
conjugation to protein.
• E) Nosocomial infection with GDS (Enterococcus faecalis) cannot
be prevented with vancomycin because of drug resistance genes.
• 9) Which of the following statements concerning the prevention
of streptococcal diseases is not correct?
• A) Neonatal meningitis caused by GBS is prevented by
vaccination of pregnant women with capsular conjugate
vaccine.
• B) Otitis media caused by Streptococcus pneumoniae is prevented
by immunization with capsular conjugate vaccine.
• C) The further development of acute rheumatic fever is prevented
with penicillin prophylaxis.
• D) Pneumococcal pneumonia is prevented with a 23-valent
capsular polysaccharide vaccine without polysaccharide
conjugation to protein.
• E) Nosocomial infection with GDS (Enterococcus faecalis) cannot
be prevented with vancomycin because of drug resistance genes.
• 10) Which of the following statements concerning the
pneumococcal conjugate vaccine (PCV13) is not correct?
• A) PCV13 is comprised of 13 capsular polysaccharide types
conjugated to protein adjuvant.
• B) PCV13 immunization is recommended for all children (<5
yoa) and for adults (>65 yoa).
• C) PCV13 immunization is recommended for high risk
individuals (sickle cell anemia, CSF leak, cochlear implant,
asplenia, malignancy).
• D) PCV13 immunization in the United States has diminished
the colonization and carrier state with S. pneumoniae.
• E) PCV13 immunization in the United States has diminished
pneumococcal disease caused by PCV13-serotype S.
pneumoniae strains.
• 10) Which of the following statements concerning the
pneumococcal conjugate vaccine (PCV13) is not correct?
• A) PCV13 is comprised of 13 capsular polysaccharide types
conjugated to protein adjuvant.
• B) PCV13 immunization is recommended for all children (<5 yoa)
and for adults (>65 yoa).
• C) PCV13 immunization is recommended for high risk individuals
(sickle cell anemia, CSF leak, cochlear implant, asplenia,
malignancy).
• D) PCV13 immunization in the United States has diminished the
colonization and carrier state with S. pneumoniae.
• E) PCV13 immunization in the United States has diminished
pneumococcal disease caused by PCV13-serotype S. pneumoniae
strains.
Rules of thumb for bacterial pathogens
• If you want to invade a host - stick to it
• Adherins: ex Vibrio cholerae
• If you don’t want to get killed - bring your weapons and
fight
• Proteins that mess with the immune system, ex S. aureus
superantigen Protein A
• If you want to invade another host - get out if you can
• Think about modes of transmission (contact, sexual, IV,
insects, etc)
• If you want to get all of it done - bring your proteins out
• Secretion systems
Genetic structure in bacteria
• Most bacterial chromosomes are circular and doublestranded
• Plasmids are also DNA that is circular and double-stranded
but they are smaller than the chromosome. They often carry
genes for resistance and virulence
• Bacteria have little junk DNA – tight packed genes
• Genes can be clumped together into a polycistronic operon,
which means that they are all regulated and transcribed
together. The proteins these genes encode usually work
together
Transformation
• DNA is the “transforming principle”
• Transformation = taking up DNA from the
environment
• Free DNA can be taken up  homologous
recombination with a section of chromosomal DNA
• Plasmid DNA can be taken up and exist separately
in the cell
• Competent bacteria take up DNA naturally
Transposons
• These are jumping pieces of DNA. Sometimes when
they jump, they take a bit of the surrounding
chromosomal DNA, which is one mechanism of
creating bacterial genetic diversity
• They often carry antibiotic resistance genes and
provide an easy way for lots of bacteria to pick up
resistance
Conjugation
1. One bacterium has F
plasmid (F+). The other
doesn’t (F-). F is for fertility
2. F+ cell extends sex pilus
(encoded on F plasmid) to
bring F- cell closer
3. F plasmid in F+ gets cut,
and as it starts to replicate
to fix the error, the
extending strand projects
into F-.
4. Complementary
strands are
synthesized and
both are now F+
Hfr: the F plasmid can integrate into the chromosome. Then, the F
plasmid starts conjugation as above. There is not enough time for all of
the F plasmid and then the rest of the chromosome to be transferred
before they get interrupted, so only the F plasmid contents and then
whatever bits of chromosome follow are transferred.
Phage
• Virus that infects bacteria: made up of genetic material and
protein coat
• Often carry virulence or abx resistance genes (ex. cholera
toxin, diptheria toxin)
• The phage DNA incorporates into the bacterial chromosome
• The phage monitors nutritional status of the bacterium
• Bounty of food--> phage in lysogenic phase (doesn’t hurt
bacterium, lets bacterium replicate phage DNA as the bacterium
grows and divides)
• Starvation--> lytic cycle- the virus assembles its protein coat, lyses
the bacterial cell and goes out to find a new home
Transduction
• Transfer of bacterial DNA from one bacterium to
another by way of a phage
• Two forms (not specified in lecture)
• “Generalized transduction” = when bacterium is infected
with phage, some of its DNA gets chopped up and
accidentally packaged as the phage capsid is forming
• “Specialized transduction”: as the phage DNA that is
incorporated in the chromosome comes out for the lytic
cycle, some downstream genes from the chromosome
get carried along too (analogous to Hfr conjugation)
Adhesins
• Pili/fimbriae
• Membrane bound proteins
These enable the
bacteria to bind to
an epithelium so
that they can
invade/not get
washed away/etc.
For your interest:
Pili identified in B. cereus by Jon Budzik,
a former MSTP in Olaf’s lab (Budzik et al
2007) – Now at UCSF for ID
Toxins
• Endotoxin: lipid A is toxic part of LPS. Innate immune system
recognizes TNF and IL-1 are produced  shock (fever, hypotension,
systemic clotting)
• Exotoxins: secreted molecules with specific effect on the host. These
are the various toxins we’ve learned (ex. Clostridium toxin, shiga toxin,
etc.)
• Superantigens: an exotoxin that binds to
the T cell receptor and MHC but NOT
through the antigen-binding domain so
that any T cell can be stimulated,
regardless of its specificity. As a result, you
have an over-activated immune system,
which is eventually depleted
Secretion systems (overview)
• Secretion in Gram positives: simple—protein that
needs to be exported has a signal that directs it to
the membrane, it is transported across plasma
membrane, and then either gets covalently linked
to the cell wall or floats away
• Secretion in Gram negatives: More complicated…
Secretion Systems:
Sec Pathway
A peptide sequence
at the front of the
protein tells the
protein to go to the
Sec proteins in
membrane
The Sec proteins transport the
protein through the membrane
(How much of a barrier cell wall
poses to these proteins seems to
be a point of contention among
microbiologists, but beyond the
scope of this class…)
Gram negative bacteria can use
homologous systems to get proteins
through the inner membrane.
Secretion Systems:
Autotransporters
4. The protein cleaves itself,
separating the soluble part
from the beta-barrel
3. The cross-hatched part
folds into a beta barrel and
inserts in membrane
2. Now protein
precursor is in the
periplasm and starts to
fold.
1. Protein has signal
peptide that sends it to
Sec system like on last
slide
Secretion Systems:
Type I secretion (ABC Transporter)
Three proteins spanning the inner and outer membrane form a channel for
secretion of target protein. One of those proteins (ATP-binding cassette)
creates the energy to allow the transport in one step.
Membrane-spanning channel
Protein to be exported
ATP-binding cassette
Secretion Systems:
Type II Secretion (aka “General Secretory pathway”)
2. Proteins in periplasm
fold and assemble
1. Protein has signal
peptide that sends it to
Sec system
3. Secreted through
outer membrane
transport protein in a
second step
Secretion Systems:
Type III Secretion
(T3SS)
Gram negative bacteria
assemble a complex structure
composed of many proteins that
extend a needle into a target
eukaryotic cell. “Effector” proteins
of the bacteria then travel
through the needle into the
eukaryotic cell where they have
pathogenic effects
Ex. Chlamydia, Salmonella,
Yersinia
Secretion Systems:
Type IV Secretion
Modification of bacterial
conjugation system.
Ex. Legionella
2. Multimers assembled in periplasm
1. Protein has signal peptide
that sends it to Sec system
• 11) Which of the following statements concerning the
secretion systems of Gram-negative bacteria is correct?
• A) Signal-peptide bearing precursors are transported via the
Sec pathway into the extracellular medium.
• B) The type I secretion pathway transports proteins across
the bacterial inner and outer membrane into the
extracellular medium.
• C) The type II secretion pathway transports proteins across
the plasma membrane of host cells.
• D) The type III secretion pathway secretes activated toxins,
after proteolysis and sulfhydryl oxidation, into the
extracellular medium.
• E) The type IV secretion pathway occurs only in bacteria that
are pathogenic to plants.
• 11) Which of the following statements concerning the
secretion systems of Gram-negative bacteria is correct?
• A) Signal-peptide bearing precursors are transported via the
Sec pathway into the extracellular medium.
• B) The type I secretion pathway transports proteins across
the bacterial inner and outer membrane into the
extracellular medium.
• C) The type II secretion pathway transports proteins across
the plasma membrane of host cells.
• D) The type III secretion pathway secretes activated toxins,
after proteolysis and sulfhydryl oxidation, into the
extracellular medium.
• E) The type IV secretion pathway occurs only in bacteria that
are pathogenic to plants.
Iron Acquisition
• Bacteria need iron. We hide most of our Fe inside
hemoglobin (Hb) inside RBCs
• Bacteria have various methods to get Fe:
• Siderophores: Fe chelators (not a protein) that bind free Fe3+ and
then get transported back into bacteria
• Hemolysins: toxins lyse RBCs to release the Hb
• Hemophores: proteins that bind Hb, bind bacterial receptor, and
get taken up into the bacterium, thereby acquiring Fe
• Host fights back with siderocalins (bind siderophore and
prevents Fe acquisition)
• 12) Which of the following statements concerning iron
restriction/nutritional immunity is not correct?
• A) Under physiological conditions, iron is sequestered in
human tissues and is not available to bacterial invaders.
• B) Lysis of red blood cells triggers haptoglobin- and
hemopexin-mediated sequestration of hemoglobin and
heme, respectively.
• C) Lipocalins are host proteins that sequester bacterial
siderophore:iron complexes.
• D) Hemochromatosis, whether of adult or juvenile disease
onset, perturbs the nutritional immunity of human tissues.
• E) Intracellular or endosomal iron is freely available to
bacterial pathogens as long as they can enter the host cell.
• 12) Which of the following statements concerning iron
restriction/nutritional immunity is not correct?
• A) Under physiological conditions, iron is sequestered in
human tissues and is not available to bacterial invaders.
• B) Lysis of red blood cells triggers haptoglobin- and
hemopexin-mediated sequestration of hemoglobin and
heme, respectively.
• C) Lipocalins are host proteins that sequester bacterial
siderophore:iron complexes.
• D) Hemochromatosis, whether of adult or juvenile disease
onset, perturbs the nutritional immunity of human tissues.
• E) Intracellular or endosomal iron is freely available to
bacterial pathogens as long as they can enter the host cell.
Other pathogenic elements
• Flagella: complex protein structures for motility
• Capsule: generally a polysaccharide coating that
protects bacterium from phagocytosis
• Exception: Bacillus anthracis (D-glutamic acid coat)
The human microbiome
Hypotheses on how to perturb the interactions between microbiota,
host and pathogen
Respiratory Infections
Gram +
• Corynebacterium diphtheriae
Gram • Pseudomonas aeruginosa
• Klebsiella
• Legionella
• Bordetella pertussis
• Haemophilus
Gram + Non-spore forming rod
Corynebacterium diphtheriae
• This would still cause disease if we didn’t vaccinate
everyone--it hasn’t gone away!
• Diphtheria toxin: AB toxin that ADP-ribosylates EF-2
so proteins aren’t made, encoded on a phage
• Causes croup: pharyngitis & laryngitis with greyishwhite pseudomembrane, swollen neck, respiratory
stridor, asphyxia, mildly elevated temperature
100.4°F, cardiomyopathy
• Toxin also affects cardiac conduction, nerves
• Culture: Loeffler’s medium, potassium tellurite
• Treatment: diphtheria antitoxin (DAT), abx, Vaccine:
diphtheria toxoid (inactivated toxin)
Diphtheria (tetanus and pertussis)
vaccine
Emil von Behring
Balto & Gunnar Kaasen
of the Iditarod race
• Behring used heat inactivated diphtheria toxin to
immunize guinea pigs & protect against C. diphtheriae;
also immunized humans against diphtheria and used
diphtheria-immune serum for therapy (1901 Nobel Prize)
• DT=diphtheria & tetanus toxoid, no pertussis vaccine
• Td= tetanus & diphtheria vaccine for adults (booster
immunization following exposure)
• DTaP= DT & acellular pertussis vaccine
• Children should get five doses of DTaP: 2, 4, 6, 12-15
months and 4-6 years
• Tdap= Td & acellular pertussis vaccine
• Tdap for 7-10 yo and for women should receive Tdap
during each pregnancy
• 13) Which of the following statements concerning the
pathogenesis of diphtheria is not correct?
• A) Diphtheria is typically an upper respiratory tract infection
caused by toxigenic C. diphtheriae.
• B) Diphtheria is rare and in the past three years not a single
case has been reported in the United States.
• C) Because of low disease incidence, CDC no longer
recommends diphtheria immunization for Americans.
• D) Individuals who suffered from diphtheria acquire life-long
immunity against this disease.
• E) Without therapy, the mortality of diphtheria is high
(>15%) and caused by suffocation (asphyxia) and/or
cardiomyopathy.
• 13) Which of the following statements concerning the
pathogenesis of diphtheria is not correct?
• A) Diphtheria is typically an upper respiratory tract infection
caused by toxigenic C. diphtheriae.
• B) Diphtheria is rare and in the past three years not a single
case has been reported in the United States.
• C) Because of low disease incidence, CDC no longer
recommends diphtheria immunization for Americans.
• D) Individuals who suffered from diphtheria acquire life-long
immunity against this disease.
• E) Without therapy, the mortality of diphtheria is high
(>15%) and caused by suffocation (asphyxia) and/or
cardiomyopathy.
Bordetella pertussis
http://www.buddycom.com/bacteria/gnr/acinetc1259.jpg
Lab:
Aerobic, Bordet-Gengou (potato) agar,
requires nicotinamide, slow growing
*Most bacteria*
Complications: 2° infection, damage from intrathoracic pressure
Whole cell vaccine: better immunity, worse reactogenicity (only used in adults under
special circumstances for control of hospital outbreaks. )
Acelluar vaccine: several components, including PT. Immunity lasts ~12 years --> we’re
susceptible!
Rx: erythromycin or other macrolides
Pertussis cases must be reported through the National Notifiable Diseases Surveillance System
B. Pertussis pathogenesis
Highly contagious, airborne, infects respiratory tract
Survivors acquire immunity
Whooping cough can be caused by B. pertussis or B. parapertussis
(lacks PT)
Toxins:
Pertussis Toxin: ADP-ribosylating AB5 toxin modifies α-subunit of
heterotrimeric Gi proteins, increases cAMP synthesis and
suppressing pro-inflammatory cytokine production
ACT: increases cAMP synthesis and suppresses all kinds of immune
response
FHA/Fim/Prn: Filamentous haemagglutinin (FHA) and Fim proteins
(fimbriae) are involved in adhesion, required for persistence. Prn
(pertactin) may help resist neutrophil clearance
Pertussis treatment and prevention
• Erythromycin or trimethoprim-sulfamethoxazole for
pertussis cases and as a post-exposure prophylaxis (new
CDC recommendation)
• Antibiotic therapy has little effect at the time of diagnosis
(clinical pertussis disease): the patient is already
intoxicated! It prevents dissemination.
• Supportive therapy and pertussis immune globin (PT
specific antibodies)
• Surveillance for apnea and vomiting
• whole cell vaccine safety was controversial and no longer
recommended by CDC
• acellular pertussis (subunit) vaccine recommended by
CDC
• 14) Which of the following has a proven
therapeutic effect for infants with manifest
pertussis disease (paroxysmal phase)?
• A) intravenous pertussis immune globin
• B) trimethoprim-sulfamethoxazole
• C) erythromycin
• D) acellular subunit vaccine
• E) whole cell pertussis vaccine
• 14) Which of the following has a proven
therapeutic effect for infants with manifest
pertussis disease (paroxysmal phase)?
• A) intravenous pertussis immune globin
• B) trimethoprim-sulfamethoxazole
• C) erythromycin
• D) acellular subunit vaccine
• E) whole cell pertussis vaccine
Legionella
• This is the air conditioning bug
• Difficult to Gram stain,
grow on BCYE buffered charcoal yeast extract (rapid detection methods
available for Dx)
• Pathogenesis:
• Adherence (Properly working cilia in host respiratory tree are key to
prevention)
• Prevent phagolysosomal fusion
• Multiplies inside monocytes and then causes rupture
• Diseases:
• Pontiac fever: flu-like, no pneumonia, self-limited
• Legionnaire’s Disease: Pneumonia
• Rx: antibiotics that get intracellular (not beta-lactams): think azithromycin
• No human-to-human transmission
Ventilator associated pneumonia (VAP)
• Critically ill patients in the ICUs of hospitals that are unable to
sustain breathing by themselves and receive mechanical
ventilation
• Rate of infection increases with the duration of mechanical
ventilation (>5 days)
• VAP: new chest infiltrate on chest X-ray, body temperature
>100.5°F, blood leukocytosis (>109 ml-1) , purulent sputum,
hypoxemia, positive culture [endotracheal aspirate or BAL, 2
blood cultures (25% sensitivity], CPIS=clinical pulmonary
infection score
• ~300,000 cases in the US per year; 5-10 per 1,000 hospital
admissions
• Case fatality 15-50%
Ventilator associated pneumonia (VAP)
• Pseudomonas aeruoginosa (20-40%), S. aureus/ MRSA (15-30%),
S. pneumoniae, K. pneumoniae, S. marcescens, Enterobacter,
Citrobacter, A. baumannii, S. maltophila
• Treatment is initiated before culture diagnosis is established as
mortality for VAP is as high as 50%
• Pick antibiotics from three lists (A-C) to cover (A) drug-resistant
P. aeruginosa, (B) drug-resistant enterobacteria, and (C) MRSA
• List A: cephalosporin (Cefepime, Ceftazidime), carbapenem
(Imipenem, Meropenem), β-lactam/ β-lactamase inhibitor
(Piperacillin-tazobactam)
• List B: fluoroquinolone (Ciprofloxacin), aminoglycoside
(Amikacin, Gentamycin, Tobramycin)
• List C: Vancomycin or Linezolid
Pseudomonas aeruginosa
• Most common cause of VAP
• Forms biofilms: expolysacharides promote biofilms
and protect against phagocytic clearance
• Type III secretion system
• Causes chronic lung infections in cystic fibrosis
patients
• 15) Which of the following statements concerning the diagnosis
and therapy of ventilator associated pneumonia (VAP) is correct?
• A) High incidence of VAP infection with drug-resistant bacteria
mandates that antibiotic therapy commence only after culture
diagnosis (and antibiotic-resistance spectrum) has been
established.
• B) Streptococcus pneumoniae is a frequent cause of VAP.
• C) Risk for VAP is correlated with the duration of assisted
ventilation, with a sharp increase in the incidence of VAP after 5
days.
• D) A single broad spectrum antibiotic can be used as an early
therapeutic against the most frequent causes of VAP.
• E) Mortality associated with VAP is less than that caused by
Legionella pneumophila, the agent of Legionnaires disease.
• 15) Which of the following statements concerning the diagnosis
and therapy of ventilator associated pneumonia (VAP) is correct?
• A) High incidence of VAP infection with drug-resistant bacteria
mandates that antibiotic therapy commence only after culture
diagnosis (and antibiotic-resistance spectrum) has been
established.
• B) Streptococcus pneumoniae is a frequent cause of VAP.
• C) Risk for VAP is correlated with the duration of assisted
ventilation, with a sharp increase in the incidence of VAP after 5
days.
• D) A single broad spectrum antibiotic can be used as an early
therapeutic against the most frequent causes of VAP.
• E) Mortality associated with VAP is less than that caused by
Legionella pneumophila, the agent of Legionnaires disease.
Causes of bacterial meningitis in the United
States (1998-2007)
Microbe
Age group
Preventive US cases Case
vaccine
per year fatality
S. pneumoniae
Adolescents,
young adults
yes
58%
13%
S. agalactiae (GBS) Newborns
no
18%
15%
N. meningitidis
Adolescents,
young adults
yes
14%
15%
H. influenzae
Infants
yes
7%
6%
L. monocytogenes
Newborns,
immune comp.
no
3%
21%
E. coli
Newborns
no
<1%
NA
C. fetus
Immunecompromised
no
<1%
NA
All causes
NA
NA
4,100
500 (15%)
• N. gonorrhea (no
capsule, local)
• N. meningitidis
(capsule,
disseminates)
• LOS (short LPS) looks
like self sphingolipid
• Antigenic variation
Neisseria
Gram negative cocci
• Pili are turned on and
off by recombination
• Opas are on/off by
polymerase slippage
Species
Phenotype
Sequence
N. gonorrhoeae
opa
(CTCTT)n
N. meningitis
capsule (siaD)
(C )n
N. meningitis
Capsule (siaA)
IS1301
N. gonorrhoeae
pili
conserved
repeats
Neisseria meningitidis
• G- diplococcus
• Produces polysaccharide capsule (serotypes A, B, C, W, Y)
• Spread thru respiratory droplets/close quarters (soldiers, college
students)
• Enters epithelium from damage or in phagocytes (unencapsulated)
• Disseminates thru blood (encapsulated)  Brain and crosses vascular
epithelium into meninges and CSF
• Colonizes the nasopharynx of approximately 10% of the human
population (carrier state)
• Can invade healthy individuals to establish bacteremia and meningitis;
cases are typically sporadic (95%)
• Outbreaks (5%) occur in close communities over a short period of time
and are caused by the same isolate.
• Colonization involves pili and Opc/Opa proteins, invasion requires
capsule and factor H binding protein (fHBP), molecules that are
antigenically variable
• Meningitis is a severe disease with high case fatality (up to 15%) and
long term disabilities (retardation, loss of limb) in survivors (15-30%)
Symptoms and signs of meningococcal disease
• Headache, fever, nuchal rigidity, obtunded
sensorium
• Rash, petechia and/or ecchymosis
• Shock
• Neurological signs, vanishing reflexes, coma
• Disseminated intravascular
coagulation, spontaneous
bleeding, necrosis of
extremities
• Rapid progression toward
lethal outcome
CSF: neutrophils with
Gram-negative diplococci
Meningitis
• Nuchal rigidity
• Make pt try to put their chin on their chest
• Fever, headache, confusion
• Lumbar puncture
• If it’s infected  it’s cloudy
• If it’s not infected  it’s clear
• Gram stain/Giemsa stain the CSF
• PCR tests to distinguish bacteria
• Meningococcus often also produces skin
petechiae, may progress to DIC, destruction of
adrenals (Waterhouse-Friderichsen)
• Therapy = IV or IM penicillin
• Vaccine = polysaccharide conjugated to diphtheria
toxin, doesn’t hit type B (33% of cases)
Meningococcal vaccines
Quadrivalent capsule vaccine (A, C, W135, Y)
• MCV4 (Menactra® and Menveo® conjugate-vaccine: Emil Gotschlich
11-18 & >55yoa (prime booster) +>9 month yoa (high risk
individuals)
Group B meningococcal vaccine (10-25 yoa; factor H binding
protein (fHbp) as key ingredient
• The group B capsule is NOT immunogenic
Haemophilus influenzae
• G- coccobacillus, colonizes most people
• Auxotroph for heme and NAD, grows on supplemented
chocolate agar with CO2; catalase and oxidase positive
• Causative agent of pediatric diseases: otitis media,
sinusitis, pneumonia, meningitis, epiglottitis
• Therapy: for severe cases i.v. cefotaxime or ceftriaxone;
oral ampicillin & sulbactam (β-lactamase inhibitor) or
ciprofloxacine
• Prevention: poly-ribosyl-ribitol-conjugated to tetanustoxoid= Hib vaccine (3 injections first six months, 1 year
booster)
Listeriosis
caused by Listeria monocytogenes
• G+ rod
• Foodborne pathogen that can cross the intestinal mucosa, the blood
brain barrier and the placental barrier
• Causes meningitis, meningoencephalitis, septicemia, abortions and
gastroenteritis
• Usually not a problem in adults
• Can be a problem in pregnancy and neonatal meningitis
• Prevention: Food safety is the key prevention of L. monocytogenes
infections; in pregnant women, monitoring of fetal growth; no vaccine
available
• Therapy: ampicillin; alternatively trimethoprim-sulfamethoxazole or
erythromycin
Listeria monocytogenes pathogenesis
• 16) Which of the following statements concerning the
causative agents of bacterial meningitis is not correct?
• A) Listeria monocytogenesis, a food-born pathogen, can
infect the placenta of pregnant women and cause fetal
meningitis with high mortality.
• B) Hib immunization has reduced the incidence of infant
meningitis caused by Haemophilus influenza.
• C) PCV13 immunization has reduced the incidence of
pneumococcal meningitis caused by PCV13 vaccine
serotypes.
• D) Antibiotic prophylaxis has reduced the incidence of early
onset bacterial meningitis caused by Group B streptococci
(Streptococcus agalactiae).
• E) E. coli is a frequent cause of neonatal meningitis.
• 16) Which of the following statements concerning the
causative agents of bacterial meningitis is not correct?
• A) Listeria monocytogenesis, a food-born pathogen, can
infect the placenta of pregnant women and cause fetal
meningitis with high mortality.
• B) Hib immunization has reduced the incidence of infant
meningitis caused by Haemophilus influenza.
• C) PCV13 immunization has reduced the incidence of
pneumococcal meningitis caused by PCV13 vaccine
serotypes.
• D) Antibiotic prophylaxis has reduced the incidence of early
onset bacterial meningitis caused by Group B streptococci
(Streptococcus agalactiae).
• E) E. coli is a frequent cause of neonatal meningitis.
• 17) Which of the following statements concerning the prevention
of meningococcal meningitis is not correct?
• A) MCV4 (Menactra® or Menveo®), quadrivalent capsule
conjugate vaccines (serotypes A, C, W135, Y), are recommended
for 11-18 yoa and >55yoa Americans as prime-booster vaccines.
• B) MCV4 vaccines cannot protect against meningitis caused by N.
meningitidis serotype B.
• C) N. meningitidis serotype B capsular polysaccharide [(α2-8) Nacetylneuraminic acid] is not immunogenic.
• D) Protective immunity against N. meningitidis requires
antibodies that promote phagocytic uptake, not complement
mediated killing of bacteria.
• E) Group B meningococcal vaccines (Trumenba® and Bexsero®)
include factor H binding protein (fHbp) as a key ingredient.
• 17) Which of the following statements concerning the prevention
of meningococcal meningitis is not correct?
• A) MCV4 (Menactra® or Menveo®), quadrivalent capsule
conjugate vaccines (serotypes A, C, W135, Y), are recommended
for 11-18 yoa and >55yoa Americans as prime-booster vaccines.
• B) MCV4 vaccines cannot protect against meningitis caused by N.
meningitidis serotype B.
• C) N. meningitidis serotype B capsular polysaccharide [(α2-8) Nacetylneuraminic acid] is not immunogenic.
• D) Protective immunity against N. meningitidis requires
antibodies that promote phagocytic uptake, not complement
mediated killing of bacteria.
• E) Group B meningococcal vaccines (Trumenba® and Bexsero®)
include factor H binding protein (fHbp) as a key ingredient.
STDs
• Chlamydia trachomatis (intracellular pathogen)
• N. gonorrhoaea
• Treponema pallidum (spirochete)
• Haemophilus ducreyi
Haemophilus ducreyi – chancroid
STD that is difficult to diagnose
•
•
•
•
In men, chancroid on the penis
Usually asymptomatic in women
Incubation period 5-7 days
Tender papular lesion with erythema
that disintegrates into a non-indurated
ulceration (differential diagnosis:
syphilis) with lymphadenopathy
• Swab culture to establish culture
(difficult) or PCR diagnosis
• Treatment: oral azithromycin or
erthyromycin
Neisseria gonorrheae (gonorrhea)
frequent, notifiable STD complicated by antibiotic resistance
• G- diplocci
• Transmitted by sexual contact or perinatally; primarily affects
the mucous membranes of the lower genital tract and less
frequently those of the rectum, oropharynx, and conjunctivae
• Due to Abx resistance, dual therapy (ceftriaxone and either
azithromycin or doxycycline)
• In women: cervicitis, urethritis, accessory gland infection, PID,
perihepatitis, infertility, tubular pregnancy
• Extragenital:
•
•
•
•
Anorectal infection
Pharyngeal infection
Conjunctivitis
Disseminated infection
Diagnosis and therapy of gonorrhea
• Culture diagnosis through isolation of N. gonorrheae on
laboratory media (chocolate agar with hemin and
antibiotics incubated with CO2 for 2 days); oxidase + and
biochemical tests; allows antibiotic susceptibility testing
• Methylene blue smear of secretions for microscopic
detection of diplococci and neutrophils (picture)
• NAATs (nucleic acid amplification tests): PCR detection of
N. gonorrheae; great for first urine and vaginal swabs, for
rectal, oropharyngeal and conjunctival testing; useful for
detection of Chlamydia trachomatis and DD of mixed
infections
• Treatment: ceftriaxone & azithromycin or
ceftriaxone & doxycycline
• 18) Which of the following statements concerning the
diagnosis and treatment of gonorrhea is not correct?
• A) Cefixime is recommended by CDC as a monotherapy for
gonorrhea.
• B) Culture isolation of Neisseria gonorrhea enables
antibiotic sensitivity testing.
• C) Gonorrhea is a diagnosis that must be reported to CDC.
• D) NAATs (nucleic acid amplification tests) allow detection of
N. gonorrheae in urine and vaginal, rectal, oropharyngeal as
well as conjunctival swabs.
• E) NAATs are useful for the detection of mixed infections
with N. gonorrheae and Chlamydia trachomatis.
• 18) Which of the following statements concerning the
diagnosis and treatment of gonorrhea is not correct?
• A) Cefixime is recommended by CDC as a monotherapy for
gonorrhea.
• B) Culture isolation of Neisseria gonorrhea enables
antibiotic sensitivity testing.
• C) Gonorrhea is a diagnosis that must be reported to CDC.
• D) NAATs (nucleic acid amplification tests) allow detection of
N. gonorrheae in urine and vaginal, rectal, oropharyngeal as
well as conjunctival swabs.
• E) NAATs are useful for the detection of mixed infections
with N. gonorrheae and Chlamydia trachomatis.