Download Pathogenic Cocci

They role in human pathology.
Principles of microbiological diagnosis,
specific therapy.
Lector Tvorko M. S.
Classification.
S. aureus,
S. epidermidis,
S. saprophyticus
VIRULENCE FACTORS OF
STAPHYLOCOCCUS AUREUS
Staphylococcus
epidermidis Growing
on Blood Agar
Staphylococcus aureus Growing
on Blood Agar
Staphylococcus
saprophyticus Growing on
Blood Agar
Coagulase Test on
Staphylococcus aureus
Coagulase Test on
Staphylococcus epidermidis
Staphylococcus
aureus
Growing on Yelk-salt Agar
Staphylococcus aureus Growing on
Mannitol Salt Agar.
Staphylococcus epidermidis Growing on
Mannitol Salt Agar
Staphylococcus aureus
Growing on DNase Agar
Staphylococcus epidermidis
Growing on DNase Agar
Staphylococcal Skin Infections
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Localized infections
 Folliculitis (sties, pimples, and carbuncles) result from
S. aureus entering natural openings in the skin – hair
follicle
Impetigo of the newborn
 highly contagious superficial skin infection
caused by S. aureus.
Toxemia occurs when toxins enter the bloodstream;
• Scalded skin syndrome
• Toxic shock syndrome
Figure 21.4
Staphylococcus aureus
enterotoxin
Staphylococcal
Food Poisoning
Figure 25.6
Electron Micrograph of
Streptococcus pyogenes
Note gram-positive (purple) cocci in chains (arrows).
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Streptococcus are gram-positive cocci
classified according to their hemolytic
enzymes and cell wall antigens.
Group A beta-hemolytic streptococci
(including Streptococcus pyogenes)
are the pathogens most important to
humans.
Produce a number of virulence factors:
 M protein,
 erythrogenic toxin,
 deoxyribonuclease,
 streptokinases,
 hyaluronidase.
Figure 21.5
Streptococcus in chains (Gram stain)
hemolysis reaction - sheep blood agar
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(alpha)
 partial hemolysis
 green color
(beta)
 complete clearing
 A and B
(gamma)
 no lysis
White colonies
Beta Hemolysis on Blood Agar (Indirect Lighting)
Alpha Hemolysis on Blood
Agar (Indirect Lighting)
A Plate of Blood Agar showing
Alpha, Beta, and Gamma Hemolysis
(Indirect Lighting)
Gamma Reaction on Blood Agar
Streptococcal pharyngitis

Strep throat

Streptococcus pyogenes
 Resistant to phagocytosis
 Streptokinases lyse clots
 Streptolysins are cytotoxic

Pharyngitis - Scarlet Fever
Erythrogenic toxin produced
by lysogenized S. pyogenes
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
Diagnosis by indirect agglutination
Figure 24.3
Streptococcal Skin Infections
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Erysipelas
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infects the dermal layer
reddish patches
Can progress to local tissue
destruction
Enter the bloodstream
Impetigo

isolated pustules
Streptococcal toxic shock
syndrome

Cellulitis, myositis and
necrotizing fasciitis
Figure 21.6, 7
Bacterial Infections of the Heart
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
The inner layer of the heart is the endocardium.
Inflammation of the endocardium
Endocarditis
Subacute bacterial endocarditis –

from microbs in the mouth.( Arises from a focus of infection, such as a
tooth extraction).
 alpha-hemolytic streptococci
 staphylococci
 enterococci
 Preexisting heart abnormalities
are predisposing factors.
 Signs include fever, anemia, and heart murmur.


Acute bacterial endocarditis
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Staphylococcus aureus
The bacteria cause rapid destruction of heart valves
Rheumatic Fever

Rheumatic fever is an autoimmune complication of streptococcal
infections.
Rheumatic fever is expressed as arthritis
or inflammation of the heart.
 It can result in permanent heart damage.
 Rheumatic fever can follow a streptococcal

infection, such as streptococcal sore throat.
 Streptococci might not be present at the
time of rheumatic fever.

Prompt treatment of streptococcal infections can reduce the incidence of
rheumatic fever.
 Penicillin is administered as a preventive measure against subsequent
streptococcal infections.
 Antibodies against group A beta-hemolytic streptococci react with
streptococcal antigens deposited in joints or heart valves or cross-react
with the heart muscle.
Figure 23.5
Dental Caries

Streptococcus mutans, found in the mouth

uses sucrose
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form dextran from glucose
lactic acid from fructose.
Bacteria adhere to teeth and produce sticky dextran,
forming dental plaque.
Acid produced during carbohydrate fermentation destroys
tooth enamel at the site of the plaque.
Gram-positive rods and filamentous bacteria can
penetrate into dentin and pulp.
Caries are prevented by restricting the ingestion of
sucrose and by the physical removal of plaque.
Figure 25.4
Pneumomoccal Pneumonia
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Streptococcus pneumoniae:
 Gram-positive encapsulated diplococci
Diagnosis by culturing bacteria
Penicillin is drug of choice
Figure 24.13
Scanning Electron Micrograph
of Streptococcus pneumoniae
Streptococcus pneumoniae (diplococcus). Fluorescent stain
Streptococcus pneumoniae on Blood Agar (Indirect Lighting)
Enterococcus faecalis in a
Blood Culture
A bile esculin slant
before inoculation.
Enterococcus faecalis
growing on a bile
esculin slant. Note
black color.
Meningococci
Meningococci Gram staining
Identification of Neisseria
meningitidis : Carbohydrate
Utilization
Colonies of Neisseria meningitidis on
Blood agar
Clinical symptoms of meningococcal infection
Clinical symptoms of meningococcal infection
Clinical symptoms of meningococcal infection
Pathological changes of brain (meningococcal infection)
Spinal fluid
Diagnosis and Treatment of the Most Common Types of
Bacterial Meningitis

Diagnosis is based on Gram stain and serological tests of
the bacteria in CSF.

Cultures are usually made on blood agar and incubated in
an atmosphere containing reduced oxygen levels.
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Cephalosporins may be administered before identification
of the pathogen.
Neisseria gonorrhoeae


Gram-, diplococcus
 Gram stain pus, intracellular
diplococcus
Virulence factors
 Pili
 Initial attachment
 Antigenic and phase variation
 Opacity protein (Opa)
 Tighter contact and invasion
 Antigenic variation
 LOS (lipooligosaccharide, lack OAg)
 Inflammatory, major cause of
symptom
 IgA protease
Affected Populations
STI Rates World-Wide
http://www.agi-usa.org/pubs/ib_std.html
Gonococci (methylen blue staining)
Gonococci
Electron Micrograph of Neisseria gonorrhoeae
Colonies of gonococci onto blood agar
Identification of Neisseria : MTM
Chocolate Agar with a Taxo
(Oxidase) Disc
Identification of Neisseria
gonorrhoeae : Carbohydrate
Utilization
A Positive Direct Fluorescent Antibody
Test for Neisseria gonorrhoeae
Neisseria gonorrhoeae (3)

Pili: facilitate attachment, impede phagocytosis

Lipopolysaccharide: marked endotoxin activity; local
cytopathic effect

IgA protease: cleaves IgA-1 subclass of
immunoglobulins
Neisseria gonorrhoeae (4)
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Porin (“Por”, formerly protein I): may facilitate
endocytosis
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Opacity proteins (“Opa,” formerly protein II):
contribute to attachment to human cells
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Reduction-modifiable protein (“Rmp,” formerly
protein III: stimulates blocking antibodies that
reduce serum bactericidal activity
GC Sexual Transmission

Efficiently transmitted by sexual contact

Greater efficiency of transmission from male to female
 Male to female: 50 - 90%
 Female to male: 20 - 80%
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Vaginal & anal intercourse more efficient than oral
Can be acquired from asymptomatic partner
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Increases transmission and susceptibility to HIV 2-5 fold
Gonorrhea
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Many asymptomatic
 Reason for spread
Male- Urethritis, urethral discharge
Female - Endocervicitis, discharge, dysuria,
bleeding
Pharyngitis
Proctitis
Disseminated gonococcal infection (DGI)
 Pustular skin lesions
 Septic arthritis
Pelvic inflammatory disease (PID)
 Endometritis, salpingitis, peritinitis
 Infertility, ectopic pregnancy
Ophthalmia neonatorum
Gonococcal Infections in Women
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Cervicitis
 Pharyngitis
Urethritis
 DGI
Proctitis
Accessory gland infection (Skene, Bartholin)
Pelvic inflammatory disease (PID)
Peri-hepatitis (Fitz-Hugh-Curtis)
Pregnancy morbidity
Conjunctivitis
Many infections asymptomatic
Gonococcal Cervicitis
Incubation 3-10 days
Symptoms:
Vaginal discharge
Dysuria
Vaginal bleeding
Cervical signs :
Erythema
Friability
Purulent exudate
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Pelvic Inflammatory Disease
Adhesions
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Tube
STD Atlas, 1997
Sx: lower abdominal pain
Signs: CMT, uterine/
adnexal tenderness, +/fever
Laparoscopy may show
hydrosalpinx,
inflammation, abscess,
adhesions
Gonococcal Infections in Men
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 Pharyngitis
Urethritis
 DGI
Epididymitis
 Urethral stricture
Proctitis
 Penile edema
Conjunctivitis
Abscess of Cowper’s/Tyson’s glands
Seminal vesiculitis
Prostatitis
Many infections asymptomatic
Gonococcal Urethritis
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Incubation 2-7 days
Abrupt onset of severe
dysuria
Purulent urethral
discharge
Most urethral infections
symptomatic
Epididymitis
Epididymitis
 Swollen painful
epididymis
 Urethritis
 Epididymal tenderness
or mass on exam
Gonococcal Infections in
Women & Men
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Urethritis
Proctitis
Pharyngeal infections
Conjunctivitis
Disseminated Gonococcal
Infection
Blenorrhea
Gonorrhea

Diagnosis
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Intracellular Gram negative diplococci in
discharge
Growth on selective media, oxidase positive
colonies
Flourescent antibody
Treatment
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Cover for probable association with C.
trachomatis
GC Diagnostic Methods
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Gram stain smear
Culture
Antigen Detection Tests: EIA & DFA
Nucleic Acid Detection Tests
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Probe Hybridization
Nucleic Acid Amplification Tests (NAATs)
Hybrid Capture
Gonorrhea Diagnostic Tests
Sensitivity
Gram stain
90-95%
(male urethra exudate)
DNA probe
Culture
NAATs *
85-90%
80-95%
90-95%
Specificity
 95%
 95%
 99%
 98%
* Able to use URINE specimens
Gram Stain for GC: Urethral Smear
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Numerous PMNs
Gram negative
intracellular
diplococci
Gram Stain for GC: Cervical Smear
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PMN with Gram
negative
intracellular
diplococci
GC Culture
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Requires selective media with antibiotics to inhibit
competing bacteria (Modified Thayer Martin Media,
NYC Medium)
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Sensitive to oxygen and cold temperature
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Requires prompt placement in high-CO2 environment
(candle jar, bag and pill, CO2 incubator)
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In cases of suspected sexual abuse, culture is the only
test accepted for legal purposes
GC Culture Candle Jar
GC Culture Specimen Streaking
Cervical and Urethral
GC Culture After 24 Hours
Treatment
http://www.cdc.gov/STD/treatment/4-2002TG.htm#Gonococcal
Prevention
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Abstinence
Safe/”smart” sex
Barrier contraceptives
Educational programs
Reduce misuse of
antimicrobials