Download Staphylococcus aureus

Welcome to Pathogen Group 8
• Staphylococcus aureus
– Staphylococcus infections
– Food poisoning
• Streptococcus pyogenes
– Streptococcal infections
– Scarlet fever
– Rheumatic fever
• Streptococcus pneumoniae
• Enterococcus faecium
• Escherichia coli
• Pseudomonas aeruginosa
• Klebsiella pneumoniae
Staphylococcus aureus
• Gram + cocci in grapelike
clusters
• everyone carries on skin, in
nasopharynx
• can infect almost any part of
body
• pus-forming infections and
abscesses
Staph.
• Impetigo
• Many toxins released:
enterotoxin
toxic shock syndrome toxin
exfoliative toxin
hemolysins
coagulase
Staph on skin
Staph.
• scalded skin
syndrome
Staph.
• pus
Staph.
• cerebrospinal
fluid from
meningitis
Staph
• sputum from
pneumonia
Staph.
• on MSA (mannitol
salt agar)
MRSA
• Staphylococcus aureus organisms which are
resistant to methicillin
• Presents challenges for clinical management of
patients
• Outbreaks have occurred in correctional facilities,
hospital intensive care units, and long term care
facilities
• Emerging antimicrobial resistance represents a
significant threat by complicating patient care and
endangering patient safety
Staph
food poisoning
• enterotoxin is heat-stable
exotoxin
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Streptococcus pyogenes
• Gram + cocci in twisting chains
• A. Strep infections: almost any
part of body
• Most common cause infant
bacteremia and meningitis
Strep. pyogenes
• beta hemolysis
Strep.
pyogenes
• impetigo
Strep. pyogenes throat infection
Streptococcus in throat
Strep. pyogenes
meningitis (CSF)
eye infection (pus)
Strep. pyogenes
• peritonitis
Strep. pyogenes
• B. Scarlet fever: erythrogenictoxin-forming strain of Strep.
pyogenes
scarlet fever
• strawberry
tongue
• C. Rheumatic fever: autoimmune response to a Strep
infection (next slide):
Streptococcus pneumoniae
•
•
•
•
the pneumococcus
pneumococcal pneumonia
Gram + diplococci
virulent strains have capsules
“Lancet” shape
Strep. pneumoniae
• a leading cause of death for all ages
• most common cause of pneumonia (500,000 per year),
septicemia (50,000), meningitis (3000), otitis media (7
million = 2/3 of ear infections)
• invasive disease most common in young, old,
immunocompromised
• peaks in winter
Vaccines against Strep. Pneumoniae
• Purified polysaccharide from 7 strains = PPV
• For adults with certain chronic diseases; people over
65; children 2-23 months
• Also PCV (pneumococcal conjugate vaccine) for infants
under 2 years
– Results in 6-7% decrease in otitis media
Strep. pneumoniae
in sputum
in CSF (meningitis)
Enterococci
• Enterococcus faecalis and E. faecium
• Major nosocomial pathogens: UTI, surgical incision,
blood
• Normal intestinal flora
• Often highly drug resistant
• VRE = vancomycin resistant enterococcus
Enterococcus faecium
• Facultative anaerobe, in pairs or short chains,
fastidious, salt & bile resistant!
• colonizes the large intestines. Risk factors for
enterococcal infections are urinary or intravascular
catheterization in addition to long-term hospitalization
with broad-spectrum antibiotics. This bacterium has
developed multidrug antibiotic resistance and uses
colonization and secreted factors in virulence (enzymes
capable of breaking down fibrin, protein and
carbohydrates to regulate adherence, bacteriocins to
inhibit competitive bacteria, for examples)
Escherichia coli (E. coli)
• Gram - bacillus (short)
• normal flora in human and
animal colon
• #1 cause of urinary tract
infections
• #1 cause of infant diarrhea
• #1 cause of
traveler’s diarrhea
• can infect many
parts of the body
E. coli in urine sediment
Types of E. coli
• Most not pathogenic
• Different strains produce
different infections
• Older system uses serotypes based on O and H
antigens, e.g. O157:H7 (O is in cell wall, H in flagella)
• Newer system based on virulence factors, e.g.:
– Enterotoxic E. coli: toxins cause diarrhea
– Enterohemorrhagic E. coli: shiga toxins cause
bleeding of intestine and kidneys (e.g. O157:H7)
E. coli O157:H7
• O157:H7 produces shiga toxins: can be fatal
• Source usually cattle feces (e.g. in ground beef)
• Hemorrhagic colitis (bloody diarrhea) and hemorrhagic
uremic syndrome (kidney infection with bloody urine)
• Seizures, coma, colonic perforation, liver damage,
cardiomyopathy
• 60 deaths/year in U.S. (mostly <5 yrs or >60 yrs age)
• Infectious dosage low as 4
E. coli
EMB agar (top)
EMB agar (bottom)
MacConkey agar
Pseudomonas aeruginosa
• Gram - bacillus
• most strains
strictly aerobic
• polar flagellum
• water-soluble
green pigment
– green pus
– green stained
agar or broth
• among most
drug-resistant
of bacteria
Pseudomonas hot tub dermatitis
fatal systemic Pseudomonas
Klebsiella pneumoniae
• Gram - bacillus
• capsule
Klebsiella in sputum (gram stain)