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Transcript
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 QuickTime™ and a Photo - JPEG decompressor are needed to see this picture 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)