Escherichia E. coli –Theodore Escherich in 1885 – most significant species –common isolate from the colon flora –black/green metallic sheen on EMB –posesses O (Shigella), H and K (Group B N. meningitidis) Ag. –other species: blattae, vulneris, fergusonii, hermanii
Diarrheal Infections * EPEC – enteropathogenic E. coli - infantile diarrhea - watery stool w/ mucus but w/o blood * ETEC – enterotoxigenic E. coli - traveller’s diarrhea - infective dose of 10 6 - produce LT and ST toxin (hypersecretion) - non-bloody, watery diarrhea with abdominal cramps and low grade fever
Diarrheal Infections EIEC – entero invasive E. coli –cause dysentery ( direct penetration, invasion and destruction of the intestinal mucosa) – similar with dysentery –scanty stool with pus, mucus and blood –Sereny test – determines the invasiveness of EIEC (+) result – keratoconjunctivitis in guinea pig
Diarrheal Infections EAEC – enteroadherent E. coli cause diarrhea by adhering to the mucosal surface of intestine. watery diarrhea, vomiting and dehydration EHEC – enterohemorrhagic E. coli or VTEC (E. coli 0157:H7) Hemorrhagic diarrhea, colitis and hemolytic uremic syndrome (HUS) Bloody diarrhea and crampy abdominal pain
Edwardsiella –tarda (human pathogen – bacteremia and wound infection) –hoshinae (snakes, birds and water) –ictaluri (enteric septicemia in fish)
Salmonella –2200 species –3 common species (cholerasuis, typhi, enteritidis) –7 subgroups (with Arizona as groups 3A & 3B) –Virulence factors O, H and Vi antigens
Gram negative rods Do not ferment lactose Produce H 2 S Major cause of food poisoning in the U.S. Cause intestinal infections (enterocolitis); enteric fevers (typhoid fever); and systemic infections (septicemia) Chickens are a major reservoir for this bacteria Identification on basis of antigens (O, H, Vi) Salmonella
Enterocolitis:invasion of epithelial cells of intestines infectious dose (ID50) ~ 100,000 organisms infection of gut - inflammation and diarrhea, self correcting Typhoid:starts in small intestine: enters and multiplies in mononuclear cells; spreads to liver, gallbladder, spleen. Leads to bacteremia with onset of fever. carrier state - organisms excreted in feces Septicemia:minority of infections, usually in patients with underlying disorder Salmonella - pathogenesis
Citrobacter resembles Salmonella but are ONPG (+) & LDC (-) Citrobacter species –freundii (UTI, pneumonia, intraabdominal abscess) –diversus (neonatal meningitis) –amalonaticus (extraintestinal infections) C. freundiiS. diversus H2S+- Indole-+ KCN+-
Klebsiella Klebsiella-Enterobacter-Serratia-Hafnia K. pneumoniae >Friedlander’s bacilli (encapsulated and mucoid) > (+) String test K. oxytoca – similar w/ K. pneumoniae except for its indole production K. ozanae – from nasal secretions K. rhinoschleromatis – rhinoscleromatis (infection of nasal cavity with intense swelling and malformation of the entire face and neck)
Morganella Formerl known as Proteus M. morganii – only specie UTI’s and wound infections
Providencia Providencia ( 4 species – P. alcalifaciens, P. rustigianii) P. rettgeriP. stuartii Urease+- Citrate++
Yersinia 11 species –Y. pestis (plague) – bipolar staining (wayson) Bubonic – bite of infected flea Pneumonic Prefered growth at 25 deg C –Y. enterocolitica (acute enteritis – appendictis like) Pig, cats and dogs Cold enrichment Motile at RT –Y. pseudotuberculosis Pathogen in animals (turkey, geese, doves, farm and domestic animals)
Agent of bubonic plague, pneumonic and septicemic plagues Bubonic plague contracted via flea bites Y. pestis sheds capsule while growing in invertebrate host. In humans most of the microbe is taken up and killed by PMN cells Some organisms taken up by Macrophages which can’t kill pestis. Organism multiples in Mac and resynthesizes capsule Organism kills Mac and is released into extracellular environment. The encapsulated microbe resists phagocytosis and spreads to lymph nodes which become swollen, and hemorrhagic giving the black buboes characteristic of the disease. Microbe rapidly spreads through blood, liver, spleen, lung giving rise to highly contagious pneumonia (highly fatal).
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