Lecture 05 - Enteric Bacteria - Lecture 05 Enteric Bacteria...

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Lecture 05 - Enteric Bacteria: Invasive Infectons MI-18a. Describe the biological function of lipopolysaccharide (LPS) and the toxis effects of LPS (endotoxin) and its role in diseases caused by gram-negative organisms. Describe the distinction between endotoxin and exotoxin. MI-18c. Describe the role of porins in Gram negative nutrition and antibiotic susceptibility, and secretion systems used for the export of virulence factors. MI-18b. Describe the microbiological characteristics and identification of E. coli, Klebsiella pneumoniae, Proteus mirabilis, Salmonella, Shigella, and Yersinia MI-18d. Describe the epidemiology, pathogenesis, and clinical manifestations of infection with E. coli, K. pneumoniae, P. mirabilis, Salmonella, Shigella, and Yersinia Enteric Bacteria: Gram (-) bacteria associated with GI flora or disease. enteric just means in the gut 6 families of Enteric Bacteria Enterobacteriaceae Vibrionaceae Pseudomonadaceae Campylobacteraceae Bacteroidaceae Helicobacteraceae Basic Enterobacteriaceae characteristics: - GM (-) rods o Aerobes and facultative anaerobes o like to have oxygen and if there is no oxygen can be anaerobes - Ferment glucose - Oxidase negative – They do not have cytochrome C oxidase o They are not fastidious, not inhibited by bile or bile salts (e.g., MacConkey’s agar) MacConkey’s agar, that inhibit gram +ve, differentiate lactose from non lactose fermenters o Can survive well in bile salt and can survive well in bile (not inhibited by bile) this obvious this organism must survive in the gut so must tolerate bile - Catalase (+) - Reduce nitrate nitrite - Grow on media à EMB (eosin-methylene blue) - Have Flagella o Peri trichous flagella (if motile; trichouse=hair) Hair all around If they have lots of flagella à lots of movement o Examples of bacterial flagella arrangement schemes. - Gut sterile and begin to colonize at the first few months of your life o From your mother you will get lactose i.e. E coli able to use lactose o Thus it is one of the big differentiator LACTOSE FERMENTERS C- Citrobacter E- Enterobacter E- E. Coli K- Klebsiella, Nonmotile LACTOSE NON- FERMENTERS Sh- Shigella ( Nonmotile ; no H 2 S) Y - Yersinia ( Nonmotile ; no H 2 S) P - Proteus S - Salmonella ** Pseudomonas: Does not ferment glucose /lactose; is oxidase positive; polar flagella ; obligate aerobe Pathogenic or virulent? (determined by the genes) - Virulence genes encoded on Plasmids , Bacteriophages or Chromosome . o Insertions of DNA containing multiple genes are called islands . o That are related, cooperate together for the same function à when work together form virulence function - When one or more genes has a virulence function, the region is called a “Pathogenicity Island” - i.e. E.coli 0157:H7 o Pathogenicity island encodes tight binding to intestinal epithelium.

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