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19 Cards in this Set
- Front
- Back
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What are the main genera of Enterobacteriaceae? |
1. Escherichia 2. Salmonella 3. Klebsiella 4. Proteus 5. Shigella (man & primates) |
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General characteristics of Enterobacteriaceae? |
GRAM NEGATIVE RODS or COCCOBACILLI - Usually motile or flagellated - Facultative anaerobes - Biochemically active - Oxidase negative - Grow well on MacConkey (LF: E. coli, Klebsiella spp; NFL: Salmonella sp, proteus sp, yersinia sp) - Lg white, round colonies on Blood agar Predilection site: Intestinal tract of vertebrates |
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How are enterobacteriacaea species subdivided? |
1. SEROPTYPING = all species subdivided using common scheme based on LPS 'O' antigens (somatic), flagellar 'H' antigens, Fimbriae/pili "F" antigen, or capsule 'K' antigen 2. Pathotypes 3. Biotypes 4. Phage typing 5. Pulse field gel electrophoresis (PFGE) |
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What are the surface antigens present on Enterobacterial cells? |
1. O antigen = LPS 2. H antigen = Flagella 3. F antigen = Fimbriae/pili 4. K antigen = capsule * Salmonella and E. coli have many different types of surface antigens which are used as markers when identifying. |
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Describe the slide agglutination test. Which enterobacterial species is this test commonly use for? |
Antibodies are added to a sample on the slide and if the antigens are present for the antibodies, the bacteria will rise and be seen in the sample. - Important for Salmonella |
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General characteristics of Salmonella? |
Enterobacteriaciaea - Gram negative bacteria with long flagella - NON-Lactose Fermenter - Infects via fecal-oral route - Invasive, facultative intracellular pathogens! - Suspected commensal of cold blooded animals - Many zoonotic - Antibiotic resistance is a problem; need vaccines! |
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Syndromes caused by Salmonella? |
- Important syndromes are: 1. Enteritis = diarrhea; often zoonotic 2. Septicemia = spread throughout body; lead to abortion, joint infections or pneumonia 3. Chronic infection = chronic ear tips in calves 4. Many zoonotic |
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Methods of identifying Salmonella? |
1. Serotyping = for O (LPS) & H (Flagella) antigen 2. Slide agglutination test 3. Phage typing - Further subdivision by Pulse field gel electrophoresis 4. DNA Typing
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Salmonella enterica subspecies I serotype Typhimurium is clinically the most important type of salmonella.
What is the short way of saying this species? |
Salmonella Typhimurium (>99% of clinical isolates) - Enteritis & septicemia in pigs; food poisoning in man - O group = B |
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What are the non-host specific serotypes of salmonella that cause enteritis in young animals and food poisoning in humans? |
S. Tymphimurium & S. enteritidis |
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What are the host specific serotypes of salmonella that cause systemic infections in animals of all ages? |
S. gallinarum, S. abortusovis, S. typhi |
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Host-RESTRICTED serovars of Salmonella? |
Preferentially infect one host but can infect others: 1. S. Dublin - Cattle - Septicemia, enteritis, abortion, meningitis, joint ill, dry gangrene 2. S. choleraesuis - Pigs - Septicemia * Both can infect humans; rare, but serious! |
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Describe type III secretion systems (TTSS): appearance? Function? |
APPEARANCE: Resemble molecular syringe caps and essentially act as molecular syringes for gram negative bacteria FUNCTION: Allow transfer of effector proteins (enzymes, toxins) from the gram negative bacteria into the cytoplasm of the host cell membrane - Salmonella spp have TTSSs, which aid in their engulfment process by the host cell membrane |
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What are pathogeniticity islands (PI)? How are they acquired? |
Large chromosomal regions that encode (often many) virulence genes (toxins, adhesins, invasins, secretion systems) - Acquired horizontally! |
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How many pathogenicity islands do salmonella spp have? What are the two main PIs of salmonella? |
17 PIs in salmonella
Main two (contained by all S. enterica subsp I serotypes): 1. SP1 = encodes for TTSS that allows invasion of epithelial cells and remaining in the gut = enteritis 2. SP2 = TTSS & survival in macrophages |
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Describe how SPI1 Salmonella spp invade epithelial cells. |
1. Initial attachment via fimbriae of salmonella dimer 2. Secretion via TTSS of effector proteins 3. Host cell engulfs bacteria 4. Eventually is released within cell |
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Is gut inflammation beneficial to Salmonella? |
Yes, salmonella exploits inflammation to compete with normal flora of the body, as well as altering local environment. - The altered local environment accommodates a respiratory electron acceptor for salmonella (tetrathionate) |
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Describe how SPI2 Salmonella spp allows survival within macrophages. |
Prevention of phagolysosome formation! |
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Pathogenesis of Salmonella? |
1. Salmonella attaches via it's fimbriae to the host cells 2. It then penetrates the host cell lamina propria either through M-cells or through enterocytes by injecting effector proteins causing the cell membrane to ruffle up and engulf the bacteria 3. Once within the lamina propria, the bacteria may either: I. Be taken up by neutrophils, which restrict the bacteria to the gut = ENTERITIS (non-host adapted serotypes) or II. Be taken up by macrophages, breeds and is spread throughout the blood = SEPTICEMIA (host adapted serotypes) commonly to spleen and liver |
