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50 Cards in this Set
- Front
- Back
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Name the geneses of the enterobacteriacea family
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E. coli
Klebsiella Enterobacter Salmonella Proteus Yersinia |
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What are the defining characteristics of the enterobacteriaceae family?
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1. Small
2. Gram Neg 3. Non spore forming 4. Facultative anaerobes 5. Grow on McConkey |
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What are primary pathogens?
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Organisms capable of causing disease in anyone
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What is an opportunistic pathogen?
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Organisms that can only cause disease under certain conditions or in certain hosts
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What are some examples of opportunistic pathogens?
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Proteus, serratia, enterobacter.
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What bacteria of the enterobacteriaceae family are both obligate and opportunistic pathogens?
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E. Coli, Klebsiella pneumonia
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What do obligate or primary pathogens depend on for their propagation?
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That it will cause disease in its host
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What are accidental pathogens?
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causes disease in a given host but they are not spread by means of the pathology and therefore do not gain an evolutionary advantage as a result of the infection
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What is serology?
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Differentiating bacteria based upon the structure of antigens
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How are members of the enterobacteriaceae differentiated?
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Presence of cytochrome oxidase,
indoles, particular sugars fermented, colonial morphology, |
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What is a serotype?
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Isolates sharing similar antigenic structures
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What are the main groups of antigenic structures?
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O - Somatic Antigens
H - motility (flagellar) antigens K - capsular antigens |
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What are somatic antigens? What are they typically associated with?
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Most external part of gram neg bacteria (example : polysaccharide portion of LPS). Associated with diarrhea and UTI. Heat and alcohol resistant.
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What are H antigens? Why can they be difficult to use when serotyping bacteria?
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Located on the flagella; cells produce specific peptides expressed on the motile organs. Flagella can be phasic and therefore not always present, limiting the accurate serotyping.
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What is serotyping useful for?
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Tracing epidemics
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What are K antigens?
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Capsular organs external to the O antigens; they are expendable and not always present. Can indicate the virulence.
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Why do we need to identify microorganisms?
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1. Antibiotic resistance
2. Virulence 3. Potential danger to contacts 4. Also determining that the cause is infectious |
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What is an endotoxin?
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The toxic component of LPS on the surface of gram negative bacteria
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Is E. coli Lac + or Lac -?
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Lac +
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Which is typically more virulent : Lac+ or Lac- ?
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Lac -
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What type of pathogen is E. coli?
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Typically opportunistic, but can develop mechanisms of primary
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How are the diseases of E. coli classified?
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Intestinal
Extra intestinal (UTI, mastitis) |
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What is the pathophysiology of an endotoxin?
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Fever, leukopenia, hypoglycemia, hypotension, shock, impaired, organ perfusion, intravascular coagulation, death, premature labor, abortions.
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What is enteropathogenic E. coli?
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Strains of E. coli not associated with any known toxin
Known as EPEC |
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What is enterotoxigenic E. coli?
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Strains which produce one of two well known enterotoxins (Heat liable toxin and heat stable toxin)
Known as ETEC |
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What is enteroinvasive E. coli?
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Strains which invade the colonic mucosa but can't progress past the lamina propria
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What are the enterohemorrhagic E. coli?
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Strains which produce a shigella dysenteria type toxin. They efface the microvilli of intestinal epithelia.
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What is heat labile toxin?
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(LT) Virulence factor that is denatured by heat
Transmissible on plasmid Hypersecretion of water and chlorides, inhibits reabsorption of sodium in small intestine leading to watery diarrhea |
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What is heat stable toxin?
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Virulence factor that is encoded on a group of F plasmids. Stimulates fluid secretion leading to severe diarrhea.
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How do enterotoxigenic E. coli persist in the upper intestines?
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Fimbrial Adhesions (pili); a virulence factor.
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H.W Smith performed an experiment displaying the requirement of which two virulence factors for the E. coli strain to be pathogenic?
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Adhesion factor, toxin (LT, ST)
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What are iron sequestration mechanisms?
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Method of acquiring available iron for growth by synthesizing special iron siderophores.
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What is alpha hemolysin?
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A protein that lyses RBCs
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What are examples of serum resistance factors in E coli?
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K1 capsular antigen, traT, iss
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What are the intestinal virulence factors?
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1. Endotoxins
2. Adhesions (K88, K99) |
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What are the extra intestinal virulence factors?
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1. Iron sequestration
2. Hemolysis 3. Serum resistance 4. Adhesions |
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Describe neonatal enteritis in pigs.
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ETEC with LT and/or ST
or ST and K88 Watery diarrhea in first 12 hrs; high mortality Vaccine of dams with K88 usually protects piglets |
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Describe weanling enteritis in pigs
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ETEC with LT/ST but no adhesions
Lower mortality rate, usually hemolytic. Sudden change of flora or environment lead to multiple ETEC in small intestines |
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What is edema disease in pigs?
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EHEC isolates are frequently hemolytic. Vasoactive toxin causes toxemia;
Edema leads to neuropathy, to angiopathy, to high mortality |
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What is White scour?
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Intestinal E. coli infection caused by
1. EPEC (nonspecific) 2. ETEC (ST, K99( 3. Clones of these can become systemic in calves without colostrum. Can cause endotoxic shock |
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What are the characteristics of salmonella?
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Lac -, Indole -, Motile
Only 2 real species: S. borgori (reptiles typically) and S. enterica |
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Why is salmonella complicated?
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Different serotypes will cause different diseases depending on what host they are in
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What is S. typhi?
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The salmonella strain with a serotype adapted for pathogenic behavior in humans. Can be maintained in population after recovery asymptomatically (travels to cells within the gallbladder)
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What is the disease caused by S. typhi?
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Typhoid Fever
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Why is there a different disease caused by S. typhi?
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Reacts specially with Peyer's patches (lymph regions in the intestine) and become systemic. They do not produce a major inflammatory response
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How do other strains of salmonella differ from S. typhi?
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A very abrupt disease
Can invade cell of distal ilium Induce a violent inflammatory response which quickly begins to clear the disease |
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What is Salmonella enterititis?
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Can have properties of host specific and eneritis salmonella.
Can infect the internal side of eggs by traveling to ovaries of poultry. But also not exclusively adapted to poultry, and can therefore infect others |
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How are salmonella species transmitted?
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By fecal/oral route (typically) or eating infected food
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What are the characteristics of Proteus?
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Lac -
Swarm blood agar plates Opportunisitic pathogen No specific disease associated Very Motile Can cause UTI in indwelling catheter or diarrhea in young animals |
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What are the characterisitics of yersinia?
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Lac -
Gram - pleomorphic Cause of bubonic plague |
