gram negative: citrobacter, enterobacter, escherichia

genus overview of citrobacter:

-natural habitat: intestinal tract, soil, water, sewage, and food

-small gram-negative rods

-coliform bacteria

-strict anaerobic

-survives poorly in the environment and are easily inactivated by common disinfectants

-biochemical differentiation:

• motility +

• lactose + fermentation

• catalase +

• TSI alkaline/acid or acid/ acid

citrobacter freundii:

• characteristics: 2-4mm translucent to opaque colonies with a glossy surface

• lab results: MR +, VP -, urease +, citrate +, TSI: alkaline/acid or acid/acid (H2S negative), EMB positive growth

• diseases associated with it: sepsis, respiratory, UTI, WOUNDS, meningitis, GI upset (humans and dogs), mastitis (cattle)

• organs: systemic, respiratory, urinary, CNS, skin, soft tissue, mammary

• treatment: supportive care, antidiarrheals, antibiotics pending culture and sensitivity

enterbacter genus overview:

-natural habitat: normal intestinal flora, opportunistic, often nosocomial pathogens. also isolated from skin, plants, soil, water, sewage, dairy products (contamination)

-gram negative rods

-facultative anaerobes

-lab results/plates: macconkey + growth and + fermentation, catalase +, VP +, MR -, EMB: purple to pink (+ fermentation for lactose)

-coliform bacteria (in sewage bc of feces in soil)

enterobacter cloacae:

• characteristics: 2-3mm, low convex, moist, shiny, entire margins, variable hemolysis, no swarming, not mucoid

• lab results: indole -, MR -, VP +, urease -, citrate +, TSI: acid/acid, H2S -, motility +

• diseases associated with it: mastitis, uterine infections/metritis (MMA in sows)

• organs: mammary gland, reproductive tract, urinary tract, wounds

• treatment: antibiotics pending culture and sensitivity

***MMA: mastitis metritis agalactae (mammary infection, uterine infection and no milk production)

escherichia coli “E. coli”:

ZOONOTICS

• Characteristics: large greyish colonies, entire edges, hemolytic and non-hemolytic strains possible macconkey + growth, pink colonies present, EMB: metallic green sheen (+ fermentation of lactose), brilliant green agar: lactose/sucrose fermentation (yellow-green)

• lab results: indole +, VP -, MR +, motility +, catalase +, urease -, citrate -, TSI: acid/acid, gas: +, H2S: -

• diseases associated with it: neonatal D+, post weaning diarrhea, edema disease, MMA syndrome (pigs), neonatal D+, colisepticemia, joint illness post septicemia (older calves), coliform mastitis (cattle), neonatal colibacillosis/colisepticemia, watery mouth, coliform mastitis (sheep), neonatal septicemia (dogs, often fatal) ***some strains produce enterotoxins= toxins get absorbed from small intestine and go everywhere in body

• organs: GI, respiratory, systemic, mammary glands, nervous, joint, urinary (kidney)

• treatment: supportive care, antibiotics pending culture and sensitivity