Enterobacteriacea Flashcards
Which genus typically has a fruity odor?
Pseudomonas
All fermenters in the Enterobacteriacea are oxidase ___?
Negative
What are the 3 non-motile genus that are fermenters?
Shigella, Klebsiella & Yersinia(all 3 spp. non-motile @ 37C, only Y. pestis @ 25 & 37 C)
On an HE plate shigella species appear as what color?
Green/Blue or colorless colonies with black dots in the center due to H2S production.
What are the 5 main characteristics of Enterobacteriacea?
Gram negative bacilli Ferment glucose with acid production Reduce nitrates to nitrites Oxidase negative Facultative anaerobes
What are Yersinia’s motility characteristics?
Non-motile at 37C and motile at 22C
What are the most common bacteria to cause iatrogenic infections?
K. pneumoniae, E. coli, P. mirabilis
What is the sorbitol MAC plate used for?
Used as a screen for E. coli 0157:H7 which is sorbitol negative.
What is the significance of the SIM deep?
Tests for motility, indole, and H2S production
What are the only 3 organisms that are PAD positive?
Proteus, Providencia, and Morganella
What is the significance of the CIN agar?
Used in the isolation and detection of Yersinia spp which grow as clear colonies with red bullseye center is a presumptive ID.
What is in the CIN agar?
Peptone base with a yeast extract, manntiol as a source of carbohydrate, antibiotics, crystal violet, neutral red (indicator), and bile salts for inhibiting gram positive and gram negative bacteria other than Yersinia.
What is the SS agar and how is it used?
Salmonella-Shigella agar. Contains bile salts and sodium citrate and brilliant green for inhibiting gram positive and gram negative non-fermenters. Neutal red as the indicator and ferric acid and sodium thiosulfate to help visualize gas and H2S production.
What does it mean is the SS agar is pink or red?
A negative result
What is the O antigen?
Somatic, heat stable, lipopolysaccharide
What is the H antigen?
Flagellar, surface of the flagella, heat labile, protein
What is the K antigen?
Capsular, species specific, heat labile, polysaccharide, inhibits detection of underlying antigens (O Ag)
What is the Vi antigen?
Surface polysaccharide, heat labile, prevents phagocytosis, specific for Salmonella typhii.
How do you come into contact with Salmonella?
Ingestion of contaminated food/water, undercooked poultry, eggs, dairy products, contaminated cooking utensils. *It is susceptible to gastric acids.
What do you have to do if you have a positive Salmonella culture?
Must do a serotyping and then send a sample to the Ohio Department of Health for confirmation.
S. typhii has what type of antigen?
Vi antigen
S. typhii and S. paratyphii do what to the intestines?
Penetrates the intestinal mucosa and gains access to the lymph nodes, can travel to the liver and spleen and multiplies in the phagocytes.
How was Typhoid Mary a carrier?
Organisms are harbored in the gall bladder and are shed periodically in the stool without causing infection or illness in the carrier.
What are some important reaction characteristics of Salmonella?
H2S positive, citrate positive, ornithine positive, MR positive.
What is Shigella group A?
Shigella dysentariae
What is Shigella group B?
Shigella flexerni
What is Shigella group C?
Shigella boydii
What is Shigella group D?
Shigella sonnei
Which Shigella species is the most virulent?
Group A, S. dysentariae
Which Shigella species is the most common in the U.S.?
Group D, S. sonnei
What does the fecal sample of Salmonella contain?
Blood and mucous, NO WBC
What does the fecal sample of Shigella contain?
Blood, mucous and wbc’s
How do you do Shigella serotyping?
Prepare a suspension of the organism, add the Group A, B, C, or D antisera. A positive reaction is clumping. A negative reaction you must boil the suspension and retest with the antisera due to the capsule.
What is a good way to differentiate Salmonella and Shigella?
H2S. Salmonella is positive, Shigella is negative.
If you have urea negative, oxidase positive, indole negative, and catalase positive what is your presumptive ID?
Yersinia. *A sample must be sent to the health department.
How is Yersinia pestis spread and what are the forms?
Rodents are the reservoir, transmitted through the rat of flea bite. Has 2 forms: Bubonic- develops 2-5 days after the infection, fever and pain in lymph nodes. Pneumonic- can be passed person to person and affects the repsiratory and blood stream.
How do you treat Y. pestis?
Streptomycin or chloramphenicol
What does Y. pestsis look like microscopically?
Short plump gram negative rods, when stained with methylene blue stain they show an intense bipolar staining which gives a safety pin appearance
What does Y. enterocolitica cause?
Causes acute enteritis
What are the reservoirs for Y. enterocolitica
Lakes, domesticated swine, dogs, and cats. Transmitted by handling inected animal or ingestion of contaminated food or water.
What are the symptoms of Y. enterocolitica?
Diarrhea, fever, headache, nausea, and abdominal cramps that mimic appendicitis. *lower right quadrant pain
Y. enterocolitica is urea ___, ornithine ___, and sucrose___?
Urea positive, ornithine positive, and sucrose positive
Y. pestsis is urea ___, ornithine ___, and sucrose ___?
Urea negative, ornithine negative, and sucrose negative.
EPEC is what kind of E.coli?
causes infantile diarrhea and occurs in hospitalss or daycares. Stool has large amounts of mucous but no blood or wbcs
ETEC is what kind of E. coli?
Traveler’s diarrhea that releass enterotoxins LT (heat labile) and ST (heat stable). Stool has no blood, no mucous and no wbcs.
EIEC is what kind of E. coli?
Dysentery, with similar symptoms to Shigella. Directly penetrates and destroys the intestinal mucosa. Stool contains blood, wbcs, and mucous. Definitive ID with DNA probes. *Lactose and lysine negative
What kind of E. coli is EaggEC?
Adheres to the intestinal mucosa, recovered primarily in children with chronic diarrhea.
What kind of E. coli is EHEC?
Produces Shiga toxin, and associated with HUS, colitis, and hemorrhagic diarrhea. Acquired form undercooked hamburger or unpasteritzed milk. *Low infectious dose. E. coli 0157:H7 Stool has blood, mucous with no wbc’s
How do you isolate EHEC?
Sorbitol MAC plate.
What is the IMVC for E. coli?
IMVC ++–
Klebsiella, Enterobacter, Serratia, and Hafnia all have what in common?
VP positive, normal flora of the animal/human intestines
Klebsiella spp. have what characteristics?
Non-motile, Lactose positive, Ornithine negative, and restistant to ampicillin, tricarcillin, and carbenicillin.
What is the IMVC reaction for K. pneumoniae?
IMVC –++
K. oxytoca is different from all the other Klebsiella spp. by what reaction?
K. oxytoca is indole positive, while all the others are indole negative.
Enterobacter is lactose ___, ornithine ___, and IMVC ___?
Lactose positive, ornithine positive, and IMVC –++
How do you differentitate between Enterobacter and Klebsiella?
Ornithine, Enterobacter is ODH + and Klebsiella is ODH -
What is unique about Serratia marcescens?
DNase positve *the only one
How do you differentiate between all the Shigella spp. and Shigella sonnei?
All the Shigella spp. are ornithine negative while S. sonnei is ornithine positive.
True of False?
Y. pestsis is non-motile at all temperatures
TRUE
How do you differentiate between E. cloacae and E. aerogenes?
E. cloacoae = Lysine - and Arginine +
E. aerogenes = Lysine + and Arginine -
What are the key characteristics of P. agglomerans?
LDH, ADH, ODH negative, has a yellow pigment on the BAP (which all other Enterobacteriacea have no pigment)
True of False?
S. marcescens is a slow lactose fermenter
TRUE
True of False?
S. marcescens can liquefy gelatin
TRUE
What are the key characteristics of Proteus spp.?
H2S positive, urea positive, and resistant to polymixins, nitrofuratoin, and tetracycline
How do you differentiate between P. mirabilis and P. vulgaris?
Ornithine.
P. mirabilis = ODH +
P. vulgaris = ODH -
*Lactose is another way of diff. and the reactions are opposite of ODH
How do you differentiate between P. rettgeri and P. stuartii?
Adonitol
P. rettgeri = Adonitol +
P. stuartii = Adonitol -
What is the differentiating characteristic between Proteus spp. and Morganella?
H2S production. Proteus is H2S pos. and Morganella is H2S neg
What is the differentiating characteristic between Morganella and Providencia spp?
Citrate. Morganella is negative and Providencia is positive
What is Edwardsiella associated with?
Reptiles and fresh water fish, common with wound infections
Which enteric organisms are lactose positive?
E. coli, Klebsiella pneumoniae, E. aerogenes, and E. cloacae
Vibrio is known by what kind of stool?
Rice water stool
Vibrio has what kind of motility under a dark field microscope?
Shooting star motility
Vibrio are gram ___, and what shape?
Gram negative rods that can be pleomorphic and comma shaped
What does TCBS tell you?
Agar for vibrio and it differentiates between the sucrose fermenting (yellow colonies) and the non-sucrose fermenting (blue colonies). *Quick screen for cholera which is a sucrose fermenter.
What does Campylobacter look like on a gram stain?
Gram negative rods that are curved and have a seagull appearance.
Campylobacter likes what kind of environment?
Microaerophilic, and capnophilic at 42C
What do you do if you suspect you have H. pylori?
Do not culture due to lack of growth. Test for serum antibodies using an ELISA or immunochromatography
What is H. pylori associated with?
Gastric ulcers and gastric cancer
How can you do a rapid screen for H. pylori?
Christensens medium 37C for 2 hours (CLO test) which is a rapid urease test or a urea breath test
What is the main difference between diarrhea and dysentery?
Diarrhea has no histological changes in the intestinal wall and usually due to an enterotoxin.
Dysentery causes epithelial necrosis, ulceration, and inflammation due to bacterial invasion.
