MLSCI340 Enterics Flashcards
Common genera in family of Enterobacteriaceae that are associated with human pathogenicity
- Klebsiella
- Shigella
- Salmonella
- Escherichia
- Proteus
- Citrobacter
- Serratia
- Hafnia
- Yersinia
- Enterobacter
- Providencia
- Morganella
Normal flora in the gastrointestinal tract
- Enterobacteriaceae
- CNS
- Anaerobes
- Diphtheroids
- Enterococcus sp.
- Candida sp.
Obligate pathogens in the GI
- Aeromonas hydrophilia
- Salmonella enterica
- STEC; E.coli O157:H7
- Plesiomonas shigelloides
- Yersinia enterocolitica
- Shigella sp.
- Campylobacter jejuni
- Vibrio cholerae
Which pathogens are implicated in food poisoning/ food toxemias ?
- S. aureus
- B. cereus
- Clostridioides difficile
- C. perfringens
- C. botulinum
Which bacteria is associated with gastric, peptic and duodenal ulcers ?
Helicobacter pylori
Salmonella on MAC and HEK
MAC: wh
HEK: translucent blue-green +/- black center
Shigella on MAC and HEK
MAC: wh
HEK: translucent green
Yersinia on MAC and HEK
MAC: wh
HEK: pink/yellow
Yersinia on CIN
Cefsulodin Irgasan Novobiocin:
- translucent with red center
E. coli O157:H7 on SORB/SMac and CHROMagar Stec
colorless
Campylobacter on CBF
Campylobacter Blood Free:
- gy, moist, fltspr, or raised
Describe Principle of Tube Indole
- bacteria capable of hydrolyzing tryptophan (in peptone water) to form indole ?
- detected by colour rxn with dimethylamino benzaldehyde (Kovac’s)
- tube test could check for motility before adding Kovac’s by performing a wet mount
- differentiates lactose fermenters:
a). E. coli = POS
b). Klebsiella oxytoca (POS) vs K. pneumoniae (NEG)
red = POS
What is the general rule for order of inoculation of media plates and biochemicals ?
- liquid to solid
- least selective to most selective
What is the purpose for CNA ?
Colistin Naladixic Acid:
- selects for gram POS bacteria
- inhibits gram neg, normal flora
What is the purpose of PEA when incubated anaerobically ?
- isolates strict anaerobes
- facultative gram neg anaerobes (ie. Enterobacteriaceae) DO NOT GROW
- gram pos will grow (S. aureus)
Which planting media is used for a spot indole ?
BAP or CHOC; tryptophan is present
Describe Principle of Spot Indole
- more sensitive than tube indole
- can’t check for motility first
- useful for organisms that won’t grow in peptone water (anaerobes)
- colony transferred to filter paper; saturated w/ spot indole reagent (p-dimethylaminocinnanaldehyde);
- blue/green = POS
- pink = neg
List 2 conditions that must be met for decarboxylation to occur. Why is a control tube needed ?
- Acidic (due to decarboxylation of amino acids)
- Anerobic (mineral oil)
- control tube ensures that color change = decarboxylation
Describe CHROMagar STEC media. Why do Shiga-Toxin-producing organisms need to be identified ?
CHROMagar STEC:
- selective and differential
- qualitative, direct differentiation of Shiga-like toxin producing E. coli
- toxic shock syndrome is fatal
When is susceptibility testing performed on enteric pathogens ?
- Shigella
- Vibrio
- treatment failure
- Immunocompromised (children, elder, chemo, transplant) patients
Under what circumstance would yeast be reported from a stool specimen ?
- pure/ predominant Candida sp. in a body site NOT NORMALLY FOUND
- normal flora has been replaced
3 sugars (%) in TSI
Glucose (0.1%) - butt
Sucrose (1.0%) - slant
Lactose (1.0%) - slant
Which organism is a sick A/A on TSI ?
Yersinia enterocolitica
Tube indole reagent
(Kovac’s) Dimethyl benzaldehyde
Spot indole reagent
p-dimethyl aminocinnaldehyde
Test results to ID Aeromonas hydrophilia
What is Cary-Blair media for ?
- transport of rectal and fecal specimens
- preserves enteric pathogens
Test results to ID Serratia marcescens
col morph: red
MAC: red
HE: red
Orient: blu
TSI: K/A
Lys and Orn= pos
What food product is Campylobacter jejuni associated with ?
poultry
Source of Aeromonas hydrophilia
fresh water
NOTE: HYDRO + philia = loves water
Which 2 enteric pathogens can be from shellfish ?
- Plesiomonas shigelloides
- Vibrio cholerae
What food product is Yersinia enterocolitica associated with ?
Pork
T or F: toxins of C. perfringen causes fever and vomiting
FALSE; C. perfringen DOES NOT cause fever and vomiting
