Question

A 35-year old female was admitted to the hospital with a history of fever, headache, myalgia, rose spots on the abdomen, malaise and anorexia. These symptoms had appeared one week prior to admission. The patient’s admitting diagnosis was “fever of undetermined origin”. Blood cultures were drawn. The next day the blood cultures were growing a gram negative rod. The following biochemical tests were found:

ONPG: Negative                                ADH: Negative                                  Citrate: Negative                   

Glucose: Fermentor                           LDC: Positive                                    Voges-Proskauer: Negative

H₂S: Weakly positive                         ODC: Negative                                  Motile

Lactose: Non-fermentor                     Indole: Negative                   

Question:

a. What is the most likely etiologic agent isolated in the blood culture?

Question:

b. What confirmatory testing must be completed on this organism? And what processing must be completed for a successful test?

Question:

c. Name three differential, selective media, other than MacConkey agar, this organism could be used for isolation of this organism?

Question:

d. What are the two primary routes of transmission for this organism?

Answer 1

A. According to the symptoms the etiologic factor isolated in blood culture is SALMONELLA TYPHI. Salmonella is a gram-negative enteric bacillus belonging to the family Enterobacteriaceae.

B. Polyvalent Flagellar (H) Test, Urease test, Polyvalent somatic (O) test.

C. Differential media: Salmonella Chromogen Agar, Triple sugar iron agar,  S-S agar.

Selective media:Hekteon Enteric agar, Deoxycholate citrate agar, Bismuth sulfite agar

D. Feco -oral route and contaminated , uncooked foods are two important routes of transmission.