An organism occasionally misidentified as an enteric pathogen because some isolates produce H2S is

An organism occasionally misidentified as an enteric pathogen because some isolates produce H2S is

• A. Burkholderia cepacia
• B. Burkholderia pseudomallei
• C. Pseudomonas putida
• D. Citrobacter freundii

Answer: (D)

Hydrogen sulfide production on differential media can lead to mistaking a non-Salmonella-like organism for an enteric pathogen that also makes H2S. Citrobacter freundii, an Enterobacteriaceae member, often produces H2S, which shows up as a black precipitate in media such as triple sugar iron agar or SIM. This visible reaction can prompt initial misidentification as an H2S-producing enteric pathogen, even though Citrobacter freundii is commonly an opportunistic GI and environmental organism. The other listed bacteria do not typically produce hydrogen sulfide under standard testing conditions, so they wouldn’t be mistaken for H2S-positive enterics for this reason.

Hydrogen sulfide production on differential media can lead to mistaking a non-Salmonella-like organism for an enteric pathogen that also makes H2S. Citrobacter freundii, an Enterobacteriaceae member, often produces H2S, which shows up as a black precipitate in media such as triple sugar iron agar or SIM. This visible reaction can prompt initial misidentification as an H2S-producing enteric pathogen, even though Citrobacter freundii is commonly an opportunistic GI and environmental organism. The other listed bacteria do not typically produce hydrogen sulfide under standard testing conditions, so they wouldn’t be mistaken for H2S-positive enterics for this reason.