Escherichia coli strains producing hydrogen sulfide in iron-agar medium.

Abstract

An organism biotypical of Escherichia coli except for H2S production, and incompatible biochemically or serologically, or both, with Edwardsiella, Salmonella, Citrobacter, Arizona, Proteus, or Klebsiella, was isolated from the urinary tracts of three elderly women with urinary tract infections. It appears unlikely that these were identical hospital-acquired strains, as one of these was obtained from an outpatient who had been out of the hospital for more than a month, and each had distinctive biochemical or antibiotic susceptibility patterns. The attention of clinical microbiology laboratory personnel is directed to the existence of this group of organisms, not documented in standard reference sources. In the light of recent observations, they unquestionably represent variant strains of E. coli . They are likely to be encountered in clinical laboratory practice with sufficient frequency to require that all laboratory personnel be alerted to their recognition, both as potential pathogens and as biotypes complicating the detection of enteric pathogens in stool specimens.