Abstract
BackgroundShiga toxin producing E. coli (STEC) is an emerging zoonotic pathogen that can cause acute renal failure, especially in children. Clinical microbiology laboratories may fail to detect STEC and other diarrhoeic E. coli unless purposive rigorous screening procedures are followed using appropriate diagnostic technology; CHROMagar™STEC has rarely been used for isolation of African diarrhoeic E. coli hence characteristics of isolates on this medium are not yet fully understood. This study aimed to determine the prevalence and characteristics of STEC and other diarrhoeic E. coli isolated on CHROMagar™STEC from stool samples submitted to the microbiology laboratory of a South African public sector tertiary care hospital.ResultsIn total, 733 stool samples were tested. Of these, 4.5% (33/733) possessed diarrhoeic E. coli. Of the diarrheic E. coli, 5/33 (15.2%) were STEC, 15/33 (45.5%) EAggEC, 6/33 (18.2%) atypical EPEC, 5/33 (15.2%) typical EPEC, and 1/33 (3%) DAEC. None of the STEC isolates had been identified by routine testing (based on using sorbitol media to test for E. coli O157: H7 strains and not the other STEC) in the laboratory. Of the 33 strains, 55% (95% CI = 40.8–72.7) showed resistance to ampicillin.ConclusionsCHROMagar™STEC enabled detection of tellurite - resistant diarrhoeic E. coli that would be missed using routine methods. Further studies are needed to determine the proportion and characteristics of those which might have been missed using this approach.
Highlights
Shiga toxin producing E. coli (STEC) is an emerging zoonotic pathogen that can cause acute renal failure, especially in children
Of the mauve colonies obtained from direct culture, 5.9% (12/204)were diarrhoeic E. coli while 39.6% (21/53) of the mauve colonies obtained following enrichment in Tryptic Soy Broth (TSB) were diarrhoeic E. coli
Tellurite resistant diarrhoeic E. coli were obtained from 5% (33/733) of the stool specimens
Summary
Shiga toxin producing E. coli (STEC) is an emerging zoonotic pathogen that can cause acute renal failure, especially in children. The STEC serotypes commonly associated with severe disease globally (O26, O45, O103, O111, O121, O145, and O157) [4] can readily be isolated on CHROMagarTMSTEC because they are commonly tellurite resistant [5]. Tellurite resistance is defined as growth at a minimum inhibitory concentration of 2.5 μg/ml to ≥20 μg/ml), [6] the concentration of potassium tellurite in CHROMagarTMSTEC is proprietary. On this agar, the STEC serotypes that are commonly associated with severe human infections (O26, O45, O103, O111, O121, O145, and O157) [4, 7] form mauve colonies, other Enterobacteriaceae form blue or colourless colonies, while the growth of gram-positive bacteria is inhibited
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
