Comparative Evaluation of EMB Agar and Hicrome E. coli Agar for Differentiation of Green Metallic Sheen Producing Non E. coli and Typical E. coli Colonies from Food and Environmental Samples

Ally C. Antony1,2*, Mini K. Paul2, Reshma Silvester1, Aneesa P.A.1, Suresh K.1, Divya P.S.1, Simmy Paul3, Fathima P.A.4 and Mohamed Hatha Abdulla1

1Department of Marine Biology, Microbiology and Biochemistry, School of Marine Sciences, Cochin University of Science and Technology, Lakeside Campus, Cochin – 682 016, India. 2 M.E.S. College, Marampally, Ernakulam – 683 107, India. 3School of Medical Education, Mahatma Gandhi University, Kottayam, India. 4State Council of Educational Research and Training, Trivandrum, India.

Received on 01 June 2016 and accepted on 25 July 2016



The performance of Hicrome E. coli agar (Himedia) versus EMB agar (Himedia) was compared for the detection of E. coli from food and environmental sources. Four hundred bacterial isolates producing typical E. coli like green metallic sheen on EMB agar were subjected to biochemical analysis by IMViC tests and they exhibited 6 different types of reactions. Isolates exhibiting only two distinct reaction types were proved to be typical E. coli, which were reconfirmed by molecular detection of species-specific uid A gene as well as 16S rRNA sequencing. Isolates exhibiting the remaining four reaction types comprised of Enterobacter asburiae, Kluyvera georgiana, Pantoea agglomerans and Phytobacter diazotrophicus respectively, all belonging to the family Enterobacteriaceae. The E. coli strains recovered from Hicrome E. coli agar comprised of 20 different serogroups including glucuronidase positive atypical O157: H7. Hicrome E. coli agar had better sensitivity (100%), specificity (99%) and efficiency (99.5%) than EMB agar in differentiating the false positives and false negatives and does not require any further confirmatory tests.

Keywords :

 Escherichia coli; EMB agar; Hicrome E. coli agar, metallic sheen.