Isolation of pathogenic escherichia coli from stool samples of diarrhoeal patients with history of raw milk consumption

Abstract

Aim: To detect the occurrence of pathogenic Escherichia coli from stool samples of diarrhoeal patients with history of raw milk consumption and to determine the public health significance of isolates, especially their role in causing human diseases. Materials and Methods: A total of 100 stool samples from diarrhoeal patients, with history of raw milk consumption were collected from primary health centres in and around Anand city, under aseptic conditions and a total of 50 raw milk samples were collected from milk vendors, retail shops located in Anand city in sterilized sample bottles. MacConkey broth was used for the enrichment of all the samples and inoculation was done on MacConkey agar and EMB agar was used as the selective media. This was followed by the confirmation of isolates using biochemical tests. For the serotyping, E. coli isolates were sent to the National Salmonella and Escherichia Centre, Central Research Institute (CRI), Kasauli, Himachal Pradesh. Detection of virulence genes was performed using PCR technique. Results: During the present investigation, 26 (52%) E. coli isolates from 50 milk samples and 59 (59%) E. coli isolates from 100 stool samples were recovered. Out of 85 E. coli isolates sent for serotyping, 74 isolates could be typed which were further distributed into 13 different serogroups O2, O4, O8, O17, O22, O25, O29, O36, O45, O60, O90, O116 and O172, whereas 8 isolates were found untypable and 3 isolates were reported rough isolates. Of the 59 E. coli isolates from stool samples of diarrhoeal patients tested, 15 isolates (25.42%) were reported to be positive for stx genes, among that 6 (10.16%) were positive for stx1 gene, 9 (15.25%) isolates were positive for stx2 gene, while 3 isolates (5.08%) were positive for eaeA gene. In this study, 21 E. coli isolates were found to be Shiga toxin producing E. coli (STEC) while none of the isolates were positive for the serotype O157. Conclusions: Our present findings indicate that raw milk may act as a source of pathogenic E. coli and it may be responsible for the occurrence of diarrhoea and various other health-related complications in humans. We therefore recommend proper managemental practices and effective control measures for improved hygiene and sanitation.