Ashish Roy

Serogroups, Atypical Biochemical Characters, Colicinogeny and Antibiotic Resistance Pattern of Shiga Toxin-producing Escherichia coli Isolated from Diarrhoeic Calves in Gujarat, India

This study was designed to investigate the antibiotic resistance, colicinogeny, serotyping and atypical biochemical characteristics of 41 Shiga toxin‐producing Escherichia coli (STEC) strains detected using polymerase chain reaction from 90 E. coli strains isolated from 46 diarrhoeic calves. The STEC strains belonged to 14 different serogroups. Seventeen per cent of the STEC strains carried the eaeA gene while 14.28% of the 49 non‐STEC strains were eaeA positive. Twenty eight (68.29%) of the 41 STEC strains were rhamnose non‐fermentors. All the STEC strains revealed resistance to at least three of the antibiotics tested. 100% resistance was found against kanamycin and cephalexin followed by cephaloridine, enrofloxacin, amikacin, ampicillin, tetracycline, ceftiofur, ciprofloxacin, colistin and co‐trimoxazole. Eighteen (44%) of the STEC strains produced colicin and all these colicinogenic strains were resistant to three or more antibiotics. Eleven STEC strains (26.82%) showed urease activity. The results of this study suggest that diarrhoeic calves are an important reservoir of STEC strains that are potentially pathogenic for farm animals and humans. Moreover, rhamnose fermentation, colicinogeny and atypical biochemical behaviour, such as urease activity, may serve as important markers or diagnostic tools for epidemiological surveys to trace the source of infection in disease outbreaks.

Prevalence of Listeria spp Including Listeria monocytogenes from Apparently Healthy Sheep of Gujarat State, India

A total of 1002 samples comprising blood (n = 248), faecal swabs (n = 248), nasal swabs (n = 248) and deep vaginal swabs (n = 248) collected from the 248 sheep and 10 environmental samples of 10 sheep flocks were examined for the presence of pathogenic Listeria spp. Confirmation of the isolates was based on biochemical tests followed by phenotypic characterization by haemolysis on sheep blood agar, Christie Atkins Munch‐Petersen (CAMP) test phosphatidylinositol‐specific phospholipase C (PI‐PLC) assay and phosphatidylcholine‐specific phospholipase C (PI‐PLC) assay. The isolates were subjected to genotypic characterization with the help of PCR assay for five virulence‐associated genes, plcA, prfA, hlyA, actA and iap. The L. monocytogenes isolates were further subjected for multiplex‐PCR‐based serotyping. From 1002 samples screened, 16 (1.60%) were found positive for Listeria spp. Of these, seven samples (0.7%) were confirmed as L. monocytogenes and nine (0.9%) as L. innocua. All the seven isolates of L. monocytogenes were haemolytic, CAMP‐positive, PI‐PLC‐positive, hlyA, pclA and prfA‐positive by PCR, while only four isolates turned out to be PC‐PLC‐positive (opaque zone surrounding the growth). All the seven isolates of L. monocytogenes were serotyped as 4b. In conclusion, the PI‐PLC assay and the virulence genes targeted PCR (plcA, prfA and hlyA plcA, prfA and actA genes for L. monocytogenes) hold a promise for rapid and reliable in vitro alternatives to in vivo pathogenicity tests.