Are non-lactose-fermenting important diarrhoeal pathogens in children and adults?

INTRODUCTION

Diarrhoeagenic (DEC) remains one of the major causes of acute diarrhoea episodes in developing countries. The percentage of acute diarrhoea cases caused by DEC is 30-40 % in these countries. Approximately 10% of isolates obtained from stool specimens have been reported to be non-lactose-fermenting (NLF). The available literature is sparse regarding the pathogenicity of NLF causing infectious diarrhoea.

AIM

We aimed to elucidate the importance of NLF in causing diarrhoea in both adults and children by detecting various DEC pathotypes among NLF in stool samples taken from gastroenteritis cases.

MATERIAL AND METHODS

A total of 376 NLF isolates from 3110 stool samples from diarrhoea/gastroenteritis patients were included in the study. Up to three NLF colonies that were not confirmed as , spp., spp. or spp., but were identified as using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), were carefully picked up from each MacConkey agar plate and then meticulously streaked onto freshly prepared, sterilized nutrient agar plates, and biochemical reactions were conducted. Multiplex PCR was conducted for the EAEC, EPEC, ETEC and EHEC pathotypes and PCR for the gene was conducted for EIEC. The disc diffusion method was used for antibiotic sensitivity testing.

RESULTS

Using multiplex PCR and PCR, a total of 63 pathotypes of DEC were obtained, with EAEC being the most predominant (=31) followed by EIEC (=22), EPEC (=8) and ETEC (=2). To further differentiate EIEC from , additional biochemical tests were performed, including acetate utilization, mucate and salicin fermentation, and aesculin hydrolysis. Antimicrobial susceptibility testing (AST) showed that maximum resistance was seen against ciprofloxacin (82.5 %) followed by ampicillin (77.8 %) and cotrimoxazole (68.2 %), and minimum resistance was seen against ertapenem (4.8 %).

CONCLUSION

In our study two pathotypes (EAEC, EIEC) were predominant among NLF and these were not only important aetiological agents in children, but also in adults. Our study also sheds light on the epidemiology of EIEC, which is one of the most neglected DEC pathotypes, as hardly any microbiological laboratories process NLF for EIEC.