Prevalence and Antimicrobial Resistance of Diarrhoeagenic Escherichia coli and Cytolethal Distending Toxin-producing Escherichia coli in Children from North India.

BACKGROUND: Diarrhoeagenic Escherichia coli (DEC) is a leading bacterial cause of acute diarrhoea in children. DEC is characterised by diverse virulence factors that contribute to its pathogenicity. Cytolethal Distending Toxin (CDT), an E. coli genotoxin that induces DNA damage and cell-cycle arrest, remains poorly characterised in paediatric diarrhoeal disease. This study assessed DEC prevalence, antimicrobial resistance, and CDT production among children with diarrhoea and healthy controls. METHODS: A prospective case-control study was conducted from November 2022 to October 2023, including 250 diarrhoeal cases and 250 age-matched healthy controls aged 0-14 years at tertiary care hospitals in North India. Organisms were isolated by culture, and presumptive E. coli isolates were confirmed using standard biochemical tests and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS). Polymerase chain reaction (PCR) was used to detect the cdtB gene and other DEC virulence genes. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method as per CLSI guidelines. RESULTS: Overall DEC prevalence was 14% in cases and 6.4% in controls (p = 0.006; OR = 2.38). Enteroaggregative E. coli (EAEC) was the most common pathotype, followed by enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli (ETEC). Among the 35 DEC isolates from diarrhoeal cases, high antimicrobial resistance (AMR) was observed to nalidixic acid (74.3%), followed by cotrimoxazole (48.6%) and ciprofloxacin (45.7%), and 54.3% were multidrug-resistant. The cdtB gene was detected in 1.6% of cases and 0.4% of controls, predominantly in children aged 1-<5 years, with two isolates co-harbouring eae. CONCLUSION: The high prevalence of antimicrobial resistance among DEC highlights the need for strengthened AMR surveillance and antimicrobial stewardship. Although the prevalence of CDT-producing E. coli was low, their predominance among diarrhoeal cases highlights the need for larger multicentric studies to determine their clinical and epidemiological significance.