Enteric Bacterial Aetiology, Antimicrobial Resistance Profiles, and Evaluation of Epidemiological Risk Factors Among Elderly Patients with Diarrhoea in an Urban Kenyan Hospital: A Cross-Sectional Study

Background Diarrhoeal disease remains a major cause of morbidity and mortality among older adults, yet data on enteric bacterial isolates and antimicrobial resistance in elderly populations in sub-Saharan Africa are limited. This study investigated the bacterial aetiology, antimicrobial resistance profiles, and associated risk factors among elderly patients presenting with diarrhoea at an urban Kenyan referral hospital. Methods A hospital-based cross-sectional study was conducted among 271 patients aged ≥60 years presenting with acute diarrhoea at Mama Lucy Kibaki Hospital, Nairobi, between February and December 2025. Stool specimens were cultured using selective and differential media, and bacterial isolates were identified by standard biochemical methods. Escherichia coli isolates were identified biochemically only; pathotype (e.g., ETEC, EPEC, EAEC, STEC, EIEC) was not determined, so their contribution to the diarrhoeal illness reported here cannot be established with certainty. Clostridioides difficile was confirmed on isolates recovered by anaerobic culture, using glutamate dehydrogenase (GDH) antigen and toxin A/B immunoassays performed on colony suspensions rather than directly on unprocessed stool. Antimicrobial susceptibility testing was performed using Kirby–Bauer disk diffusion (CLSI M100, 35th edition) and Etest methods, with organism-specific interpretive criteria applied only where validated for the organism tested. Results Potential enteric bacterial isolates were recovered from 118 of 271 participants (43.5%); this falls to 84/271 (31.0%) if untyped E. coli is excluded from the numerator, since its causal role in the presenting illness could not be confirmed without pathotyping. Escherichia coli was the most frequently recovered isolate (28.8%), followed by Clostridioides difficile (15.3%), Campylobacter jejuni (10.2%), and Shigella flexneri (8.5%). Among the 80 isolates belonging to organisms with validated, organism-specific disk-diffusion interpretive criteria (i.e., excluding C. difficile, Campylobacter , and organisms lacking a validated breakpoint standard for the panel used), and after excluding categories representing intrinsic rather than acquired resistance, the pooled multidrug resistance (MDR) prevalence was 62.5% (50/80). Salmonella typhi demonstrated 100% MDR (8/8); after excluding its intrinsic ampicillin resistance, Klebsiella pneumoniae showed an MDR rate of 66.7% (2/3), and E. coli 70.6% (24/34). Campylobacter jejuni showed extensive non-susceptibility across the same six-agent panel (9/12 isolates non-susceptible in ≥3 categories), but because disk diffusion is not validated by CLSI or EUCAST for this organism, these findings are reported separately as exploratory, epidemiological data only and were excluded from the pooled MDR estimate and from clinical interpretation. No significant associations were identified between infection status and water, sanitation, hygiene, or dietary factors (exact p ≥ 0.85 for all comparisons). Conclusion Elderly patients in urban Kenya carry a substantial burden of enteric bacterial isolates with high rates of multidrug resistance among the organisms for which resistance could be validly classified. Because many bacterial diarrhoeal illnesses are self-limiting and do not require antimicrobial therapy, these findings support selective, culture- and susceptibility-guided prescribing rather than blanket empirical antibiotic use. Strengthened antimicrobial stewardship, expanded diagnostic and pathotyping capacity, and integration of elderly populations into diarrhoeal disease surveillance programmes are needed.