Understanding the etiology of diarrheal illness in Cambodia in a case-control study from 2020 to 2023

Diarrheal infection remains a major public health problem in low and middle-income countries (LMICs). Prevention and control of diarrheal diseases are considered a global health priority. This case-control study aims to describe the prevalence of diarrhea etiologic agents and antimicrobial resistance in bacterial enteropathogens for acute diarrhea among children, adult civilians, and military personnel in Cambodia, detecting over 20 bacterial species, viruses, and parasites. A total of 918 subjects with acute diarrhea (cases), 791 aged-matched subjects without diarrhea (controls), and 675 follow-up cases were enrolled from five hospitals in Battambang and Oddor Meanchey provinces from 2020 to 2023. Pathogens were identified from collected stool samples via bacteriology, molecular techniques, immunoassays, and microscopy. Bacterial isolates were tested for antibiotic resistance patterns. From enrolled diarrhea cases, 533 stool samples (58%) were positive for enteric pathogens, compared to 389 samples (49%) in controls, underscoring the high carriage rate of enteric pathogens in this population as well as the difficulties in establishing the etiology of diarrhea cases. The most common enteric pathogens in cases were enteric bacteria with Aeromonas (15%), followed by Plesiomonas (12%), and enteroaggregative E. coli (EAEC) (10%). Shigella (p < 0.05), enterotoxigenic E. coli with heat-stable toxins (ETEC-ST) (p < 0.01), and Plesiomonas (p < 0.01) had a statistically significant association with acute diarrhea cases. Rotavirus was the most common virus found (51% of cases with virus), followed by norovirus (19%), and sapovirus (16%). In terms of antimicrobial resistance, 84% of Shigella isolates were highly resistant to trimethoprim/sulfamethoxazole (SXT), almost 80% of Campylobacter jejuni isolates were resistant to ciprofloxacin (82%) and nalidixic acid (85%). Over 50% of ETEC, Shigella, and EAEC isolates were resistant to ceftriaxone, ciprofloxacin, and SXT, respectively. Overall, our study highlights the high endemicity of enteric bacterial pathogens and the significant carriage rates of these pathogens even in individuals without overt symptoms. Although the overall antimicrobial resistance was moderate, prevalent isolates harbor a significant resistance to the first-line of treatment. This highlights the importance of ongoing diarrhea etiology and antimicrobial resistance (AMR) surveillance efforts to guide the development and implementation of an effective AMR management program in diarrheal infections.