Antimicrobial resistance in bloodstream isolates of Escherichia coli and Staphylococcus aureus from a provincial hospital, Cambodia, 2020-2022.

Antimicrobial resistance (AMR) is a global concern. However, in Cambodia, as in other countries in the World Health Organization's Western Pacific Region, the magnitude of the problem is largely unknown. Thus, this study aimed to determine the prevalence of AMR in common pathogens, namely Escherichia coli and Staphylococcus aureus, isolated from blood cultures at one provincial hospital, a national sentinel site for AMR surveillance, during a 3-year period. Sample processing and analysis were conducted at the hospital's on-site microbiology laboratory. Blood cultures were processed manually, and conventional methods were used for bacterial identification. Antibiotic susceptibility testing (AST) was performed by disk diffusion and Etest minimum inhibitory concentration measurement, in accordance with current Clinical and Laboratory Standards Institute guidelines. Blood culture data from 1 January 2020 to 31 December 2022 were extracted from the hospital's microbiology database and, for the AST analysis, deduplicated to include results only for the first isolate per patient per year. Of 6102 blood cultures collected, 529 (9%) were positive. The most common blood culture pathogens found were E. coli (150, 28% of positive isolates) and S. aureus (65, 12% of positive isolates). For E. coli, resistance to ceftriaxone was detected in 110/148 (74%) isolates and resistance to imipenem in 3/147 (2%). For S. aureus, 18/56 (32%) isolates were methicillin-resistant, but vancomycin resistance was not detected. These rates of resistance to first-line treatments are of concern and have the potential to negatively impact patient outcomes.