Acinetobacter baumannii is a significant opportunistic pathogen causing nosocomial infections. Infections caused by A. baumannii are often difficult to treat because this bacterium is often multidrug-resistant and shows high environmental adaptability. Here, we report on the analysis of three A. baumannii strains isolated from hospital effluents in South Africa.

Strains were isolated on Leeds Acinetobacter agar and were identified using VITEK®2 platform. Antibiotic susceptibility testing was performed using the Kirby-Bauer Disk diffusion method. Whole-genome sequencing was performed. The assembled contigs were annotated. Multilocus sequence type, antimicrobial resistance, and virulence genes were identified.

The strains showed two multilocus sequence types, ST231 (FA34) and ST1552 (PL448, FG116). Based on their antibiotic susceptibility profiles, PL448 and FG116 were classified as extensively drug-resistant and FA34 as pandrug-resistant. FA34 harbored mutations in LpxA, LpxC, and PmrB, conferring resistance to colistin, but not mcr genes. All three strains encoded virulence genes for immune evasion (capsule, lipopolysaccharide [LPS]), iron uptake, and biofilm formation. FA34 was related to human strains from South Africa; PL448 and FG116 were related to a strain isolated in the United States from a human wound.

The detection of extensively drug- and pandrug-resistant A. baumannii strains in hospital effluents is of particular concern. It indicates that wastewater might play a role in the spread of these bacteria. Our data provide insight into the molecular epidemiology, resistance, pathogenicity, and distribution of A. baumannii in South Africa.