Molecular profiling, antibiotic susceptibility patterns and pathogenic traits of ESBL producing Acinetobacter baumannii Isolated from wastewater discharges from Goranchatbari sub-catchment area in Dhaka city

Abstract

Acinetobacter baumannii is one of the six pathogens for which new antibiotic formulations must be developed, as recommended by the World Health Organization. In this study, 28 wastewater samples were collected from the Goranchatbari sub-catchment area in Dhaka city over several seasons. The samples were characterized for the presence of Acinetobacter spp. and the isolates were subjected to phenotypic testing for ESBL production, presence of major antibiotic resistance and pathogenic genes, biofilm production and antibiotic susceptibility testing. Furthermore, the isolates were phylogenetically clustered based on their ERIC profiles and correlation matrix. Out of 28 samples, 27 were positive for Acinetobacter spp. and a total of 106/249 (42.6%) representative isolates were positive for ESBL production. Out of these 106 isolates, 97 (91.5%) were genotypically confirmed to belong to the Acinetobacter spp. and of which, 72 (74.2%) were genotypically confirmed as Acinetobacter baumannii. Among the distribution of β-lactamase genes, blaTEM was the most prevalent being present in 40/72 (55.6%) isolates, followed by blaSHV in 3/72 (4.2%) isolates. With respect to the pathogenic genes, pgaB and bfmS were the most prevalent being present in 80.6% and 69.4% of isolates respectively. A large percentage of the isolates concomitantly carried one or more pathogenic genes with 1/72 (1.4%) and 6/72 (8.3%) of isolates carrying 7 and 6 pathogenic genes each respectively. The antibiotic susceptibility testing revealed a diverse range of resistance patterns with high levels of intermediate resistance being observed for cefotaxime and ceftriaxone. The biofilm formation screening revealed the widespread ability of Acinetobacter baumannii to form biofilm at different temperatures, with 35/72 (48.6%) of isolates forming strong biofilm at 37°C and 32/72 (44.4%) of isolates forming strong biofilm at 25°C. The phylogenetic clustering of the A. baumannii isolates resulted in the formation of 10 clusters at a 60% similarity index, and correlation matrix helped reveal important associations between genotypic and phenotypic traits. These results demonstrate the continued prevalence of A. baumannii within these environmental reservoirs and its ability to persist despite seasonal variations, prioritizing changes in environmental health policies that aim to reduce the widespread prevalence of these pathogens.