Potential of Surface Water Gram-negative Bacterial Flora as a Reservoir of Heterogeneous Plasmid and Multi-drug Resistance Phenomenon

Aims: Present study highlights the diversity of Gram-negative bacterial community at surface water and their potential as a reservoir of antibiotic resistance genes. We also explore the potential of this heterogeneous community to host plasmids of diverse origin.

Place and Duration of Study: The study was carried out at the Department of Microbiology, Jahangirnagar University, Bangladesh during a period from July 2016 to June 2017.

Methodology: Water samples were cultured onto MacConkey plates for selective isolation of Gram-negative bacteria and identified according to Bergey’s Manual of Systematic Bacteriology. Antimicrobial susceptibility was done by disc-diffusion method followed by determination of MIC assay by agar dilution method. Plasmid extraction was done according to the hot alkaline method.

Results: A total of 197 representative isolates from 310 water sample culture, 110 were identified as E. coli and 87 as non- E. coli belonged to 14 different species of the genera Escherichia, Enterobacter, Citrobacter, Klebsiella, Serratia, Proteus, Kluyvera, Obesumbacterium and Yersinia. Susceptibility test showed highest incidence of resistance phenomenon against amoxicillin (66.5%), followed by cefixime (56.8%), sulfamethoxazole-trimethoprim (33.5%), ciprofloxacin (20.3%), tetracycline (19.79%) and gentamicin (18.78%). A notable proportion of the isolates (33.9%) showed multi-antibiotic resistance (MAR) phenomenon. The occurrence of MAR phenotype was almost twice (42%) as much as in E. coli population in compared to non-E. coli (22%) population. Plasmid extraction revealed that majority (57%) of the isolates contained plasmids with 59 different profile, incidence and diversity being higher in E. coli population.

Conclusion: The study indicates that surface-water Gram-negative bacterial flora is a reservoir of plasmids and multidrug resistance gene. E. coli population seems to be more potential in compared to non- E. coli population as a reservoir of both multi-antibiotic resistance genes and heterogeneous plasmids.