Situation of antibiotic resistance in Bangladesh and its association with resistance genes for horizontal transfer

The study investigated the spectrum of antibiotic resistance and the associated genes for aminoglycoside, macrolide and ESBL class of antibiotics using clinical isolates. A total of 430 preserved bacterial strains (Acinetobacter baumannii, n= 20; Pseudomonas aeruginosa, n= 26; Klebsiella pneumoniae, n= 42; E. coli , n= 85; Staphylococcus aureus, n= 84; Salmonella Typhi, n= 82; Enterococcus spp., n= 27; Streptococcus pneumoniae, n= 36 and CNS, n = 28) were examined. The strains were isolated from patients admitted to various tertiary hospitals of Dhaka city between 2015 and 2019 with either acute respiratory infections, wound infections, typhoid fever or diarrhea. The isolates were reconfirmed by appropriate microbiological and biochemical methods. Antimicrobial susceptibility tests were done using Kirby–Bauer disk diffusion approach. PCR amplification using resistance gene-specific primers for aminoglycoside, macrolide and ESBL class of antibiotics was done and the amplified products were confirmed by Sanger sequencing. Of the total isolates, 53% came out as MDR with 96.6% of E. coli and 90% of Staphylococcus aureus. There was a year-wise gradual increase of MDR isolates from 2015-2018 and by 2019 the increase in MDR isolates became almost 2-fold compared to 2015. Among the five ESBL genes investigated, CTXM-1 came out as the most prevalent (63%) followed by NDM-1 (22%) and E. coli isolates were the predominant reservoir of these genes. ErmB (55%) was the most frequently detected macrolide resistance gene, whereas aac ( 6 ) -Ib (35.44%) was the most prevalent aminoglycoside resistance gene and these genes were most prevalent in E. coli and P. aeruginosa isolates, respectively. CTXM-1 and ErmB (16.66%) were the most frequent partners of coexistence followed by CTXM-1 and aac ( 3 ) -II.