Antibiotic resistant genes from surface water

Description

During this study, E. coli (60) and Klebsiella spp (40) were isolated from 40 different sites in the Bagmati River. The isolates were characterized by morphological observation and biochemical tests. The colony morphology characteristics were examined on 24 h culture on nutrient agar. The isolates were Gram-negative rod, non-spore-forming, catalase-positive, and oxidase-negative and other biochemical test. It was observed that all of the isolated strains of E. coli and Klebsiella spp were sensitive to imipenem and ofloxacin, cotrimoxazole (Figure 1A and 1B), whereas isolated E. coli strains, 1 strain was resistant to ceftriaxone, 2 strains to cefotaxime, ceftazidime and amikacin and 6 strains to aztreonam and ampicillin, and 5 strains to gentamycin. Similarly, 3 strains of Klebsiella spp were resistant to ceftriaxone, 12 strains to cefotaxime, 11 to ceftazidime and 4 strains to aztreonam and amikacin, 5 to ampicillin, and 10 to gentamycin. Of 100 isolated bacteria, 5% of E. coli and 30% of Klebsiella spp were ESBL producers (Figure 2). Of 15 ESBL producers, 100% of the isolated strains were sensitive to imipenem and ofloxacin (Figure 3A and 3B). However, 93.3%, 86.7%, 26.7%, and 26.7% of ESBL producers were resistant to cefotaxime, ceftazidime, ceftriaxone, and aztreonam, respectively. Additionally, among 85 non ESBL producers, all isolated strains were sensitive to imipenem, ofloxacin, cefotaxime, ceftazidime, and ceftriaxone. However, 7.1% of isolates were resistant to aztreonam. Most common types of β-lactam resistance genes, which include blaCTX-M, blaSHV, and blaTEM, were detected, and NDM-1 and OXA-48 genes were also detected. Of 60 isolated strains of E. coli, the TEM gene was the most prevalent, followed by NDM-1 and CTX-M genes. OXA-48 gene was not detected in the isolated E. coli strains (Figure 4). Additionally, out of 40 Klebsiella spp, TEM and CTX-M genes were the most prevalent, followed by OXA-48 and NDM-1 genes. In the case of 85 non ESBL producers, TEM and CTX-M genes were the most prevalent, followed by NDM-1, SHV, and OXA-48 genes. Among 15 ESBL producers, CTX-M and TEM genes were the most prevalent, followed by SHV, OXA-48, and NDM-1 genes. Out of 100 isolated bacteria, the TEM gene was the most prevalent. However, the combination of CTX-M and TEM was the most predominant (97.7%), followed by SHV and TEM (5.4%). Only 2 strains were positive for TEM, SHV, and CTX-M genes. Only one strain was positive for NDM-1 and OXA-48 genes (Figure 5).

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