Incidence and transferability of antibiotic resistance in the enteric bacteria isolated from hospital wastewater

Abstract

This study reports the occurrence of antibiotic resistance and production of β-lactamases including extended spectrum beta-lactamases (ESβL) in enteric bacteria isolated from hospital wastewater. Among sixty-nine isolates, tested for antibiotic sensitivity, 73.9% strains were resistant to ampicillin followed by nalidixic acid (72.5%), penicillin (63.8%), co-trimoxazole (55.1%), norfloxacin (53.6%), methicillin (52.7%), cefuroxime (39.1%), cefotaxime (23.2%) and cefixime (20.3%). Resistance to streptomycin, chloramphenicol, nitrofurantoin, tetracycline, and doxycycline was recorded in less than 13% of the strains. The minimum inhibitory concentration (MIC) showed a high level of resistance (800-1600 μg/mL) to one or more antibiotics. Sixty three (91%) isolates produced β-lactamases as determined by rapid iodometric test. Multiple antibiotic resistances were noted in both among ESβL and non-ESβL producers. The β-lactamases hydrolyzed multiple substrates including penicillin (78.8% isolates), ampicillin (62.3%), cefodroxil (52.2%), cefotoxime (21.7%) and cefuroxime (18.8%). Fifteen isolates producing ESβLs were found multidrug resistant. Four ESβL producing isolates could transfer their R-plasmid to the recipient strain E. coli K-12 with conjugation frequency ranging from 7.0 × 10(-3) to 8.8 × 10(-4). The findings indicated that ESβL producing enteric bacteria are common in the waste water. Such isolates may disseminate the multiple antibiotic resistance traits among bacterial community through genetic exchange mechanisms and thus requires immediate attention.

Keywords: Antibiotic resistance; ESβL; Enteric bacteria; beta-lactamase; plasmid transfer.

Figure 1

Agarose gel electrophoresis profiling of plasmids isolated from ESβL producing drug resistant enteric bacteria. Lane a, Super mix lambda DNA; lane b, E. coli; c, Shigella sonnei; d, Citrobacter sp.; e, Salmonella typhimurium; f, Shigella dysenteriae and g, Shigella sp. (plasmid DNA isolated from the enteric bacteria) and lane h, E. coli V 517 reference plasmids. Values marked with arrows show the molecular wt of E. coli V 517 reference plasmids.