Incidence and molecular characterization of multidrug resistance in Gram-negative bacteria of clinical importance from pharmaceutical wastewaters in South-western Nigeria

Abstract

Background: The occurrence of antimicrobial resistant bacteria in the environment presents a major threat to public health because it reduces the effectiveness of antimicrobial treatment. Aims: The study was set out to molecularly characterize Gram-negative bacteria with multidrug resistance and resistance determinants from pharmaceutical wastewaters in Nigeria. Materials and Methods: Susceptibility of the bacterial isolates to 25 antibiotics belonging to 10 categories was tested using the disc diffusion method and Vitek 2. Screening for AmpC, Extended Spectrum Beta-lactamase and carbapenemase production was done by Polymerase Chain Reaction and sequencing. Results: Ninety-seven Gram-negative bacteria, comprising 27 Enterobacteria and 70 nonfermenter bacterial isolates were detected. Antibiotic resistance observed was highest (70.1%) for sulfamethoxazole / trimethoprim and multidrug resistance was revealed in 17 bacterial strains (Klebsiella pneumoniae [7], Enterobacter gergoviae [3], Sphingomonas paucimobilis [1], Empedobacter brevis [1], Chryseobacterium indologenes [1], Pseudomonas aeruginosa [1], Burkholderia cenocepacia [1], Burkholderia cepacia and Stenotrophomonas maltophilia [1]). Extended Spectrum Beta-lactamase (CTX-M-15, SHV-12, SHV-2) was positive for 6 K. pneumoniae strains; there were neither AmpC detected nor the production of carbapenamase in all isolates tested. Discussion: The study confirmed the presence of multidrug resistant Gram-negative bacteria with resistance determinants in wastewaters from pharmaceutical industries in Nigeria. Compounds of the wastewater may directly select or co-select these multidrug resistance strains. Conclusion: The output of drug resistant bacteria into the environment is a potential risk to public health and may facilitate the spread of resistant genes.