Colistin Resistance in WHO-Designated Global Priority Pathogens Isolated from Wastewater Effluents of Two Hospitals in Enugu Metropolis, South East Nigeria

Introduction: Hospitals are breeding grounds for multidrug-resistant (MDR) bacteria, posing treatment challenges and increasing the risk of spreading "superbugs." This study investigates the prevalence of colistin-resistant bacteria, a last-resort antibiotic, in wastewater from tertiary hospitals in Enugu, Nigeria. Methods: Twenty wastewater samples were collected over three months from two tertiary hospitals in Enugu. A standardized protocol by the American Public Health Association (APHA) was followed. Samples were collected aseptically from key drainage points and transported to the lab within ۲ hours. Bacteria were isolated using the pour-plate method and characterized by morphological and biochemical tests, including Catalase, Oxidase, and Glucose Fermentation. Antibiotic susceptibility was assessed using Kirby-Bauer disc diffusion, and colistin resistance was confirmed via broth microdilution. Multiplex PCR detected mcr genes indicating plasmid-mediated resistance. Data were analyzed using SPSS version ۲۳ with Chi-Square and ANOVA tests at a significance level of P < ۰.۰۵. Results: Gram-negative bacteria were isolated from ۶۳.۱% of samples, with Klebsiella spp. being the most prevalent, accounting for ۲۴.۶%. Colistin resistance was phenotypically observed in E. coli (۸۳%), Klebsiella spp. (۷۵%), and Pseudomonas aeruginosa (۱۰۰%). Genotypically, E. coli harbored mcr-۱ (۱۷%) and mcr-۳ (۸۳%), while all Klebsiella and Pseudomonas isolates carried multiple mcr genes. Additionally, these bacteria showed resistance to multiple antibiotics, including Septrin, Gentamycin, and Ceftriaxone. Conclusion: The significant presence of colistin-resistant bacteria, especially E. coli and Klebsiella, poses a public health concern, potentially leading to treatment failures and spreading resistance genes. Stricter monitoring of hospital wastewater is necessary to identify emerging resistance trends and improve antibiotic practices in hospitals.

Keywords:

Colistin resistance , Antibiotic resistance , Enterobacteriaceae , Hospital wastewater , mcr-۱ gene , mcr-۲ gene , mcr-۳ gene , Multidrug resistance , Nigeria