Screening of Multidrug-Resistant Gram-Negative Bacteria in Sewage Samples from General Hospital Environments in Owerri, Imo State

Hospital sewage represents a concentrated reservoir of pathogenic and antibiotic-resistant microorganisms, and its microbiological characterization is essential for understanding resistance dissemination dynamics. This study screened for multidrug-resistant (MDR) Gram-negative bacteria in sewage samples collected from three general hospitals in Owerri, Imo State, South East Nigeria. Sewage samples were collected from four points per hospital including ward drains, surgical unit outflows, and the final treatment effluent over six weeks. Gram-negative bacteria were isolated on MacConkey agar, identified using standard biochemical tests, and subjected to disk diffusion susceptibility testing against 14 antibiotics across six drug classes. MDR was defined as resistance to at least three antibiotic classes. PCR was used to confirm ESBLs and carbapenemase genes (bla-NDM and bla-KPC). Results showed that 82 percent of all Gram-negative isolates were MDR. E. coli and Klebsiella pneumoniae were the most prevalent species. ESBL genes were detected in 54 percent of Klebsiella isolates, and bla-NDM was confirmed in 8.3 percent of Acinetobacter baumannii isolates. Final treatment effluent from all three hospitals still contained MDR organisms, indicating inadequate sewage treatment capacity. The study calls for upgrading hospital sewage treatment infrastructure in Owerri and establishing a hospital environmental AMR surveillance network for South East Nigeria. Keywords: hospital sewage, multidrug resistance, ESBL, carbapenemase, Owerri.