Assessment of Antimicrobial Resistance Isolates in Microbiology Laboratory Wastes in Tertiary Institutions of Port Harcourt Metropolis

Antimicrobial resistance (AMR) is a growing public health challenge in Nigeria, orchestrated by environmental reservoirs, including improperly managed laboratory wastes. This study assessed antimicrobial resistance in microbiology laboratory waste from tertiary institutions in the Port Harcourt metropolis. Soil samples were collected from waste dumpsites at the University of Port Harcourt and Rivers State University, and an uncontaminated soil sample was used as a control. The spread plate technique determined total heterotrophic bacteria, Pseudomonas, staphylococci, and coliform counts. Isolates were identified using morphological and biochemical tests, screened for virulence (haemolysis, biofilm formation, coagulase, and starch hydrolysis), and tested against selected antibiotics using the Kirby-Bauer method. Multiple Antibiotic Resistance (MAR) Indices were determined. Bacterial counts in dumpsite soils were significantly higher for Pseudomonas (1.0 × 10⁴–1.3 × 10⁵ CFU/g) and coliforms (1.3 × 10⁵–4.3 × 10⁵ CFU/g) than in control soil. Thirteen bacterial species were isolated, dominated by Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli, as well as various Enterobacteriaceae. Most isolates exhibited virulence traits and multidrug resistance, with MAR indices ranging from 0.2 to 1.0, suggesting high-risk contamination sources. These dumpsites could be a reservoir of multidrug-resistant and virulent bacteria. Inadequate waste treatment practices should be avoided. Thus, strict decontamination protocols and regulatory enforcement are urgently required to mitigate this public health risk.