Isolation and antibiotic susceptibility profile of βeta-lactamase producing gram-positive bacteria isolated from open urination spots across Obafemi Awolowo University, Ile-Ife, Nigeria

Abstract

Urine-contaminated soils are increasingly recognized as environmental reservoirs of antimicrobial resistance, contributing to the spread of resistant bacteria within human-associated ecosystems. However, data on the resistance profiles of Gram-positive bacteria inhabiting such environments within Obafemi Awolowo University remain limited. This study investigated the occurrence, antibiotic susceptibility patterns, and β-lactamase producing Gram-positive bacteria isolated from urine-contaminated soils across selected open urination spots on campus. Ten soil samples from visible open urination spots were aseptically collected and microbiologically analyzed within six hours. Bacterial isolates were recovered using standard microbiological techniques and identified through cultural and biochemical characterization. Susceptibility of isolates to a panel of antibiotics was determined following the standard organization (CLSI) guide. Using the nitrocefin test, the ability of the test isolates to produce β-lactamase was determined. The identity of β-lactamase-positive isolates was confirmed by partial 16S rRNA gene sequencing. A total of 29 bacterial isolates were recovered, comprising 15 Gram-positive and 14 Gram-negative bacteria. The Gram-positive isolates were identified as members of the genera Enterococcus, Streptococcus, Listeria, Bacillus, and Staphylococcus. High levels of resistance (>90%) to β-lactam antibiotics were observed across all isolates, alongside
variable resistance to other antibiotic classes. Multiple antibiotic resistance indices ranged from 0.58 to 1.00, indicating substantial exposure to antibiotic selective pressure. Two isolates, identified as Bacillus species through molecular analysis were confirmed as β-lactamase producers. These findings highlight urine-contaminated soils as significant reservoirs of multidrug-resistant Gram-positive bacteria, posing potential public health risks. The study underscores the need for improved sanitation infrastructure and enforcement of policies to eliminate open urination practices within university environments.