Molecular Characterization of Methicillin and Aminoglycoside-Resistant Staphylococcus Species from Drinking Water and Clinical Samples in Dutsin-Ma, Northwestern Nigeria.

Abstract

Background: Methicillin-resistant Staphylococcus species (MRSS) are a global public health threat, causing substantial morbidity, mortality, and economic burden. Understanding the characteristics of MRSS from various niches can support the control of these bacterial species. Herein, we examined the prevalence, biofilm formation, hemolytic activity, and selected aminoglycoside resistance genes in MRSS isolates from potable water and clinical samples in Dutsin-Ma, northwestern Nigeria.

Methods: A total of 200 samples, including 100 water and 100 clinical samples, were collected and analyzed. Staphylococcus species was recovered following standard microbiological procedures. Antibiotic susceptibility testing (AST) and minimum inhibitory concentration (MIC) determination were performed using Kirby-Bauer disk diffusion and microdilution methods, respectively. Methicillin-resistant isolates were defined as those resistant to cefoxitin with elevated oxacillin MICs. Coagulase production, biofilm formation, and hemolytic activity were assessed using slide coagulase test, Congo red agar and blood agar, respectively. Multidrug resistant (MDR) isolates were selected for PCR to detect tuf and selected aminoglycoside resistance genes. Fisher's exact test was performed to check for a significant difference in their occurrence (p ≤ α 0.05).

Results: Thirty (15%) isolates were putatively identified, comprising both coagulase-positive staphylococci (CoPS) and coagulase-negative staphylococci (CoNS): 19 (63.3%) from the clinical samples and 11 (36.7%) from the water sources. Of these, 17 strains (41.2%, 7/17) from wound swabs and 58.8% (10/17) from water samples were MDR and methicillin resistant. Virulence traits were present in isolates from both sources; however, there was no significant difference (p ≤ α 0.05) in their occurrence in CoPS and CoNS isolates from both source. Of the selected MDR strains, 16 /17 (94.1%) revealed at least one virulence trait (coagulase, hemolysis, or biofilm). PCR confirmed that 23.5% (4/17) of the selected MDR isolates exclusively from water samples harbored at least one of ant(4')-Ia, aph(2')-Ib, aph(3')-IIIa, or aac(6'), which encode aminoglycoside resistance.

Conclusion: These findings suggest the potential role of potable water as a dissemination route for MDR MRSS in the study locality. Further studies are needed to identify the circulating species and sequence types (STs), and to evaluate the prevalence of other antibiotic resistance genes.