Antibiotic Resistance Profile and Biofilm Formation in Staphylococci isolated from surfaces of Public Transport

Abstract

An alarming number of fatalities occur annually due to the growing global problem of antibiotic resistance. Members of the Staphylococcus genus play a critical role among those responsible for the spread of antibiotic resistance. Staphylococcus species thrive in communal situations, multiplying within families, close-knit communities, and even using transportation systems as a means of transmission. This study examines the antibiotic resistance characteristics of 175 staphylococcal species isolates obtained from a variety of public transportation vehicles, including taxis, buses, and vans from Islamabad and Rawalpindi as well as passenger trains from Karachi. Through culture on Mannitol Salt Agar (MSA), morphological characteristics of the isolates were evaluated. Biochemical analyses included catalase and coagulase tests, which allowed the distinction between coagulase-positive and coagulase-negative staphylococcal species was done. The Kirby-Bauer disk diffusion technique was used for the Antimicrobial Susceptibility Testing (AST) and microtiter plate (MTP) test was performed to assess biofilm development capacity of isolates. The cefoxitin disk diffusion test was used to phenotypically identify MRSA (methicillin resistant S. aureus) isolates. Polymerase chain reaction (PCR)-based mecA gene amplification was also done for MRSA molecular identification. Of 175 isolates,141 were mannitol fermenter and 34 of the isolates were found to be non-mannitol fermenter. Whereas 150 were coagulase-positive staphylococci (CoPS) and 25 were found to be coagulase negative staphylococci (CoNS) by biochemical identification. The study evaluated the trend of antibiotic resistance in Staphylococcus species. Notably, resistance was observed for penicillin (83%), clindamycin (57%), erythromycin (53%), cefoxitin (49%), quinupristin/dalfopristin (49%), linezolid (47%), rifampicin (40%), trimethoprim-sulfamethoxazole (32%), ciprofloxacin (20%), nitrofurantoin (19%), tetracycline (18%), gentamycin (7%), and chloramphenicol (5%). Using the cefoxitin disk-diffusion test, 43.6% of isolates were found to be methicillin-resistant Staphylococcus aureus (MRSA) bacteria. Significant robust in biofilm formation was observed ix under shaking conditions. Of 175 isolates, 12 isolates were shown to be strong biofilm producers under stationary conditions whereas 21 isolates exhibited potential to form strong biofilm under shaking conditions. Out of the 72 methicillin-resistant isolates, 62 were MRSA, and 10 were methicillin-resistant coagulase-negative Staphylococci (MRCoNS). In addition, PCR-based amplification revealed that 38 out of 72 methicillin-resistant isolates carried the mecA gene. In this study penicillin had the highest resistance, whereas chloramphenicol exhibited the lowest resistance level and 79% of the isolates were found to be MDR (multi-drug resistant). The presence of MRSA in areas associated with public transportation acts as a possible reservoir for transmission. The findings underline the urgent need for enhanced antimicrobial stewardship and infection control measures.