ABSTRACT

Antibiotic resistance poses a significant global health threat, with Escherichia coli (E. coli) emerging as a prominent multidrug-resistant (MDR) pathogen. This study investigates the prevalence of MDR E. coli among apparently healthy students and explores plasmid-mediated mechanisms contributing to antibiotic resistance. A cross-sectional study was conducted among apparently healthy students at the University of Benin, Nigeria. Stool samples were collected from 311 participants, and E. coli isolates were characterized for antibiotic resistance profiles before and after plasmid curing. Plasmid transfer and curing frequencies were determined, and statistical analyses were performed to explore correlations between drug sensitivities. The analysis of the resistance profiles of E. coli isolates before plasmid curing revealed that all isolates showed 100% resistance to amoxicillin (ALX), cefuroxime (CXM), and nalidixic acid (NA). Notably, the isolates displayed varying degrees of resistance to other antibiotics. For instance, ceftriaxone (CRO) exhibited resistance in 10 out of 27 isolates, while 17 isolates were susceptible. The frequencies and percentages of resistance were calculated for each antibiotic. Analysis on the sensitivity and resistance profiles of E. coli isolates after plasmid curing demonstrated changes in antibiotic susceptibility post-curing. Notably, some antibiotics showed increased sensitivity after plasmid curing, such as ceftriaxone (CRO), while others exhibited persistent resistance. The mean sensitivity and resistance were calculated for each antibiotic, highlighting the efficacy of plasmid curing in altering bacterial resistance patterns. In the context of plasmid profiling, the study assessed the percentage of plasmid transfer during curing, revealing varying transfer rates among E. coli strains, with some strains exhibiting higher transfer rates than others. Mean transfer rates were calculated to gain insights into the efficiency of plasmid transfer, and these observed rates were scrutinized for their significance in elucidating the potential dissemination of antibiotic resistance genes through horizontal gene transfer mechanisms. Regarding the correlation between drug sensitivities, before plasmid curing, significant positive relationships between certain antibiotics, such as gentamicin (GN) and ceftriaxone (CRO), were identified, alongside significant negative relationships between others. Statistical tests were employed to ascertain the significance of these correlations, shedding light on potential cross-resistance mechanisms or shared resistance genes among antibiotics. Post-plasmid curing, changes in the relationships between antibiotics were observed, with some correlations strengthening or weakening. Noteworthy shifts in correlation patterns were evident, with significant positive and negative relationships persisting, indicative of the impact of plasmid curing on altering the correlation dynamics between antibiotics. These findings underscore the efficacy of plasmid elimination strategies in disrupting antibiotic resistance mechanisms within bacterial populations.