Background/Aims: The role of mobile genetic elements such as plasmids in the spread of multiple antibiotic resistance has continued to receive attention by researchers. Due to the diverse nature of Escherichia coli strains characteristically harbouring large proportion of genomic plasmids, the aim of the present study is to evaluate the antimicrobial susceptibility and plasmid profiles of clinical isolates of E. coli in this south eastern region of Saudi Arabia.
Methods: Bacterial isolation, antimicrobial susceptibility test were carried out using basic microbiological techniques. Dendrogram of clustering in relationship to antibiotic susceptibility of the isolates was carried out using PAST. Extracted plasmid DNA was visualised using the ultraviolet light illuminator and photo documentation system. Sizes of Plasmid were determined using standard DNA molecular weight markers at 1kb ladder. Plasmid curing was carried out using Sodium Dodecyl Sulphate (SDS).
Results and Conclusion: Antibiotic resistance ranged between 85.71%-100% for the cephalosporins, 64.29% to 92.9% resistance for penicillins, including Aztreonam, a last line drug. Results indicate that 70% of the isolates did not show any plasmid presence. However, 30% of the isolates contained plasmids with molecular weights of 30kb and above. Dendrogram of clustering in relationship to antibiotic susceptibility showed isolates were in 3 clades pre-plasmid curing and 6 clades post-plasmid curing. One isolate (EC36) was cured of its resistance to Penicillins, while isolates EC67, EC77 and EC87 initially sensitive to ciprofloxacin, became resistant to the antibiotic. The findings suggest a preponderance of chromosomal mediated resistant E. coli. The few plasmid containing resistant bacteria, were resistant to curing as they displayed continued antibiotic resistance after curing. This therefore confirms the growing presence of multiple genomic plasmid harbouring E. coli.