Antibiotic Resistance Patterns and Plasmid Profiles of Methicillin Resistant Staphylococcus aureus Isolates from Human Samples

Abstract

Antibiograms and plasmid profiles are commonly used to characterizemethicillin-resistant Staphylococcus aureus (MRSA) inepidemiologic studies. However, antibiograms are frequently inadequate to accomplish the differentiation. Plasmid profile being more informative has been reported to be useful in tracing the epidemiology of antibiotic resistance. Antibiotic resistance patterns and plasmid profiles of methicillin-resistant Staphylococcus aureus (MRSA) isolates from human specimens were investigated to determine the discriminatory power of plasmid profile analysis in conjunction with antibiotic susceptibility pattern. Specimens were analyzed using disc diffusion assay and restriction enzymes analysis of plasmid DNA procedure. The 51 methicillin-resistant Staphylococcus aureus (MRSA) isolates were grouped into 18 groups using their resistogram. Twenty four (47.1%) strains out the 51 methicillin-resistant Staphylococcus aureus (MRSA) isolates harbored plasmids. Single plasmid isolates were 14(27.5%), double plasmid isolates were 6(11.8%) while tripple plasmid isolates were 4(7.8%). The 24 isolates containing plasmids were categorized into 14 groups based on their resistogram. Plasmid profile showed greater similarity between isolates (10 profiles) than antibiotic resistance pattern which showed a higher disparity (14 patterns). However, resistance to various antimicrobial agents was not consistent with the presence of plasmids. No particular molecular size plasmid could be associated with any particular antimicrobial resistance patterns. Resistance was observed in isolates with various molecular size plasmids as well as in those that had no plasmids. Nonetheless, 2 pairs of isolates with the same plasmid profile also had similar (almost the same) resistance pattern. Plasmid profile analysis in conjunction with the antibiotic resistance typing is valuable in the epidemiological investigation of methicillin-resistant Staphylococcus aureus (MRSA).