Methicillin-resistant Staphylococcus aureus (MRSA) is a significant epidemiological problem. Detecting the sources of epidemic strains and preventing their access to patients, however, depend upon the availability of techniques to reliably distinguish among MRSA strains. Molecular typing of MRSA generally demonstrates improved discriminatory power compared with assays of phenotypic traits, and it is frequently preferred.
Objective : Evaluation of the discriminatory power and stability of restricted enzyme analysis of plasmid (REAP) DNA among MRSA strains.
Material and Methods: 54 sequential MRSA isolates from 18 patients collected within 30-36 days ( Three isolate from every patient , in average 15 days interval between each isolate) .Isolates were subjected to plasmid screening. Isolates with positive plasmid underwent typing by REAP using Hind III restriction enzyme . Comparison were done to detect plasmid stability and discriminatory power among sequential MRSA isolates.
Result :Among 54 sequential MRSA isolates; 45 were plasmid- positive isolates from 15 patients . Patient’s plasmid digestion profile remained unchanged over a period up to one month except in two cases (4.4%) . In one case , two distinctly different digestion profiles were detected from a patient ( between the initial isolate and the second successive isolate) .In the other case, two distinctly different digestion profiles were detected from a patient (between the initial isolate and the third successive isolate).Nine (16.6%) out 54 MRSA isolates from 3 patients lacked plasmid.
Conclusion The frequency of genetic alteration in plasmid among MRSA strains in vivo are infrequent and REAP typing of MRSA isolates is very stable in vivo. The diversity and stability of MRSA plasmid types make them excellent epidemiological markers.
Isolation of Mycoplasma Pneumoniae from |
