RAPD-PCR analysis of Staphylococcus aureus strains isolated from different sources

Determination of genetic relationship among Staphylococcus aureus isolates is important for epidemiological surveillance and control of infections caused by this bacterium. The present study was conducted to determine the molecular diversity of S. aureus strains isolated from human, bovine, and food samples using random amplified polymorphic DNA (RAPD)-PCR method. A total of 208 S. aureus strains including 60 human (patients and healthy carriers), 83 bovine milk, and 65 food (pastry and cheese) isolates were assessed. The isolates were confirmed to be methicillin-resistance/susceptible S. aureus (MRSA or MSSA) using common biochemical tests and a species-specific PCR, and finally, they were genetically typed using RAPD-PCR method. Forty-seven RAPD profiles (13, 21, and 15 profiles for isolates from human, bovine, and food samples, respectively) were identified in the examined isolates. Based on these profiles and the constructed dendrogram, all of 208 S. aureus strains were divided into nine major clusters from A to I, at 80% similarity. Some clusters (A, B, C, E, and H) contained S. aureus strains isolated from only one source, while the others (D, F, G, and I) contained isolates from more than one source. The results revealed that although most of S. aureus strains of the same source were placed in certain clusters, there were also some strains of different sources which shared the same RAPD profiles indicating possible transmission of S. aureus strains (especially MRSA ones) among different hosts. Thus, effective hygiene measures should be considered to break transmission chains.