Distribution of staphylococcal cassette chromosome mec types among methicillin-resistant coagulase negative staphylococci in central Iran

Abstract

Background and Objectives:

Methicillin-resistant coagulase-negative staphylococci (MR-CoNS) are important nosocomial pathogens. They may serve as a reservoir of SCC mec, the genomic island encoding amongst other methicillin resistance. This study was designed to determine the distribution of different SCC mec types from MR-CoNS isolated from clinical specimens in a tertiary hospital in central Iran, having high frequency of nosocomial methicillin-resistant staphylococcal infections.

Materials and Methods:

We evaluated isolates from patients attending the Vali-Asr Hospital located in the center of Iran, from February to December 2012. Multiplex PCR was performed for SCC mec typing. For isolates in which SCC mec could not be typed directly, additional ccr and mec complex analyses were performed.

Results:

Totally, 70 MR-CoNS isolates, comprising of 47 S. epidermidis strains (67%), 10 S. saprophyticus (14.3%), 9 S. hemolyticus (13%) and 4 S. lugdunensis (5.7%) were identified. Thirty-nine were characterized as type IVa 19 (27%), type III 11 (16%), type II 7 (10%) and type V 2 (3%). Only 20 isolates (28.6%) carried the ccr complex, while the current methods could not characterize the 11 remaining isolates.

Conclusion:

A high level of SCC mec genetic diversity was found among MR-CoNS isolates. MR-CoNS may act as a reservoir of SCC mec IV for MRSA. This issue should be taken into consideration seriously.