Virulence and resistance profiles of MRSA isolates in pre- and post-liver transplantation patients using microarray

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Methicillin-resistant Staphylococcus aureus (MRSA) screening plays a great role in preventing infections in surgical patients. This study aims to evaluate clonality, virulence and resistance of MRSA in pre- and post-liver transplantation (LT) patients. Nasal and groin swabs of 190 patients were collected. PCR for virulence genes and staphylococcal cassette chromosome mec (SCCmec) types, microarray, PFGE, multilocus sequence typing and MIC were performed. MRSA carriers were detected in 20.5 % (39/190) of the patients. However, only three colonized patients developed infections post-LT. Sixty-nine MRSA isolates were identified, and the most frequent SCCmec type was type II (29/69; 42.0 %). Most isolates (57/69; 82.6 %) were susceptible to trimethoprim-sulfamethoxazole (TMP/SMX) and harboured the lukD, lukE, clf and fnbA genes as determined by PCR. Five sequence types (ST) were identified among nine clones; 36.2 % (25/69) isolates belonged to a predominant clone (ST105 and SCCmec type II) that was susceptible to TMP/SMX, mupirocin and chlorhexidine, which had 87.9 % similarity with the New York/Japan clone. The array showed virulence difference in isolates of the same clone and patients and that colonized isolates (pre-LT patients) were less virulent than those post-LT and those infected. Therefore, despite the high frequency of MRSA colonization, infection due to MRSA was uncommon in our LT unit. MRSA isolates presented great diversity. Isolates of the same clone expressed different virulence factors by array. Colonizing isolates pre-LT expressed less virulent factors than post-LT and infecting isolates.

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