Methicillin-resistant Staphylococcus aureus strains carrying Panton-Valentine leukocidin genes: clinical and molecular characteristics

Abstract

Objective To isolate and identify the methicillin-resistant Staphylococcus aureus (MRSA) strains carrying Panton-Valentine leukocidin genes (pvl+ -MRSA) from clinical samples and to further understand their molecular characteristics and infections caused by them. Methods Drug susceptibility test was performed to detect the drug resistance in 259 MRSA strains. pvl+ -MRSA strains were screened out from those MRSA strains using cefoxitin slip test and mecA gene detection by PCR. Multiple PCR and multilocus sequence typing (MLST) were used for SCCmec and ST typing. Pulsed-field gel electrophoresis (PFGE) and cluster analysis were used to understand the genetic and epidemic features of the pvl+ -MRSA strains. Different types of infections and diseases caused by the pvl+ -MRSA strains were analyzed. Results Among the 259 MRSA strains, 51 pvl+ -MRSA strains were identified (19.7%, 51/259), of which 29 and 22 strains were respectively isolated from patients with community-acquired and hospital-acquired infections. ST59-SCCmecⅢ (35.3%, 18/51) was the predominant type of the 51 pvl+ -MRSA strains, followed by ST59-SCCmecⅣ(25.5%, 13/51). But no predominant clone among those strains was revealed by the result of PFGE. Children, young- and middle-aged patients (≤44 years old) had a significantly higher positive rate of pvl+ -MRSA than patients aged ≥45 years (P<0.05). Skin and soft tissue infection (47.1%, 24/51) was the most common disease caused by the pvl+ -MRSA strains (P<0.05), followed by pneumonia (17.6%, 9/51). The pvl+ -MRSA strains showed lower resistance to levofloxacin, gentamycin and rifampicine (7.8%-21.6%). No moxifloxacin-, nitrofurantoin- or linezolid-resistant pvl+ -MRSA strains were identified. Conclusion The rate of pvl+ -MRSA infection is high in the local population. ST59-SCCmecⅢ and ST59-SCCmecⅣ are the predominant types of pvl+ MRSA strains. Children, young- and middle-aged persons are the susceptible population. Skin and soft tissue infection and pneumonia are the common diseases caused by pvl+ -MRSA. Key words: Methicillin-resistant Staphylococcus aureus; Infection; Panton-Valentine leucocidin; Molecular typing; Disease type