Multidrug-resistant clones of community-associated meticillin-resistant Staphylococcus aureus isolated from Chinese children and the resistance genes to clindamycin and mupirocin

This study aimed to correlate the multidrug resistance (MDR) and sequence type (ST) clones of community-associated (CA) meticillin-resistant Staphylococcus aureus (MRSA) to identify the genes responsible for clindamycin and mupirocin resistance in S. aureus isolates from paediatric hospitals in mainland China A total of 435 S. aureus isolates were collected. Compared with CA meticillin-susceptible S. aureus (MSSA), the resistance rates of CA-MRSA to ciprofloxacin, chloramphenicol, gentamicin and tetracycline were higher (19.0 vs 2.6%, P<0.001; 14.7 vs 3.1%, P<0.001; 14.7 vs 3.1%, P<0.01; and 46.0 vs 13.3%, P<0.001, respectively). Compared with hospital-associated (HA)-MRSA, the resistance rates of CA-MRSA to ciprofloxacin, gentamicin, rifampicin, tetracycline and trimethoprim-sulfamethoxazole were lower (19 vs 94.8%, P<0.001; 14.7 vs 84.4 %, P<0.001; 5.5 vs 88.3%, P<0.001; 46 vs 94.8%, P<0.001; and 1.8 vs 9.1%, P<0.01, respectively). The resistance rates of CA-MRSA, HA-MRSA and CA-MSSA to clindamycin (92.0, 77.9 and 64.1%o, respectively) and erythromycin (85.9, 77.9 and 63.1%, respectively) were high. The MDR rates (resistance to three or more non-beta-lactams) were 49.6, 100 and 14% in the CA-MRSA, HA-MRSA and CA-MSSA isolates, respectively. Five of seven ST clones in the CA-MRSA isolates, namely ST59, ST338, ST45, ST910 and ST965, had MDR rates of >50% (67.9, 87.5, 100, 50 and 83.3%, respectively). The constitutive phenotype of macrolide-lincosamide-streptogramin B (MLSB) resistance (69%) and the ermB gene (38.1%) predominated among the MLSB-resistant CA S. aureus strains. The resistance rate to mupirocin was 2.3% and plasmids carrying the mupA gene varied in size between 23 and 54.2 kb in six strains with high-level resistance as determined by Southern blot analysis. The present study showed that resistance to non-beta-lactams, especially to clindamycin, is high in CA-MRSA isolates from Chinese children and that the profile of resistance is related to clonal type. This study revealed distinctive patterns of MLSB-resistant genes among CA S. aureus isolates.