Find in Library

Macrolides, lincosamides, and type B streptogramins (MLS_B) are important therapeutic options to treat methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) infections; however, resistance to these antibiotics has been emerging. In Chile, data on the MLS_B resistance phenotypes are scarce in both community-(CA) and hospital-acquired (HA) MRSA isolates. Antimicrobial susceptibility to MLS_B was determined for sixty-eight non-repetitive isolates of each HA-(32) and CA-MRSA (36). Detection of SCC<i>mec</i> elements, <i>ermA</i>, <i>ermB</i>, <i>ermC</i>, and <i>msrA</i> genes was performed by PCR. The predominant clones were SCC<i>mec</i> I-ST5 (HA-MRSA) and type IVc-ST8 (CA-MRSA). Most of the HA-MRSA isolates (97%) showed resistance to clindamycin, erythromycin, azithromycin, and clarithromycin. Among CA-MRSA isolates, 28% were resistant to erythromycin, azithromycin, and 25% to clarithromycin. All isolates were susceptible to linezolid, vancomycin, daptomycin and trimethoprim/sulfamethoxazole, and over 97% to rifampicin. The <i>ermA</i> gene was amplified in 88% of HA-MRSA and 17% of CA-MRSA isolates (<i>p</i> < 0.001). The <i>ermC</i> gene was detected in 6% of HA-SARM and none of CA-SARM isolates, whereas the <i>msrA</i> gene was only amplified in 22% of CA-MRSA (<i>p</i> < 0.005). Our results demonstrate the prevalence of the cMLSB resistance phenotype in all HA-MRSA isolates in Chile, with the <i>ermA</i> being the predominant gene identified among these isolates.