Antimicrobial Susceptibility Patterns and Staphylococcal Cassette Chromosome mec Types of, as Well as Panton-Valentine Leukocidin Occurrence among, Methicillin-Resistant Staphylococcus aureus Isolates from Children and Adults in Middle Tennessee

Abstract

ABSTRACT Antimicrobial susceptibility patterns, Panton-Valentine leukocidin (PVL) occurrence, and staphylococcal cassette chromosome mec (SCC mec ) types in methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from children and adults at Vanderbilt University Medical Center during a 12-month period were evaluated. A total of 1,315 MRSA isolates were collected, of which 748 (36.7%) were recovered from children. Among all isolates, 448 (34.1%) were SCC mec -II, and 847 (64.4%) were SCC mec -IV. More SCC mec -IV isolates were recovered from children than SCC mec -II isolates (424 [50.1%] versus 50 [11.2%]; odds ration [OR] = 7.98; P < 0.000001). The PVL gene was detected in 93.6% of SCC mec -IV isolates, in contrast to 0.2% in SCC mec -II isolates. Within SCC mec -IV isolates, a statistically higher PVL occurrence was noticed in children (98.1%) than in adults (89.1%) (OR = 6.34; P < 0.000001). Overall, SCC mec -II strains showed greater resistance than SCC mec -IV strains to clindamycin, erythromycin, levofloxacin, gentamicin, rifampin, minocycline, and trimethoprim-sulfamethoxazole. Both SCC mec -II and SCC mec -IV strains recovered from adults were more resistant to these antibiotics than those recovered from children. SCC mec -II strains were predominantly recovered from the respiratory tract, whereas SCC mec -IV strains were predominantly recovered from skin, soft tissue, abscesses, and surgical wounds. These data indicate that SCC mec -IV MRSA isolates frequently infect children in middle Tennessee and are likely to harbor the PVL gene.