Empyema caused by MRSA ST398 with Atypical Resistance Profile, Spain

To the Editor: We report a case of empyema caused by methicillin-resistant Staphylococcus aureus (MRSA) sequence type ST398 in a 79-year-old man in Spain who had severe chronic obstructive pulmonary disease. In 2009, the patient was hospitalized in the intensive care unit because of decompensation of his chronic obstructive pulmonary disease, profound iliofemoral venous thrombosis, right pneumothorax, and lung carcinoma. Thoracic drainage, support measures, and intravenous levofl oxacin were initiated, but no clinical improvement was seen. Purulent exudates from the thoracic drainage tube and of a trache-al aspirate were cultured. MRSA was isolated from both samples and from a nasal swab. Antimicrobial drug therapy was changed from levofl oxacin to intravenous linezolid, but the patient's clinical situation rapidly worsened, and he died of multiorgan failure. The 3 MRSA isolates were typed (multilocus sequence typing-, spa-, staphylococcal cassette chromosome [SCC] mec-, and agr-typing, in addition to pulsed-fi eld gel electropho-resis [PFGE]), likewise, the antimi-crobial drug–resistance phenotypes and genotypes, and virulence genes were determined (1,2). All 3 MRSA isolates were typed as sequence type (ST) 398, spa-type t011, SCCmecV, and agrI. The 3 isolates had the same resistance phenotype, including to β-lactams, tetracycline, clindamycin (but not erythromycin), ciprofl oxa-cin, and levofl oxacin. We confi rmed the presence of mecA, tetM, tetK, and vga(A) genes by PCR and se-quencing; however, PCRs for lnu(A), lnu(B), lnu(C), lnu(D), cfr, vga(C), lsa(B), and tetL genes were negative. Primers used for detection of vga(A) gene were F-5′-GAAACTCTTATTC GAACYATTCTAGC-3′ and R-5′-GGTTCAATACTCAATCGACT-GAG-3′. Specifi c amino acid changes in the quinolone-determining region of GyrA and ParC proteins (S84L and S80F, respectively) were detected by PCR and sequencing (1). All 3 MRSA isolates were negative by PCR for the Panton-Valentine leukocidin, toxic shock syndrome toxin 1, and exfolia-tive toxins A and B. The patient lived with his wife and 2 sons near a pig farm. Both sons worked on the farm; the patient, but not his wife, helped sporadically on the farm. Nasal samples from the 3 family members indicated MRSA carriage in 1 son but not in the other son or the pa-tient's wife. The characteristics of the nasal MRSA strain recovered from the son were identical to those previously detected in MRSA strains from the patient (Table). In addition, nasal swabs from 18 pigs on the farm were randomly taken, and MRSA isolates were detected in 9 (50%) pigs; 1 MRSA isolate per animal was further characterized. Eight isolates …