Analysis of Slovenian MRSA strains with susceptibility patterns suggestive of CA-MRSA

Abstract

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) differs from healthcare-associated MRSA (HA-MRSA) in its molecular and microbiological characteristics. Six Slovenian regional public health institutes and the National Institute of Public Health took part in monitoring CA-MRSA infections. S. aureus isolates resistant to oxacillin and susceptible to > or = two of the four antibiotics ciprofloxacin, erythromycin, clindamycin or gentamicin were defined as CA-MRSA and further analyzed. The presence of the gene for Panton-Valentine leukocidin (PVL) was confirmed using PCR, the type of staphylococcal cassette chromosome (SCCmec) using multiplex PCR, and macrorestriction analysis of chromosomal DNA using pulsed-field gel electrophoresis (PFGE). A total of 31 strains from 31 patients were analyzed during a period of 21 months: 23 specimens were sent from hospitals, six from primary care, two from a long-term care facility. All 31 isolates contained the gene mecA. Sixteen (51.6%) isolates were identified as SCCmec type IV, three isolates were PVL positive. Using PFGE, the CA-MRSA strains were classified into 15 similarity groups. Results of antibiotic susceptibility showed there were five resistance types among the 31 strains. Simultaneous resistance against ciprofloxacin and gentamicin was often associated with the presence of SCCmec type I, strongly resembling HA-MRSA. PVL-positive strains of CA-MRSA have been isolated in Slovenia only rarely. We will continue to monitor strains of MRSA in order to obtain the complete microbiological and epidemiological features.