563. Antimicrobial Susceptibility Patterns and Genetic Characteristics of Community-Associated Methicillin-Resistant Staphylococcus aureus Colonizing Surgical Patients
Session: Poster Abstract Session: MRSA Surveillance and Infection Prevention
Friday, October 21, 2011
Room: Poster Hall B1
  • kosmidis IDSA ca-mrsa.pdf (94.2 kB)
  • Background: Community-associated methicillin-resistant S. aureus (CA-MRSA) has been traditionally susceptible to most non-beta-lactam agents, although changing susceptibility patterns have been recently observed. We describe the phenotypic and genetic characteristics of CA-MRSA colonizing surgical patients.

    Methods: Consecutive patients admitted to the surgical wards of a tertiary care hospital between January and July 2009 were screened for MRSA carriage from nasal and inguinal area within 48 hours of admission. CDC epidemiological criteria were used for classification into CA- and healthcare-associated MRSA (HA-MRSA). Susceptibility testing to commonly used antimicrobials was performed by disk diffusion method. All MRSA isolates were tested for the presence of lukF and lukS genes by PCR. SCCmec typing and multilocus sequence typing (MLST) were performed by PCR and sequencing. 

    Results: 925 patients (50.7% males, median age 62.8 years) were screened and 55 samples were positive for MRSA (5.95%). Susceptibility rates for CA-MRSA and HA-MRSA, respectively, were: ciprofloxacin (Cp) 73.7% and 38.9%, erythromycin (E) 73.7% and 30.6%, clindamycin (Cl) 73.7% and 36.1%, fusidic acid (F) 42.1% and 38.9%, co-trimoxazole (Co) 73.7% and 63.9%, gentamicin (G) 84.2% and 77.8%, tetracycline (T) 42.1% and 41.7%, rifampin (R) 94.7% and 94.4%. Of the CA-MRSA isolates, 9 of 19 (47.4%) were Panton-Valentine Leucocidin (PVL)-positive, whereas 8 (22.2%) of the 36 HA-MRSA isolates were PVL-positive. Eight PVL-positive isolates belonged to ST80 and one belonged to ST30. PVL-negative CA-MRSA isolates belonged to ST5, ST105, ST109 and ST239. Resistance phenotypes of PVL-positive isolates were: FT (5 isolates), FTCo (1), FTECl (1), FTEClCpCoG (1), GR (1) and phenotypes of PVL-negative isolates were: pansensitive (4 isolates), CpEClCo (2), FT (2), Cp (1) and CpEClFCoGT (1). SCCmec IV was carried by 8 and SCCmec V by 1 PVL-positive isolate, whereas PVL-negative isolates carried SSCmec IV (5 isolates), SSCmec III (2), SSCmec II (2) and SSCmec V (1).

    Conclusion: Multidrug resistant strains were observed among PVL-positive CA-MRSA in our geographic region. We report the presence of resistance among colonizing strains of ST80, a highly successful European clone.

    Subject Category: A. Antimicrobial agents and Resistance

    Linos Hadjihannas, MD, Chris Kosmidis, MD, Mina Psichogiou, MD, Dimitris Goukos, MMSc, Georgia Bouzala, MD and George L Daikos, MD, Infectious Diseases, University of Athens Medical School, Athens, Greece


    L. Hadjihannas, None

    C. Kosmidis, None

    M. Psichogiou, None

    D. Goukos, None

    G. Bouzala, None

    G. L. Daikos, None

    Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.