Methicillin-resistant Staphylococcus aureus heterogeneously resistant to vancomycin in a Turkish university hospital.
OBJECTIVE
We investigated vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneously vancomycin-intermediate S. aureus (hetero-VISA) isolates from clinical specimens of hospitalized patients at Hacettepe University over a 4 year period.


METHODS
Strains were screened for VISA and hetero-VISA by using brain heart infusion agar containing 4 mg/L vancomycin (BHI-V4) and macro Etest. Confirmation of the isolates that were found to have intermediate susceptibility to vancomycin with either of the methods was done by population analysis of subpopulations with reduced susceptibility to vancomycin. The MIC of vancomycin for the isolates grown on BHI-V4 was determined by the microdilution method.


RESULTS
Among 256 methicillin-resistant S. aureus (MRSA) isolates, 145 grew on BHI-V4. Forty-six of these were also found to be heterogeneously vancomycin-intermediate strains when screened with the macro Etest. There were no VISA among 256 MRSA tested but 46 (17.97%) S. aureus strains with reduced susceptibility to vancomycin were identified by population analysis. Vancomycin MIC values for all isolates with reduced susceptibility were between <or=0.125 and 4 mg/L. Twelve of the 46 patients with hetero-VISA had a history of previously being treated with vancomycin or teicoplanin.


CONCLUSIONS
To our knowledge, this study is the first publication showing the presence of hetero-VISA in Turkey. In order to understand the epidemiological relationship between our isolates, molecular typing methods are needed.
Sancak
Banu
B
Department of Clinical Microbiology and Microbiology, Hacettepe University Medical School, Ankara, 06100, Turkey. banusancak@yahoo.com
Ercis
Serpil
S
Menemenlioglu
Dilek
D
Colakoglu
Sule
S
Hasçelik
Gülsen
G
D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D024901:Drug Resistance, Multiple, Bacterial; D006785:Hospitals, University; D006801:Humans; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects*; D017334:Teicoplanin / Q000627:therapeutic use; D014421:Turkey; D020713:Vancomycin Resistance
D000900:Anti-Bacterial Agents; D017334:Teicoplanin