Clonal dissemination of meticillin-resistant and vancomycin-intermediate Staphylococcus aureus in a Taiwanese hospital.

Meticillin-resistant and vancomycin-intermediate Staphylococcus aureus (VISA) has emerged worldwide. However, clonal dissemination of VISA in hospitals has rarely been reported. We investigated 43 isolates of meticillin-resistant VISA [vancomycin minimum inhibitory concentrations (MICs) of 4 microg/mL in 35 isolates and 8 microg/mL in 8 isolates) recovered from 21 hospitalised patients. A glycopeptide was given prior to isolation of VISA in 14 of the patients. Five patients (23.8%) died despite vancomycin therapy. All isolates were inhibited by tigecycline at 0.5 microg/mL, linezolid at 1 microg/mL and ceftobiprole at 2 microg/mL. Five isolates (11.6%) had reduced susceptibility to daptomycin (MICs of 1-2 microg/mL). In addition, 6 of the 43 VISA isolates had decreased susceptibility to autolysis by 0.05% Triton X-100. All 43 VISA isolates carried staphylococcal chromosome cassette mec (SCCmec) type III and accessory gene regulator (agr) group I but none carried the Panton-Valentine leukocidin gene (lukS-lukF). None of the enterococcal van genes were detected in the 43 VISA isolates. Molecular typing generated by pulsed-field gel electrophoresis revealed that all isolates belonged to one pulsotype, indicating clonal dissemination of VISA isolates in the hospital. The high rate of non-susceptibility to daptomycin amongst these VISA isolates is alarming and indicates the limitation of this agent for the treatment of infections due to VISA. Copyright 2010 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.