Unstable vancomycin heteroresistance is common among clinical isolates of methiciliin-resistant Staphylococcus aureus.
We tested 109 unique, vancomycin-susceptible, methicillin-resistant Staphylococcus aureus (MRSA) strains for vancomycin heteroresistance by a selection method, i.e., step-wise exposure of large inoculums to increasing concentrations of vancomycin. Although no strains demonstrated stable heteroresistance, 81 strains (74%) demonstrated unstable heteroresistance. Unstable heteroresistance is common among clinical isolates of MRSA and may represent a cause of therapeutic failure.
Plipat
Nottasorn
N
Division of Pediatric Infectious Diseases, Department of Pediatrics, Siriraj Hospital, Mahidol University, 2 Prannok Road, Bangkoknoi, Bangkok 10700, Thailand. nplipat@msn.com
Livni
Gilat
G
Bertram
Heidi
H
Thomson
Richard B
RB
D000328:Adult; D002648:Child; D024881:Drug Resistance, Bacterial; D006801:Humans; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D013203:Staphylococcal Infections / Q000188:drug therapy; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification / Q000648:ultrastructure; D014640:Vancomycin / Q000494:pharmacology*
D014640:Vancomycin