Bacteremia due to Staphylococcus aureus with reduced susceptibility to vancomycin

Four cases of bacteremia caused by Staphylococcus aureus with heteroresista nce to vancomycin (hetero-VRSA) were described. In at least two of these fo ur mortalities, the cause of death was temporally related to the hetero-VRS A bacteremia. The vancomycin and teicoplanin MICs of the resistant subpopul ations of these four hetero-VRSA were 8 and 24 mu g/ml, respectively. All i solates were producers of beta-lactamase, produced penicillin-binding prote in PBP2a, and possessed the mecA gene accounting for methicillin resistance . Thickening of the peptidoglycan cell wall was observed by electron micros copy. When ampicillin was combined with vancomycin, in vitro synergism was detected using the checkerboard titration method (epsilon FIC = 0.13). The use of vancomycin plus ampicillin-sulbactam could be a viable option in tre ating severe hetero-VRSA infection in view of the higher affinity of ampici llin toward PBP2a. (C) 2000 Elsevier Science Inc. All rights reserved.