The clinical significance of
bacteremia due to
vancomycin-heteroresistant staphylococci and a rapid laboratory screening method were examined; 203 strains of staphylococci isolated from patients with clinically significant
bacteremia were screened by the disk-
agar method with use of
vancomycin-
salt agar to demonstrate satellitism around an
aztreonam disk as well as by conventional population screening. Eighteen isolates (three Staphylococcus aureus and 15
coagulase-negative staphylococci) were shown to be heteroresistant to
vancomycin. A case-control clinical study showed that the interval between admission and
bacteremia, admission to the intensive care unit, prior use of
vancomycin and/or
beta-lactams, and isolation of methicillin-resistant staphylococci were significantly more common among patients with
bacteremia due to staphylococci with heteroresistance to
vancomycin; these patients had an overall mortality of 44.4%. The use of
vancomycin and admission to the intensive care unit were independently significant risk factors on multivariate analysis.
Vancomycin heteroresistance is inducible by
salt and
beta-lactams. Indiscriminate sequential use of
beta-lactams and
glycopeptides may facilitate the emergence of
glycopeptide resistance.