Abstract
Eight heterogeneous vancomycin-intermediate S. aureus (h-VISA) and seven VISA clinical isolates confirmed by the population analysis profile/area under the curve ratio (PAP/AUC) were collected. We further performed the PAP/AUC, time-killing methods and MIC tests using vancomycin/teicoplanin alone or combination with susceptible breakpoint concentrations of cefazolin, cefmetazole, cefotaxime, and cefepime for these isolates. The PAP/AUC MIC curve shifted left after addition of cephalosporins with vancomycin or teicoplanin for both h-VISA and VISA isolates. With the combination of different cephalosporins with vancomycin or teicoplanin, the AUC/Mu3 AUC ratio decreased to <0.9 for the standard Mu3 isolate which are compatible with the definition of vancomycin susceptible S. aureus. These decreases ranged between 1.81–2.02 and 2.37–2.85-fold for h-VISA treated with cephalosporins and vancomycin or teicoplanin, and 2.05–4.59, and 2.93–4,89-fold for VISA treated with cephalosporins with vancomycin or teicoplanin. As measured by time-killing assays, the combinations of different cephalosporins with vancomycin concentrations at 1/2 and 1/4 MIC, exhibited a bactericidal and bacteriostatic effect in VISA. The mean fold of MIC decline for vancomycin base combinations ranged from 1.81–3.83 and 2.71–9.33 for h-VISA and VISA, respectively. Overall, this study demonstrated the enhanced antibacterial activity of vancomycin/teicoplanin after adding cephalosporins against clinical h-VISA/VISA isolates.
Highlights
Aside from vancomycin, there are some viable alternative antimicrobial agents, such as daptomycin, linezolid, ceftaroline, trimethoprim/sulfamethoxazole, tigecycline, and quinupristin/dalfopristin[13]
We conducted a comparative study of the combination of cephalosporins of all generations with either vancomycin or teicoplanin against heterogeneous vancomycin-intermediate S. aureus (h-vancomycin-intermediate S. aureus (VISA))/VISA isolates by three laboratory methods to evaluate the in vitro antibacterial activity among different glycopeptide/cephalosporin (G/C) combinations
This study assesses the effect of addition of different cephalosporins with glycopeptides against h-VISA/VISA isolates and has several significant findings
Summary
Aside from vancomycin, there are some viable alternative antimicrobial agents, such as daptomycin, linezolid, ceftaroline, trimethoprim/sulfamethoxazole, tigecycline, and quinupristin/dalfopristin[13]. Dilworth et al.[14] showed the synergistic activity of vancomycin with piperacillin-tazobactam or oxacillin against VISA. No investigation has assessed the activity of combination of any of the four generations of cephalosporins with either vancomycin or teicoplanin against h-VISA/VISA. We conducted a comparative study of the combination of cephalosporins of all generations with either vancomycin or teicoplanin against h-VISA/VISA isolates by three laboratory methods to evaluate the in vitro antibacterial activity among different glycopeptide/cephalosporin (G/C) combinations
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