Vancomycin bactericidal effects

Two important new streptogramins are quinu-pristin (Fig. 10.15A) and dalfopristin (Fig. 10.15B), which are derivatives of pristinamycin I and IIA, respectively. Individually, the two components are bacteristatic but in combination they act synergistically to produce a bactericidal effect by inhibiting early (dalfopristin) and late (quinupristin) phases of bacterial protein synthesis. These two antibiotics are used intravenously in combination (ratio 30 70) for the treatment of serious or life-threatening infections associated with vancomycin-resistant Enterococcus faecium bacteraemia, although the effect against this organism is bacteristatic. 

Lactams and vancomycin display time-dependent bactericidal effects. Killing activity is enhanced only marginally if drug... 

Vancomycin should be used only to treat serious infections and is particularly us ul in the management of infections due to methicillin-resistant staphylococci and in severe staphylococcal infections in patients who are allergic to penicillins and cephalosporins. Vancomycin is less rapidly bactericidal than the antistaphylococcal J3-lactams (e.g., nafcillin or cefazolin) and may be less efficacious. Treatment with vancomycin is effective and convenient when there is disseminated staphylococcal infection or localized shunt infection in a patients receiving hemodialysis or peritoneal dialysis, because the drug can be administered once weekly or in the dialysis fluid. 

Lapidot B.licheniforwis cells treated with vancomycin at bacteriostatic doses show a reduction in the intensity of the 252.8 ppm acetamido resonance. The effect resembles that observed during cell plasmolysis in 2N sucrose, which may be related to the reported plasmolysis of bacilli by vancomycin. Bactericidal doses of vancomycin lead to a general reduction in the intensity of cell wall resonances and the appearance of new peptidoglycan resonances in the whole cell spectra of B.licheniformis cells, harvested when lysis reached 30%. The binding of vancomycin to non-growing cells had no effect on the cell wall reso" nances however, the binding of vancomycin to H.lysodeikticus cell walls led to a marked increase in the NOE of cell wall resonances. 

Answer Yes. Vancomycin is the drug of choice (in fact, the only effective drug currently available) for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. It is bactericidal and thus important for treatment of a leukopenic individual. 

In controlled phase III studies, linezolid was as effective as vancomycin in patients with infections caused by MRSA and VRE. It is effective both intravenously and orally. Although technically classified as bacteriostatic against a number of pathogens in vitro, linezohd behaves in vivo hke a bactericidal antibiotic. 

FIGURE 100 Vancomycin, a bactericidal antibiotic, inhibits cell-wall synthesis in Gram-positive bacteria. It is effective against methicillin-resistant organisms and as an alternate to semisynthetic penicillins or cephalosporins in patients with severe staphylococcal infections. 

Daptomycin (CUBICIN) is a cyclic lipopeptide that was resurrected in response to increasing need for bactericidal antibiotics effective against vancomycin-resistant gram-positive bacteria... 

Stratton CW, Weeks LS. Effect of human serum on the bactericidal activity of daptomycin and vancomycin against staphylococcal and entetococcal isolates as determined by titiK kill kinetic studies. Diagn Microbiol Infect Dis 1990 13 245-252. 

Lamp KC, Rybak MJ, Bailey EM, Kaatt GW. In vitro pharmacodynamic effects of conccn-tration, pH, and growth phase on serum bactericidal activities of daptomycin and vancomycin. Antimicrob Agent Chemother 1992 36 2709-2714. 

A. Gonzalez Della Valle, M. Bostrom, B. Brause, C. Harney and E.A. Salvati, Effective bactericidal activity of tobramycin and vancomycin eluted from acrylic bone cement. Acta Orthop. Scand. 12 273-240, 2001. 

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