may be pre-treated with acetaminophen and diphenhydramine before an extended infusion of vancomycin at least 90–120 minutes ahead.

For oral treatment of MRSA and MRSE Linezolid is the antibiotic of choice. Linezolid is a synthetic antibacterial agent of a new class of antibiotics, the oxazolidinones that has joined the armamentarium against MRSA and MRSE. Linezolid inhibits bacterial protein synthesis by binding to a site on the bacterial 23S ribosomal RNA of the 50S subunit and prevents the formation of a functional 70S initiation complex, which is an essential component of the bacterial translation process [32]. The results of time-kill studies have shown linezolid to be bacteriostatic against enterococci and staphylococci. For streptococci, linezolid was found to be bactericidal for the majority of the strains. In vitro studies, however, show that point mutations in the 23S ribosomal RNA are associated with linezolid resistance and have been reported with some strains of Enterococcus faecium and Staphylococcus aureus [32]. S. aureus and S. epidermidis both showed 96% susceptibility and S. haemolyticus showed 99% susceptibility to linezolid.

Side effects of linezolid include myelosupression (e. g. anemia leucopenia, pancytopenia and thrombocytopenia), which is generally reversible upon discontinuation of the drug, and Clostridium diffi- cile-associated colitis. Linezolid is also a weak, nonselective, reversible inhibitor of monoamine oxidase (MAO) and may cause increased serotonin serum levels and serotonin syndrome in patients on various serotonin re-uptake inhibitors such as fluoxetine and sertraline.

Staphylococcal infections may also be treated with quinupristin/dalfopristin (Synercid ). Quinupristin/dalfopristin is bactericidal and inhibits bacterial protein synthesis by binding to different sites on the 50S ribosomal subunit thereby inhibiting protein synthesis in the bacterial cell [32]. We found S. aureus showed 97% susceptibility, S. epidermidis showed 99% susceptibility and S. haemolyticus showed 100% susceptibility to this drug.

Major adverse cardiovascular effects are seen when quinupristin/dalfopristin is given concomitantly with cytochrome P-450 isoenzyme 3A4 substrates such as cyclosporine, midazolam, and nifedipine that may cause QT prolongation [32]. The concomitant administration results in increased se-

rum concentrations of those substrates and potentially prolonged/increased therapeutic or adverse effects. Clostridium difficile-associated diarrhea and colitis has also been reported with this drug ranging in severity from mild to life threatening. Adverse venous effects (e. g. thrombophlebitis) may occur; therefore, flushing infusion lines with 5% dextrose injection following completion of peripheral infusions is recommended. Do not flush with sodium chloride injection or heparin because of possible incompatibilities. Arthralgia and myalgia, severe in some cases, of unknown etiology have been reported. Some patients improved with a reduction in dosing frequency to every 12 hours [32].

Enterococcal bacterial infections

The enterococcal microbial isolates most frequently isolated from burn wounds at our Hospital are E. faecalis and E. faecium. Most enterococcal bacteria are susceptible to vancomycin. At our institution all E. faecalis and E. faecium isolates showed 100% susceptibility to vancomycin. Vancomycin-resistant enterococci usually vancomycin-resistant E. faecium, or VRE, will require treatment with a combination of agents such as ampicillin and aminoglycosides. If this combination is not effective, the VRE may be treatedwiththequinupristin/dalfopristin(Synercid ) combination or linezolid. The reports in literature show that the use of quinupristin/dalfopristin resulted in resistance in one study and a superinfection in another study during the treatment of VRE infection [32]. In our institution E. faecalis showed 94% susceptibility and E. faecium showed 96% susceptibility to linezolid. Linezolid, however, is a bacteriostatic agent and resistance has been reported with some strains of E. faecium.

Gram-negative bacterial infections

The most common gram-negative organisms in our hospital include Pseudmonas aeruginosa, Echerichia coli, Klebsiella pneumoniae, Enterobacter cloacae and A. baumannii/haemolyticus. The efficacy of the antibiotic arsenal varies based on the individual susceptibility of the microbial isolate. Synergy between different classes of antibiotics is often tested to determine efficacy for a multiply drug-resistant