Staphylococcus Aureus Pneumonia: Emergence of MRSA in the Community

Suzanne F. Bradley, MD

Disclosures

Semin Respir Crit Care Med. 2005;26(6):643-649. 

In This Article

Treatment Options for CA-MRSA Pneumonia

Empirical antibiotic choices for treatment of CAP are increasingly difficult to make in the era of CA-MRSA. Vancomycin has remained the cornerstone of therapy for suspected CA-MRSA. However, once CA-MRSA is identified, is vancomycin the optimum treatment for respiratory infection? Failure rates of 40% have been reported and attributed to an inadequate duration of therapy < 21 days.[46] In addition, poor vancomycin penetration into epithelial cell lining fluid and rising vancomycin minimum inhibitory concentrations for MRSA have led some experts to increase trough levels to 20 µg/mL.[47]

Unfortunately, although there are more antibiotic choices, there is little information about the use of alternative agents for pneumonia due to CA-MRSA. Most information on the use of other antimicrobial agents is based on treatment of HA-MRSA infection.

Linezolid (Zyvox; Pfizer Inc., New York, NY) is an oxazolidinone antibiotic that is bacteriostatic for MRSA.[48] In an open-label trial of linezolid versus vancomycin for confirmed MRSA pneumonia, rates of clinical cure were equivalent (75% vs 75%) by intent to treat analysis, as were rates of microbiological cure (52% vs 54%) in evaluable patients.[49] Outcomes for linezolid and vancomycin groups did not differ for patients with multilobar involvement, bacteremia, or effusion. When, a retrospective subanalysis of MRSA cases was done from two prospective double-blinded clinical trials of HAP, results suggested that linezolid treatment was superior to vancomycin with clinical cure rates of 59% versus 36%, OR 3.3 (95% CI 1.3-8.3, p < .01).[50,51,52,53] No differences were seen in outcomes for pneumonia patients with bacteremia, but the efficacy of linezolid in patients with documented endocarditis has not been formally studied.

The streptogramin, quinupristin-dalfopristin (Synercid; Monarch Pharmaceuticals, Inc., Bristol, Tennessee) is a bactericidal for clindamycin-susceptible isolates of MRSA.[54] However, clinical response rates of MRSA pneumonia were only 19% for quinupristin-dalfopristin when compared with a 40% response rate for vancomycin.[55] Experience with trimethoprim-sulfamethoxazole and clindamycin for treatment of HA-MRSA pneumonia and bacteremia has also been very limited.[9,56,57]

For MRSA infections failing conventional therapy, the addition of quinupristin-dalfopristin or imipenem to vancomycin has been tried with some success, but pneumonia has rarely been studied.[58] Addition of rifampin to conventional therapies has also been tried in patients with refractory pneumonia due to MRSA, but no controlled trials demonstrating superiority have been done.[2] Daptomycin cannot be recommended for treatment of MRSA pneumonia because its activity is inhibited by pulmonary surfactant, penetration into epithelial lining fluid is poor, and its efficacy was not established in trials of CAP.[9,59]

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