SAN FRANCISCO — A quarter of adult patients who completed the recommended initial therapy for methicillin-resistant Staphylococcus aureus infection experienced clinical failure, results from an urban hospital study showed.
In addition, among a subset of patients who had osteomyelitis, 46% relapsed.
“We have a high rate of failure of treating MRSA infections in this urban population, especially among people with bone infections,” Dr. Julie Dombrowski said in an interview during a poster session at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy. “Even with appropriate standard-of-care treatment at this time, which is IV vancomycin for bone infection, we still are having failures. We need better antibiotics or different antibiotics.”
The researchers reviewed the clinical data from 215 patients at San Francisco General Hospital who completed the recommended therapy for MRSA infections between 1998 and 2004.
Of the 215 patients, 54 (25%) had infections at more than one site. There were 81 cases of osteomyelitis (38%); 60 cases of bloodstream infections without endocarditis (28%); 45 cases of pneumonia (21%); 32 cases of endocarditis (15%); 23 joint infections (11%); 18 epidural abscesses (8%); 15 surgical wound infections (7%); and 1 case of meningitis (0.5%).
The most common comorbidities were diabetes (19%) and HIV (14%). About a third of patients (34%) were homeless, 46% reported they used injection drugs, and 26% reported they abused alcohol, said Dr. Dombrowski, of the department of medicine at the University of California, San Francisco.
She also reported that 53 patients (25%) failed initial antibiotic therapy. Vancomycin monotherapy was used in 159 of the patients (74%), whereas rifampin and gentamicin were the antibiotics used most commonly in combination with vancomycin (in 12% and 8% of cases, respectively.) Of the 81 patients who had osteomyelitis, 37 (46%) relapsed.
Bivariate analysis revealed that the following factors were associated with treatment failure: male gender, diabetes, injection drug use, ICU admission, admission to orthopedics, and pneumonia, endocarditis, or osteomyelitis.
Multivariate analysis of the data revealed that osteomyelitis was the only factor independently associated with treatment failure.
The degree of treatment failure seen in patients with osteomyelitis surprised Dr. Dombrowski. “I expected that we would have more failures among bone infections than other kinds of infections like endocarditis or pneumonia, but we were surprised that we weren't able to cure almost half of the bone infections,” she said at the conference, which was sponsored by the American Society for Microbiology.