Those figures are based on efforts to collect every unique MRSA isolate over a 1-year period in every hospital in San Francisco. A total of nine hospitals (90%) participated from 2004 to 2005. At San Francisco General Hospital alone, more than 1,000 unique isolates were collected in that time.
“There is one MRSA isolate for every 250 persons per year in San Francisco at the current time—now, that's a lot of burden of MRSA disease,” Dr. Chambers said.
He also presented data from the Integrated Soft Tissue Infection Service clinic, which performs as many as 2,000 incision and drainage procedures and other surgical procedures in the outpatient setting. For many years, the drug of choice there has been cephalexin.
To evaluate the role of antimicrobials in skin and soft tissue infections in patients who were treated with incision and drainage, Dr. Chambers and his colleagues conducted a randomized, double-blind, placebo-controlled trial.
Patients at the clinic were enrolled if they were 18 years of age or older and had an abscess requiring incision and drainage that was severe enough that the treating physician thought antibiotics were indicated. Patients were fairly young, with an average age of 26 years in the group that received cephalexin and 30 years in the placebo group. Roughly two-thirds of each group had abscesses that went down to subcutaneous tissue.
The predominant isolate identified was S. aureus alone, found in 69% of those in the cephalexin group and 67% of those in the placebo group. Of the S. aureus isolates, 88% and 90% were MRSA in the cephalexin and placebo groups, respectively.
“You could see the typical pattern of resistance for a community-onset phenotype,” Dr. Chambers said.
The cure rate was 87% in the cephalexin group and 92% in the placebo group, a difference that was not statistically significant. “The cure rates for the placebo suggest that incision and drainage is sufficient for treatment of skin and soft tissue infections with abscess,” he said. The results of this trial are consistent with the findings of several other studies.
“If we can define patients who do not need antibiotic therapy and actually live with that and act as though they don't need antibiotic therapy, we'll be a whole lot better off with this problem [of drug resistance] in general,” Dr. Chambers said.