WASHINGTON — The percentage of Staphylococcus aureus isolates resistant to methicillin was about 68% in a survey of more than 100 long-term care facilities, Susan Beekmann, R.N., M.P.H., reported in a poster presented at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
This “extraordinarily high” rate was higher than the documented MRSA rates from surveys of acute care hospitals nationwide, noted Ms. Beekmann and her colleagues at the University of Iowa, Iowa City.
The multicenter, longitudinal surveillance study included 1,060 S. aureus and 1,979 Enterococcus isolates collected from long-term care facilities across the United States during three 1-year periods from 1999 to 2004, Dr. Beekmann reported. The S. aureus isolates included 325 skin or soft tissue specimens, 489 urine specimens, and 246 other specimens. The Enterococcus isolates included 81 skin or soft tissue specimens, 1,835 urine specimens, and 63 other specimens.
The MRSA rate remained fairly stable (66%–71%) throughout the study period. By contrast, the overall infection rate of vancomycin-resistant enterococcus was relatively low (5%), and ranged from 4% in 1999 to 7% in 2003. No evidence of VRE was found in any of the skin or soft tissue isolates, the investigators noted.
Only five MRSA isolates showed no coresistances to other antibiotics. An additional 22 were resistant to ciprofloxacin only; these 22 were also susceptible to clindamycin. Only two of the Enterococcus isolates were linezolid resistant, and eight were intermediate resistant to linezolid, whereas none of the S. aureus isolates was resistant to linezolid.
The meeting was sponsored by the American Society for Microbiology.