Methicillin-Resistant Staphylococcus aureus in Nursing Home Residents

To the Editor: We were encouraged to read the article by Hsu on methicillinresistant Staphylococcus aureus (MRSA) in nursing home residents’ and the accompanying editorial by Boyce.2 There currently are more residents of nursing homes in the United States than there are patients in our acute care hospitals. In spite of this, nursing homes are not used as sites for conducting research as often as they should be. But if an investigator is planning a study in this setting, familiarity with the increasing literature on functional assessment of the elderly is essential. It is with this aspect of Dr. Hsu’s study that we have the most concern. Table 4 lists prevalence rates of MRSA among residents with or without various clinical conditions; bedridden or chair/bed confined are two of the variables quoted. How these variables are defined or how they were measured is not described at all in the methods section. These are very unprecise measures of function, mean different things to different people, and vary from institution to institution based on nursing practices. There are many well-established, validated, and easily administered functional assessment scales that could have been used in the study described.3 The Philadelphia Geriatric Center Scale is one such measure that would have been applicable.4 We also wonder if the results in Table 4 would have been more meaningful if odds ratios with 95% confidence intervals for each had been calculated and reported. In the results section, it is stated that debilitated patients had a significantly high incidence of MRSA colonization @K . OOl>. But at no stage in the article is debilitated defined, nor is any mention made as to how it was measured. We feel these points are important because our own initial investigations, in a similar population, indicate that impaired physical function is a risk factor for developing MIE? L~~~ MRSA colonization in nursing home residents may be a marker for degree of illness and an indicator of a poor outcome rather than an independent risk factor for a poor outcome. lb address this question, rigorous measures of function and disease burden in the subjects studied will be required. In Dr. Hsu’s article, data are presented on antibiotic sensitivities of the MRSA isolates identified. A high rate of resistance to ciprofloxacin was reported, with only 23% of strains being sensitive. Muder et al reported universal resistance to ciprofloxacin among MRSA isolates in a Veterans’ Affairsaffiliated long-term care unit.7 A review of 50 MRSA isolates from 35 patients of a 36@bed skilled nursing facility associated with our academic family medicine program indicated that only 4% of the isolates (2/50) were sensitive to ciprofloxacin (minimum inhibitory concentration [ MIC] < 1 kg/ml). These isolates were obtained from a variety of body sites including urine (20), wound (14), nares (5), and sputum (4) from June 1989 to the present. We feel the high rate of ciprofloxacin resistance found by Hsu deserved more emphasis and discussion, especially because tip mfloxacin recently has been recommended for treating MRSA colonization and infection.8*g