Antimicrobial Therapy for Methicillin-Resistant Staphylococcus aureus Colonization in Residents and Staff of a Veterans Affairs Nursing Home Care Unit

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Abstract
Objective: To evaluate the effect of antimicrobial therapy on patients and staff colonized with methicillin-resistant Staphylococcus aureus (MRSA) in a skilled nursing facility and to assess the role of the environment as a potential reservoir for MRSA in the nursing home setting. Design: As part of a comprehensive program to control an MRSA outbreak in a nursing home, patients and staff colonized with MRSA received 1 of3 antimicrobial decolonization regimens depending upon the site and extent of colonization. Followup cultures were performed during therapy and on days 2, 7, 14, and 30 following the completion of therapy. Cultures of the patients' inanimate environment (pajamas, sheet, and floor) were obtained during and after therapy. Antimicrobial susceptibility tests were performed on 54 MRSA isolates obtained before and 44 MRSA isolates recovered after therapy. Setting: A 120-bed Veterans Affairs nursing home care unit. Participants: Thirty-six patients and 7 staff nurses colonized with MRSA at 1 or more sites. Intervention: Decolonization therapy with rifampin, trimethoprim-sulfamethoxazole, and clindamycin used alone or in various combinations for 5 or 10 days in conjunction with other infection control measures employed to combat the MRSA outbreak. Results: Twenty (56%) of the 36 NHCU patients were either persistently colonized or became recolonized with MRSA during the 30day followup period. Positive cultures on day 3 during therapy frequently identified patients who subsequently exhibited persistent or recurrent colonization. Before therapy, 92% of MRSA isolates were susceptible to rifampin, whereas only 43% of the isolates obtained after therapy were susceptible. Sixteen (80%) of 20 patients with persistent or recurrent colonization had rifampinresistant strains of MRSA isolated after therapy. Twenty-three (18%) of 125 environmental cultures obtained during and after therapy from patients who exhibited persistent or recurrent colonization were positive for MRSA, in contrast to 9 (8%) of 107 from patients who were successfully decolonized. Conclusions: The decolonization component of the outbreak control program was judged to be ineffective and potentially hazardous because colonization persisted or recurred in more than half of the patients, and substantial antimicrobial resistance was noted in MRSA strains isolated after therapy. Resistance, especially to rifampin, and possibly re-acquisition of MRSA from other human or environmental sources were 2 factors that appeared to impede the decolonization effort.