Comparison of the bacterial isolates and antibiotic resistance patterns of elderly nursing home and general community patients

Background: Nursing home-acquired infections may differ from general community-acquired infections in bacteriology and antibiotic resistance. However, there are currently limited data on this topic in the Australian setting. Aims: To compare bacterial isolates and antibiotic resistance patterns, from pathology specimens of nursing home and community patients, and to comment on the suitability of empiric antibiotic guidelines for nursing home-acquired infection. Methods: This was a retrospective cohort study of patients, aged =65 years, who resided in either nursing homes or the general community. Patients with a hospital admission in the previous 28 days were excluded. Positive specimen cultures, collected between July 2003 and June 2008 in the Emergency Department and Outpatient Clinics of the Austin Hospital (Melbourne), were examined. The main outcome measures were the bacterial isolates, and their antibiotic resistance patterns, of patients from nursing homes and the general community. Results: Specimens of blood (638), sputum (425), urine (4044) and wound cultures (785) were examined. The bacteriology of blood culture isolates did not differ between the two groups (P= 0.3). However, the bacteriology of sputum, urine and wound cultures differed significantly between the groups (P= 0.025, P < 0.001, P= 0.004 respectively). There were also higher proportions of antibiotic resistance among some bacteria in nursing home patients, especially methicillin resistance among Staphylococcus aureus isolates across all specimen types, and resistance to several empiric antibiotics among Enterobacteriaceae isolates in urine cultures. Conclusion: Empiric antibiotic guidelines appear adequate to treat nursing home-acquired septicaemia and pneumonia. However, guidelines for urinary tract infections and wound infections may need to be refined.