Increased multi-drug resistance among the elderly on admission to the hospital--a 12-year surveillance study.

Resistance to antimicrobials continues to increase worldwide. Data suggest that older patients are among the main reservoirs of multidrug-resistant organisms (MDROs) in the hospital. We hypothesized that older patients (≥ 65 years of age) are more likely to harbor MDRO at hospital admission. We compared rates of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE) and multidrug-resistant gram-negative bacteria (MDRGN) recovered from clinical cultures within the first 48 h of admission to an adult acute care hospital between the elderly (≥ 65 years old) and young per 1000 age-stratified admissions over a 12-year study period. Trends in antimicrobial resistance, sites of recovery and species for MDRGN were also characterized. An average of 7534 positive bacterial cultures were collected per year. The admission prevalence per 1000 age-stratified admissions was consistently higher among the elderly for all three MDRO under investigation. Among the elderly, the admission prevalence increased significantly for VRE (0.89 in 1998 to 3.62 in 2009 per 1000 admissions; p < 0.001) and MDRGN (1.41 in 1998 to 11.33 in 2009 per 1000 admissions; p < 0.001). Percentage resistant for all three MDRO increased as well. These data suggest that elderly patients are contributing substantially to the influx of MDRO into the hospital setting.