Multidrug-Resistant Gram-Negative Bacteria within a Long-Term Acute Care Hospital: a Review of Five Years of Clinical Cultures

Background: The long-term acute care hospital (LTACH) is an increasingly common health care setting designed to provide care for medically complex patients after their discharge from an acute care hospital.  The population of LTACH’s has been identified as harboring high rates of infection and colonization with MRSA, VRE and a prevalence of individual antimicrobial resistance among infections that exceeds the 90^th percentile for ICU’s participating in the National Nosocomial Infections Surveillance (NNIS) system.  The emergence of multidrug-resistant gram-negative (MDRGN) pathogens, those resistant to ≥3 antimicrobial classes, is an increasing concern in many heath care settings, including hospitals, ICU’s, dialysis units and long-term care (nursing home) facilities.  Concern about infections caused by MDRGN has been heightened by the recognition that they result in higher rates of morbidity, mortality, longer lengths of stay and increased costs of care.  Despite awareness that the population within LTACH harbor many known risk factors for MDRGN, the prevalence of MDRGN bacteria has not been assessed within this setting.

Objective: To describe the prevalence of MDRGN organisms within a LTACH.

Methods: All clinical microbiological records between January 1^st 2005 and December 31^st 2009 were reviewed.  Cultures obtained for surveillance of colonization with MRSA or VRE were excluded, as were repeated cultures from a single individual within 30 days, and those without bacterial growth or “normal flora”.  Information on antibiotic treatment, and disposition upon discharge from the LTACH was obtained for the calendar year January 1^st 2009 – December 31^st, 2009.  MDRGN was defined as resistance to ≥3 antibiotics or antimicrobial classes.

Results: A total of 1,692 cultures were included in the analysis, with 1,138 demonstrating gram-negative bacteria; among these cultures 471(41.4%) met criteria for MDRGN.  The prevalence of MDRGN was high among all sites of infections with 66.8% of respiratory, 53.1% of blood stream, 38.7% of urinary tract, and 36.3% of skin and wound infections respectively. The prevalence of MDRGN rose significantly during the study period (P<0.005).  Rates of resistance to many individual antibiotics exceeded the 90^th percentile reported for ICU’s participating in the National Nosocomial Infection Surveillance (NNIS) system.  Transfer to another health care setting occurred for more than two thirds of the patients.

Conclusions: The prevalence of MDRGN is exceptionally high within the LTACH setting.  High levels of individual and multi-drug antibiotic resistance create a daunting clinical challenge and few effective antibiotic choices.  The frequent transition of LTACH residents to other health care settings raises concerns about the potential dissemination of MDRGN to other populations.