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BACKGROUND: The Colorado Department of Public Health and Environment (CDPHE) conducts active population based surveillance of Clostridium difficile infections (CDI) for residents of the five-county Denver metropolitan area (Adams, Arapahoe, Denver, Douglas, Jefferson counties). Overall case counts and incidence rates vary among the five counties. We explored the effect that nursing home CDI burden might have on county-specific CDI incidence rates.
METHODS: County-level case counts, incidence rates, and proportions of nursing home (NH) cases were determined using 2012 CDI surveillance data. Toxin or molecular assay positive tests from patients residing in the five counties without a positive test in the previous 8 weeks were considered cases. Location of stool collection provided by the reporting laboratory was used to determine location of onset. Population denominators were obtained from the State Demography Office and used for calculating rates and population distributions among age groups and counties. C.difficile positive stool samples collected at a long term care facility or a skilled nursing facility were defined as NH-onset cases. Numbers of NHs and NH beds were obtained from licensing entities and used to calculate distributions of NH beds by county and population. Ratios of CDI cases to the number of NH beds, and NH-onset cases per 100 NH beds were calculated and compared among counties.
RESULTS: Arapahoe county had the highest CDI incidence rate of the five counties (182.0 per 100,000 population); Arapahoe also had the highest NH-onset CDI incidence rate (42.6 per 100,000), more than double the next highest county (Adams, 21.2). NH-onset cases for Arapahoe county accounted for almost half (45.6%) of all NH-onset cases. Arapahoe county had a ratio of NH-onset cases to 100 NH beds (11.1) almost twice that of the next highest county, Adams (5.9). However, Arapahoe county does not have the most NHs, NH beds, or ratio of NH beds per population, nor a population older than other counties. Of 22 NHs located in Arapahoe county, 5 (22.7%) had ratios of NH-onset cases to 100 NH beds greater than 20.
CONCLUSIONS: Differences in CDI incidence rates in the Denver metropolitan area, particularly the high incidence rates in Arapahoe county, might be partially explained by differences in NH-onset rates. It is unclear why counties have differences in NH rates not explained by the density of NH beds per county, nor age differences. Higher NH-onset cases in Arapahoe county should be further explored to aid in CDI prevention efforts.