C diff Risk Increases if Previous Patient Received Antibiotics

Ricki Lewis, PhD

October 11, 2016

Risk for Clostridium difficile infection (CDI) in a hospitalized patient is elevated if the previous patient who occupied the same bed received antibiotics, according to results of a study published online October 10 in JAMA Internal Medicine. The increase in risk remained even when the current patient did not receive antibiotics.

Certain antibiotics are known to increase CDI risk. Moreover, it is known that bacterial spores can persist for months in the environment, and that risk for infection increases for patients who occupy a room previously occupied by a patient with CDI. Until now, however, it has not been known whether the use of antibiotics by a prior hospital bed occupant might affect a current patient's risk for CDI.

To find out, Daniel Freedberg, MD, from the Division of Digestive and Liver Diseases, Columbia University Medical Center, New York City, and colleagues conducted a retrospective cohort study testing the possible association between antibiotic use by the prior bed occupant and CDI risk for the subsequent patient.

The researchers followed adults hospitalized in any of 4 affiliated hospitals in the New York City area between 2010 and 2015. To be included in the study, the previous occupant had to have been in the bed within a week before the next patient's arrival, and for at least 24 hours. The researchers excluded subsequent patients who had recent CDI, developed it within 48 hours of admission, or had inadequate follow-up time.

The researchers identified antibiotic use through a computerized clinician order entry system for the prior bed occupant; CDI diagnosis was based on polymerase chain reaction tests for the toxin B gene in a stool sample.

Of 100,615 pairs of patients who sequentially occupied the same hospital bed, 576 (0.57%) of the second patients were diagnosed with CDI within 2 to 14 days. The median time from bed occupancy to CDI diagnosis for the second patients was 6.4 days (interquartile range, 4.0 - 9.5).

The cumulative incidence of CDI in subsequent patients was 0.72% when the prior bed occupants received antibiotics; it was 0.43% when prior bed occupants did not receive antibiotics (log-rank P < .01).

In the final Cox proportional hazards model, antibiotic use by the prior patient was associated with a 22% increased risk for CDI in the subsequent patient (adjusted hazard ratio [aHR], 1.22; 95% confidence interval [CI], 1.02 - 1.45). All other factors associated with the prior patient did not affect risk. Moreover, the authors note that the subsequent patient's own risk factors, such as age or antibiotic use, had a larger effect on CDI in the final model risk than the prior patient's antibiotic use.

In sensitivity analyses, the author found that the prior patient's antibiotic use remained a significant risk factor even after excluding 1497 patient pairs in which the first patient had CDI (aHR, 1.20; 95% CI, 1.01 - 1.43).

"Our study may be the most direct example to date of the potential effect of antibiotics in patients who do not themselves receive the antibiotics," the investigators write. "In patients colonized by C difficile, antibiotics may promote C difficile proliferation and the number of C difficile spores that are shed into the local environment. In turn, this may result in a higher environmental burden of C difficile and greater risk for acquisition and infection in future patients who share the same environment." They suggest further research on this apparently detrimental herd effect of certain antibiotics.

Limitations of the study include the observational design; generalizability beyond the New York City–based hospitals, because environment is so critical; the nonoutbreak setting; and use of historical data rather than assessing current situations that might have revealed the exact route of infection.

The researchers have disclosed no relevant financial relationships.

JAMA Intern Med. Published online October 10, 2016. Abstract

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