Atlanta, GA—The more hospitals use four specific classes of antibiotics, the greater the prevalence of hospital-associated Clostridioides difficile becomes, with the problem especially acute in teaching hospitals.

That is according to a new study published in Infection Control & Hospital Epidemiology, the journal of the Society for Healthcare Epidemiology of America.

In fact, a research team from the CDC and industry found that, for every 100 days of facility-wide antibiotic therapy using one of high-risk antibiotics, hospital-associated C difficile infection increased 12%. When analyzed separately, however, only cephalosporins were significantly correlated with hospital-associated C difficile, the authors point out.

“This highlights the importance of ongoing monitoring of antibiotic use in hospitals for patient safety as it relates to the effect of antibiotics on C. difficile infections. In the future it will also be important to look at the effect of antibiotic use on both C. difficile infection and antibiotic resistance simultaneously, rather than examining each piece as separate endeavors,” explained coauthor L. Clifford McDonald, MD, medical epidemiologist at the CDC.

“This is possible in our era of electronic medical records because antibiotic usage data has become more available. A facility can use the National Healthcare Safety Network Antibiotic Use and Resistance Module and interpret results using the standardized antibiotic administration ratio (SAAR) to have a better understanding of how antibiotics are being used and identify areas for improvement,” Dr. McDonald added.

The study team evaluated previously defined high-risk antibiotic use in relation to C difficile infections (CDIs), analyzing 2016–2017 data from 171 hospitals.

The focus was on high-risk antibiotics including second-, third-, and fourth-generation cephalosporins, fluoroquinolones, carbapenems, and lincosamides. CDI was determined by a positive stool C difficile toxin or molecular assay result from a patient without a positive result in the previous 8 weeks.

Hospital-associated (HA) CDI cases included specimens collected more than 3 days after admission or 3 or fewer days from a patient with a prior same-hospital discharge within 28 days.

Researchers report that the median days of therapy for high-risk antibiotic use was 241.2 (interquartile range [IQR], 192.6-295.2) per 1,000 days present, with an overall hospital-acquired CDI rate of 33 (IQR, 24-43) per 10,000 admissions.

The study points out that the overall correlation of high-risk antibiotic use and HA CDI was 0.22 (P = .003), and a higher correlation was observed in teaching hospitals (0.38; P = .002).

It also calculates that, for every 100-day (per 1,000 days present) increase in high-risk antibiotic therapy, there was a 12% increase in HA CDI (relative risk [RR], 1.12; 95% CI, 1.04-1.21; = .002) after adjusting for confounders.

“High-risk antibiotic use is an independent predictor of HA CDI,” the authors conclude. “This assessment of post-stewardship implementation in the United States highlights the importance of tracking trends of antimicrobial use over time as it relates to CDI.”

In addition to teaching hospitals, higher C difficile infection rates were also associated with a larger portion of patients over age 65 years, higher rates of community-onset C difficile, and longer length of stay.

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