A new study found a 12% rise in hospital-associated Clostridium difficile infections (CDIs) for every 100 days of high-risk antibiotic use. But all antibiotics may not be contributing equally to the problem.
The study, published in Infection Control & Hospital Epidemiology, highlighted changing patterns in the previously established association between antibiotic use and the incidence of the infection commonly referred to as C. diff.
Specifically, the study looked at the use of second- through fourth-generation antibiotic classes including cephalosporins, carbapenems, fluoroquinolones and lincosamides, which together account for approximately half of all antibiotic use.
The overall results reinforced previous studies showing an association between the use of these antibiotics and higher C. diff rates, said L. Clifford McDonald, M.D., a medical epidemiologist at the Centers for Disease Control and Prevention and one of the study’s authors.
However, when the researchers looked at the results of each class of antibiotics in isolation, they found that only cephalosporins were significantly correlated with higher C. diff incidence.
There could be plenty of reasons for the findings, researchers said. For instance, compared to previous data, the use of fluoroquinolones has decreased in relative amount while the use cephalosporins and carbapenems has increased.
The study underscores the importance of consistently updating assessments of the association between antibiotic use and outcomes such as C. diff.
“While C. difficile is not an antibiotic resistant organism in the sense of it developing important resistance to the drugs used to treat CDI, it is intrinsically resistant to many antibiotics and commonly acquires new resistance to antibiotics used to treat other common infections," McDonald told FierceHealthcare. This "use of these antibiotics then selects for specific strains of C. difficile, some of which may be more virulent and likely to spread, causing serious infections and deaths."
For example, a fluoroquinolone-resistant strain of C. diff emerged in 2000 but has since declined, which may account for the reduction in association rates between that class of antibiotics and CDI incidence. As prescribing patterns change in response to stewardship practices or otherwise, keeping tabs on these associations between antibiotic use and outcomes can guide local, regional and national policy efforts.
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McDonald points out that the National Health Safety Network’s (NHSN’s) Antimicrobial Use and Resistance module currently includes three classes of antibiotics in its standardized antibiotic administration ratio (SAAR) for high-risk antibiotics associated with CDIs. “Our results suggest that SAARs such as this one, designed to guide stewardship for the reduction of specific antibiotic-resistant outcomes, should be regularly re-evaluated to be sure the most relevant antibiotics are included,” he said.
Provided the study’s findings are validated in other contemporary data sets, McDonald suggests the next step should be to develop processes for implementing ongoing reassessments in the NHSN Antimicrobial Use and Resistance module.