Antibiotic Cycling Not Linked to Lower MRSA, C Diff Incidence

Antibiotic cycling is not linked to a reduced incidence of health care-associated methicillin-resistant Staphylococcus aureus (MRSA) or health care-associated Clostridium difficile infection, the results of a recent study suggest.

In the January 2019 issue of Emerging Infectious Diseases, the monthly peer-reviewed public health journal of the US Centers for Disease Control and Prevention, investigators at a teaching hospital in Northern Ireland discuss the results of implementing a 2-year antibiotic cycling policy.

“[Health care-associated C diff infection] incidence did not change, [and] health care-associated-MRSA incidence increased significantly in the intervention hospital,” Geraldine Mary Conlon-Bingham, MPharm, PhD, from Queen’s University, Belfast, Northern Ireland, United Kingdom, and colleagues wrote.

According to Dr. Conlon-Bingham and colleagues, antibiotic cycling has been suggested as a method to both increase antimicrobial heterogeneity and reduce the emergence of antimicrobial resistance.

With this in mind, the investigators designed a study to examine the effect of antibiotic cycling on the incidence of health care-associated-MRSA and health care-associated C diff infection, as well as on the incidence of infections caused by extended-spectrum β-lactamase (ESBL)—producing organisms.

From October 2013 to September 2015, they introduced cyclical restrictions of amoxicillin-clavulanic acid, piperacillin-tazobactam, and clarithromycin.

They developed their policy based on a retrospective study of epidemiologic data that helped to identify which antimicrobial drugs to restrict—because of significant associations with health care-associated C diff infection and health care-associated MRSA—and for which time periods.

In the antibiotic cycling schedule, use of piperacillin-tazobactam and macrolides was restricted to alternate months, while use of amoxicillin-clavulanic acid was restricted to 2 consecutive months every 4 months.

The investigators used segmented regression analysis to compare outcomes between the hospital where the cycling policy was implemented (intervention) and another hospital with a standard policy (control hospital).

These outcomes included: the incidences of health care-associated MRSA, health care-associated C diff infection, and new ESBL isolates, as well as changes in resistance patterns of the health care-associated MRSA and ESBL organisms.

The team found that, during antibiotic cycling, the incidence of health care-associated C diff infection did not change at the intervention hospital, and that of health care-associated-MRSA increased significantly. Conversely, they found that the resistance of new ESBL isolates to amoxicillin-clavulanic acid and piperacillin-tazobactam decreased significantly.

However, when the antibiotic cycling policy ended and the intervention hospital returned to using its standard policy, the incidence of health care-associated MRSA decreased, the incidence of new ESBLs increased, and ESBL resistance to piperacillin-tazobactam increased.

The team noted that their antibiotic cycling policy was not designed to reduce ESBL incidence. However, they monitored this to identify for inadvertent increases as a result of the policy. Because the increase in ESBLs did not continue throughout the postintervention period, they suggest that the rise may have been a delayed effect of the policy.

“Our results suggest that antibiotic cycling is not an appropriate strategy to reduce the incidence of [health care-associated] MRSA or [health care-associated C diff infection] but might be effective in reducing ESBL resistance,” the investigators concluded.

“The increased use of fluoroquinolones in a cyclical fashion was not associated with any increase in [health care-associated C diff infection], suggesting that this method may help diversify antimicrobial drug use while mitigating adverse effects.”