Table 1. Overview of a study on the effects of an antibiotic drug cycling policy on the incidence of HA-MRSA and HA-CDI in 2 hospitals according to the Orion Statement, Northern Ireland, UK*.

Variable	Definition
Population characteristics	The NHSCT is 1 of 5 Health and Social Care Trusts in Northern Ireland, serving ≈436,000 persons. The NHSCT has 2 acute care hospitals: AAH (intervention hospital), containing 447 beds, and CH (control hospital) containing 213 beds. These hospitals provide acute medical, surgical ICU, neonatal, pediatric, and maternity services for the NHSCT. Study wards comprised all adult inpatient wards; ICU, NNU, pediatric, and palliative care wards were excluded.
Retrospective study, 2007 Apr–2012 Mar	The intervention design was as follows: An antibiotic cycling policy was devised based on results of an analysis of HA-CDI and HA-MRSA incidence in AAH during April 2007–March 2012. This analysis identified macrolides and TZP as significantly associated with HA-MRSA with lag times of 1 mo. AMC was identified as significantly associated with HA-CDI with a lag time of 2 mo. Consequently, an antibiotic cycling policy was implemented in AAH that restricted the use of TZP and macrolides in alternate months, and AMC was restricted for 2 consecutive months in every 4 months over a 2-year period.
Comparison of effect of antibiotic cycling policy between AAH and CH, 2011 Nov–2016 Sep†	Comparison of outcome measures before and after the introduction of an antibiotic cycling policy in AAH and between the intervention hospital (AAH) and control hospital (CH). Reintroduction of standard antibiotic policy in AAH during October 2015–September 2016 to determine whether any effect observed during the intervention period was reversed upon return of the standard policy. Comparison of outcome measures between intervention and postintervention periods occurred for AAH only.
General infection control measures	Chlorine dioxide 275 ppm was used for routine environmental decontamination through the study period in both hospitals. Monthly environmental cleanliness audits were conducted on all wards. Throughout the intervention period, infection control practices did not change.
Isolation and elimination policy	All patients in whom CDI was diagnosed were placed in an isolation room. Patients identified as colonized or infected with MRSA were placed in an isolation room when one was available. However, in the event of a shortage of these rooms, these patients were placed in cohort bays.
MRSA admission screening	In both hospitals all patients with a history of MRSA; admitted from a residential or nursing home; admitted from another hospital; admitted to the ICU, NNU, or renal unit; and oncology patients were screened.
Antibiotic stewardship activities	After a CDI outbreak in 2008, restrictions were put in place throughout the NHSCT regarding use of fluoroquinolones, cephalosporins, clindamycin, and carbapenems (4). All requests for restricted antibiotic drugs are reviewed by the antimicrobial pharmacists and consultant microbiologists. Weekly audits were conducted on adherence to empirical antibiotic guidelines on all wards.
Definitions	1. HA-CDI incidence: No. patients presenting with CDI >48 h after admission to AAH or CH or any patient presenting with CDI <48 h after admission to these hospitals who had an admission to the same hospital in the preceding 4 wks (24).
	2. Other CDI incidence: No. patients presenting with CDI <48 h from admission with no admission to AAH or CH in the preceding 4 wks.
	3. HA-MRSA incidence: No. patients who tested negative or were not screened for MRSA on admission but tested positive for MRSA >48 h after admission (24). Each patient was counted once per admission.
	4. Other MRSA incidence: No. patients who tested positive for MRSA <48 h after admission.
	5. New ESBL incidence: No. newly identified patients from whom an ESBL-producing organism was isolated or known patients from whom a new ESBL strain was isolated. Each patient was counted once per admission
	6. Resistant patterns (MRSA and ESBL): No. isolates per month. Duplicate isolates identified within 7 d were excluded.

*Based on (25). AAH, Antrim Area Hospital; AMC, amoxicillin/clavulanic acid; CDI, Clostridioides difficile infection; CH, Causeway Hospital; ESBL, extended-spectrum β-lactamase; HA, healthcare-associated; ICU, intensive care unit; MRSA, methicillin-resistant Staphylococcus aureus; NHSCT, Northern Health and Social Care Trust; NNU, neonatal unit; TZP, piperacillin/tazobactam.
†Preintervention period, 2011 Nov–2013 Sep; intervention period, 2013 Oct–2015 Sep; postintervention period, 2015 Oct–2016 Sep.