Identification of thresholds in relationships between specific antibiotic use and carbapenem-resistant Acinetobacter baumannii (CRAb) incidence rates in hospitalized patients in Jordan.

Background Antibiotic resistance is a major threat to public health worldwide. The relationship between the intensity of antibiotic use and resistance might not be linear, suggesting that there might be a threshold of antibiotic use, beyond which resistance would be triggered. Objectives To identify thresholds in antibiotic use, below which specific antibiotic classes have no significant measurable impact on the incidence of carbapenem-resistant Acinetobacter baumannii (CRAb), but above which their use correlates with an increase in the incidence of CRAb. Methods The study took place at a tertiary teaching hospital in Jordan. The study was ecological in nature and was carried out retrospectively over the period January 2014 to December 2019. The outcome time series for this study was CRAb cases. The primary explanatory variables were monthly use of antibiotics and the use of alcohol-based hand rub (ABHR). Non-linear time-series methods were used to identify thresholds in antibiotic use. Results Non-linear time-series analysis determined a threshold in third-generation cephalosporin and carbapenem use, where the maximum use of third-generation cephalosporins and carbapenems should not exceed 8 DDD/100 occupied bed days (OBD) and 10 DDD/100 OBD, respectively. ABHR had a significant reducing effect on CRAb cases even at lower usage quantities (0.92 L/100 OBD) and had the most significant effect when ABHR exceeded 3.4 L/100 OBD. Conclusions The identification of thresholds, utilizing non-linear time-series methods, can provide a valuable tool to inform hospital antibiotic policies through identifying quantitative targets that balance access to effective therapies with control of resistance. Further studies are needed to validate the identified thresholds, through being prospectively adopted as a target for antimicrobial stewardship programmes, and then to evaluate the impact on reducing CRAb incidence.