title: Mathematical model to quantify the effects of risk factors on carbapenem-resistant Acinetobacter baumannii.
abstract: Carbapenem-resistant Acinetobacter baumannii (CRAB) infections are increasing, and they are associated with an increased risk of mortality in hospitalized patients. Linear regression is commonly used to identify concurrent trends, but it cannot quantify the relationship between risk factors and resistance. We developed a model to quantify the impact of antibiotic consumption on the prevalence of CRAB over time. Data were collected from January 2007 to June 2013 from our institution. Quarterly antibiotic consumption was expressed as defined daily dose/1,000 inpatient days. Six-month prevalence of CRAB was expressed as a percentage of all nonrepeat A. baumannii isolates tested. Individual trends were identified using linear regression. Antibiotic consumption from 2007 to 2011 was input as a step function in a relationship with CRAB. Model fit was evaluated by visual inspection and the residual sum of squares. The final model was validated using the best-fit (95% confidence interval) parameter estimates and antibiotic consumption to predict CRAB prevalence from January 2012 to June 2013. Cefepime, ertapenem, and piperacillin-tazobactam consumption and CRAB prevalence increased significantly over time. CRAB prevalence was best correlated to ertapenem (use sensitive; r2=0.76), and accounting for additional concurrent antibiotic use did not significantly improve model fit. Prospective validation with ertapenem consumption correlated well with CRAB observations, suggesting good predicting ability of the model. Our model provided the quantitative impact of antibiotic consumption on CRAB. We plan to further refine this model to account for multiple risk factors. Interventions should focus on controlling risk factors with the highest impact on resistance.
authors: Department of Pharmacy, Faculty of Science, National University of Singapore, Singapore Department of Pharmacy, Tan Tock Seng Hospital, Singapore.
authors: Michelle W
authors: MW
authors: Tan
authors: Communicable Disease Center, Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore.
authors: David C
authors: DC
authors: Lye
authors: Department of Pharmacy, Tan Tock Seng Hospital, Singapore.
authors: Tat-Ming
authors: TM
authors: Ng
authors: Department of Chemical & Biomolecular Engineering, College of Engineering, University of Houston, Houston, Texas, USA.
authors: Michael
authors: M
authors: Nikolaou
authors: Department of Chemical & Biomolecular Engineering, College of Engineering, University of Houston, Houston, Texas, USA Department of Clinical Sciences and Administration, College of Pharmacy, University of Houston, Houston, Texas, USA vtam@uh.edu.
authors: Vincent H
authors: VH
authors: Tam
mesh_terms: D000151:Acinetobacter Infections / Q000188:drug therapy* / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000187:drug effects*; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D015780:Carbapenems / Q000627:therapeutic use*; D003428:Cross Infection / Q000188:drug therapy / Q000382:microbiology / Q000517:prevention & control; D006801:Humans; D015233:Models, Statistical; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D018440:beta-Lactam Resistance
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems