Association between antibiotic pressure and the risk of colonization/infection by multidrug-resistant Acinetobacter baumannii complex: a time series analysis.

OBJECTIVE

To analyze the association between antibiotic pressure and the risk of colonization/infection by Acinetobacter baumannii complex (AB), evaluating both the individual and general prescriptions of antibiotics.

METHODS

This is an analytical, observational, case-control study on patients admitted to an Intensive Care Unit (ICU) during an AB outbreak (14 months). A five-year time series was constructed with the monthly incidence of cases of infection/colonization with strains of AB resistant to each antibiotic administered and with the monthly consumption of these antibiotics in the ICU.

RESULTS

We identified 40 patients either infected (23) or colonized (17) by AB and 73 controls. We found an epidemic multidrug-resistant clone of AB in 75% of cases. Risk factors associated with the development of AB infection/colonization were: greater use of medical instruments, the presence of a tracheostomy, cutaneous ulcers, surgical lesions and prior antibiotic therapies. The regression analysis of individual use of antibiotics showed that prior treatment with ceftazidime, ceftriaxone, amoxicillin/clavulanate, imipenem, levofloxacin, linezolid, and vancomycin was a risk factor for acquiring AB. ARIMA models showed that the relationship were greatest and statistically significant when the treatment occurred between 6 months (ceftazidime) and 9 months (imipenem and levofloxacin) prior.

CONCLUSIONS

The dynamic and aggregate relationship between the incidence of infection/colonization by multidrug-resistant strains of AB and prior antibiotic treatment was statistically significant for intervals of 6 to 9 months.