Molecular epidemiology of multidrug-resistant Acinetobacter baumannii infection in two hospitals in Central Brazil: the role of ST730 and ST162 in clinical outcomes.

Abstract

Acinetobacter baumannii is a major cause of multidrug-resistant nosocomial infections. The characteristics of A. baumannii at two hospitals in a city in Central Brazil are described by analysing the phenotypes and molecular profiles of isolates recovered from 87 patients. The isolates were identified and their antimicrobial susceptibility was evaluated using the the Bact/Alert 3D and Vitek2 methods. Patients' clinical data were obtained from medical files. Genes associated with resistance to carbapenems were analysed by multilocus sequence typing, clinical and bacteriological variables were analysed by descriptive statistics, and logistic models were generated to adjust the associations. Sixty-four (73.5 %) out of 87 A. baumannii isolates analysed were from patients in intensive care. The mortality rate was 43.7 %. Eighty (91.9 %) isolates were resistant to imipenem and 86 were susceptible to colistin (98.8 %). The blaOXA-23 gene (78.2 %) and its upstream insertion ISAba1 (55.2 %) were predominant, followed by blaOXA-24 (55.2 %) and blaOXA-143 (28.7 %). The blaOXA-23 gene and ISAba1 were independently associated with resistance to imipenem (P<0.05). There were 13 different sequence types (STs) among the 35 isolates. ST1 (nine; 25.7 %), ST162 (eight; 22.8 %) and ST730 (six; 17.1 %) were the most common, and four new STs were identified. The isolates were grouped into five clonal complexes (CC1, CC15, CC79, CC108 and CC162) plus a singleton using eburst. Respiratory infection, age >60 years and use of noradrenaline were factors associated with fatality. ST730 (CC79) was associated with higher mortality (P<0.05) and ST162 (CC162) was associated with increased survival probability (P<0.05).