Bacteremia and meningitis caused by OXA-23-producing Acinetobacter baumannii - molecular characterization and susceptibility testing for alternative antibiotics

Abstract

Background: Carbapenem-resistant Acinetobacter baumannii infection is a concern in developing countries due to high incidence, few therapeutic options, and increasing costs.

Objective: Characterize and analyze the antibiotic susceptibility patterns of carbapenem-resistant A. baumannii isolates and evaluate clinical data of meningitis and bacteremia caused by this microorganism.

Methods: Twenty-six A. baumannii isolates from 23 patients were identified by MALDI-TOF and automated methods and genotyped using pulsed field genotyping electrophoresis. Clinical data and outcomes were evaluated. Susceptibility of isolates to colistin, tigecycline, meropenem, imipenem, and doxycycline was determined.

Results: Mortality due to A. baumannii infections was 73.91%; all patients with meningitis and 7/8 patients with ventilator-associated pneumonia died. All isolates were susceptibility to polymyxin (100%; MIC₅₀, MIC₉₀: 1μg/mL, 1μg/mL) and colistin (100%; MIC₅₀, MIC₉₀: 2μg/mL, 2μg/mL), and 92% were susceptible to tigecycline (MIC₅₀, MIC₉₀: 1μg/mL, 1μg/mL) and doxycycline (MIC₅₀, MIC₉₀: 2μg/mL, 2μg/mL). bla_OXA-23 was identified in 24 isolates. Molecular typing showed 8 different patterns: 13 isolates belonged to pattern A (50%).

Conclusion: Carbapenem-resistant A. baumannii infections mortality is high. Alternative antimicrobial therapy (doxycycline) for selected patients with carbapenem-resistant A. baumannii infection should be considered.

Keywords: Acinetobacter baumannii; Carbapenem; Doxycycline; Multidrug resistance; Oxacillinases.

Fig. 1

Dendrogram of 26 isolates from 23 patients with Acinetobacter baumannii causing infection. See Table 1 to correlation of isolates and site of infection.