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: 1 µg/mL, 1 µg/mL) and colistin (100%; MIC₅₀, MIC₉₀: 2 µg/mL, 2 µg/mL), and 92% were susceptible to tigecycline (MIC₅₀, MIC₉₀: 1 µg/mL, 1 µg/mL) and doxycycline (MIC₅₀, MIC₉₀: 2 µg/mL, 2 µg/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; Oxacillinases; Carbapenem; Multidrug resistance; Doxycycline