Matrix-assisted laser desorption ionization-time of flight: a promising alternative method of identifying the major coagulase-negative Staphylococci species

Abstract INTRODUCTION. This study aimed to evaluate different methods for differentiation of species of coagulase-negative staphylococci (CoNS) that caused infections in hospitalized immunocompromised patients. METHODS. A total of 134 CoNS strains were characterized using four different methods. RESULTS. The results of matrix assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) analysis were in complete agreement with those of tuf gene sequencing (kappa index = 1.00). The kappa index of Vitek 2® Compact analysis was 0.85 (very good) and that of the conventional method was 0.63 (moderate). CONCLUSIONS . MALDI-TOF MS provided rapid and accurate results for the identification of CoNS (134; 100%).

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.