Susceptibility to antibiotic combinations of <i>Klebsiella pneumoniae</i> and <i>Acinetobacter baumannii</i> strains isolated from COVID-19 patients

Abstract

Objective. To assess the susceptibility of K.pneumoniae and A.baumanii strains isolated from hospitalized COVID-19 patients to antibiotics and their combinations.Materials and methods. The minimum inhibitory concentrations (MICs) of meropenem and colistin were determined for 47 A.baumannii and 51K.pneumoniaestrains isolated from the hospitalized COVID-19 patients by the broth microdilution method. The susceptibility to 11 antibiotic combinations was assessed using the method of multiple combination bactericidal testing.Results. Colistin resistance was detected in 31.9 % of A.baumannii strains (MIC50 — 0.5 mg/l, MIC90 — 16 mg/l) and in 80.4 % of K.pneumoniaestrains (MIC50 — 16 mg/l, MIC90 — 256 mg/l). It has been shown that double antibiotic combinations with the inclusion of colistin exhibit bactericidal or bacteriostatic activity against 76.6–87.2 % of A.baumannii strains. Combinations with the addition of meropenem, colistin and macrolides exhibited bactericidal activity against 78.4–80.4 % of K.pneumoniae strains. Combinations of two carbapenems were not active, the combination of meropenem-colistin had a bactericidal effect only in 13.7 % of K.pneumoniae strains.Conclusion. Widespread colistin resistance was found in carbapenem-resistant K.pneumoniae and A.baumannii strains isolated from the hospitalized COVID-19 patients. The combinations of antibiotics that have a synergistic antibacterial effect in their pharmacokinetic/pharmacodynamic concentrations have been determined.