Antibiotic resistance mechanisms in Acinetobacter spp. strains isolated from patients in a paediatric hospital in Mexico

Objectives: The aim of this study was to identify Acinetobacter spp. strains from paediatric patients, to determine their genetic relationship, to detect antibiotic resistance genes and to evaluate the role of efflux pumps in antibiotic resistance. Methods: A total of 54 non-duplicate, non-consecutive Acinetobacter spp. isolates were collected from paediatric patients. Their genetic relationship, antibiotic resistance profile, efflux pump activity, antibiotic resistance genes and plasmid profile were determined. Results: The isolates were identified as 24 Acinetobacter haemolyticus, 24 Acinetobacter calcoaceticus-baumannii (Acb) complex and 1 strain each of Acinetobacterjunii, Acinetobacter radioresistens,Acinetobacter indicus, Acinetobacter lwoffii, Acinetobacter ursingii and Acinetobacter venetianus. The 24 A. haemolyticus were considered genetically unrelated. One strain was resistant to carbapenems, two to cephalosporins, two to ciprofloxacin and sixteen to aminoglycosides. The antibiotic resistance genes bla(OXA-214) (29%), bla(OXA-215) (4%), bla(OXA-264) (8%), bla(OXA-265) (29%), bla(NDM-1) (4%), aac(6 )-Ig (38%) and the novel variants bla(OXA-575) (13%), bla(TEM-229) (75%), aac(6 )-Iga (4%), aac(6 )-Igb (13%) and aac(6)-Igc (42%) were detected. Among 24 Acb complex, 5 were multidrug-resistant, carbapenem-resistant strains carrying bla(OXA-51) and bla(OXA-23); they were genetically related and had the same plasmid profile. Other species were susceptible. In some strains of A. haemolyticus and Acb complex, the role of RND efflux pumps was evidenced by a decrease in the MIC5 for cefotaxime, amikacin and ciprofloxacin in the presence of an efflux pump inhibitor. Conclusions: This study identified isolates of A. haemolyticus carrying new beta-lactamase variants and shows for the first time the contribution of efflux pumps to antibiotic resistance in this species. (C) 2020 The Author(s). Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy.