Acinetobacter species in laboratory mice: species survey and antimicrobial resistance.

The extra-hospital epidemiology of Acinetobacter infections is a subject of debate. In recent years, the prevalence of animal multidrug-resistant Acinetobacter infections has increased considerably. The goal of the present study was to specify Acinetobacter species isolated from laboratory mice and to test them for their antimicrobial susceptibility. During routine microbiological monitoring of laboratory mice, 12 Acinetobacter spp. were isolated. By means of 16S rRNA and rpoB gene sequencing, seven of the isolates were identified as Acinetobacter radioresistens, three isolates belonged to Acinetobacter genomospecies 14BJ, one isolate was classified as Acinetobacter pitii and one as Acinetobacter sp. ANC 4051. The distribution of the minimal inhibitory concentration (MIC) values was uniform for 21 of the 23 antimicrobial agents tested, whereas a broad MIC distribution was recorded for tulathromycin and streptomycin. The MIC values recorded were low for the majority of the antibiotics tested. Nevertheless, very high MIC values, which will probably render a therapeutic approach using these substances unsuccessful, were recorded for florfenicol, tiamulin, tilmicosin and cephalothin in most of the isolates. In conclusion, we document colonization of laboratory mice with different Acinetobacter species, displaying similar antibiotic susceptibility profiles, with possible implications in the Acinetobacter epidemiology as well as in the husbandry and experimentation of the colonized animals.