Recognition of two novel phenons of the genus Acinetobacter among non-glucose-acidifying isolates from human specimens

Genomic species diversity among 147 Acinetobacter clinical isolates not bel onging to the A. calcoaceticus-A. baumannii (ACB) complex was investigated by phenotypic and genotypic identification methods. The isolates were obtai ned between 1991 and 1999 from numerous diagnostic laboratories in the Czec h Republic and were studied by numerical probabilistic identification using two biochemical frequency matrices and amplified rDNA restriction analysis (ARI)RA), Their final identification was derived from the combined phenoty pic and ARDRA results. In total, 102 isolates were unambiguously (n = 89) o r presumptively (n = 13) identified as A. lwoffii (n = 63), genomic species 13BJ/14TU (n = 9), A, johnsonii (n = 7), A. haemolyticus (n = 6), A, junii (n = 5), and other genomic species (n < 5 isolates each). Forty-five isola tes could not be identified as belonging to any described species, Among th e unidentified isolates two large groups of non-glucose-acidifying, nonhemo lytic, and non-gelatinase-producing isolates were distinguished. These grou ps, designated phenon 1 (n = 17) and phenon 2 (n = 15), had distinctive phe notypic features and novel ARE)RA profiles, which suggests that they repres ent hitherto undescribed Acinetobacter species. Phenon 2 included mainly cl inically insignificant isolates from outpatients, while phenon 1 comprised clinically relevant isolates mostly from the blood of hospitalized patients , and its precise taxonomic definition may therefore be of medical importan ce. Overall, the development of practical methods for identification requir ed for the elucidation of the biological significance of the (genomic) spec ies within the genus Acinetobacter remains a challenging task.