and Virulence Potential of the Emergent Species of the (Ab) Group.

The increased use of molecular identification methods and mass spectrometry has revealed that spp. of the (Ab) group other than are increasingly being recovered from human samples and may pose a health challenge if neglected. In this study 76 isolates of 5 species within the Ab group ( = 16, = 12, = 16, = 20, and = 12), were compared in terms of antimicrobial susceptibility, carriage of intrinsic resistance genes, biofilm formation, and the ability to kill in an infection assay. In agreement with previous studies, antimicrobial resistance was common among while all other species were generally more susceptible. Carriage of genes encoding different efflux pumps was frequent in all species and the presence of intrinsic class D β-lactamases was reported in , (heterotypic synonym of ) and but not in and . and presented weaker pathogenicity in our and models than , and, especially, . Isolates from the former species showed decreased biofilm formation and required a longer time to kill nematodes. These results suggest relevant differences in terms of antibiotic susceptibility patterns among the members of the Ab group as well as highlight a higher pathogenicity potential for the emerging species of the group in this particular model. Nevertheless, the impact of such potential in the human host still remains to be determined.