Relationship Between Different Resistance Mechanisms and Virulence in .

This study analyzed the virulence of several strains expressing different resistance mechanisms using the infection model. Strains susceptible/resistant to carbapenems (presenting class D (OXA-23, OXA-24), class B metallo-β-lactamase (MBL) (NDM-1), penicillin binding protein (PBP) altered and decreased expression of Omp 33-36 kDa) and isogenic strains susceptible/resistant to colistin (presenting loss of lipopolysaccharide (LPS) and A mutations) were included to evaluate the virulence using the infection model. The nematode killing assay, bacterial ingestion in worms, and bacterial lawn avoidance assay were performed with the Fer-15 mutant line. strains generally presented low virulence, showing no difference between carbapenem-resistant strains (expressing class D, MBLs, or altered PBP) and their isogenic susceptible strains. In contrast, the absence of the Omp 33-36 kDa protein in the was associated with a decrease of virulence, and a significant difference was observed between colistin-resistant mutants and their susceptible counterpart when the mechanism of resistance was associated with the loss of LPS but not with its modification. Resistance to carbapenems in associated with the production of OXA-type or NDM-type enzymes does not seem to affect their virulence in the infection model. In contrast, the presence of Omp 33-36 kDa, and high level resistance to colistin related with the loss of LPS, might contribute with the virulence profile in