Virulence profile of tigecycline-resistant Gram-negative bacilli isolated from river waters using the Caenorhabditis elegans infection model / Perfil de virulência de bacilos Gram-negativos resistentes à tigeciclina isolados das águas dos rios usando o modelo de infecção por Caenorhabditis elegans

Last-resort antibiotics act as ultimate force to overcome multidrug-resistant strains infections. Cases of tigecycline resistance in gram-negative bacilli in clinical settings are reported worldwide, however, there is no data related to tigecycline resistant strains in river water. This study demonstrates seven tigecycline gram-negative bacilli isolated from river water in Rio de Janeiro metropolitan area, their resistance genes, ability of biofilm formation with/without antibiotics and behavior using the nematode Caenohabidits elegans as infection in vivo model. From 24 gram-negative isolated strains, 16 (66.6%) were classified as multidrug-resistant, however, seven (29.1%) presented resistant to all antimicrobial agents tested, including tigecycline and have been identified by MALDI-TOF as A. baumannii, E. aerogenes and P. agglomerans. All tigecycline-resistant strains presented amplification products for ESBL, AME and PMQR and ability of biofilm formation on hydrophilic and hydro­phobic abiotic surfaces with and without antimicrobial agents. The presence of antimicrobials did not inhibit biofilm formation. Tigecycline-resistant strains differed of OP50 control with P<0,0001 indicating its virulence potential, however, none of them were capable to kill all nematodes during 5 days infection. In conclusion, tigecycline-resistant gram-negative strains have important global public health implications due to the therapeutic problems they pose. Further studies and continuous surveillance of tigecycline-resistant strains in both clinical and aquatic environment remains necessary to track and understand the dissemination of tigecycline resistance