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

Whipworm infection promotes bacterial invasion, intestinal microbiota imbalance, and cellular immunomodulation

Infections with Trichuris trichiura are among the most common causes of intestinal parasitism in children worldwide, and the diagnosis is based on microscopic egg identification in the chronic phase of the infection. During parasitism, the adult worm of the trichurid nematode maintains its anterior region inserted in the intestinal mucosa, which causes serious damage and which may open access for gut microorganisms through the intestinal tissue. The immune-regulatory processes taking place during the evolution of the chronic infection are still not completely understood. By use of the Swiss Webster outbred mouse model, mice were infected with 200 eggs, and tolerance to the establishment of a chronic Trichuris muris infection was induced by the administration of a short pulse of dexamethasone during nematode early larval development. The infected mice presented weight loss, anemia, an imbalance of the microbiota, and intense immunological cell infiltration in the large intestine. It was found that mice have a mixed Th1/Th2/Th17 response, with differences being found among the different anatomical locations. After 45 days of infection, the parasitism induced changes in the microbiota composition and bacterial invasion of the large intestine epithelium. In addition, we describe that the excretory-secretory products from the nematode have anti-inflammatory effects on mouse macrophages cultured in vitro, suggesting that T. muris may modulate the immune response at the site of insertion of the worm inside mouse tissue. The data presented in this study suggest that the host immune state at 45 days postinfection with T. muris during the chronic phase of infection is the result of factors derived from the worm as well as alterations to the microbiota and bacterial invasion. Taken together, these results provide new information about the parasite-host-microbiota relationship and open new treatment possibilities.Fil: Schachter, Julieta. Universidade Federal do Rio de Janeiro; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: De Oliveira, Dayane Alvarinho. Universidade do Estado de Rio do Janeiro; BrasilFil: Da Silva, Camila Marques. Universidade Federal do Rio de Janeiro; BrasilFil: De Barros Alencar, Alba Cristina Miranda. Hospital Universitario Antonio Pedro; BrasilFil: Duarte, Michelle. Universidade Federal do Rio de Janeiro; BrasilFil: Müller Pereira da Silva, Matheus. Universidade Federal do Rio de Janeiro; BrasilFil: De Paula Rosa Ignácio, Ana Claudia. Universidade do Estado de Rio do Janeiro; BrasilFil: Lopes Torres, Eduardo José. Universidade do Estado de Rio do Janeiro; Brasi