Phenotypic and genotypic characterization of Gram-negative bacilli resistant to antimicrobials of clinical interest isolated from healthy cats

• Grant number: 24/01213-2
• Support Opportunities: Scholarships in Brazil - Master
• Start date: April 01, 2025
• End date: January 31, 2026
• Field of knowledge: Biological Sciences - Microbiology - Applied Microbiology
• Principal Investigator: Ana Lúcia da Costa Darini
• Grantee: Stella Cabral
• Host Institution: Faculdade de Ciências Farmacêuticas de Ribeirão Preto (FCFRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

Antimicrobial resistance is considered a global public health problem. The spread of resistance genes is a critical issue, especially in the context of the One Health approach, which brings the idea of connecting human, animal, and environmental health. The project aims to identify and phenotypically and genotypically characterize antibiotic-resistant gram-negative bacilli (GNB) isolated from rectal swabs of healthy cats with no clinical manifestations that have not been treated with antibiotics in the last month. To this end, the isolates are being selected on MacConkey culture medium (Oxoid), plus cefotaxime (MC-CTX) at a concentration of 2µg/mL. The bacterial samples are being identified by MALDI-TOF MS (Matrix Associated Laser Desorption-Ionization - Time of Flight) and the species of the Klebsiella pneumoniae complex and the Klebsiella oxytoca complex are being confirmed using the MALDI TypeR platform of the Pasteur Institute (https://maldityper.pasteur.fr/). In addition, the antibiotic sensitivity profile of the selected BGNs is being determined using the diffusion disk method and interpreted as described and recommended by the Clinical Laboratory Standards Institute (CLSI, 2023 and CLSI VET, 2023). The detection of resistance genes to beta-lactam antibiotics, aminoglycosides, plasmid-mediated quinolones, and polymyxin, as well as the genetic diversity of plasmids carrying resistance genes of interest, will be carried out by polymerase chain reaction (PCR). Pulsed-field electrophoresis (PFGE) will be used to determine the genetic variability of Enterobacterales species isolated from cats living together. Bacteria that show resistance to carbapenems will have their complete genome sequenced and analyzed. To date, 76 rectal swabs have been collected from cats, 20 of which showed BGN growth. From these 20 cats, 30 BGN were isolated, 16 of which were Enterobacterales, and 11 were non-fermenting gram-negative bacilli (BGN-NF). Eleven Enterobacterales were considered multi-drug resistant (MDR), as they were resistant to three or more classes of antimicrobials. Understanding that the cat population has been increasing in Brazil in recent years (2020-2023), this project will contribute to the epidemiology of antimicrobial resistance genes and expand knowledge about the zoonotic potential of these bacteria that can affect human and animal health.