Biofilm formation and multiresistance to antimicrobials in Rhodococcus species, identified by mass spectrometry, isolated from foals.

• Grant number: 24/20675-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2025
• End date: January 31, 2026
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Preventive Veterinary Medicine
• Principal Investigator: Marcio Garcia Ribeiro
• Grantee: Giovanna Bertelli Borges
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

Rhodococcus equi is a well-known opportunistic bacteria found in soil and organic matter of livestock farms, and eliminated through the feces of multihost domestic animals. The pathogen is characterized by facultative intracellular infections in phagocytes, inducing pyogranulomatous lesions. Among foals, R. equi infections occur mainly secondary inhalation of aerosols, and ingestion of water and food contaminated with fecal material. Pyogranulomatous pneumonia (cavitary), mesenteric lymphadenitis, colitis, arthritis, and organ abscesses have been seen as the main clinical signs of equine rhodococcosis. To date, an increase of multidrug-resistant R. equi isolates has been reported among drugs commonly used in therapy of rhodococcosis in foals (i.e., rifampin, erythromycin, and sulfonamides/trimethoprim). Due to relation between human infections and contact with horses and farm environment, has been hypothesized that the treatment of R. equi in foals could increase the selective pressure to multidrug-resistant isolates, as well as favor the human infections by resistant ones, impairing the therapy of human patients. Thus, is crucial the epidemiological vigilance of multidrug resistance of R. equi isolated from foals. In addition to R. equi resistance to drugs related to improper use of antimicrobials, the resistance of the pathogen could also be influenced by biofilm formation, which comprises a complex aggregated communities of the bacteria that may limit the action of conventional antimicrobials. Considering this scenario, the present study aims to investigate biofilm formation and antimicrobial susceptibility patterns of ~40 R. equi isolates from foals with pneumonia. The isolates will be identified at the species level using mass spectrometry, and subjected to in vitro disk diffusion method, using 16 antimicrobials from eight distinct classes (i.e., aminoglycosides, phenicols, carbapenems, fluoroquinolones, macrolides, penicillins and derivatives, rifamycins, and sulfonamides. Also, all isolates will be subjected to in vitro minimal inhibitory concentration test (MIC) using impregnated tapes with concentration gradients of antimicrobials of the three main associations used in vivo therapy (rifampin + erythromycin, rifampicin + clarithromycin, and rifampicin + azithromycin). The present study pretends contribute to molecular identification of Rhodococcus species, the epidemiological vigilance of multidrug-resistant isolates, in addition to biofilm formation investigation among strains recovered from foals with pneumonia.