Patógenos emergentes para a piscicultura: caracterização genética e sensibilidade a antimicrobianos

Abstract

Fish production and consumption are increasing in a specific way around the world. In Brazil, despite its vast territory, marine fish farming is still found here in the production of fish in inland waters. In both types of cultivation, health problems cause economic losses. Edwardsiella tarda and Francisella salimarina (syn. F. marina) are Gram-negative bacteria capable of causing harm to freshwater and marine fish, respectively. Know the epidemiological aspects regarding these pathogens, favoring the construction of disease prevention and control measures. Therefore, the objective was to describe outbreaks on clothing and cobia, performing the isolation and identification of the bacterial isolates found. Furthermore, analyze the genetic and peptide diversities of E. tarda and F. salimarina strains, and evaluate the resistance profile of the isolates to antimicrobials. Ten groupers and ten cobias were sent for bacteriological examination. Grouper and cobia organs were subjected to histopathological examination. The isolates found were identified by MALDI-ToF and molecular methods. The genetic diversity of E. tarda isolates, from tambaquis, and F.salimarina was confirmed using the REP-PCR technique and peptide typing using a Main Spectra Profile (MSP) dendrogram. Susceptibility to antimicrobials was assessed by antibiogram and, in addition, the presence of resistance genes was extracted from E. tarda isolates. The fish received showed non-specific clinical signs of infectious diseases. In histopathology, granulomatous lesions were seen in the spleen, liver and heart of some cobias. F. salimarina was predominantly isolated from groupers and cobia. The analyzes of genetic and peptide diversities typified E. tarda strains into different groups. Regarding F. salimarina, all isolates were clonally related. Provisional epidemiological breakpoints were calculated for E. tarda isolates with respect to antimicrobials. A total of 26.76%, 26.76%, 7.04%, 18.30%, 11.26% and 8.45% of these isolates were classified as NWT for oxytetracycline, norfloxacin, lincomycin-spectinomycin, amoxicillin, florfenicol and trimethoprim-sulfamethaxazole, respectively. Of these, 15.49% were considered multidrug resistant. The blaTEM, tetA, sul1 and floR genes were found in 39.43%, 47.88%, 11.26% and 19.71% of the isolates, respectively. All F. salimarina isolates were resistant to amoxicillin and trimethoprim-sulfamethoxazole. Therefore, it can be concluded that the E. tarda evidence strains have intraspecific options and are not clonally related. The E. tarda isolates evaluated were resistant to antimicrobials licensed for use in Brazil, highlighting a health challenge considering the spread of strains resistant to antimicrobials used in national aquaculture. Furthermore, the world's first occurrence of F. salimarina associated with diseases on clothing and cobia was reported. The isolates obtained were clonal to each other and sensitive to antimicrobials authorized for use in fish farms in Brazil, representing alternatives for the treatment of these animals.