Caracterização de bactérias do complexo Aeromonas isoladas de Colossoma macropomum (CUVIER, 1816) e resistência a antimicrobianos: impacto em sanidade animal, saúde pública e meio ambiente

Abstract

Colossoma macropomum, evaluate resistance to antimicrobials and promote discussion of the topic within the scope of animal health, public health and the impact on the environment. To carry out the study, 40 tambaqui specimens were evaluated, including males and females, in the fattening phase, from Maranhão Island. In a laboratory environment, fragments of the caudal kidney and liver were removed to search for Aeromonas spp. using standardized and reference microbiological techniques (cultivation, isolation, phenotypic identification) and polymerase chain reaction for the genotypic characterization of isolates. Subsequently, sensitivity tests were carried out using the disk diffusion method using 10 antimicrobials representing the penicillin classes (penicillin G – 10 µg; oxacillin – 1 µg; ampicillin with subactam sodium – 20 µg); cephalosporins (cefepime – 30 µg; cefoxitin – 30 µg; cefadroxil – 30 µg; and ceftriaxone – 30 µg); quinolones (ofloxacin – 5 µg); aminoglycosides (neomycin – 300 µg); and, macrolides (azithromycin – 15 µg). The isolates were classified as sensitive, sensitive with increased exposure and resistant to the evaluated antimicrobial principles and the phenotypes were classified as having multiple resistance to three or more antimicrobials tested, from different classes. In total, 132 isolates from 25 fish (82.5%; n= 25/40) were isolated on gelatin phosphate salt agar, being confirmed for the genus Aeromonas sp. the totality of these isolates, by performing gram staining (gram negative cocorods) and catalase tests (100% positive) and oxidase (100% positive). Of these isolates, 56.81% (n= 75) came from the liver and 43.19% (n= 57) from the caudal kidney. For phenotypic confirmation of these strains, 25 biochemical tests were carried out with the identification of 114 isolates to species level, which shows a high identification rate (86.37%). Seven species of Aeromonas were identified with a biochemical profile compatible with that cited in specialized literature at the following frequencies: A. veronii by veronii (60.53%), A. caviae (18.42%), A. sobria (5.56%), A. schubertii (5.56 %), A. veronii by sobria (5.56 %), A. media (2.63 %) and A. hydrophyla (2.63 %). Primers designed for the detection of Aeromonas spp. presented satisfactory results in PCR amplification, with 47.37% (n= 54) of the isolates confirmed as belonging to the genus Aeromonas. Aeromonas spp. identified phenotypically showed widespread resistance to penicillin; high percentages of resistance to oxacillin, cefepime, cefadroxil and azithromycin. The antimicrobials to which the bacteria showed greater sensitivity were ampicillin associated with sulbactam, neomycin and ofloxacin. When evaluating multiple drug resistance, 34.21% (n= 39) of the isolates were considered multiple drug resistance phenotypes. The antimicrobial and antimicrobial classes in which the isolates showed the highest percentages of resistance, respectively, were penicillins and cephalosporins and penicillin, oxacillin and cefadroxil. To collaborate with the Aquatic Animal Health Program in the state of Maranhão in the context of animal health, public health and the environment, focusing on the results obtained, two technical materials were prepared: (i) an advisory guide “Aeromonas in Fish: what It is? how to prevent” - with the aim of providing illustrated information to different audiences interested in the topic; and, (ii) a guidance manual “Actions of the official veterinary service in the production chain of farmed aquatic animals” – with the main purpose of guiding the activities of employees linked to the agricultural health executing body with regard to the health of aquatic animals. It is concluded that all species identified in the study are considered pathogens of aquatic animals with zoonotic potential for humans and that correct surveillance of water, food and sanitation facilities, with the implementation of diagnostic procedures and detection of these agents is essential to the prevention of infections and outbreaks. Although there are no antimicrobials registered in Brazil for use in the cultivation of C. macropomum, antimicrobial resistance is present in isolates of Aeromonas spp. originating from tambaquis in the sampled area. The high frequency of multidrug resistance of Aeromonas spp. raises concern regarding the cultivation of the fish sampled, as well as human health given the possibility of human infections by multi-resistant bacteria. With the technical materials prepared, it is expected that active and passive surveillance will be more effective and faster, which, invariably, converges to the reduction of cases and outbreaks of diseases in farms, contributing to animal health and safeguarding the health of fish, consumers and the environment