Frequency of pathogens in routine bacteriological diagnosis in fish and their antimicrobial resistance

Abstract

Aquaculture is one of the sectors of animal husbandry with the fastest growth rate. However, the increase in the sector’s production chain without proper management can result in factors that favor the development of diseases, especially infectious diseases caused by bacteria. Many factors, such as agriculture or industry resides, improper use of antibiotics in animals or humans, have contributed to increased environmental pressure and the appearance of antibiotic-resistant bacteria, while residues from these drugs can remain in the carcasses and in water a risk to public and environmental health. From that, we identified the bacterial genus/species and their bacterial resistance to antibiotics from samples received from fish disease outbreaks for bacteriosis diagnosis between January 2017 and October 2020. Isolated bacteria were subjected to the Kirby and Bauer sensitivity test for five classes of antibiotics (penicillins, fluoroquinolones, aminoglycosides, amphenicols, and tetracyclines). Of the 181 analyzed outbreaks, 232 bacteria were isolated, including Streptococcus spp., Aeromonas spp., Edwardsiella spp., Plesiomonas shigelloides, Pseudomonas aeruginosa, Chromobacterium violaceum, Flavobacterium spp., Citrobacter spp., Enterococcus spp., Vibrio spp., Enterobacter spp., Chryseobacterium meningosepticum. Of the 232 bacteria, 40 strains were classified as multidrug resistant (MDR), with Plesiomonas shigelloides, Aeromonas spp., and Edwardsiella spp. representing more than half of this number (22/total). With several bacteria demonstrating resistance to Brazilian aquaculture-legalized drugs (tetracycline and florfenicol), it is mandatory to research, not only for alternatives to the use of antibiotics, but also for other drugs effective against the main circulating bacterial pathogens. In addition, vigilance over the occurrence of resistant bacteria is necessary, considering the appearance of zoonotic bacteria with multi-resistant characteristics, becoming a public health concern.

Multiplex PCR assay for correct identification of the fish pathogenic species of Edwardsiella genus reveals the presence of E. anguillarum in South America in strains previously characterized as E. tarda

“…that affect fish: E. ictaluri , E. tarda , E. piscicida and E. anguillarum . The analysis included several strains isolated in our lab in the past years (Costa, Chideroli, et al, 2021), with samples of Aeromonas spp., Streptococcus spp., Plesiomonas shigelloides and 21 E dwardsiella tarda strains identified with a commercial biochemical kit. Of these Edwardsiella , only six were classified as E. tarda , with the other 17 being identified as E. anguillarum by mPCR, demonstrating the utility of this new molecular diagnostic test in identifying a species that was considered not present in South America.…”

“…from diverse fish species and locations, as well as studies on vaccinology, immunogenicity, pathogenicity and virulence to better understand the pathogen and prevent disease (Griffin et al, 2020; Katharios et al, 2019; Leung et al, 2019; Li et al, 2020; Ye et al, 2021). These bacteria have also been linked with the infectious spleen and kidney necrosis virus in Brazil (Figueiredo et al, 2021) and are an important source of antibiotic resistance genes for other bacteria (Abdelhamed et al, 2019; Costa, Chideroli, et al, 2021).…”

Parasitism of Arapaima gigas (Schinz, 1822) in fish farms of the state of Amazonas, Brazil

“…Despite its potential for rearing, this species faces major problems in its production chain (Lima et al, 2015(Lima et al, , 2018aValladão et al, 2018;Pereira-Filho et al, 2020). From a sanitary point of view, the main challenge is to reduce the high mortality rate in the fingerling phase, mainly caused by the occurrence of parasitic and bacterial diseases (Morey et al, 2020;Pereira-Filho et al, 2020;Costa et al, 2021;Ferreira et al, 2021;Proietti-Junior et al, 2021). With emphasis on the parasitic diseases, the main groups registered in A. gigas are protozoans, myxosporids, monogeneans, digeneans, cestodes, nematodes, acanthocephalans and crustaceans (Morey et al, 2020;Pereira-Filho et al, 2020).…”