Phenotypic, molecular and pathological characterization of motile aeromonads isolated from diseased fishes cultured in Uruguay

Abstract

Information about motile aeromonads from aquaculture systems of the Neotropical region is scarce. The aim of this study was to characterize motile Aeromonas isolated from ornamental and consumable fishes cultured in Uruguay. Biochemical and molecular methods were used for species identification. Antimicrobial susceptibility and the presence of virulence genes were evaluated. Genetic diversity was analysed by rep-PCR, and virulence of the most representative isolates was determined by calculating the fifty lethal dose in experimentally challenged fish (Australoheros facetus). Aeromonas hydrophila and A. veronii were the most prevalent identified species (38.2% and 32.4%, respectively), whereas A. allosacharophila, A. bestiarium, A. caviae and A. punctata were less prevalent. This study constitutes the first report of these last four species in Uruguay. All isolates were resistant to at least three antimicrobials, and 82.3% of them showed multidrug resistance. Virulence genotypes were correlated with the Aeromonas species and haemolytic activity. The genotype act+/alt+/ast+/ela+/lip+ was the most prevalent (26.5%). A correlation between virulence genotypes and Aeromonas species was found. A. punctata showed a clonal structure according to rep-PCR analysis, whereas other species showed high genetic diversity. The number of virulence genes of the isolates was related with virulence according to the experimental challenge assays.

Antibiotic susceptibility and pathogenicity of Aeromonas hydrophila isolated from red hybrid tilapia (Oreochromis niloticus×Oreochromis mossambicus) in Malaysia

“…Infection by A. hydrophila is usually characterized by hemorrhagic ulcers on the skin and fin erosion [3]. It has been previously reported in various freshwater fish including channel catfish (Ictalurus punctatus), Siberian sturgeon (Acipenser baerii), Russian sturgeon (Acipenser gueldenstaedtii), banded knifefish (Gymnotus omarorum), and Nile tilapia (Oreochromis niloticus) [4][5][6].…”

Experimental co‐infection by Aeromonas hydrophila and Aeromonas jandaei in pirarucu Arapaima gigas (Pisces: Arapaimidae)

“…Virulence factors in Aeromonas species are also associated with the structural components of the bacterial cell and with exotoxins that are secreted during bacterial metabolism. Thus, the nature of virulence is complex and apparently varies between strains of Aeromonas (Fowoyo & Achimugu, 2019; Janda & Abbott, 2010; Li et al., 2011; Perretta et al., 2018; Rasmussen‐Ivey et al., 2016).…”

“…Aeromonas hydrophila and A. jandaei that were isolated from A. gigas were positive for genes relating to expression of hly A and aer A cytotoxic exotoxins, gcat and dnase protease coders and the lipase lip . Expression of these factors indicates that potential for pathogenicity exists (Janda & Abbott, 2010; Perretta et al., 2018; Rasmussen‐Ivey et al., 2016). Hence, experimental inoculation of A. hydrophila and/or A. jandaei that were isolated from an outbreak in A. gigas resulted in the similar clinical signs.…”

Pathogenic profile and cytotoxic activity of Aeromonas spp. isolated from Pectinatella magnifica and surrounding water in the South Bohemian aquaculture region

“…(reviewed, e.g., in Beaz‐Hidalgo & Fig ueras, 2013). One approach to determine whether strains have the potential to be virulent is by screening for specific virulence genes (Aravena‐Román, Inglis, Riley, & Chang, 2014; Gonzalez‐Serrano, Santos, Garcia‐Lopez, & Otero, 2002; Perretta, Antúnez, & Zunino, 2018; Rather, Willayat, Wani, Hussain, & Shah, 2019). In this study, 14 virulence genes in Aeromonas strains isolated from invasive bryozoan P. magnifica and ambient water from four localities of South Bohemian aquaculture region were investigated.…”

“…In a majority of studies on the pathogenic outcomes of Aeromonads in aquatic animals, proof of diseases development have been performed mainly via challenge and cytotoxicity assays; the aim has been to detect a few virulence associated genes, if at all, without consideration of their mutual linkage (Dong et al., 2017; Perretta et al., 2018; Rahman et al., 2002; Wahli et al., 2005). Thus, conclusions regarding the discrepancy or correlation between the ability to elicit fish disease or mortality, and the detection of virulence‐associated genes are possibly irrelevant in some cases.…”