Expansion of the pRAS3 Plasmid Family in Aeromonas salmonicida subsp. salmonicida and Growing Evidence of Interspecies Connections for These Plasmids

Abstract

Aeromonas salmonicida subsp. salmonicida is a pathogenic bacterium responsible for furunculosis in salmonids. Following an outbreak of furunculosis, the infection can be treated with antibiotics, but it is common to observe ineffective treatment due to antibiotic resistance. This bacterium has a wide variety of plasmids responsible for this resistance. Among them, pRAS3 carries a tetracycline resistance gene. Several variants of this plasmid have been discovered over the years (pRAS3-3432 and pRAS3.1 to 3.4). During the present study, two new variants of the plasmid pRAS3 were identified (pRAS3.5 and pRAS3-3759) in strains of A. salmonicida subsp. salmonicida. Plasmid pRAS3-3759, which has been found in many strains from the same region over the past three years, has an additional genetic element identical to one found in pRAS3-3432. This genetic element was also found in Chlamydia suis, a swine pathogen. In this study, we analyzed the bacteria’s resistance to tetracycline, the number of copies of the plasmids, and the growth of the strains that carry five of the pRAS3 variants (pRAS3.3 to 3.5, pRAS3-3432, and pRAS3-3759). The results show no particular trend despite the differences between the plasmids, except for the resistance to tetracycline when analyzed in an isogenic background. Blast analysis also revealed the presence of pRAS3 plasmids in other bacterial species, which suggests that this plasmid family has widely spread. This study once again highlights the ability of A. salmonicida subsp. salmonicida to adapt to furunculosis antibiotic treatments, and the still-growing family of pRAS3 plasmids.

Host Dependent-Transposon for a Plasmid Found in Aeromonas salmonicida subsp. salmonicida That Bears a catB3 Gene for Chloramphenicol Resistance

“…We recently described this situation for the pRAS3 plasmids increasingly found in strains of A. salmonicida subsp. salmonicida in Quebec and which confer resistance to tetracycline, an antibiotic with limited use in aquaculture, but widely used in the pork industry in the same province [14].…”

“…salmonicida infections are widely used in fish farms. This bacterium contains a very diverse plasmidome [7], including a large variety of plasmids that carry antibiotic resistance genes (ARGs), especially in Canadian isolates [8][9][10][11][12][13][14]. Some strains even bear plasmids that make them resistant to all antibiotics authorized by Health Canada for aquaculture, leaving the fish farmers without curative resources to fight furunculosis [10].…”

Chlamydia suisdisplays high transformation capacity with complete cloning vector integration into the chromosomalrrn-nqrFplasticity zone

“…C. suis is an opportunistic pathogen primarily located in the gut of pigs and is one of the closest phylogenetic relatives of C. trachomatis ( 4 , 5 ), a causative agent of severe ocular disease and the most common bacterial agent of sexually transmitted infections (STIs) in humans ( 6 ). The Tet-island of C. suis shares high similarity with a mobilizable plasmid family termed pRAS3 ( 7 , 8 ), such as pRAS3-3432, recently isolated from Aeromonas salmonicida subsp. salmonicida ( 9 ) and a near-identical plasmid found in Edwardsiella tarda ( 10 ), both known as bacterial fish pathogens.…”

DataSheet_1.zip

“…salmonicida subsp. salmonicida contains a very diverse plasmidome (Vincent et al, 2021), including a large variety of plasmids that carry antibiotic resistance genes (ARGs), especially in Canadian isolates (McIntosh et al, 2008;Vincent et al, 2014;Tanaka et al, 2016;Trudel et al, 2016;Massicotte et al, 2019;Vaillancourt et al, 2021;Vincent et al, 2021;Fournier et al, 2022). Some strains even bear plasmids that make them resistant to all antibiotics authorized by Canadian authorities for aquaculture (Trudel et al, 2016).…”

“…Some strains even bear plasmids that make them resistant to all antibiotics authorized by Canadian authorities for aquaculture (Trudel et al, 2016). Tetracycline resistance is increasing in Quebec (Fournier et al, 2022), and various genes have been observed in A. salmonicida subsp. salmonicida in a myriad of plasmids (Table 1).…”