Incidence of class 1 integron and other antibiotic resistance determinants in Aeromonas spp. from rainbow trout farms in Australia

Abstract

There is limited information on antibiotic resistance determinants present in bacteria of aquaculture origin in Australia. The presence of integron and other resistance determinants was investigated in 90 Aeromonas isolates derived from nine freshwater trout farms in Victoria (Australia). Polymerase chain reaction was carried out for the detection of integrase genes Int1, Int2 and Int3, gene cassette array, integron-associated aadA, sul1 and qac1 genes, streptomycin resistance genes strA-strB, β-lactamase resistance genes bla(TEM) and bla(SHV) , and tetracycline resistance genes tetA-E and tetM. Clonal analysis was performed by pulsed-field gel electrophoresis (PFGE). Class 1 integrons were detected in 28/90 (31%) and class 2 and class 3 in none of the strains, aadA gene in 19/27 (70%) streptomycin-resistant strains, sul1 in 13/15 (86.7%) sulphonamide-resistant strains and qac1 gene in 8/28 (28.6%) integron-bearing strains. Five strains from two different farms carried gene cassettes of 1000 bp each containing the aadA2 gene and PFGE analysis revealed genetic relatedness. tetC was detected in all and tetA in 9/18 (50%) tetracycline-resistant strains. The strA-strB, bla(TEM) or bla(SHV) genes were not detected in any of the strains. Aeromonas spp. carrying integrons and other resistance genes are present in farm-raised fish and sediments even though no antibiotics were licensed for use in Australian aquaculture at the time of the study.

Class 1 Integrons in <i>Aeromonas hydrophila</i> Isolates from Farmed Nile Tilapia (<i>Oreochromis nilotica</i>)

“…Therefore, the presence of the resistance gene cassettes was wellcorresponded to the resistance phenotype. The dfrA12-aad2 cassette array was prevalent in this study that is not in agreement with previous studies suggesting that class 1 integrons from fish pathogens and environmental bacteria predominantly carry a single gene cassette [19,25,29]. Difference of antimicrobial use in different geographical regions that creates different selective pressure could be an explanation for this inconsistency.…”

“…from humans in Mexico [32], Aeromonas spp. from rainbow trout in Australia [29], V. cholerae from human and environmental samples in Thailand [9] and S. enterica from food in Portugal [2]. The dfrA1-orfC gene array was previously found in V. cholerae from human in India [37,41] and S. enterica from humans and animals in Australia [28].…”

Inadequately Treated Wastewater as a Source of Human Enteric Viruses in the Environment

“…The absence of gene cassettes in those isolates could be possible due to the presence of a cassette array that is too large to amplify (Partridge et al 2009). Similar findings were also noted by Ndi and Barton (2011) and Yu et al (2003). Since occurrence of sulfonamide resistance gene (sul1) and quaternary ammonium compounds resistance gene (qacEΔ1) is often associated with classic class 1 integrons (Paulsen et al 1993), in all intI1-positive isolates, presence of those genes was tested.…”

Detection of antibiotic resistance, virulence gene determinants and biofilm formation in Aeromonas species isolated from cattle

“…Similarly, the presence of class 1 integron was detected in Aeromonas spp. isolated from rainbow trout farms in Australia (Ndi and Barton 2011). However, the incidence of class 1 integrons in clinical samples has been documented by Pérez-Valdespino et al (2009), and there is a significant amount of information on class 1 integrons in animal faeces.…”