Molecular detection of enterotoxins in environmental strains of Aeromonas hydrophila and Aeromonas jandaei

Abstract

Aeromonas species are widely distributed in aquatic environments and recent studies include the genus in the emergent pathogens group because of its frequent association with local and systemic infections in immunocompetent humans. Aiming to search for virulence genes in environmental strains of Aeromonas hydrophila and Aeromonas jandaei, we designed specific primers to detect act/hly A/aer complex and alt genes. Primers described elsewhere were used to detect ast. Eighty-seven strains previously identified using phenotypic and genotypic tests as A. hydrophila (41) and A. jandaei (46) were analysed for the presence of the virulence genes using PCR. DNA fragments of expected size were purified and directly sequenced. Among the 41 strains of A. hydrophila 70.7% (29), 97.6% (40) and 26.8% (11) possessed act/hly A/aer complex, ast and alt genes, respectively. Among the 46 strains of A. jandaei, 4.4% (2), 0% (0) and 32.6% (15) were positive for act/hly A/aer complex, ast and alt genes, respectively. Sequencing allowed for the confirmation of amplified products using BLAST. The present work proposes a specific and rapid diagnostic method to detect the main virulence determinants of Aeromonas, a genus potentially pathogenic to humans.

Prevalence of Hemolytic and Enterotoxigenic Aeromonas Spp. in Healthy and Diseased Freshwater Food Fishes as Assessed by Multiplex PCR

“…It has been observed in this study that the occurrence of the ast gene was restricted to the strains of A. hydrophila which were in accordance with the earlier reports (Balsalobre et al, 2009;Bin Kingombe 2010). Bin Kingombe et al (2010) speculated that an Aeromonas isolate harbouring the molecular enterotoxin profiles of control strains of A. hydrophila (ATCC 7966), an ast-positive strain, may induce not only an infection but also intoxication due to the presence of heat stable enterotoxin even if the contaminated food vehicle was heat treated.…”

“…In disagreement with some of the earlier reports (Sen and Rodger, 2004;Balsalobre et al, 2009) but in accordance with the others (Pablos et al, 2009;Bin Kingombe et al, 2010;Ottaviani et al, 2011;Pinto et al, 2012), the alt gene was found to be dominant among the MPCR positive isolates of Aeromonas spp. Balsalobre et al (2009) reported that 70.7%, 97.6% and 26.8% of the A. hydrophila strains tested were positive for act/hlyA/aer, ast and alt genes, respectively, and 2.4% and 36.6% of the A. jandaei strains were positive for act/hlyA/aer complex and alt genes. Bin Kingombe et al (2010) reported that 36 % of isolates of food borne Aeromonas spp.…”

“…The Act and AerA toxins have haemolytic, cytotoxic and enterotoxic activities, as well as lethality in mice (Galindo et al, 2006). Thus, to overcome this problem, a complex primer of act/hlyA/aer was chosen that amplifies these three virulence factors as a complex gene (Balsalobre et al, 2009). …”

“…The primer act/hlyA/aer complex amplifies 400 bp fragment of cytotoxic enterotoxin, aerolysin and hemolysin gene of Aeromonas spp. (Balsalobre et al, 2009). All the primer sequences were synthesized by Ocimum Biosolutions Inc., Indianapolis, USA.…”

Distribution and phenotypic and genotypic detection of a metallo-β-lactamase, CphA, among bacteraemic Aeromonas isolates

“…Compared with other class B enzymes, CphA MBL has a very specific substrate profile, being active on penem and carbapenem only, and not on penicillin and cephalosporins (Segatore et al, 1993). The distribution of cphA-related genes is species-related: they are mainly found in isolates of A. hydrophila, A. veronii and Aeromonas jandaei, but not in A. caviae (Balsalobre et al, 2009;Rossolini et al, 1995). However, CphA MBL production is not easily detected by in vitro susceptibility testing unless using large inocula.…”