Plasmid associated virulence properties of environmental isolates of Aeromonas hydrophila

Abstract

Summary. The plasmid profiles, and their association with antimicrobial resistance, of 60 strains of Aeromonas hydrophila isolated from fish, shellfish and water were investigated. Only two strains were susceptible to all the antimicrobial agents tested ; the highest incidences of resistance were to tetracycline (93.7%), prystanamycin (93.379, ampicillin (9 1 -7%) and cephalothin (91.7%). Forty strains harboured one or more plasmids and the plasmid profile most frequently detected (15%) was the association of three small plasmids of 4-2, 3.2 and 2.8 Mda. Curing experiments indicated that the plasmid-free derivative strains simultaneously lost their resistance determinants to tobramycin, neomycin, gentamicin and kanamycin. More than 90% of the strains tested produced siderophores and displayed haemolytic activity. However, the relationship between these virulence characters and the presence of plasmids was different; in 74.5% of the strains there was siderophore production and plasmids were detectable, whereas only 60% of the strains simultaneously possessed plasmids and haemolytic activity.

Prevalence, species differentiation, haemolytic activity, and antibiotic susceptibility of aeromonads in untreated well water

“…Antibiotic-resistant strains of Aeromonas have been isolated from aquatic environments and this resistance is principally plasmid mediated (Hedges et al 1985, Borrego et al 1991. Similar to other reports (Altwegg & Geiss 1989) all our isolates were resistant to ampicillin and 95% to cephaloridine.…”

“…Although the isolates were also susceptible to trimethoprim-sulphamethoxazole and nalidixic acid, recently we isolated aeromonads from children with diarrhoea and from chicken carcases that were highly resistant to trimethoprim-sulphamethoxazole and nalidixic acid respectively (Ghenghesh et al 1998). Because of the isolation of multiple-resistant Aeromonas species (including to trimethoprimsulphamethoxazole and nalidixic acid) from freshwater in other parts of the world (Borrego et al 1991), our findings warrant the need to take proper measures to prevent the introduction of aeromonads, that are resistant to these drugs, to water sources used by humans. In Libya, as it is in other developing countries, it is common to use water obtained from wells and other untreated sources, in addition to drinking, for bathing and other purposes and this may be hazardous to individuals with wounds, lacerations or abrasions (Janda & Duffey 1988, Gold & Salit 1993, Kelly et al 1993, Newton & Kennedy 1993.…”

Aeromonas hydrophila and Aeromonas veronii Predominate among Potentially Pathogenic Ciprofloxacin- and Tetracycline-Resistant Aeromonas Isolates from Lake Erie

“…Antibiotic resistance genes among Aeromonas organisms have been associated with integron-associated R plasmids, and tetracycline resistance, in particular, has been associated with an array of different plasmids within A. hydrophila isolates (36). Ciprofloxacin resistance among environmental and clinical Aeromonas isolates has been attributed to plasmids (37,38) as well as chromosomal mutations in quinolone resistance-determining regions of gyrA (39,40).…”

Gentamicin-induced nephrotoxicity and nephroneogenesis in Oreochromis nilotica, a tilapian fish

“…The study of the bacterial pathogens of fish and their sensitivity to antimicrobial agents, including gentamicin, has expanded rapidly (Ceschia et al 1987, Schmitt et al 1989, Fryer et al 1990, Baya et al 1991, Borrego et al 1991, and the use of aminoglycosides 'Addressee for correspondence. E-mail: stsmith7@vt.edu in the treatment of fish bacterial infections is well described (Stoskopf et al 1986, Stoskopf 1988.…”