The Journal of Medical Microbiology, Vol 35, Issue 5 264-269, Copyright © 1991 by Society for General Microbiology
Plasmid associated virulence properties of environmental isolates of Aeromonas hydrophila
J. J. Borrego, M. A. Morinigo, E. Martinez-Manzanares, M. Bosca, D. Castro, J. L. Barja and A. E. Toranzo
Department of Microbiology, Faculty of Sciences, University of Malaga, Spain.
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 (96.7%), prystanamycin (93.3%), ampicillin (91.7%) 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.
