Virulence and antibiotic susceptibility of Aeromonas spp. isolated from drinking water

Abstract

Aeromonas isolates from tap water, mineral water, and artesian well water were investigated for their ability to produce different potential virulence factors or markers such as hemolysins, cytotoxins, phospholipase, DNase, hydrophobicity and their ability to adhere to epithelial cells and to abiotic surfaces. The susceptibility to antibiotics of Aeromonas isolates was also examined. Majority of the isolates displayed hemolytic activity against sheep erythrocytes, while only 7 of the 23 Aeromonas strains displayed DNase activity and 4 of the 23 Aeromonas strains tested were regarded as positive for phospholipase production. Most of the isolates showed cytotoxic activities in culture filtrate dilutions at titer of 1/8 or lower. No general relation between the strain isolated and the ability to interact with epithelial cells could be established. Using the bacterial adherence to hydrocarbons method, most of the strains were classified as highly hydrophilic. All five Aeromonas jandaei strains isolates, 9 of the 12 Aeromonas sp strains and four of the five Aeromonas hydrophila were multidrug resistant. The most active antimicrobial was ciprofloxacin (susceptible in 100% of the isolates), and the least active antibiotic was ampicillin (resistance in 92% of the isolates). The majority of the isolates tested were not killed by chlorine at 1.2 mg/l. Whether the high tolerance to chlorine of Aeromonas isolates can be linked to greater virulence is not know.

Characterization of the microbial community in a lotic environment to assess the effect of pollution on nitrifying and potentially pathogenic bacteria

“…A hydrophila was found in both study areas (see Figure 3). This result was expected because these microbes are primarily aquatic organisms and, as reported by Scoaris et al (2008), A. hydrophila can be found in treated and non-treated water. P. aeruginosa, a free-living bacteria ubiquitous in the environment, is another potential human pathogen.…”

Isolation and characterization of virulent Aeromonas veronii from ascitic fluid of oscar Astronotus ocellatus showing signs of infectious dropsy

“…Elastase activity on solid medium was detected by spot inoculating the organisms on LB medium supplemented with 0.2% elastin-Congo red (Sigma-Aldrich) with a clear zone around the growth and diffusion of Congo red into the clear zone, and haemolytic activity on LB agar containing 5% (vol/vol) human blood (Swift et al 1999). The other virulence traits tested were slime formation (Freeman et al 1989) and surface hydrophobicity (Rosenberg et al 1980, Scoaris et al 2008). Cytotoxicity of culture supernatant was examined on Hep-2 cells by incubating exponentially growing cells with the supernatant following the 3-(4, 5-dimethylthiazol-2-yl)2, 5-diphenyltetrazolium bromide (MTT) assay (Mosmann 1983, Greenman et al 1997.…”

A Keystone Methylobacterium Strain in Biofilm Formation in Drinking Water

“…Among culturable bacteria, the most commonly found genera in drinking water are Pseudomonas [5][6][7][8][9][10][11], Sphingomonas [4,[6][7][8]10,12], Methylobacterium [4,[6][7][8]12], Aeromonas [8,13], and Acinetobacter [5,6,8]. A small number of species, such as the Methylobacterium species [12], Acinetobacter calcoaceticus [4], and Mycobacterium species [12,14] have been implicated in promoting aggregation in pure or simple mixed cultures.…”