Variable expression of O-antigen and the role of lipopolysaccharide as an adhesin in<i>Aeromonas sobria</i>

Francki, Kathy T.; Chang, Barbara J.

doi:10.1111/j.1574-6968.1994.tb07150.x

Cited by 19 publications

(24 citation statements)

References 19 publications

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“…Ourselves and other workers have associated LPS O-Ag expression with adherence of A. hydrophila and A. veronii bv. sobria clinical isolates to HEp-2 cells (1,8,23). Furthermore, LPS O-Ag transposon mutants of A. hydrophila O:34 were shown to be unable to colonize the germfree chicken gut model (22).…”

Section: Discussionmentioning

confidence: 99%

Role of flm Locus in Mesophilic Aeromonas Species Adherence

et al. 2001

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The adherence mechanism of Aeromonas caviae Sch3N to HEp-2 cells was initially investigated through four mini-Tn5 mutants that showed a 10-fold decrease in adherence. These mutants lost motility, flagella, and their lipopolysaccharide (LPS) O antigen (O-Ag). Three genes, flmB-neuA-flmD, were found to be interrupted by the transposon insertions; additionally, two other genes, one lying upstream (flmA) and one downstream (neuB), were found to be clustered in the same operon. While the flmA and flmB genes were present in all mesophilic Aeromonas spp. (A. hydrophila, A. caviae, A. veronii bv. veronii, and A. veronii bv. sobria) tested, this was not the case for the neuA-flmD-neuB genes. Construction and characterization of flmB insertion mutants in five other mesophilic Aeromonas strains revealed the loss of motility, flagella, and adherence but did not alter the LPS composition of these strains. Taking Mesophilic Aeromonas has been associated with gastrointestinal and wound infections of healthy humans, and less commonly with septicemias of immunocompromised patients (12). A. caviae, in particular, is reported as the most prevalent paediatric enteropathogenic species of the genus (26, 39).A number of putative pathogenicity determinants have been reported for aeromonads; these include toxins, adhesins, and invasins (34). There is still little known about their adherence process, although long-wavy pili have been implicated as important colonization factors of A. hydrophila and A. veronii bv. sobria (14). However, many clinical isolates are poorly piliated or nonpiliated (15) In this study, we describe five genes of A. caviae that belong to a putative operon involved in the biosynthesis of LPS O-Ag and flagellum assembly. We have also investigated the distribution of these genes among the mesophilic Aeromonas species, which allowed us to draw conclusions about the roles of these two surface structures in the adherence of aeromonads to human epithelial cells. MATERIALS AND METHODSBacterial strains, plasmids, and growth conditions. Bacterial strains and plasmids used in this study are listed in Table 1. E. coli strains were grown on Luria-Bertani (LB) Miller broth and LB Miller agar, while Aeromonas strains were grown either on tryptic soy broth or agar or in brain heart infusion broth (BHIB) (Oxoid). Ampicillin (50 g/ml), nalidixic acid (50 g/ml), kanamycin (50 g/ml), chloramphenicol (25 g/ml), rifampin (100 g/ml), and tetracycline (20 g/ml) were added to the different media when needed.HEp-2 cell culture and adherence assay. Tissue culture was maintained as described by Thornley et al. (34). The adherence assay was conducted as a slight modification of that described by Carrello et al. (4). Bacteria were grown statically in BHIB at 37°C, harvested by gentle centrifugation (1,600 ϫ g for 5 min), and resuspended in phosphate-buffered saline (PBS), pH 7.2, at approximately 10 6 to 10 7 CFU/ml (A 600 Ϸ 0.07). The monolayer was infected with 1 ml of the bacterial suspension for 90 min at 37°C in 5% CO 2 . Following infec...

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Section: Discussionmentioning

confidence: 99%

Role of flm Locus in Mesophilic Aeromonas Species Adherence

et al. 2001

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“…Aeromonas lateral flagella, in addition to mediating swarming motility, appear to be adhesins in their own right, contribute to micro-colony formation and efficient biofilm formation on surfaces, and possibly facilitate host cell invasion (Kirov 2003). Both flagella and pilli of A. caviae have been linked to adherence to epithelial cells in vitro (Kirov et al 1998;Rabaan et al 2001) but lipopolysaccharides and membrane proteins have also been implicated in this property in other Aeromonas species (Francki and Chang 1994;Quinn et al 1994;Merino et al 1996). Moreover, these pilli were probably responsible for the cell hydrophobicity.…”

Section: Biofilm Formationmentioning

confidence: 98%

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

Scoaris

Colacite

Nakamura

et al. 2007

Antonie van Leeuwenhoek

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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.

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“…Other virulence-related factors such as pili (Atkinson & Trust, 1980), haemagglutinins (Atkinson et al, 1987), lipopolysaccharide (Francki & Chang, 1994) and outer-membrane proteins (Quinn et al, 1993) have been associated with virulence in aeromonads. The construction of multiple mutations for these factors and testing for further attenuation in the suckling mouse model would be a way of testing the relative contribution of these factors.…”

Section: Discussionmentioning

confidence: 99%

Inactivation of two haemolytic toxin genes in Aeromonas hydrophila attenuates virulence in a suckling mouse model

1998

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The contribution of two unrelated Aeromonas hydrophila fihaemolytic toxins to virulence was assessed in a suckling mouse model. The first haemolysin gene, isolated from an A. hydrophila A6 cosmid bank, encoded a potential gene product of 621 amino acids and a predicted molecular size of 690 kDa. The inferred amino acid sequence showed 89% identity to the AHHI haemolysin of A. hydrophila ATCC 7966, and 51 O/ O identity to the HlyA haemolysin of Vibrio cholerae E l Tor strain 017. The second haemolysin gene (designated aerA), which encodes aerolysin, a pore-forming toxin, was partially cloned by PCR for the purpose of mutant construction. This PCR product was a 1040 bp fragment from the C-terminal region of aerA. It is proposed that the 69.0 kDa V. cholerae-HlyA-like haemolysin gene be termed hlyA to contrast with the aerA terminology for the aerolysin. A suicide vector was used to inactivate both the hlyA and aerA genes in A. hydrophila A6. When assessed in the suckling mouse model, only the hlyA aerA double mutant showed a statistically significant reduction in virulence -a 20-fold change in LD,, (Scheffe test, P < 0 0 5 ) . Cytotoxicity t o buffalo green monkey kidney cell monolayers and haemolysis on horse blood agar were eliminated only in the hlyA aerA double mutants. This is the f i r s t report of cloning and mutagenesis of two unrelated haemolytic toxin genes in the same strain of a mesophilic aeromonad. For A. hydrophila, a two-toxin model provides a more complete explanation of virulence.

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Variable expression of O-antigen and the role of lipopolysaccharide as an adhesin inAeromonas sobria

Cited by 19 publications

References 19 publications

Role of flm Locus in Mesophilic Aeromonas Species Adherence

Role of flm Locus in Mesophilic Aeromonas Species Adherence

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

Inactivation of two haemolytic toxin genes in Aeromonas hydrophila attenuates virulence in a suckling mouse model

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