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PubMed2003

A polar flagella operon (flg) of Aeromonas hydrophila contains genes required for lateral flagella expression.

Aeromonas spp. are pathogens of both humans and poikilothermic animals, causing a variety of diseases. Certain strains are able to produce two distinct types of flagella; polar flagella for swimming in liquid and lateral flagella for swarming over surfaces. Although, both types of flagella have been associated as colonisation factors, little is known about their organisation and expression. Here we characterised a complete flagellar locus of Aeromonas hydrophila (flg) containing 16 genes, this was analogous to region 1 of the Vibrio parahaemolyticus polar flagellum, with the difference that no flagellin genes were found on A. hydrophila while V. parahaemolyticus showed three flagellin genes. The flg region was present in all Aeromonas strain tested. Defined insertion mutants in flgL, were unable to swim, had a drastic reduction in swarming, lateral flagella, HEp-2 cell adhesion and biofilm formation. Mutations in flgN caused a drastic reduction in lateral flagella, inability to swarm, but these strains were still able to swim. Whereas the cheV mutants still produced both types of flagella and were able to swim and swarm. These results suggest that FlgN is required for lateral flagella formation and swarming motility, but not for polar flagellum-mediated swimming.

Aeromonas hydrophila↗
PubMed1991

Susceptibilities of motile Aeromonas sp. to antimicrobial agents.

Resistance to antimicrobial agents of 106 isolates of motile Aeromonas sp. was characterized. The results indicated that in vitro susceptibilities among the three species of the motile Aeromonas sp. were similar, and only the distribution of susceptibility to cephalothin was different. The percentage of resistance of A. sobria strains was lower than the percentage of the resistant strains of A. hydrophila and A. caviae. All of the isolates were susceptible to kanamycin, nalidixic acid, tobramycin, amikacin, netilmicin, cefuroxime, ceftriaxone, cefoperazone and cefotaxime. Three of the tested strains (two A. hydrophila and one A. caviae) transferred resistance plasmids to the Aeromonas hydrophila recipient.

Aeromonas↗
PubMed1996

A biochemical protocol for the differentiation of current genomospecies of Aeromonas.

A data file consisting of 40 biochemical and physiological tests for the differentiation of aeromonads was constructed based upon existing published data from various geographical locations and laboratories. The data file covers all the current genomospecies (or hybridisation groups) of Aeromonas and is therefore applicable to bacteriologists from a wide variety of fields. The protocol derived from the data file was adapted for use with a semi-interactive computer identification program. This program was challenged with the type strains of all the currently recognised genomospecies and each genomospecies was correctly identified, with only one strain (ATCC 7966, HG1) having an identification probability of less than 90%. The program was also tested with environmental and clinical isolates and again identifications were achieved with high probabilities. This protocol is designed for use on presumptive isolates of Aeromonas spp. and can be carried out in routine laboratories not equipped to perform the complex DNA hybridisation techniques which are currently used for the differentiation of genomospecies of Aeromonas.

Aeromonas↗
PubMed1994

Toxin production, adherence and protein expression by clinical Aeromonas spp. isolates in broth and human pooled ileostomy fluid.

The physiological behaviour of clinical Aeromonas spp. isolates was compared following culture in a conventional broth and human pooled ileostomy fluid (PIF). Protein expression was markedly affected by the growth medium, with an overall reduction in whole cell proteins in bacteria grown in ileostomy fluid. In addition, novel outer membrane proteins were produced in PIF but not in broth. The majority of A. hydrophila and A. sobria isolates produced toxin in both broth and PIF, whereas no cytotoxin positive A. caviae were found. Toxin titres were at least two doubling dilutions higher in 40% and 21% of A. hydrophila and A. sobria isolates, respectively, following culture in brain heart infusion broth compared with PIF. Bacterial adherence to Vero and A-549 cells was significantly more common in A. hydrophila (53%) and A. sobria (64%) than in A. caviae (15%) (P < 0.01). We observed increased adherence by 6 aeromonas strains previously classified as adherence-positive, but not by 6 non-adherers, in PIF compared with brain heart infusion broth. The influence of growth medium on the expression of potential virulence determinants by Aeromonas spp. provides a rationale for the use of human ileostomy fluid in future in vitro studies, in order to simulate the nutrient conditions found in vivo.

Aeromonas↗
PubMed1988

Isolation and characterization of motile Aeromonas from human, food and environmental specimens.

From July 1985 to March 1987, the occurrence of motile Aeromonas sp. in stool, food and environmental specimens was investigated to assess their pathogenic significance and to determine sources and routes of infection. A total of 9366 stool specimens were examined; Aeromonas was isolated from 11.1% of diarrhoeal stools and 2.2% of normal stools (P less than 0.001). Aeromonas counts in food specimens, which included minced beef, pork and chicken, seafood and various vegetables and their products, were unexpectedly high suggesting that infection might be food-borne rather than water-borne. About 70% of the isolates from meat products were A. hydrophila and A. sobria, while A. caviae was the most common in sea-fish, vegetables and their products. Most A. hydrophila and A. sobria strains produced haemolysin, but haemagglutinin was found more frequently in A. sobria.

Aeromonas↗
PubMed1995

Adhesion of Aeromonas sp. to cell lines used as models for intestinal adhesion.

Adhesion to HEp-2 cells has been shown to correlate with enteropathogenicity for Aeromonas species. Such adhesion is thought to reflect the ability of strains to adhere to human intestinal enterocytes, although HEp-2 cells are not of intestinal origin. In this study strains of Aeromonas veronii biotype sobria isolated from various sources were investigated in parallel assays for their ability to adhere to HEp-2 cells and to an intestinal cell line (Caco-2). Quantitative assays showed identical adhesion values were obtained with both cell lines. Adhesion was best when bacteria were grown at 22 degrees C compared with 37 degrees C and 7 degrees C. Some environmental isolates showed greater adhesion when grown at 7 degrees C than when grown at 37 degrees C. Filamentous structures on these strains are also optimally expressed under the above conditions (reported elsewhere). Mechanical shearing or trypsin treatment to remove surface structures from several adhesive strains grown at 22 degrees C decreased adhesion to cell lines by 50-80% providing further indirect evidence that filamentous adhesins may play a role in cell adhesion for this Aeromonas species.

Aeromonas↗
PubMed2001

Detection of Aeromonas caviae in the common housefly Musca domestica by culture and polymerase chain reaction.

Aeromonas caviae has been implicated in diarrhoeal disease of livestock and humans. The potential role of houseflies in the epidemiology of this pathogen was investigated by examining the prevalence of A. caviae in houseflies collected from two South Carolina farms and one restaurant. Isolation was accomplished by culture of flies in alkaline peptone water followed by identification with Aeromonas-specific PCR using novel primers (APW-PCR). All isolates cultured from houseflies were identified as A. caviae by biochemical characteristics and direct sequencing approximately 800 bp of the 16S rRNA gene. Aeromonas caviae was detected in 78% (272/349) dairy farm flies, 55% (54/99) pig farm flies and 39% (77/200) restaurant flies. Faeces from cows and pigs at the farms also were positive for A. caviae (58% and 100%, respectively). The APW PCR method provided a rapid, convenient way to identify A. caviae from faeces and houseflies that contained hundreds of bacterial species.

Aeromonas↗
PubMed1998

Bactericidal effect of chlorine on motile Aeromonas spp. in drinking water supplies and influence of temperature on disinfection efficacy.

The susceptibility of toxigenic Aeromonas spp. to free chlorine in drinking water supplies, and the influence of environmental temperature on the bactericidal activity of the oxidant, were evaluated. The results showed inactivation curves characterized by an initial phase of rapid reduction of viable cells followed by a slow inactivation of bacteria. The effect of the chlorine compound was markedly influenced by water temperature. At a summer water temperature (20 degrees C), the efficacy of the chlorine concentrations tested was found to be two to three times lower compared to that found at a winter temperature (5 degrees C). Resistance was moderately, but significantly, greater in Aer. hydrophila vs Aer. caviae and Aer. sobria, but all Aeromonas spp. were more susceptible than Escherichia coli. Selective pressure with free chlorine did not produce Aeromonas cells with higher levels of chlorine resistance.

Aeromonas↗
PubMed1990

Sensitivities of Aeromonas hydrophila cultured from medicinal leeches to oral antibiotics.

Infections associated with medicinal leech application are caused by Aeromonas hydrophila, an organism that resides in the leech gut. We cultured the intestinal tracts of 25 leeches and evaluated the efficacy of oral antibiotics against Aeromonas hydrophila. Cultures of this organism showed no sensitivity to ampicillin and inconsistent sensitivity to cephalothin (equivalent to cephalexin). The Aeromonas hydrophila cultures did show consistent sensitivity to ciprofloxacin, tetracycline, and trimethoprim-sulfamethoxasole. These three antibiotics should be considered if oral antibiotic coverage is used in association with leech application.

Administration, Oral↗
PubMed1987

[Aeromonas hydrophila as an autochthonous causative agent of infectious enteritis in Germany].

Aeromonas hydrophila was identified by culture technique in diarrhoeal stools and ascites in a patient of 57 years of age who suffered from known alcoholic cirrhosis and additional acute gastroenteritis. No other pathogens that would produce acute diarrhoea were found. The isolated Aeromonas hydrophila strain was characterised by the pathogenic properties known to date as pertaining to this species (formation of haemolysin and enterotoxins). Hence it is evident that Aeromonas hydrophila occurs in Germany also as an autochthonous pathogen of acute infectious enteritis.

Aeromonas↗
PubMed1986

The clinical significance of stool isolates of aeromonas.

The purpose of this study was to determine the clinical significance of different Aeromonas species isolated from stool. During a 17-month period, 29 strains of Aeromonas were isolated and identified to species with the following results: 22, A. caviae, 5, A. hydrophila, and 2, A. sobria. Clinical significance was determined independently of knowledge of speciation result. Nineteen isolates represented colonization, implying that Aeromonas can be recovered from the gastrointestinal tract without causing primary disease. The remaining 10 isolates were of indeterminate significance and may have played a role in infection, but pertinent tests to rule out other enteric pathogens had not been done. A correlation between species and clinical significance could not be established. Antimicrobial susceptibility testing was performed on the 29 isolates. A. caviae showed an unexpected resistance to cefazolin and cefoxitin, whereas representatives of all three species displayed resistance to trimethoprim/sulfamethoxazole.

Adolescent↗
PubMedDate not supplied

Aeromonas hydrophila and Plesiomonas shigelloides as causes of intestinal infections.

Infections due to Aeromonas hydrophila and Plesiomonas shigelloides in immuno-compromised hosts have been well documented, but the role of these organisms in causing gastrointestinal disease in healthy persons is controversial. Despite difficulties in characterizing the exotoxins produced by Aeromonas species, there is accumulating evidence that these bacteria are capable of causing usually mild, self-limited diarrheal disease in previously healthy adults. Some pediatric patients may have protracted dysenteric symptoms. P. shigelloides, an organism closely related to Aeromonas species, may also cause diarrhea in the healthy host, but no exotoxins have yet been identified by the assays used to identify other bacterial enterotoxins. Replacement of fluid and electrolytes is the basis of treatment, and antimicrobial agents should be reserved for patients with chronic or serious illness, or for those at particular risk of serious illness (hepatobiliary disease, septicemia, neoplasms).

Adolescent↗
PubMed1992

Aeromonas hydrophila infections following use of medicinal leeches in replantation and flap surgery.

Aeromonas hydrophila infections are a recognized complication of postoperative leech application, and can occur with measurable frequency in populations of patients treated with leeches. We review 11 previously reported leech-related Aeromonas infections and analyze seven unreported cases. These infections range from minor wound complications to extensive tissue loss and sepsis. Often, these infections followed leech application to tissue with questionable arterial perfusion. Onset of clinical infection in these patients ranged from within 24 hours of leech application to 10 days or more after leech application. Late infections may represent bacterial invasion from colonized necrotic tissue. Based on these observations, we recommend that leech applications be restricted to tissue with arterial perfusion to minimize contamination of necrotic tissue. We also recommend that patients treated with leeches receive antibiotics effective against Aeromonas hydrophila before leech application. Patients treated with leeches and discharged with eschars or open wounds might benefit from oral antibiotic therapy until wound closure. These precautions may minimize or eliminate this complication of leech use.

Adolescent↗
PubMed1989

Treatment with ciprofloxacin of Aeromonas hydrophila associated colitis in a male with antibodies to the human immunodeficiency virus.

A 36-year-old white male intravenous drug abuser and homosexual, with antibodies in the serum to the human immunodeficiency virus and a history of ulcerative colitis, had bloody diarrhea and spiking fevers that did not respond to treatment for 1 month with total parenteral nutrition, orally administered sulfasalazine, and 5-amino-salicylic acid enema. Aeromonas hydrophila was isolated from bacterial culture of a biopsy specimen obtained by sigmoidoscopy. The symptoms resolved after a 2 week course of treatment with orally administered ciprofloxacin. Although ciprofloxacin has been reported to be effective against Aeromonas hydrophila in vitro, this is the first report of successful treatment of Aeromonas-associated colitis with ciprofloxacin.

Adult↗
PubMed1990

Aeromonas hydrophila water-associated traumatic wound infections: a review.

The bacterium Aeromonas hydrophila is commonly found in natural bodies of water, and is a potential invasive pathogen for those who suffer trauma while submerged in water. Five patients treated by the authors and 18 previously reported patients were reviewed to further define the characteristics of A. hydrophila wound infections. Although Aeromonas has been isolated from salt and brackish water, all 23 cases occurred following contact with fresh water. Signs of infection usually appeared 8-48 hours following puncture or laceration injury. The foot or leg were most commonly involved. Infection was frequently rapidly progressive; fascia, tendon, muscle, bone, or joint involvement occurred in 39% of cases. In addition to A. hydrophila, other aerobic and anaerobic bacteria were found in 48% of cases. Aeromonas infection should be suspected in cases of early and rapidly progressive wound infection following trauma in fresh water. Broad-spectrum antimicrobial therapy and appropriate surgical care should be promptly instituted.

Aeromonas↗
PubMedDate not supplied

Aeromonas septicemia in infants and children.

Our experience at the Ramathibodi Hospital with 20 infants and children who had Aeromonas septicemia is reviewed. Their ages were from 1 day to 14 years. Eighteen patients had underlying diseases: leukemia, 5; aplastic anemia, 4; cirrhosis, 2; thalassemia/hemoglobinopathy, 3; renal failure, 1; ileal perforation, 1; marasmus, 1; and cavernous hemangioma with thrombocytopenia, 1. Blood cultures yielded Aeromonas hydrophila in all patients, and four patients had polymicrobial bacteremia. Fifteen episodes of septicemia were community-acquired and five were hospital-acquired. The clinical manifestations of these patients were similar to septicemia due to other Gram-negative enteric bacilli. Two patients each had ecthyma gangrenosum, necrotizing fasciitis and meningitis. Antibiotic treatment included penicillins, cephalosporins, aminoglycosides and sulfamethoxazole-trimethoprim. The overall case fatality rate was 50%; eight of the nine patients with acute leukemia or aplastic anemia died. With the exception of one child the blood cultures were sterile in all patients before death. Aeromonas septicemia is an uncommon but severe infection which occurs predominantly in compromised hosts.

Acute Disease↗
PubMed1994

Phylogenetic analysis and assessment of the genera Vibrio, Photobacterium, Aeromonas, and Plesiomonas deduced from small-subunit rRNA sequences.

We sequenced nearly complete small-subunit rRNAs of 54 reference strains belonging to the genera Vibrio, Photobacterium, Aeromonas, and Plesiomonas. We then performed a phylogenetic analysis by comparing the sequences which we obtained with all other known sequences for bacteria belonging to the gamma subgroup of the Proteobacteria (thus providing a data base consisting of 70 sequences for the genera investigated), using methods such as neighbor joining, maximum likelihood, and maximum parsimony, as well as bootstrap, to assess the robustness of each topology. Our results confirmed that the family Vibrionaceae should include only Photobacterium and Vibrio species (but not Vibrio marinus); that Aeromonas species deserve family rank; and that Plesiomonas shigelloides is linked to the family Enterobacteriaceae. The genera Vibrio, Photobacterium, Aeromonas, and Plesiomonas, together with the family Enterobacteriaceae, the family Pasteurellaceae, and probably the genus Alteromonas, form a robust monophyletic unit within the gamma 3 subgroup of the Proteobacteria.

Aeromonas↗
PubMed1985

Molecular cloning and expression of a xylanase gene of alkalophilic Aeromonas sp. no. 212 in Escherichia coli.

A gene coding for a xylanase activity of alkalophilic Aeromonas sp. no. 212 (ATCC 31085) was cloned in Escherichia coli HB101 with pBR322. Plasmid pAX1 was isolated from transformants producing xylanase, and the xylanase gene was located in a 6.0 kb Hind III fragment. The pAX1-encoded xylanase activity in E. coli HB101 was about 80 times higher than that of xylanase L in alkalophilic Aeromonas sp. no. 212. About 40% of the enzyme activity was observed in the periplasmic space of E. coli HB101. The pAX1-encoded xylanase had the same enzymic properties as those of xylanase L produced by alkalophilic Aeromonas sp. no. 212, but its molecular weight was lower (135 000 vs 145 000, as estimated by SDS polyacrylamide gel electrophoresis).

Aeromonas↗