Role Of Aeromonas Research Articles

Gastrointestinal infection with Aeromonas: incidence and relationship to inflammatory bowel disease

Abstract Introduction Aeromonas can cause several diseases in humans, with gastroenteritis accounting for most cases. The role of Aeromonas as a pathogen in human enterocolitis has been questioned in recent years. Objectives To determine the incidence of gastrointestinal infection caused by Aeromonas in our area and its possible relationship to inflammatory bowel disease. Patients and methods This was a retrospective observational study. All adult patients with a positive stool culture for Aeromonas were identified between January 2015 and December 2017 at Hospital Galdakao-Usansolo (Vizcaya, Spain). Results Ninety-eight patients were identified (median age 62 years; 51% women). Therefore, the incidence in our area was 32 cases per 105 inhabitants per year. Eleven per cent of them had been previously diagnosed with inflammatory bowel disease (four with ulcerative colitis and seven with Crohn's disease). Patients with inflammatory bowel disease more often received immunosuppressive therapy. Conversely, patients without inflammatory bowel disease suffered from more comorbidities. We also found comorbidity to be the risk factor most associated with Aeromonas infection. Conclusion Aeromonas infection is a common gastrointestinal infection that may occur in both immunocompetent and immunocompromised patients. Immunosuppression is a significant factor in inflammatory bowel disease patients, while comorbidity seems to confer a higher risk on patients without this disease.

Role of Aeromonas sp. involving in adaptive immune response of adult Lethenteron reissneri

Identifying the intestinal microorganisms involved in host immune functions could supply information for understanding the interaction between microbes and the host. The composition and comparison of the intestinal bacterial community in larval and adult Lethenteron reissneri are discussed. Significant differences could be observed in the bacterial community composition and the abundance of specific members. At the genus level, Aeromonas was detected as one of the dominant members in larvae, while Simplicispira was dominant in adult L. reissneri. Using isolated gut-derived Aeromonas as the antigen, the stimulation of adult L. reissneri could lead to the up-regulation of variable lymphocyte receptors (VLRs), such as VLRA, VLRB, and VLRC, in the mRNA level. Furthermore, the abundance of Aeromonas increased by 3.6 times after the lipopolysaccharide (LPS) stimulation in adult L. reissneri. Therefore, gut-derived Aeromonas were considered involved in the adaptive immune response of adult L. reissneri. The analysis of the bacterial community composition in the gut content of L. reissneri will broaden the understanding of this unique organism. The comparison of the intestinal bacterial composition between larval and adult L. reissneri will supply information for specific members that are involved in the adaptive immune system development in lampreys.

Infección gastrointestinal por Aeromonas: incidencia y su posible relación con la enfermedad inflamatoria intestinal

IntroductionAeromonas can cause several diseases in humans, with gastroenteritis accounting for most cases. The role of Aeromonas as a pathogen in human enterocolitis has been questioned in recent years. ObjectiveTo determine the incidence of gastrointestinal infection caused by Aeromonas in our area and its possible relationship to inflammatory bowel disease. Patients and methodsThis was a retrospective observational study. All adult patients with a positive stool culture for Aeromonas were identified between January 2015 and December 2017 at Hospital Galdakao-Usansolo (Vizcaya, Spain). ResultsNinety-eight patients were identified (median age 62 years; 51% women). Therefore, the incidence in our area was 32 cases per 105 inhabitants per year. Eleven per cent of them had been previously diagnosed with inflammatory bowel disease (four with ulcerative colitis and seven with Crohn's disease). Patients with inflammatory bowel disease more often received immunosuppressive therapy. Conversely, patients without inflammatory bowel disease suffered from more comorbidities. We also found comorbidity to be the risk factor most associated with Aeromonas infection. ConclusionAeromonas infection is a common gastrointestinal infection that may occur in both immunocompetent and immunocompromised patients. Immunosuppression is a significant factor in inflammatory bowel disease patients, while comorbidity seems to confer a higher risk on patients without this disease.

Reassessment of the Enteropathogenicity of Mesophilic Aeromonas Species.

Cases of Aeromonas diarrhea have been described all over the world. The genus Aeromonas includes ca. 30 species, of which 10 have been isolated in association with gastroenteritis. The dominating species that account for ca. 96% of the identified strains are Aeromonas caviae, A. veronii, A. dhakensis, and A. hydrophila. However, the role of Aeromonas as a true enteropathogen has been questioned on the basis of the lack of outbreaks, the non-fulfillment of Koch’s postulates and the low numbers of acute illnesses in the only existing human challenge study. In the present study we reassess the enteropathogenicity of Aeromonas using dose response models for microbial infection and acute illness. The analysis uses the data from the human challenge study and additional data from selected outbreak investigations where the numbers exposed and the dose were reported, allowing their inclusion as “natural experiments”. In the challenge study several cases of asymptomatic shedding were found (26.3%, 15/57), however, only 3.5% (2/57) of those challenged with Aeromonas developed acute enteric symptoms (i.e., diarrhea). The “natural experiments” showed a much higher risk of illness associated with exposure to Aeromonas, even at moderate to low doses. The median dose required for 1% illness risk, was ~1.4 × 104 times higher in the challenge study (1.24 × 104 cfu) compared to natural exposure events (0.9 cfu). The dose response assessment presented in this study shows that the combined challenge and outbreak data are consistent with high infectivity of Aeromonas, and a wide range of susceptibility to acute enteric illness. To illustrate the outcomes, we simulate the risk associated with concentrations of Aeromonas found in different water and food matrices, indicating the disease burden potentially associated with these bacteria. In conclusion this study showed that Aeromonas is highly infectious, and that human susceptibility to illness may be high, similar to undisputed enteropathogens like Campylobacter or Salmonella.

Aeromonas: a book review

Aeromonas: a book review

Identification of extracellular DNase-producing bacterial populations on catfish fillets during refrigerated storage

Food spoilage is a major problem faced by consumers across the globe. As an enzyme that degrades DNA, DNase production on fish tissue seemed likely to aid in fish spoilage. Based on physical characteristics, bacteria producing extracellular DNase were isolated on selective media. 16S rDNA sequences were obtained identifying isolates as bacteria belonging to Aeromonas spp., Serratia spp., Shewanella spp., and Rahnella spp. Aeromonas spp. were the predominant bacteria isolated in this study; this statistically suggests that Aeromonas spp. are dominant in DNase-producing bacterial populations on catfish tissue. Results obtained in this study suggest that extracellular DNase-producing bacteria play a large role in catfish spoilage and support the need for further research on the role of Aeromonas spp. in fish spoilage. Rahnella spp. was isolated from catfish fillets in this study and identified, for the first time, as DNase producing bacteria.

Plasmid-mediated quinolone resistance in Aeromonas allosaccharophila recovered from a Swiss lake

To search for plasmid-mediated qnr genes among waterborne environmental Aeromonas spp. recovered from Switzerland. Isolates presenting MICs of nalidixic acid or ciprofloxacin > or = 1 mg/L were screened for qnr genes by a multiplex PCR approach followed by sequencing. Plasmids were transferred by transformation, and further analysis of the genetic structures surrounding the qnrS2 gene was carried out by PCR and sequencing. A qnrS2 gene was identified from a single Aeromonas allosaccharophila isolate (Lugano lake, Lugano), as part of a mobile insertion cassette located on a broad host range IncU-type plasmid. This plasmid co-harboured a class 1 integron containing the aac(6')-Ib-cr, bla(OXA-1), catB3 and arr-3 gene cassettes. These findings strengthen further the role of Aeromonas spp. as a reservoir of antimicrobial resistance determinants in the environment.

Faecal contamination indicators, Salmonella, Vibrio and Aeromonas in water used for the irrigation of agricultural products.

The faecal contamination indicators (total coliforms, faecal coliforms, Escherichia coli, enterococci) and the genera Salmonella, Vibrio, Aeromonas were investigated in water samples used for irrigation. During 4 months, 52 samples were taken. The methods used were: multiple tube fermentation method for faecal contamination indicators and membrane filtration techniques for salmonella, aeromonas and vibrio. Two samples were positive for Salmonella spp., fourteen for Aeromonas spp. and no samples for Vibrio spp. No correlation was found between aeromonas and the indicators of faecal contamination. Regarding Aeromonas spp., 21.6% of the strains were adhesive and 12.6% cytotoxic: this confirms the possible role of aeromonas in human pathologies. These results are important to determine the quality of irrigation water in relation to human health. In fact, the spray or sprinkler irrigation produces bioaerosol, which can contaminate the crops that are likely to be eaten uncooked. In addition, the flood or furrow irrigation represents a risk to field workers.

Prevalence and characterization of Aeromonas spp. isolated from foods in Uppsala, Sweden

Different food samples collected from randomly selected retail consumer shops in Uppsala (Central Sweden) were investigated for the presence of Aeromonas species. Forty-two percent ( 10/24 ) of the food samples contained organisms belonging to two Aeromonas spp. namely, Aeromonas hydrophila and Aeromonas sobria . The type of foods from which Aeromonas were isolated, were poultry, fish, beef and pork. None of the Aeromonas spp. were isolated from vegetables or raw milk samples. The Aeromonas isolates possessed the capacity to produce different potential virulence determinants such as haemolysin, cytotoxin, cytotonic toxin, enterotoxin and protease. Since A. hydrophila and A. sobria are considered to be potential human pathogens, it is concluded that in case foodborne infections are suspected or encountered, the role of Aeromonas should not be ruled out.

A note on Aeromonas spp. from chickens as possible food‐borne pathogens

The possible role of Aeromonas spp. as potential food-borne psychrotrophic pathogens was investigated by examining organisms isolated from processed raw chicken for their biochemical characteristics, ability to produce exotoxins and to grow at chill temperatures. These strains, in particular A. sobria, with identical characteristics to human diarrhoea-associated aeromonads were readily found. Chicken, and human and environmental (water) strains characterized in a previous study, were investigated for their ability to grow at refrigeration temperatures (5 +/- 2 degrees C) and, for selected strains, the theoretical minimum temperature for growth (Tmin) was determined from the growth pattern in a temperature gradient incubator. All enterotoxigenic chicken strains tested were typical mesophiles, with an optimal growth temperature of approximately 37 degrees C and Tmin values approximately 4.5 degrees C. They were rapidly outgrown by a psychrotrophic Pseudomonas sp. typical of spoilage biota found on food. Enterotoxin was not produced below 15 degrees C by any of the toxigenic food strains tested. The Aeromonas strains isolated from chickens in this study seem unlikely therefore to be a significant health risk, provided the chickens are properly stored and cooked. This would appear to be substantiated by the lack of reports of food-associated outbreaks of illness from these sources.

Aeromonas as a human pathogen.

Although the first Aeromonas strain was described by Zimmermann as early as in 1890, it took 60 years until Caselitz established human pathogenicity of strains then called "Vibrio jamaicensis". Since then, and especially in the last 10 years, there have been increasing numbers of reports on different infections caused by members of the genus Aeromonas. These include sepsis; meningitis; cellulitis; necrotizing fasciitis; ecthyma gangrenosum; pneumonia; peritonitis; conjunctivitis; corneal ulcer; endophthalmitis; osteomyelitis; suppurative arthritis; myositis; subphrenic abscess; liver abscess; cholecystitis and/or ascending cholangitis; urinary tract infection; endocarditis; ear, nose, and throat infections; balanitis; etc. The role of Aeromonas in gastrointestinal disease is very controversial. Increasing epidemiological data suggest that these organisms play a major role in enteric infections, but so far enteropathogenicity has not been demonstrable in experiments where volunteers were given high numbers of Aeromonas possessing different virulence factors. Virulence factors include hemolysin(s), enterotoxin(s), hemagglutinins, invasivity, and others; but these are not found more frequently in strains isolated from patients with diarrhea than from healthy controls. Whether there is a correlation between species and disease remains to be elucidated and requires more information about the taxonomy of this genus.

SPECIES DIFFERENTIATION AND BIOCHEMICAL MARKERS FOR TOXIGENICITY IN FECAL AEROMONAS ISOLATES FROM CHILDREN

The role of Aeromonas (Aer) in the etiology of pediatric diarrhea is incompletely defined. It is unclear whether identification of isolates at the species level or performance of toxigenicity studies help distinguish pathogenic from non-pathogenic strains. We isolated Aer from 33 of 704(children whose fecal specimens were submitted to the Microbiology Laboratory of Children's Medical Center, Dalls, over a I-year period. Isolates were identified as Aer using the API 20E system. Additional tests performed on 29 strains included gas from glucose, salicin fermentation, growth in KCN, esculin hydrolysis, and elastase production. A. caviae was the predominant species (n = 19, 66%). A. sobria and A. hydrophila accounted for 3 each and 4 (14%) strains could not be speciated. Toxin production by Aer was studied using CHO cell, adrenal Y1 cell, suckling mouse, and rabbit ileal loop assays. Twelve (39%) of 31 strains were positive in at least one of these assays including 3 (17%) of 18 A. caviae and all 9 non-caviae strains tested. Two toxigenic strains were from asymptomatic older children. Toxigenic strains were significantly more likely to be positive for arginine dihydrolase (p <0.05), lysine decarboxylase (p <0.001), and Voges-Proskauer reaction (p <0.01), produce gas from glucose (p <0.001), and not ferment arabinose (p <0.005) compared with non-toxigenic strains. We conclude that Aer differentiation at the species level is of limited clinical value and that several biochemical reactions can serve as markers for toxin production.

Isolation ofAeromonas spp. from human feces

Following our observation that Aeromonas spp. grow on Cefsulodin-Irgasan-Novobiocin (CIN) agar (Altorfer et al., Ahstr. A. Meet. Am. Soc. Microbiol. (1985)) we looked for the presence of Aeromonas spp. in stool specimens using CIN medium during 3 months in summer 1984. From 1282 specimens plated on CIN directly and after enrichment in PBS and Rappaport broth (the same procedur as used for recovery of yersiniae) 31 strains of Aeromonas spp. were isolated (2.4%). In addition, one strain from water was found. Of these 32 strains, 21 were A. eaviae, 5 were A. sobria, 1 was A. hydrophila, and 5 were atypical isolates. These findings were surprising in two ways: 1) A. caviae, our most frequent isolate, is often considered not to be pathogenic, 2) most of our isolates were from patients with intestinal disorders from whom no other enteropathogenic organisms could be isolated. So far, the role of Aeromonas spp. in diarrheal disease is controversial, but our results imply a clinical significance of isolates of all three species.