Aeromonas hydrophila, a gram-negative coccobacillus bacterium, can cause various infections in humans, including septic arthritis, diarrhea (traveler's diarrhea), gastroenteritis, skin and wound infections, meningitis, fulminating septicemia, enterocolitis, peritonitis, and endocarditis. It frequently occurs in aquatic environments and readily contacts humans, leading to high infection rates. This bacterium has exhibited resistance to numerous commercial antibiotics, and no vaccine has yet been developed. Aiming to combat the alarmingly high infection rate, this study utilizes in silico techniques to design a multi-epitope vaccine (MEV) candidate against this bacterium based on its aerolysin toxin, which is the most toxic and highly conserved virulence factor among the Aeromonas species. After retrieval, aerolysin was processed for B-cell and T-cell epitope mapping. Once filtered for toxicity, antigenicity, allergenicity, and solubility, the chosen epitopes were combined with an adjuvant and specific linkers to create a vaccine construct. These linkers and the adjuvant enhance the MEV's ability to elicit robust immune responses. Analyses of the predicted and improved vaccine structure revealed that 75.5%, 19.8%, and 1.3% of its amino acids occupy the most favored, additional allowed, and generously allowed regions, respectively, while its ERRAT score reached nearly 70%. Docking simulations showed the MEV exhibiting the highest interaction and binding energies (-1,023.4 kcal/mol, -923.2 kcal/mol, and -988.3 kcal/mol) with TLR-4, MHC-I, and MHC-II receptors. Further molecular dynamics simulations demonstrated the docked complexes' remarkable stability and maximum interactions, i.e., uniform RMSD, fluctuated RMSF, and lowest binding net energy. In silico models also predict the vaccine will stimulate a variety of immunological pathways following administration. These analyses suggest the vaccine's efficacy in inducing robust immune responses against A. hydrophila. With high solubility and no predicted allergic responses or toxicity, it appears safe for administration in both healthy and A. hydrophila-infected individuals.

Aeromonas spp. are widely distributed in surface water, sewage, untreated and chlorinated, drinking water, as well as meats, fish, shellfish, poultry, and their products. A disease caused by Aeromonas spp. is designated as aeromoniasis. It can affect different aquatic animals, mammals, and birds in different geographic regions. Moreover, gastrointestinal and extra-intestinal disease conditions may be provoked in humans as a result of food poising with Aeromonas spp. Some Aeromonas spp. have been identified, however, Aeromonas hydrophila (A. hydrophila), A. caviae, and A. veronii bv sobria may be of public health significance. Aeromonas spp. are members of family Aeromonadaceae and genus Aeromonas. They are Gram-negative rod-shaped, facultative anaerobic, and oxidase and catalase-positive bacteria. The pathogenicity of Aeromonas in different hosts is mediated by several virulence factors such as endotoxins, cytotoxic enterotoxin, cytotoxins, hemolysins, adhesins, and extracellular enzymes such as proteases, amylases, lipases, ADP-ribosyltransferases, and DNases. Most avian species are susceptible to either natural or experimental infections with Aeromonas spp. Infection usually arises through feacal-oral route. Traveler's diarrhea as well as other systemic and local infections are the clinical picture of food poisoning associated with aeromoniasis in humans. Despite Aeromonas spp. being sensitive to various antimicrobials, multiple drug resistance has been commonly reported worldwide. Accordingly, this review highlights aeromoniasis in poultry regarding Aeromonas virulence factors epidemiology, pathogenicity, zoonosis, and antimicrobial resistance.

Aeromonas infections are rare in Europe and often related to traveller's diarrhoea. A total of 185 Aeromonas isolates from river water, fish and clinical sources, recovered during a 1-year period, were used to investigate the disease spectrum and impact of multidrug-resistant (MDR) strains. They were all identified by biochemical tests and 25% of them were also identified by sequencing of the 16S rRNA gene. The minimum inhibitory concentrations (MICs) of 21 antimicrobials were determined for all isolates by broth microdilution/E-strips methods, and susceptibility was assessed according to the Clinical and Laboratory Standards Institute (CLSI). Strains pathogenicity was determined by using Swiss Webster mice as the animal model. Aeromonas diseases had an incidence of around 20 cases/million inhabitants in the metropolitan area of Valencia (Spain). Acute gastroenteritis in children with no history of travel abroad was the main pathology. These cases were related to A. caviae, A. veronii biovar sobria, A. hydrophila and A. dhakensis. A significant incidence of A. caviae in humans was found, while the other species were equally present in clinical and environmental origins. A. jandaei, A. bestiarum and A. media had mainly an environmental distribution. The prevalence of MDR Aeromonas was maximal in clinical samples, and resistance phenotypes were significantly related to this source. 7.2% of environmental Aeromonas was resistant to at least five drugs; most of them were moderately virulent for mice and, in addition, belonged to clinically significant species. The present study demonstrates a diseases spectrum similar to that reported in tropical countries, and also that pathogenic and heavily MDR Aeromonas are present in environmental reservoirs. MDR Aeromonas from any source analysed were susceptible to aztreonam, netilmicin, cefotaxime, ceftazidime, cefepime and fluoroquinolones.

Travelers diarrhea affects millions of tourists each year. Most cases are caused by a variety of bacterial enteropathogens: toxigenic Escherichia coli, Campylobacter, Shigella, Salmonella, Aeromonas, Plesiomonas and non-cholera vibrios. Treatment may include antibacterial therapy with either ciprofloxacin, or azitrhomycin, or rifaximin. Viral pathogens such as norovirus usually cause short-term illness that typically resolves before travelers seek medical attention. Chronic gastrointestinal disease in returning travelers often is caused by parasitic pathogens like Giardia lamblia. The impact of prevention of travelers diarrhea is limited, therefore travelers should be informed about early self-treatment.

We report a severe case of travellers' diarrhoea in a patient returning from Ecuador to Italy with the concomitant presence of Aeromonas veronii biovar sobria and Vibrio parahaemolyticus in their faeces. Based on diagnostic results, epidemiological information and the clinical outcome, we conclude that the real aetiological agent was A. veronii biovar sobria, while V. parahaemolyticus was only transient in the intestine of the patient.

The mono-ADP-ribosyltransferase (mART) toxins are contributing factors to a number of human diseases, including cholera, diphtheria, traveler's diarrhea, and whooping cough. VahC is a cytotoxic, actin-targeting mART from Aeromonas hydrophila PPD134/91. This bacterium is implicated primarily in diseases among freshwater fish species but also contributes to gastrointestinal and extraintestinal infections in humans. VahC was shown to ADP-ribosylate Arg-177 of actin, and the kinetic parameters were K(m)(NAD(+)) = 6 μM, K(m)(actin) = 24 μM, and k(cat) = 22 s(-1). VahC activity caused depolymerization of actin filaments, which induced caspase-mediated apoptosis in HeLa Tet-Off cells. Alanine-scanning mutagenesis of predicted catalytic residues showed the predicted loss of in vitro mART activity and cytotoxicity. Bioinformatic and kinetic analysis also identified three residues in the active site loop that were critical for the catalytic mechanism. A 1.9 Å crystal structure supported the proposed roles of these residues and their conserved nature among toxin homologues. Several small molecules were characterized as inhibitors of in vitro VahC mART activity and suramin was the best inhibitor (IC(50) = 20 μM). Inhibitor activity was also characterized against two other actin-targeting mART toxins. Notably, these inhibitors represent the first report of broad spectrum inhibition of actin-targeting mART toxins.

Traveler's diarrhea (TD) is a crucial area for research, as it affects millions of tourists each year and creates a large economic burden. More than 60% of TD cases are caused by a variety of bacterial enteropathogens: diarrhea-producing Escherichia coli, Shigella, Campylobacter, Salmonella, Aeromonas, Plesiomonas, and noncholera Vibrios. Noroviruses are also an important cause of morbidity among travelers. Recent studies have identified host genetic risk factors associated with susceptibility to pathogen-specific TD. Prevention strategies should be emphasized, as all individuals with TD experience approximately 24 hours of disability and 5-10% experience chronic functional bowel disease. Poorly absorbed rifaximin provides protection for trips lasting 2 weeks or less. TD vaccines are also currently in development. All individuals planning trips to developing regions should be armed with 1 of the 3 agents that have shown efficacy for self-treatment of TD: ciprofloxacin (or levofloxacin), rifaximin, or azithromycin, depending upon the location of the trip. Although global epidemiologic changes in etiologic agents as well as antibiotic resistance patterns have been better understood recently, changes should be expected during the next decade due to new prevention and treatment approaches.

Fifty-one published studies of travelers' diarrhea (TD) were examined to look for regional differences in pathogens identified. Enterotoxigenic E. coli was detected in 1,678/5,518 (30.4%) of TD cases overall, with rates in Latin America/Caribbean (L. America), Africa, south Asia, and Southeast Asia of 1,109/3,302 (33.6%), 389/1,217 (31.2%), 153/499 (30.6%), and 36/500 (7.2%), respectively (P < 0.001). Enteroaggregative E. coli was the second most common agent in L. America, found in 166/689 (24.1%), compared with 3/165 (1.8%) in Africa and 33/206 (16%) in south Asia (P < 0.001). Other significantly regional differences were seen for enteropathogenic E. coli, diffusely adherent E. coli, Campylobacter, Shigella spp., Salmonella, Aeromonas spp., Plesiomonas, Vibrios, rotavirus, noroviruses, Giardia, and Entoamoeba histolytica. The regional differences in pathogen identification identified will serve as a baseline for antimicrobial therapy recommendations and vaccines strategies.

Aeromonas species is an infrequent pathogen causing travelers' diarrhea and gastroenteritis. No human case of appendicitis has been reported as a complication of Aeromonas infection until now. We describe a case of acute appendicitis associated with Aeromonas sobria infection acquired in Cebu, Philippines.

Gastroenteritis is a nonspecific term for various pathologic states of the gastrointestinal tract. Gastroenteritis causing pathogens are the second leading cause of morbidity and mortality worldwide. In the developed countries diarrhea is the most common reason for missing work, while in the developing world, it is a leading cause of death. Internationally, the mortality rate is 5-10 million deaths each year. "Traveller's diarrhea" is a polyetiologic common health problem of international travellers which affects travellers generally for days, but it can result in chronic postinfectious irritable bowel syndrome as well. Infectious agents usually cause acute gastroenteritis either by adherence of the intestinal mucosa, or by mucosal invasion, enterotoxin production, and/or cytotoxin production. The incubation period can often suggest the cause of etiology. When symptoms occur within 6 hours of eating, ingestion of preformed toxin of S. aureus or Bacillus cereus should be suspected. The incidence of hypervirulent C. difficile associated colitis is an emerging problem as a healthcare system associated infection. While infectious agents do not commonly cause chronic diarrhea, those that do include C. difficile, Giardia lamblia, Entamoeba histolytica, Cryptosporidium, Aeromonas and Yersinia . Amoebiasis is the second to malaria as a protozoal cause of death. Infection with HIV is also a common cause of diarrhea.

No cause of one-third of travelers' diarrhea (TD) cases can be detected despite microbiologic assessment. We propose that these pathogen-negative TD cases include undetected enterotoxigenic Escherichia coli (ETEC). As a standard in diagnostic microbiology, samples of five E. coli colonies were tested to detect ETEC from stool cultures. We compared the sensitivities and the number of ETEC detected by 20 colonies with those of 5, 10, and 15 colonies. The percent detection of ETEC with five E. coli colonies was significantly different from that using 20 E. coli colonies. Of the 116 subjects studied, the number positive for ETEC for 5, 10, 15 and 20 colonies tested were 22 (19.0%), 37 (31.9%), 45 (38.8%) and 46 (39.7%), respectively. Based on our results, we recommend the testing of at least 10 E. coli colonies for optimum detection of ETEC in patients with TD.

Prulifloxacin, the prodrug of ulifloxacin (active component), is a newer fluoroquinolone with broad activity against enteric and nonenteric gram-negative bacilli. Ulifloxacin and other oral comparator agents were tested for activity against 582 gastroenteritis strains from global surveillance studies. Ulifloxacin was highly active against Escherichia coli, Salmonella spp., Shigella spp., Yersinia spp., Vibrio spp., Aeromonas spp., and Plesiomonas spp. (MIC(50)s and MIC(90)s, <or=0.03 microg/ml and <or=0.06 microg/ml, respectively). Only rare Aeromonas spp., Campylobacter spp., and E. coli displayed elevated MIC results (>or=4 microg/ml). Ciprofloxacin exhibited similar activity but was two- to fourfold less potent. Presently approved for clinical use in certain European countries and Japan, ulifloxacin was the most active of the antimicrobial agents tested against these gastroenteritis-causing pathogens.

A study was undertaken to look for heat-labile enterotoxin producing Escherichia coli (LT-ETEC) in patients with acute watery diarrhea resembling cholera in Chandigarh in North India. Two periods were selected, an interepidemic (2001) and an epidemic (2002) period. Heat-labile enterotoxin (LT) was detected using reverse passive latex agglutination test. LT-ETEC strains were serotyped and antimicrobial susceptibility was studied. LT-ETEC was detected in 16 of 21 stool samples during 2001. Other organisms isolated included Vibrio cholerae O1 Ogawa and Aeromonas hydrophila in 2 and 3 patients, respectively. During the epidemic period, 4 of 17 samples tested positive for LT-ETEC, whereas V. cholerae, Shigella, and Salmonella were isolated in 91, 2, and 1 patient, respectively. Similar features such as acute watery diarrhea and dehydration were common to patients examined in the interepidemic period and those examined during the cholera epidemic. The serotypes isolated were O15 (8), O63 (2), O148 (2), and O158 (2), and the remaining strains were untypable. More than 50% of patients were adults. Antimicrobial susceptibility was as follows: amoxycillin (3/20), nalidixic acid (6/20), trimethoprim (5/20), chloramphenicol (8/20), amikacin (19/20), gentamicin (13/20), cefotaxime (15/20), and ciprofloxacin (10/20). High fluoroquinolone resistance in ETEC may be a serious cause of concern for travelers visiting this region, and thus thereis a need to monitor drug resistance in this pathogen.