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.

Traveler's diarrhea (TD) is the most frequent health problem in travelers to developing countries. Several personal and environmental risk factors are at the basis of TD acquisition and are discussed in this paper. TD is caused by a wide range of infectious organisms, ETEC and EAEC bacteria strains being the main enteropathogens incriminated in TD. Other causative bacteria are: Shigella spp., Campylobacter spp., Vibrio spp., Aeromonas spp., Salmonella spp., and Plesiomonas spp. Parasite species are also included: Cyclospora cayetanensis, Giardia lamblia, Cryptosporidium, Entamoeba histolytica, as well as viruses: rotavirus, adenovirus, Norwalk virus. Due to the great diversity of pathogens incriminated, several pathophysiological mechanisms have been described and some of them are still poorly understood. The clinical symptoms present are also quite variable, although inflammatory and non-inflammatory diarrhea have been established as a classical and basic classification of diarrhea.

Traveler's diarrhea is the most common health problem of international travelers. We determined the prevalence of Aeromonas spp. associated with traveler's diarrhea and analyzed the geographic distribution, clinical features, and antimicrobial susceptibility. Aeromonas spp. were isolated as a cause of traveler's diarrhea in 18 (2%) of 863 patients. A. veronii biotype sobria was isolated in nine patients, A. caviae in seven patients, and A. jandaei and A. hydrophila in one patient each. Aeromonas spp. were isolated with a similar prevalence in Africa, Latin America, and Asia. Watery and persistent diarrhea, fever, and abdominal cramps were common complaints. All strains were resistant to ampicillin; showed variable resistance to chloramphenicol, tetracycline, and cotrimoxazole; and were susceptible to cefotaxime, ciprofloxacin, and nalidixic acid. The persistence of symptoms made antimicrobial treatment necessary.

During a 5-year period (1995-1999) a total of 7090 stool samples obtained from patients with acute diarrhoea, mostly community-acquired, were examined for bacterial pathogens, in the Greek island of Crete. One or more enteric pathogens were isolated from 987 patients (14%). Salmonella enterica were the most commonly isolated bacteria (6%), followed by Campylobacter spp. (4.2%), and enteropathogenic Escherichia coli (EPEC) (1.8%). Yersinia enterocolitica (0.6%), Shigella spp. (0.3%), and Aeromonas hydrophila (0.04%), were less frequently isolated. Clostridium difficile was isolated from 65 out of 451 diarrhoeal specimens examined (14.4%). Toxin B was detected in all cases. No verotoxigenic E. coli strains were identified. Resistance to ampicillin was observed in 31.5% of the Salmonella, 58.3% of the Shigella and 31.5% of the EPEC isolates. Resistance to trimethoprim-sulfamethoxazole was observed in 4.4% of the Salmonella, 30.5% of the Shigella, and 18.5% of the EPEC isolates. High percentages of resistance to quinolones (44.5% to norfloxacin, and 40.5% to ciprofloxacin), were found among Campylobacter isolates, while resistance to erythromycin was observed in 14.9% of them. With the present study we continue the surveillance of bacterial pathogens associated with diarrhoeal disease on the island of Crete.

Incidence of various enteropathogenic bacteria was examined from diarrheal faecal samples that were collected from the patients of Kobe City General Hospital and some station hospitals (23,862), and from overseas travelers (2,855) over a period of decade (1989-1999) in Kobe. A total of 1,580 strains were isolated from domestic and 331 strains from overseas travelers. The results are as follows. 1) Thirteen kinds of enteropathogenic bacteria were isolated from domestic diarrheal cases (6.6%). Salmonella was the most predominant bacteria followed by Campylobacter, Vibrio parahaemolyticus, enteropathogenic Escherichia coli and Shigella. 2) Eleven kinds of enteropathogenic bacteria were isolated from overseas diarrheal travelers (11.6%). The most frequently isolated species was Salmonella, followed by Vibrio parahaemolyticus, Shigella and Plesiomonas shigelloides. 3) Of Salmonella strains isolated from domestic and overseas diarrheal cases, serovar Enteritidis was the most predominant. Other frequent serovars in both cases were Typhimurium, Tennessee, Hadar, Infantis, Blockley and Montevideo. 4) Antibiotics resistant rate of the isolated Salmonella strains was 42.6% for domestic samples and 29.3% for overseas diarrheal cases. In domestic cases. Enteritidis was resistance to streptomycin only and the multiple antibiotic resistance was observed in Typhimurium serovars. In overseas samples, the multiple antibiotic resistance was seen in a few Typhimurium, Anatum and Blockley strains. 5) Among Shigella, S. sonnei was isolated from both domestic and overseas cases. The frequency of acquiring infection was the highest in India, followed by Indonesia, Thailand and Nepal. 6) With reference to the incidence of the members of the genus Vibrio, Aeromonas and Plesiomonas, V. parahaemolyticus were abundant from domestic samples where as V. parahaemolyticus, P. shigelloides, Vibrio cholerae non-O1 and Vibrio cholerae O1 were isolated more frequently from overseas samples. The frequency of acquiring infection was the highest in Thailand, followed by Indonesia and India.

A 1-year prospective study was conducted to identify enteropathogens in adults with diarrhea (n=851) and in healthy control subjects (n=203) by use of conventional laboratory methods. Virulence factor genes for diarrheagenic Escherichia coli were detected by polymerase chain reaction. Enteropathogens were identified in 56% of patients and 16% of control subjects. The isolation rate was 65% for patients with symptoms for <1 week and for travelers; >1 pathogen was found in 11% of patients. The most frequent enteropathogens were Campylobacter (13% of patients), Clostridium difficile (13%), enterotoxigenic Escherichia coli (8%), Salmonella (7%), Shigella (4%), Blastocystis hominis (4%), calicivirus (3%), rotavirus (3%), enteroaggregative E. coli (2%), Aeromonas (2%), Giardia intestinalis (2%), Cryptosporidium (2%), and astrovirus (2%). Less frequently isolated (< or =1% of patients) were verotoxigenic E. coli, enteropathogenic E. coli, enteroinvasive E. coli, Entamoeba histolytica/Entamoeba dispar, microsporidia, and adenovirus. Fifty percent of the patients were hospitalized, and 43% needed intravenous fluids. The median duration of diarrhea was 14 days. Clinical features were not helpful for predicting the etiology of diarrhea.

Although these four groups of organisms are perceived as infrequent food-borne pathogens or of dubious significance, increasing epidemiologic data indicate that L. monocytogenes is an emerging cause of infections, particularly gastroenteritis. Furthermore, if data are ever generated that prove that most fecal isolates of Aeromonas are involved in bacterial diarrhea, then aeromonads will become recognized as important food-borne pathogens. For Plesiomonas and Edwardsiella, recognition of possible involvement in food-borne disease requires detailed medical histories, including foreign travel, contact with pets or animals, and food consumption histories.

During the period of investigation from Sept. 4, 1994 to Dec, 1996, a total of 11,446,534 overseas travellers were quarantined at Kansai Airport Quarantine Station, and 22,187 voluntarily reported of episodes suffering from diarrhoea. Bacteriological examination of the stools a total of 9,299 individuals' was performed, and the following results were obtained. 1) Various enteropathogenic bacteria were isolated from 33.3% of the stools examined. Bacterial species isolated were as follows: Plesiomonas shigelloides, 2,066 cases (66.7%); Vibrio parahaemolyticus, 358 cases (11.6%); Aeromonas sobria, 360 cases (11.6%); Shigella spp., 291 cases (9.4%); Salmonella spp., 183 cases (5.9%); A. hydrophila, 126 cases (4.1%); and V. cholerae non-O1, 121 cases (3.9%). However, ETEC was not done with an object of test. 2) In 502 cases (16.2%), plural enteropathogenic bacteria were isolated from single patient, suggesting high frequency of a mixed infections. 3) From Feb. to Mar. 1995, thirteen cases cholera were found from patients who had travelled to Bali, Indonesia. Cases with enteropathogenic bacteria other than V. cholerae O1 were found without any seasonal variation. 4) The major regions where the travellers were infected with the pathogens are as follows: Vibrio spp., were from only Asia; Shigella, widely distributed but especially in India and Indonesia; P. shigelloides and Salmonella, widely distributed. 5) Among the Shigella strains, S. sonnei were isolated the most, followed by S. flexneri, S. boydii and S. dysenteriae. A strain of S. boydii provisional serovar E 16553 was isolated from a patient infected in India. 6) Among the Salmonella serovars, Salmonella Enteritidis was isolated the most frequently (49 cases, 25.7%). 7) 265 (89.2%) of 297 Shigella strains, 52 (27.2%) of 19] Salmonella strains, and 19 (95.0%) of 20 V. cholerae O1 were resistant to one or more drugs tested (SM. CP. TC. KM. ABPC. NA. OFLX). 8) All of the 20 V. cholerae O1 strains were Ogawa, E1 Tor. All of them were toxigenic strains. 9) The most frequently isolated serovar of V. parahaemolyticus was O3: K6. 89.8% of all V. parahaemolyticus strains were positive for thermostable direct hemolysin (TDH) gene, and 14.6% of them were positive for TDH-related hemolysin (TRH) gene by DNA-probe or PCR method.

In a survey examining the causes of travellers' diarrhoea treated in Tokyo between July 1986 and December 1995, Aeromonas species were isolated from 1265 (5.5%) of 23,215 travellers returning from developing countries. Aeromonas species were the fourth most frequent enteropathogen isolated, following enterotoxigenic E. coli (8.5%), Salmonella spp. (7.6%) and Plesiomonas shigelloides (5.6%). Aeromonas species were found in 1191 (5.6%) of 21,257 patients with diarrhoea and in 74 (3.8%) of 1958 healthy individuals without diarrhoea. Mixed infection was observed in 512 (40.5%) cases. No significant difference in the prevalence of Aeromonas by year, season, age distributions, or sex was observed, but a slight difference was noted depending on the country where the travellers visited. Of the 1265 Aeromonas isolates, 893 strains (70.6%) were A. veronii biovar sobria, 330 (26.1%) were A. hydrophila, and 42 (3.3%) were A. caviae. The clinical symptoms of patients from whom Aeromonas species was isolated as the only potential enteric pathogen were almost similar, which were watery diarrhoea (about 60%), abdominal cramps (43%), fever (around 15%), and nausea or vomiting (13%). Although the severity of illness was milder than that of enterotoxigenic E. coli alone, these data suggest that Aeromonas species are important enteric pathogens in travellers' diarrhoea.

The presence of numerous genera of spoilage bacteria, yeasts and molds, and an occasional pathogen on fresh produce has been recognized for many years. Several outbreaks of human gastroenteritis have been linked to the consumption of contaminated fresh vegetables and, to a lesser extent, fruits. Salads containing raw vegetables have been identified as vehicles of traveler's diarrhea, an illness sometimes experienced by visitors to developing countries. Enterotoxigenic Escherichia coli is the most common cause of this illness. Enterohemorrhagic E. coli , specifically serotype O157:H7, has been implicated as the causative agent in an outbreak of gastroenteritis resulting from the consumption of cantaloupes. Outbreaks of salmonellosis in humans have been attributed to consumption of contaminated tomatoes, mustard cress, bean sprouts, cantaloupe, and watermelon. An onion-associated outbreak of Shigella flexneri gastroenteritis has recently been reported in the United States. Outbreaks of human listeriosis have been epidemiologically linked to the consumption of fresh cabbage and lettuce. Gastrointestinal illness caused by the consumption of raw vegetable seed sprouts contaminated by Bacillus cereus has been documented. The ability of Aeromonas hydrophila and Aeromonas sobria to produce several virulence factors has been documented and their fairly common occurrence in water raises concern over public health risks that may be associated with the consumption of salad vegetables, although their role as agents in foodborne illness has not been fully confirmed. Viruses are not likely to grow on contaminated vegetables and fruits but can survive long enough to cause life-threatening illness in humans. An increased per capita consumption of fresh and lightly processed produce in the United States and other countries, coupled with an increase in importation of produce to these countries from regions where standards for growing and handling produce may be compromised, has resulted in heightened interest in outbreaks of human gastroenteritis that may be attributed to contaminated fresh produce, particularly salad vegetables. Likewise methods of handling, processing, packaging, and distribution of fresh produce on a regional or local scale within countries are receiving attention in terms of identifying and controlling microbiological hazards. Hazard analysis critical control point (HACCP) programs are being developed in an effort to minimize the risk of illness associated with consumption of fresh produce. Examples of pathogenic microorganisms associated with fresh produce as well as procedures that can be used to reduce their incidence at the point of consumption are discussed.

During the last 2 years and 8 months before the closure of Osaka Airport Quarantine Station (from Jan. 1992 to Sep. 3, 1994), a total of 7,421,909 overseas travellers were quarantined. 15,919 reported themselves of suffering from diarrhoea. Bacteriological examination of a total of 6,031 individuals' stools were performed. 1) Various enteropathogenic bacteria were isolated from 31.2% of the stools examined. Isolated species were as follows: Plesiomonas shigelloides, 1,127 cases (59.9%); Vibrio parahaemolyticus, 293 cases (15.6%); Salmonella spp., 262 cases (13.9%); Shigella spp., 235 cases (12.5%); Aeromonas sobria, 93 cases (4.9%); V. cholerae non-O1, 69 cases (3.7%). 2) The enteropathogenic bacteria were isolated through out the year without any seasonal variation. 3) The major regions where the travellers were infected with the pathogens are as follows: V. cholerae non-O1 (NAG Vibrio) and enteropathogenic Escherichia coli, South-East and South-West Asia; Vibrio other than NAG, South-East and East Asia; Shigella, widely distributed but especially in India; P. shigelloides and Salmonella, widely distributed. 4) 2 strains of toxigenic (cholera toxin-producing) V. cholerae O139 were isolated from patients who had visited Indonesia and Thailand, respectively. 5) In 320 cases (17%), plural enteropathogenic bacteria were isolated from single patients, suggesting a high frequency of the mixed infections. 6) Among Shigella strains, S. sonnei were isolated the most, followed by S. flexneri (24.7%), S. boydii (8.8%) and S. dysenteriae (2.9%). 7) Among Salmonella serovers, Salmonella Enteritidis was isolated the most frequently (39 cases, 14.1%). 8) 218 (91.6%) of 238 Shigella strains and 103 (37.6%) of 276 Salmonella strains were resistant to one or more drugs tested (SM.CP.TC.KM.ABPC.NA.OFLX). 9) All of the 22 V. cholerae O1 strains were Ogawa, E1 Tor. Among them, 19 were toxigenic strains and 3 were non-toxigenic. 10) O4:K8 was the most frequently isolated serover of V. paraemolyticus. 87.4% of all V. parahaemolyticus strains were positive with thermostable direct hemolysin (TDH) gene, and 12.6% of them were positive with TDH-related hemolysin (TRH) gene by DNA-probe methods.

Aeromonas species were isolated from 249/13,027 (1.9%) stool samples submitted to the Dept. of Bacteriology and Immunology, University of Helsinki, during 1 year, to be cultured for bacterial enteropathogens. Aeromonas was the third most common enteropathogen isolated, after campylobacter (3.6%) and salmonella (3.3%). Isolates and clinical information from 234 Aeromonas patients were available for further study. A. caviae (41%), A. hydrophila (27%), and A. veronii biovar sobria (22%) were the most frequent isolates. In 15% of the patients, other enteropathogens were found along with aeromonas. Only 2% of all aeromonas-positive patients were found to be asymptomatic, whereas no aeromonas isolates were detected in the stools of 343 asymptomatic individuals. Almost all (96%) patients with aeromonas in their feces had gastroenteritis. Patients infected with A. veronii biovar sobria had a shorter illness course and had more often travelled abroad. In conclusion, Aeromonas spp. were found to be a potential cause of diarrhea in Finnish patients.

The association of Aeromonas spp. with travellers' diarrhoea was studied among 978 Finnish tourists travelling to Morocco in winter (n = 398) and autumn (n = 580) in 1989. Fifty-five isolates from diarrhoeal patients with (n = 16) or without (n = 39) a recent travelling history in a developing country were also included. In Morocco, Aeromonas spp. were isolated from 8.7% of patients with diarrhoea and from 1.4% of non-diarrhoeal tourists (p < 0.001). Aeromonas spp. were found as the sole pathogen in 5.5% of patients (p < 0.001). Diarrhoea with multiple pathogens, including Aeromonas spp., was found in 3.1% of patients. Species identification by phenotypic and genotypic methods indicated that A. veronii biotype sobria (hybridisation group HG 8/10) and A. caviae (HG 4) were the most common Aeromonas spp. associated with travellers' diarrhoea. A. hydrophila (HG 1) and A. caviae (HG 4) were common in patients acquiring diarrhoea in Finland. Ribotyping of strains within a species showed that all strains had different ribotypes although the tourists were infected during the same trip. This study suggested that only certain Aeromonas spp. were commonly found in travellers' diarrhoea. However, the causative role of those species is unclear.

Over a period of 17 months, Aeromonas caviae was cultured 15 times as the sole enteropathogen from the feces of a man who had developed chronic diarrhea after traveling to Turkey. Determination of rRNA gene restriction patterns confirmed that the seven isolates of Aeromonas caviae studied were identical (hybridization group [HG]4). After therapy with ciprofloxacin for four weeks, the patient was culture negative for the original isolate, and six months later a novel strain of Aeromonas media with a different ribopattern (HG 5A) was isolated from the feces of the patient. The patient responded again, both clinically and bacteriologically, to a four-week course of ciprofloxacin and has remained asymptomatic since then.

We have used the polymerase chain reaction (PCR) to detect shigellae, EIEC and ETEC in stool specimens of diarrhoeic patients returning from tropical countries. As compared to culture (7.1% positive specimens), which recognizes only Shigella strains, PCR performed on bacterial growth from directly inoculated MacConkey agar plates and directed against virulence-associated genes present in both Shigella and EIEC was positive in 19.8% of the samples. We assumed that these additional positive results represent true rather than false positive samples because identical results for each single specimen were obtained using two different PCR systems and because positive results (culture as well as PCR) were exclusively found in patients with recent travel but not in those who acquired diarrhoea in a developed country where these organisms are not endemic. PCR detecting LT- and ST-specific sequences was positive in 18.5% of the patients with recent travel. Again no positive cases were identified in controls. Combining PCR and culture results, at least one bacterial pathogen was found in more than 50% of the patients with recent travel. We conclude that PCR is superior to culture methods for the detection of Shigella, EIEC and ETEC in travel-associated diarrhoea.

Clinical efficacy of norfloxacin for treatment of traveler's diarrhea in 106 Finnish tourists vacationing in Morocco was evaluated during two different seasons. When the criteria for diagnosis of traveler's diarrhea were fulfilled, norfloxacin (400 mg) or a placebo was given orally, twice daily for 3 days. All symptoms and signs subsided sooner in the norfloxacin group. The clearest difference was observed in the duration of diarrhea: 1.2 days in the norfloxacin group vs. 3.3 days in the placebo group (P < .001). The duration of diarrhea due to particular species was as follows for the two groups: in cases due to Salmonella enterica, 1.1 vs 4.1 days (P < .01); in cases due to Campylobacter jejuni, 1.8 vs. 5.0 days (P < .01); and in cases due to enterotoxigenic Escherichia coli, 1.0 day vs. 3.1 days (P < .01). The rate of full recovery during administration of norfloxacin or a placebo was also greater among the norfloxacin recipients: 84% vs. 47% (P < .001). No significant adverse effects were reported. Norfloxacin proved to be safe and effective in therapy for traveler's diarrhea.

The prevalence of enteropathogenic bacteria over a three-year period was 3.1% in an urban population in Germany. Nontyphoidal Salmonella spp. (1.8% prevalence) represented 59.3% of all positive isolates, followed by Campylobacter spp., which constituted 22.1% of such isolates. Clostridium difficile toxin was detected in 5.6% of samples submitted specifically for detection of cytotoxigenic C. difficile. The seasonal distribution showed an increase of Salmonella, Shigella and Aeromonas/Plesiomonas isolates in the post-holiday season, partly due to returning travelers. An epidemic five-fold increase of Salmonella enteritidis isolates was found over the three-year-period. Enteropathogenic bacteria such as Salmonella, Campylobacter and cytotoxigenic C. difficile were common etiologic agents of gastrointestinal tract infections in patients with AIDS. We conclude that travelers and HIV-infected subjects are especially prone to infection with enteropathogenic bacteria; preventive measures to control the Salmonella enteritidis epidemic are essential.