浦东新区腹泻样本中气单胞菌的分离鉴定及耐药性分析

目的:了解上海浦东新区感染性腹泻病人气单胞菌的感染及耐药情况,为相关防控策略的制定提供科学依据。方法:对2010年上海市浦东新区2个监测点,1245件急性腹泻样本进行气单胞菌检测,阳性菌进行药物敏感试验。结果:从1245件标本中检出气单胞菌93株,阳性率为7.47%,其中嗜水气单胞63株,温和气单胞26株,豚鼠气单胞4株。6月-8月份为高峰期。药敏试验结果:80%以上菌株对庆大,环丙沙星,阿米卡星、头孢噻肟敏感,对氨苄西林,复方新诺明、四环素、头孢噻吩、萘啶酸不同程度耐药。结论:气单胞菌感染存在季节性差异,与夏秋季腹泻关系密切。持续对气单胞菌及其耐药性的监测对细菌性腹泻病的预防与治疗具有指导意义。     

甲鱼,河蟹致病性气单胞菌的分离鉴定及其卫生评价研究

从江苏扬州5个人工养殖甲鱼场10只濒死甲鱼肝脏中分离到10株具有β溶血的气单胞菌,其中4株为温和气单胞菌、5株为嗜水气单胞菌、1株为易损气单胞菌,从5个人工养殖河蟹场10只频死河蟹肌肉中分离到10株具有β溶血的气单胞菌,其中5林为温和气单胞菌,4株为嗜水气单胞菌,1株为豚鼠气单胞菌。检菌株生长特性试验表明,4～37℃均能生长,最适生长温度为25℃～30℃。加热试验表明,65℃100min、90℃min能将细菌灭活。调味品杀菌试验表明,50％食醋5min能将细菌灭活,而33％加饭酒24h内对细菌无作用,提示应重视醉制生食水产品的卫生。     

Adherence to HEp-2 cells and enteropathogenic potential of Aeromonas spp.

Aeromonas strains (total = 60) of clinical, water and food origin were tested for adherence to HEp-2 cells. Environmental strains were selected (except for A. caviae) to include primarily those expressing other virulence-associated properties. Adhesion was markedly species-dependent (A. veronii biotype sobria, 15 of 26 [58%]. A caviae, 4 of 12 [33%] and A. hydrophila, 2 of 8 [11%]). A. veronii biotype sobria were adhesive, irrespective of source (62 and 54% for clinical and environmental strains, respectively). Adherent strains of this species were enterotoxin-positive and most (13 of 15) grew at 43 degrees C. A. caviae isolated from clinical specimens contained a higher proportion (75%) of adherent strains than environmental strains (13%). Virulent subsets of A. veronii biotype sobria and A. caviae are adherent to HEp-2 cells. The HEp-2 assay is a useful model for investigating mechanisms of adherence and enteropathogenicity of virulent Aeromonas species.     

Aeromonas species as cause of diarrhea and infections outside the gastrointestinal tract in The Netherlands

In a national survey in the period May 1986-December 1987, Aeromonas was isolated from 277 out of 16,857 (1.6%) samples of watery, bloody or mucous stool, from patients with diarrhoea. There was a clear seasonal pattern (less than 1% in winter, up to 3% in summer). A. caviae was isolated most frequently (49%), followed by A. sobria (35%) and A. hydrophila (15%). Some non-identifiable strains were isolated as well. Aeromonas were isolated in particular from faeces of patients aged over 70 years (predominantly A. sobria) or under 5 years (predominantly A. caviae). In 67% Aeromonas was isolated as the only possible bacterial cause of diarrhoea, but in 33% other enteropathogenic bacteria were found as well (17% Campylobacter, 14% Salmonella, 2% Shigella). In addition, all Aeromonas isolates were collected which were obtained in normal diagnostic activities in the participating laboratories, among others from blood, from pus or wound fluid, from faecal samples which did not meet the above mentioned criteria. A. caviae was the dominant species in 'other' faeces and 'various' body sites but was not isolated from blood. The results of this study do not indicate that routine examinations for Aeromonas in faeces of patients with diarrhoea are necessary.     

An outbreak of food poisoning suspected due to Aeromonas and characteristics of the isolated strains]

On June 7, 1990, food poisoning with main symptoms of abdominal pain and diarrhea occurred in Inuyama City, Aichi Prefecture. From results of bacteriological examination, three kinds of mesophilic Aeromonas spp. were detected from patients, leftover foods, well water, and cookers, one of which was A. hydrophila which was shown to produce haemolysin thought to be the cause of the food poisoning. On the other hand, A. sobria and A. caviae isolated from various materials did not produce haemolysin. The latter two strains of mesophilic Aeromonas spp. did not produce any other enterotoxins. Therefore, it appears that the well water containing A. hydrophila, A. sobria and A. caviae polluted the foods, which then had caused the food poisoning. Of nine strains of A. hydrophila, five do not dissolve sucrose, and these are typed as serogroup O:22 or O:23. The other four strains dissolve sucrose, and these are typed as serogroup O:16. According to the drug sensitivity test, all of these nine strains of A. hydrophila were resistant to Ampicillin, Erythromycin and Cephaloridine.     

Some observations on the faecal carriage of mesophilic Aeromonas species in cows and pigs

Replicate faecal samples from healthy individual pigs and cows were examined for the presence of Aeromonas sp. over a 12-month period. Aeromonads were found to be minor components of the faecal flora, only 8.8% of 520 samples from pigs and 4.6% of 481 samples from cows proving positive. Isolation rates in both groups of animals were seasonal. A hydrophila (62% of the isolates) was the predominant species in cows, followed by A. caviae (32%) and A. sobria (15%). This pattern was also recorded in the natural waters that the animals drank from during the period when the faecal carriage rate was at its highest. In pigs, A. caviae (59%) was more common than A. hydrophila (41%). A. sobria was not found in any of the pig-associated samples. It seems that cattle acquire their faecal aeromonads from drinking water. The source of the organisms in pigs is less clear.     

Virulence factor-activity relationships (VFAR) with specific emphasis on Aeromonas species (spp.)

The human population most commonly inflicted with Aeromonas infection includes young children, the elderly and immunocompromised individuals. Importantly, the isolation rate of Aeromonas species from children suffering from diarrhea is similar in developing and developed countries. It is becoming clear that only a small subset of Aeromonas species belonging to a particular hybridization group causes disease in humans. Human infections with this pathogen occur by consuming contaminated food and water. Aeromonas species were isolated from wounds of patients during the tsunami in southern Thailand. Further, increased numbers of this pathogen were recovered from floodwater samples during Hurricane Katrina in New Orleans. Among various species of Aeromonas, A. hydrophila, A. caviae and A. veronii biovar sobria are mainly responsible for causing disease in humans. Our laboratory has isolated various virulence factors from a diarrheal isolate SSU of A. hydrophila and molecularly characterized them. In addition to various virulence factors produced by Aeromonas species, the status of the immune system plays an important role in inducing disease by this pathogen in the host. Taken together, we have made significant advances in better understanding the pathogenesis of Aeromonas infections, which will help in differentiating pathogenic from non-pathogenic aeromonads. This review covers virulence aspects of a clinical isolate of A. hydrophila.     

Aeromonas isolates from human diarrheic stool and groundwater compared by pulsed-field gel electrophoresis

Gastrointestinal infections of Aeromonas species are generally considered waterborne; for this reason, Aeromonas hydrophila has been placed on the United States Environmental Protection Agency Contaminant Candidate List of emerging pathogens in drinking water. In this study, we compared pulsed-field gel electrophoresis patterns of Aeromonas isolates from stool specimens of patients with diarrhea with Aeromonas isolates from patients' drinking water. Among 2,565 diarrheic stool specimens submitted to a Wisconsin clinical reference laboratory, 17 (0.66%) tested positive for Aeromonas. Groundwater isolates of Aeromonas were obtained from private wells throughout Wisconsin and the drinking water of Aeromonas-positive patients. The analysis showed that the stool and drinking water isolates were genetically unrelated, suggesting that in this population Aeromonas gastrointestinal infections were not linked with groundwater exposures.     

Prevalence, pathogenesis, antibiotic susceptibility profiles, and in-vitro activity of selected medicinal plants against Aeromonas isolates from stool samples of patients in the Venda region of South Africa

The prevalence, pathogenic indices, such as haemolytic and haemagglutinating activities, antibiograms, and in-vitro activities of local medicinal plants against Aeromonas isolates in Vhembe district of Limpopo province, South Africa, were studied using standard microbiological methods. In total, 309 diarrhoeic stool samples were collected from patients attending five health centres in the region during December 2004-May 2005. Aeromonas species were identified using the API 20E system. The haemagglutinating and haemolytic activities of isolates on human, sheep, pig and chicken red blood cells were investigated. Antibiotic susceptibility profiles of the isolates to several antibiotics and in-vitro activity of local medicinal plants were also ascertained using previously-reported schemes. Results showed that 104 (33.6%) of the 309 samples were positive for Aeromonas species, of which 89 (85.6%) were Aeromonas hydrophila, 12 (11.5%) A. sobria, and three (2.9%) A. caviae. All strains of A. hydrophila and A. caviae produced haemolysis on sheep blood, while eight of the 12 A. sobria strains were haemolytic on sheep blood. The haemolytic activities of the isolates were variable on other red blood cells tested. High level of resistance was observed to amoxicillin and ampicillin, followed by cefuroxime (79%), chloramphenicol (74%), and erythromycin (65%). The carbapenems were the most active drugs with only 7% resistance to meropenem and 11% to imipenem. About 12% of the isolates were resistant to ciprofloxacin. The extracts of three of seven medicinal plants tested showed inhibitory activity against all Aeromonas isolates; these included acetone and hexane extracts of Pterocarpus angolensis, Syzygium cordatum, and Zornia milneana. The results suggest a high prevalence of Aeromonas species in the region. The isolates demonstrated multiple resistant profiles to different antibiotics tested. Some local medicinal plants were inhibitory to Aeromonas isolates, indicating a potential role in the management of Aeromonas-related infections. Structural elucidation of the active components may pave the way for the discovery of candidate templates for eventual drug design. Most isolates possessed important virulence characteristics based on their haemolytic and haemagglutinating ability. However, the genetic characterization of the isolates will further confirm their pathogenicity and the origin of multiple antibiotic resistance.     

Incidence and clinical symptoms of Aeromonas-associated travellers' diarrhoea in Tokyo.

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.     

Distribution of Aeromonas phenospecies and genospecies among strains isolated from water, foods or from human clinical samples.

A total of 332 Aeromonas spp. originating from drinking water (n = 75), fresh water (n = 57), chicken and ground beef (107), human faecal samples in association with travelling (n = 49), human faecal samples not associated with travelling (n = 38), and six strains from human blood cultures were studied by phenotypic methods and by using analysis of ribopatterns as a molecular method for the identification of the 13 known hybridization groups (HGs). Also included were the reference strains of each HG. A. hydrophila HG 1, A. caviae HG 4 and A. veronii biotype sobria HG 8/10 were the most important genospecies identified in human faecal samples. A. hydrophila HG 2 and A. media HG 5B predominated in drinking water and A. hydrophila HG 2 and HG 3, A. media HG 5A and HG 5B predominated in fresh water. In drinking water only one isolate was A. hydrophila HG 1 and two isolates were A. caviae HG 4. Clinically important Aeromonas spp. HG 1 (A. hydrophila), HG 4 (A. caviae) and HG 8/10 (A. veronii biotype sobria) were common in chicken and ground beef. In contrast to the drinking water samples, HG 5A was common in chicken and ground beef samples. Atypical, unidentified isolates were most often found in fresh water samples (12/57 strains). Although water has been suspected of being an important source of human aeromonas infections, clinically important HGs were found to be in the minority among Aeromonas spp. identified in drinking water or fresh water. The distribution of Aeromonas spp. HGs among drinking water, chicken and ground beef samples was also different, suggesting that contamination of meat or chicken may not originate from water.     

The incidence of virulence factors in mesophilic Aeromonas species isolated from farm animals and their environment

Sixty-one isolates of Aeromonas spp. from the faeces of pigs, cows and a variety of associated environmental sources were examined for the characteristics that are reputed to have roles in pathogenicity. Most isolates of Aeromonas hydrophila were cytotoxic (96.4%) and were capable of producing cell elongation factor (75%) and haemagglutinins (67.9%). In contrast few of the Aeromonas caviae isolates produced these three markers (13.6%, 27.3% and 36.4% respectively). In general, Aeromonas sobria occupied an intermediate position (36.4%, 27.3% and 54.5%), but they did produce the highest mean invasion index for HEp-2 cells. Statistical analysis revealed significant associations between the carriage of these factors and it was clear that many isolates of aeromonads from water and animals possessed the full battery of putative virulence factors.     

Aeromonas spp. and traveler's diarrhea: clinical features and antimicrobial resistance

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.     

Biofilm formation by Aeromonas hydrophila on green-leafy vegetables: cabbage and lettuce

Aeromonas hydrophila is the most well known of the six species of Aeromonas, which has been linked to two groups of human diseases: septicemia and gastroenteritis. Reference strain ATCC 7966 and biofilm strains TUB19, TUB20, and TUB21 were investigated for their ability to form biofilm in vitro (after 48 h on polystyrene surface) and on the surface of two green-leafy vegetables, cabbage and lettuce (after 1, 2, 4, and 24 h). Attachment strength (S(R)) of these strains to the vegetable surface was also measured in the same time intervals. The ATCC 7966 and TUB19 had high ability to form biofilm in vitro compared with TUB20 and TUB21 in full strength tryptone soy broth or under starvation conditions in diluted tryptone soy broth (1:20, v/v). Cell surface hydrophobicity of the biofilm strains was lower than that of the reference strain. The biofilm of all tested strains on polystyrene surfaces differed from that on the vegetable surfaces. All strains studied rapidly attached to both green leafy vegetables (after 1 h). S(R) and cell populations (loosely and strongly attached cells) significantly (p < 0.05) increased with contact time; however, no significant (p > 0.05) differences in cell populations were recorded after 4 and 24 h. The highest S(R) and cell population (log CFU cm?2) were recorded by TUB19. In conclusion, the use of A. hydrophila strains isolated from environmental biofilm samples may be more useful for understanding biofilm formation on green-leafy vegetables than the reference or laboratory strains. The attachment of A. hydrophila was significantly affected by the surfaces of green-leafy vegetables. Further studies are required to improve our understanding of the interaction between human microbial pathogens and surfaces of raw vegetables.     

The cytotoxic effect of essential oils from Origanum vulgare L. and/or Rosmarinus officinalis L. on Aeromonas hydrophila

This study aimed to evaluate the antibacterial activities of the essential oils from Origanum vulgare L. (OV) and Rosmarinus officinalis L. (RO), both singly and in combination at sub-inhibitory concentrations (? MIC?+?? MIC), against Aeromonas hydrophila and to investigate the possible mechanisms underlying these activities. Used singly (OV: 2.5?μL/mL; RO: 20?μL/mL) or in a mixture (OV: 0.625?μL/mL?+?RO: 5?μL/L), these essential oils led to a significant decrease (p<0.01) in bacterial viability after 24?h of exposure. A decrease in glucose consumption by A. hydrophila and release of cellular material were observed immediately after the addition of the essential oils, both singly and as a mixture, and continued for up to 6?h. Electron microscopy of cells exposed to the essential oils revealed severe changes in the plasma membrane, cytoplasmic appearance, and cell shape during the 6-h exposure period. OV and RO essential oils combined at sub-inhibitory concentrations could be rationally applied to inhibit the growth of A. hydrophila in food products, particularly minimally processed vegetables.     

Laboratory-based surveillance for vancomycin-resistant enterococci: utility of screening stool specimens submitted for Clostridium difficile toxin assay.

OBJECTIVE: To study vancomycin-resistant enterococci (VRE) gastrointestinal colonization prevalence in high-risk hospitalized patients and to assess the cost and utility of this laboratory-based surveillance. SETTING: Large university teaching hospital. DESIGN: Quarterly prevalence culture survey of 50 stool specimens submitted for Clostridium difficile toxin A assay from October 1996 through June 1999 (n=526). Screening culture survey of all C difficile-positive stool specimens from July 1998 through June 1999 (n=140). PATIENTS: Specimens for analysis were collected from patients who were admitted to the hospital and who had C difficile toxin A testing ordered. Patient samples were excluded from analysis if they were obtained from patients not hospitalized at UCLA Medical Center, if the C difficile toxin assay result was indeterminate, or if the patient was known to have previous VRE colonization or infection. RESULTS: During quarterly surveillance, VRE was detected in 19.8%, C difficile toxin A in 9.5%, and both VRE and C difficile toxin A in 3.2% of stool specimens submitted for C difficile toxin assay. Patients whose stool specimens were positive for C difficile toxin A were significantly more likely than those whose specimens were negative to have VRE detected (odds ratio, 2.3; 95% confidence interval, 1.2-4.5). Based on these findings, in July 1998, we began routine screening of all C difficile-positive stool specimens for VRE. From July 1998 through June 1999, 58 (41.4%) of 140 patients with C difficile-positive specimens had VRE newly detected in the stool. The combined cost of the two laboratory-based surveillance strategies was approximately $62 per VRE-positive patient identified and $5,800 per year. CONCLUSION: Quarterly surveillance of stool submitted for C difficile assay combined with screening all C difficile-positive stools is a cost-effective and efficient strategy for detecting VRE stool colonization among high-risk hospitalized patients. Such a laboratory-based surveillance should be included as part of a comprehensive program to limit nosocomial VRE transmission.     

宁波市贝(甲)壳类海产品中致病性气单胞菌的分布

目的了解市售新鲜贝（甲）壳类海产品中致病性气单胞菌的携带及分布。方法用分步筛选的方法，筛检测贝（甲）壳类海产品中疑似致病性气单胞菌，再对疑似菌株进行系统生化定型。结果从13类2431份市售贝（甲）壳类海产品中检出致病性气单胞菌8种1946株，检出率为80．05％。检出的致病性气单胞菌以嗜水气单胞菌数量最多，占总数的38．26％；海产品带菌率最高为海瓜子，达145．31％。牡蛎、淡菜、海螺3类海产品检出的致病性气单胞菌种类和数量相对较少，同一样品中检出2种以上致病性气单胞菌有542份，占22．23％。结论检测发现市售新鲜贝（甲）壳类海产品携带致病性气单胞菌较普遍，贝壳类的致病性气单胞菌携带率高于甲壳类。结果提示，市售新鲜贝（甲）壳类海产品是一类诱发气单胞菌疾病的危险因子，而本地居民对该海产品的食用习惯多为生食或半生食，进一步增加了食用不安全性。因此，建议食用时应注意烹饪方法，以减少气单胞菌等疾病的发生。     

Die Bedeutung der beweglichen Aeromonaden als Krankheitserreger für den Menschen

The genus Aeromonas belongs to the family Aeromonadaceae of the order Aeromonadales and consists of 14 phenospecies and 17 genomospecies. They are gram-negative, oxidase-positive, facultatively anaerobic and glucose-fermenting rods. Members of the mesophilic genus Aeromonas spp. are ubiquitous in the aquatic environment and can be isolated from fresh, brackish and marine water. In nutrient-enriched waters they can attain large populations, particularly in the warm seasons at higher temperatures. Sewage effluents are also a major allochthonous source of the mesophilic aeromonads in the aquatic environment. Organisms of the mesophilic aeromonads also occur in fresh and processed foods, often in very high numbers. They have been isolated from a wide range of both animal and plant food, including raw red meat, fish, seafood or vegetables. This reflects undoubtedly the contact of that food with contaminated water. Species of Aeromonas (A. hydrophila, A. caviae, A. veronii) have been shown to be associated with food borne gastroenteritis, with wound infections acquired via water or with sepsis, peritonitis or meningitis. Unlike gastroenteritis, these infections can have fatal or serious debilitating outcomes. Aeromonas sepsis generally arises secondary to gastroenteritis or wound infection and is associated with high mortality rates. Underlying diseases, particularly liver cirrhosis, or immunsuppressive states also play a major role in the acquisition and outcome of these infections.     

Aeromonas detection and their toxins from drinking water from reservoirs and drinking fountains

Aeromonads are inhabitants of aquatic ecosystems and are described as being involved in intestinal disturbances and other infections. A total of 200 drinking water samples from domestic and public reservoirs and drinking fountains located in São Paulo (Brazil), were analyzed for the presence of Aeromonas. Samples were concentrated by membrane filtration and enriched in APW. ADA medium was used for Aeromonas isolation and colonies were confirmed by biochemical characterization. Strains isolated were tested for hemolysin and toxin production. Aeromonas was detected in 12 samples (6.0%). Aeromonas strains (96) were isolated and identified as: A. caviae (41.7%), A. hydrophila (15.7%), A.allosacharophila (10.4%), A. schubertii (1.0%) and Aeromonas spp. (31.2%).The results revealed that 70% of A. caviae, 66.7% of A. hydrophila, 80% of A. allosacharophila and 46.6% of Aeromonas spp. were hemolytic. The assay for checking production of toxins showed that 17.5% of A. caviae, 73.3% of A. hydrophila, 60% of A. allosacharophila, 100% of A. schubertii, and 33.3% of Aeromonas spp. were able to produce toxins. The results demonstrated the pathogenic potential of Aeromonas, indicating that the presence of this emerging pathogen in water systems is a public health concern.     

Laboratory diagnosis of Clostridium difficile infection in Spain: a population-based survey

A survey of laboratory diagnosis of Clostridium difficile infection (CDI) was conducted in 103 Spanish hospitals. A mean of 23.2 stool specimens/1000 admissions were processed to detect CDI. Overall, 35.9% of the laboratories specifically selected stool specimens for diagnostic C.?difficile toxin testing. The most commonly used criteria were loose or watery stools, previous antibiotic therapy and nosocomial diarrhoea. Most laboratories (95.1%) processed the stool specimens in house, mainly five to seven days/week. All laboratories except one detected toxins directly in stool specimens, and 94.9% used enzyme immunoassays (EIAs). Only 16.3% of the laboratories used toxigenic culture as a diagnostic tool, and most of them used EIAs to detect toxins in isolates. The most common diagnostic strategy was toxin detection in stool specimens using EIA alone (79.6%), and the second most common strategy was the combination of toxin detection in stool specimens and isolates (10.2%). The estimated annual incidence of CDI was 1.71 cases/1000 admissions, and this was significantly higher in large hospitals. CDI is underdiagnosed in Spain because most laboratories use EIAs performed directly on stool specimens as the only diagnostic procedure. A national laboratory survey of diagnostic methods and testing protocols for the diagnosis of CDI is simple and inexpensive, and could act as the first step towards implementing national standardized criteria for optimal diagnosis of CDI.