Detecção dos genes codificantes da toxina CDT, e pesquisa de fatores que influenciam na produção de hemolisinas em amostras de Campylobacter jejuni de origem avícola / Detection of the genes encoding the toxin CDT, and research factors which influence the production of hemolysin in Campylobacter jejuni from poultry products

Membros termofílicos do gênero Campylobacter são reconhecidos como importantes enteropatógenos para o ser humano e animais. A grande diversidade ecológica destes micro-organismos em diferentes habitats tais como água, animais e alimentos predispõem ao aparecimento de novos fatores de virulência. Este trabalho teve por objetivo detectar os genes codificantes da Toxina Distensiva Citoletal (CDT) por meio da técnica de PCR, pesquisar a atividade de hemolisinas e a influência de soluções quelantes e de íons nesta atividade. Foram utilizadas 45 amostras de Campylobacter jejuni de origem avícola para pesquisa de atividade hemolítica, cultivadas em Caldo Triptona de Soja (TSB). Após o crescimento bacteriano, as amostras foram semeadas em Ágar tríptico de soja (TSA) contendo 5% de sangue de ovino. Para verificar a influência de agentes quelantes e solução de íons na atividade hemolítica, as amostras de C. jejuni foram cultivadas em TSB contendo separadamente os quelantes EDTA, ácido acético, soluções de íons CaCl2, MgCl2 e FeCl3, em atmosfera de microaerofilia. Quanto à atividade de hemolisina de C. jejuni em placas de TSA - sangue ovino foi possível observar que houve hemólise em 40% das amostras analisadas apenas com caldo TSB. Somente o ácido acético apresentou ação quelante sobre a atividade de hemolisinas em amostras de C. jejuni semeadas em placas de TSA - sangue ovino. Para detecção dos genes cdtA, cdtB e cdtC através da técnica da Reação em Cadeia da Polimerase (PCR) foram utilizadas 119 amostras de C. jejuni de origem avícola. Foi possível observar que 37,8% possuíam o perfil de genes cdtABC. Os resultados demonstraram em amostras avícolas a presença de cepas de C. jejuni com potencial virulento, devido à presença dos genes da toxina CDT e potencial hemolítico, que apresentou ação reduzida in vitro com ácido acético...

Thermophilic members of the Campylobacter genus are recognized as important enteropathogenics for humans and animals. The great variety of ecological habitats, such as water, food and milk, may promote new virulence factors. To detect the encoding genes distending cytolethal toxin (CDT) by PCR and study the hemolytic activity with influence of chelation solutions and ions, 45 Campylobacter jejuni samples from poultry production origin were used to perform the hemolytic research. To check the influence of chelation agents and solution of ions in the hemolytic activity, samples of C. jejuni strains were grown in tryptone soy broth TSB containing chelation agents separately EDTA, acetic acid, CaCl2, MgCl2 and FeCl3 ions solutions in microaerophilic atmosphere and then streaked on 5% sheep blood tryptic soy agar (TSA). To perform the detection of cdtA, cdtB and cdtC genes the technique of Polymerase Chain Reaction (PCR) was used in 119 samples of C. jejuni from poultry production origin. We found 40% of samples showing hemolysis after growing with TSB. Only the acetic acid showed reduction in hemolysis. The prevalent gene profile was cdtABC in 37.8 % of the samples. It was observed that the results showed the presence of C. jejuni strains with virulent potential, due to presence of the CDT toxin genes and the hemolytic activity, which showed in vitro reduced when acetic acid was added...

Factors associated with Clostridium difficile diarrhea in a hospital in Beijing, China

Clostridium difficile is the most common cause of hospital-acquired diarrhea in patients treated with antibiotics, chemotherapeutic agents, and other drugs that alter the normal equilibrium of the intestinal flora. A better understanding of the risk factors for C. difficile-associated disease (CDAD) could be used to reduce the incidence of CDAD and the costs associated with its treatment. The aim of this study was to identify the risk factors for CDAD in a cohort of Chinese patients in a Beijing hospital. Medical charts of a total of 130 inpatients (62 males and 68 females) with hospital-acquired diarrhea (45 with CDAD; 85 without CDAD) were retrospectively reviewed. C. difficile toxins A and B were detected in fecal samples using enzyme-linked fluorescence assays. The drugs used by patients with and without CDAD before the onset of diarrhea were compared. Factors that differed significantly between the two groups by univariate analysis were analyzed by multivariate analysis using a logistic regression model. Multivariate analysis showed that cephalosporin treatment was associated with a significantly higher risk of CDAD in hospitalized patients, while treatment with glycopeptides was significantly associated with a reduction in CDAD (P<0.001 for cephalosporin; P=0.013 for glycopeptides). Our data confirmed previous findings that empirical treatment with cephalosporins is positively associated with CDAD compared to individuals using other CDAD-related drugs. Additionally, we showed that treatment with glycopeptides was negatively associated with CDAD, compared to individuals using other CDAD-related drugs.

Evaluation of three enzyme immunoassays and a nucleic acid amplification test for the diagnosis of Clostridium difficile-associated diarrhea at a university hospital in Brazil

Introduction Despite the known importance of Clostridium difficile as a nosocomial pathogen, few studies regarding Clostridium difficile infection (CDI) in Brazil have been conducted. To date, the diagnostic tests that are available on the Brazilian market for the diagnosis of CDI have not been evaluated. The aim of this study was to compare the performances of four commercial methods for the diagnosis of CDI in patients from a university hospital in Brazil. Methods Three enzyme immunoassays (EIAs) and one nucleic acid amplification test (NAAT) were evaluated against a cytotoxicity assay (CTA) and toxigenic culture (TC). Stool samples from 92 patients with suspected CDI were used in this study. Results Twenty-five (27.2%) of 92 samples were positive according to the CTA, and 23 (25%) were positive according to the TC. All EIAs and the NAAT test demonstrated sensitivities between 59 and 68% and specificities greater than 91%. Conclusions All four methods exhibited low sensitivities for the diagnosis of CDI, which could lead to a large number of false-negative results, an increased risk of cross-infection to other patients, and overtreatment with empirical antibiotics. .

From Escherichia coli heat-stable enterotoxin to mammalian endogenous guanylin hormones

The isolation of heat-stable enterotoxin (STa) from Escherichia coli and cholera toxin from Vibrio cholerae has increased our knowledge of specific mechanisms of action that could be used as pharmacological tools to understand the guanylyl cyclase-C and the adenylyl cyclase enzymatic systems. These discoveries have also been instrumental in increasing our understanding of the basic mechanisms that control the electrolyte and water balance in the gut, kidney, and urinary tracts under normal conditions and in disease. Herein, we review the evolution of genes of the guanylin family and STa genes from bacteria to fish and mammals. We also describe new developments and perspectives regarding these novel bacterial compounds and peptide hormones that act in electrolyte and water balance. The available data point toward new therapeutic perspectives for pathological features such as functional gastrointestinal disorders associated with constipation, colorectal cancer, cystic fibrosis, asthma, hypertension, gastrointestinal barrier function damage associated with enteropathy, enteric infection, malnutrition, satiety, food preferences, obesity, metabolic syndrome, and effects on behavior and brain disorders such as attention deficit, hyperactivity disorder, and schizophrenia.

Detection of toxins A/B and isolation of Clostridium difficile and Clostridium perfringens from dogs in Minas Gerais, Brazil

The objective of this study was to detect C. difficileA/B toxins and to isolate strains of C. perfringensand C. difficile from diarrheic and non-diarrheic dogs in Brazil. Stool samples were collected from 57 dogs, 35 of which were apparently healthy, and 22 of which were diarrheic. C. difficileA/B toxins were detected by ELISA, and C. perfringensand C. difficilewere identified by multiplex PCR. C. difficileA/B toxins were detected in 21 samples (36.8%). Of these, 16 (76.2%) were from diarrheic dogs, and five (23.8%) were from non-diarrheic dogs. Twelve C. difficile strains (21.1%) were isolated, of which ten were A+B+and two were A-B-. All non-toxigenic strains were isolated from non-diarrheic animals. The binary toxin gene cdtBwas found in one strain, which was A+B+and was derived from a non-diarrheic dog. C. perfringensstrains were isolated from 40 samples (70.2%). Of these, 18 (45%) were from the diarrheic group, and 22 (55%) belonged to the non-diarrheic group. All isolates were classified as C. perfringenstype A and there was an association between the detection of the cpegene and the presence of diarrhea. Interestingly, ten strains (25%) were positive for the presence of the cpb2gene. The high rate of detection of the A/B toxins in non-diarrheic dogs suggests the occurrence of subclinical disease in dogs or carriage of its toxins without disease. More studies are needed to elucidate the epidemiology of C. difficileand C. perfringensin dogs and to better our understanding of C. difficileas a zoonotic agent. This is the first study to report the binary toxin gene in C. difficilestrains isolated from dogs in Brazil.

Effectiveness of Bacillus thuringiensis and Bacillus sphaericus isolates against Culex pipiens, Aedes aegypti and Anopheles sergenti mosquito larvae

Mosquito borne diseases are continuing to be major health problems for exposed populations. Biological control alone or as a part of integrated vector management is believed to be a better alternative to the chemical control aimed against pest mosquitoes. The present study is designed to screen the larvicidal effect of Bacillus thuringiensis [Bf] and Bacillus sphaericus [Bs] against larvae of three species of mosquitoes larvae namely, Culex pipiens, Aedes aegypti and Anopheles sergenti. Mosquito Larvae were collected from different water resources and identified by standard procedures. Fourth-instar larvae were used in the bioassays. From the 50 samples of mud [15], soil [15] and water [20], 125 microbial isolates were purified and screened for larvicidal activity. The pure solubilized protein from Bs/Bt was quantified for protein estimation. For every 100 ml of the test solution 10 larvae were added in a 250 ml flask. Concentrations that killed 50% [LC[50]] and 90% [LC[90]] of the exposed mosquito larvae were determined. From a total of 125 bacterial isolates, only 25 isolates of Bt [13] and Bs [12] were found to have mosquito larvicidal effect. The highest larval mortality occurred with four isolates of Bt [Bt1, Bt2, Bt3, Bt4] and one Bs [Bs1] isolate. Their mortality rate [LC[50]] values were 0.0151, 0.0160, 0.0217, 0.0252 and 0.0330 mgI1, respectively. The [LC[90]] values of the five Bacillus isolates [Bt/Bs] were 0.0218,0.0219,0.0225,0.0341 and 0.0367, respectively. Time taken for larvicidal activity of the four Bt isolates showed LT[50] at 6,12,12 and 18 h and LT[100] at 24, 30, 36 and 48 h respectively. Bs showed LT[50] at 24 h and LT[100] at 48 h. This study confirms the utilization of larvicidal bacteria as Bt/Bs as commercial mosquito larvicidal and biological controlling agents

Calidad bacteriológica y detección de Bacillus cereus toxigénicos en arroz blanco cocido expendido en el área metropolitana de la provincia de San José, Costa Rica

El gran consumo de arroz a nivel mundial es uno de los factores que favorece su implicación en brotes de origen alimentario y de uno de los patógenos más importantes ligado a este producto como el Bacillus cereus El objetivo del presente trabajo fue evaluar la calidad microbiológica de 50 muestras de arroz blanco cocido expendido en restaurantes de área Metropolitana de San José Costa Rica, incluyendo la determinación del recuento total aerobio mesófilo, Número Más Probable de coliformes totales, fecales y E. coli, B. cereus así como de detección de sus genes nheA, nheB, y nheC. Para el análisis bacteriológico se siguieron los procedimientos descritos en el Compendio de Métodos para el Examen Microbiológico de Alimentos y para la detección de los genes se utililzó un PCR múltiplex y la metodología descrita por Hansen et al., 2001. De las muestras analizadas 46% fueron positivas por coliformes totales, 34% por coliformes fecales, 16% por E. coli, 10% por B. cereus y un 8% por B. cereus toxigénico Lo anterior sugiere que el consumo de arroz blanco en restaurantes puede representar un riesgo para la salud pública y que es necesario implementar mejoras con el fin de brindarle al consumidor un producto inocuo y de mejor calidad.

Bacteriological quality and toxigenic Bacillus cereus detection in cooked white rice sold at the Metropolitan Area of San José, Costa Rica.. The wide use of rice is one of the factors that favors its implication in food borne diseases, and one of the most important pathogens associated to it is Bacillus cereus. The aim of this work was to evaluate the microbiological quality of 50 samples of white cooked rice sold in restaurants at the Metropolitan Area of San José, Costa Rica, including the determination of the total aerobic plate count, the Most Probable Number of total and fecal coliforms and Escherichia coli. MPN of Bacillus cereus and the detection of nheA, nheB and nHeC genes, associated to its toxicity, was also performed. Procedures described in the Compendium of Methods for the Microbiological Examination of Foods were followed for the bacteriological analysis, multiplex PCR was used for the detection of genes following the methodology described by Hansen et al, 2001. 46% of the samples analysed were positive for total coliforms, 34% for fecal coliforms, 16% for E. coli and 10% for B. cereus, being 8% toxigenic. These facts suggest that white cooked rice may represent a risk for Pubic Health and that improvements shall be performed in order to offer a safe and high quality product to consumers.

The prevalence of enterotoxigenic E. coli isolated from the stools of children aged 0-10 years with diarrhea in mid-anatolia region, Turkey

The stool samples from 245 patients with diarrhea were tested for heat labile toxin (LT) and heat stable toxins (ST) by passive latex agglutination and enzyme immunoassay methods respectively. Twelve (4.9 percent) enterotoxigenic E. Coli ETEC strains were isolated. Five strains (2 percent) expressed ST, and 7 (2.8 percent) expressed LT.

Staphylococcus aureus portadores de genes de toxinas isolados em amostras de diferentes fontes de transmissão durante a ordenha / Toxin gene-carrier Staphylococcus aureus isolated from diverse transmission sources during the milking

No presente estudo foi analisada a bactéria S. aureus isolada de diferentes fontes de transmissão durante a ordenha de vacas por meio de técnica de amplificação de genes da toxina. As amostras de leite e do sóstios foram obtidas antes da ordenha dos animais e as de teteiras antes e durante a ordenha sob diferentes condições climáticas. A análise dos genes das enterotoxinas A a D e da toxina da síndrome do choque tóxico foi efetuada por meio de técnica de amplificação das respectivas sequências codificadoras. O genes e a foi o mais prevalente dentre os pesquisados e a maioria dos isolados foi detectada em amostras de leite de quartos mamários com mastite. A presença de genes de toxinas estafilocócicas em S. aureus isolados de diferentes fontes de transmissão dentro da cadeia epidemiológica da mastite bovina evidencia a possibilidade de veiculação desse micro-organismo por meio de leite contaminado e que pode representar riscos à saúde pública.

Péptidos tóxicos y no tóxicos de cianobacterias en cuerpos de agua dulce de la V Región, Chile / Toxic and non toxic cyanobacterial peptides in freshwater bodies from the V Region, Chile

En Chile se ha detectado la presencia de algunos géneros de cianobacterias que pueden producir potentes hepatotoxinas y neurotoxinas, las que pueden ser letales para humanos y animales. En el presente trabajo se determinó la presencia de dos géneros de cianobacterias no tóxicos: Chroococcus y Spirulina; y cuatro géneros de cianobacterias productores de toxina, Anabaena, Anabaenopsis, Microcystis y Oscillatoria en tres diferentes cuerpos de agua de la V Región: Lago Peñuelas (Valparaíso), Tranque Recreo (Villa Alemana) y Embalse Los Aromos (Limache). Además se detectó la presencia de hepatotoxinas por MALDI-TOF MS encontrándose microcistina-RR, -LA, -YR y nodularina en Embalse Los Aromos, microcistina-LA en Tranque Recreo y microcistina-RR y LA en Lago Peñuelas. Adicionalmente en algunas de las muestras se detectó la presencia de péptidos no tóxicos, que presentan actividad biológica tales como aeruginosinas, cianopeptolinas y microgininas. Como estos cuerpos de agua dulce son utilizados para abastecimiento público y para la recreación, es importante diseñar planes de tratamiento y monitoreo para detectar y evitar los riesgos a la salud humana y animal provocado por estos microorganismos.

In Chile the presence of some genera of cyanobacteria that may cause potent hepatoxins and neurotoxis has been detected, which may become lethal for man and animal. In this paper the occurrence of two non toxic genera of cyanobacteria: Chroococcus and Spirulina was established along with four genera of toxin-producing cyanobacteria, Anabaena, Anabaenopsis, Microcystis and Oscillatoria in three different masses of water from the V Region: Lago Peñuelas (Valparaíso), Tranque Recreo (Villa Alemana) and Embalse Los Aromos (Limache). Likewise the presence of hepatoxins by MALDI-TOF MS was detected which resulted in the occurrence of microcystina-RR, _LA , -YR and nodularina in Embalse Los Aromos, microcystina –LA in Tranque Recreo and microcystina -RR and LA in Lago Peñuelas. Moreover, the presence of non toxic peptides developing biological activities such as aeruginosinas, cianopeptolins and microgininines was detected. Considering that these freshwater bodies are intended for public supply and recreational purposes, it is of utmost importance to design treatment and supervising plans in order to detect and prevent risks for human and animal health caused by these microorganisms.

A new black fly isolate of Bacillus thuringiensis autoagglutinating strain highly toxic to Simulium pertinax (Kollar) (Diptera, Simuliidae) larvae

Formulations containing the entomopathogenic Bacillus thuringiensis serovar israelensis strain IPS-82 has been widely applied for mosquito control around the world. Strain IPS-82 is highly active against Aedes aegypti but less active against other well-known vectors such as Culex quinquefasciatus and Simulium spp. larvae. Eighteen strains of B. thuringiensis were isolated from Simulium pertinax larvae naturally occurring in rivers of Southeast Brazil with one demonstrating special toxic effects. Simulated field tests against S. pertinax larvae showed that the native Brazilian autoagglutinanting B. thuringiensis (LFB-FIOCRUZ 1035) has an LC50 at least 25 times lower than the standard IPS-82 strain. The same bacterial preparation was also tested against Ae. aegypti larvae in laboratory trials and the LC50 values obtained with LFB-FIOCRUZ 1035 were at least three times lower than the one for the IPS 82 strain. The results indicate that this strain is more toxic than the standard B. thuringiensis serovar israelensis (H14) in the two Dipteran species tested. It is noteworthy that differences between LC50 values were more pronounced in S. pertinax larvae, the source of the original isolation.

Toxic cyanobacteria strains isolated from blooms in the Guadiana River (southwestern Spain)

This paper describes the occurrence of toxic cyanobacteria along the Guadiana River over its course between Mérida and Badajoz (Extremadura, Spain). Water sampling for phytoplankton quantification and toxin analysis was carried out regularly between 1999 and 2001 in six different locations, including two shallow, slow-flowing river sites, two streamed river sites and two drinking water reservoirs. The cyanobacterial community differed significantly between these locations, especially during the summer. The predominant genera were Microcystis, Oscillatoria, Aphanizomenon and Anabaena. Using an ELISA assay the total microcystin contents of natural water samples from the most eutrophic locations ranged from 0.10 _ 21.86 mg mcyst-LR equivalentúL-1 in Valdelacalzada and 0.10-11.3 µg mcyst-LR equivalentúL-1 in Vitonogales, and a seasonal variation of toxin content was observed. The amount of microcystins produced by each strain was determined by ELISA assay and the detection and identification of microcystin variants of three toxic strains of Microcystis aeruginosa was performed by high performance liquid chromatography (HPLC). The analysis of microcystins of the cultured strains revealed that toxin production was variable among different strains of M. aeruginosa isolated either from different blooms or from the same bloom.

Isolation and characterization of Salmonella Gallinarum cytotoxic factors.

Two distinct cytotoxic factors isolated from a Salmonella Gallinarum strain recovered from a bird died during an outbreak of fowl typhoid were purified to homogeneity through ciprofloxacin extraction, salt precipitation, dialysis, gelfiltration, ionexchange chromatography and chromatofocusing. These were designated as Salmonella Gallinarum cytotoxin I (GCT-I) and II (GCT-II). GCT-I was a glycoprotein having mol.wt and pI of Ca 70 kDa and 8.8, respectively. It was lethal to birds (LD50, 150 micrograms) inducing fowl typhoid like lesions. GCT-II, a protein with Ca 55 kDa mol.wt., was not lethal but caused haemorrhagic diarrhoea on intraperitoneal inoculation in birds. Both the cytotoxins induced cytopathic effects (CPE) in Vero and Madin Darby bovine kidney (MDBK) cells, enterotoxicity in rabbit ileal loop, dermatotoxicity in the rabbit skin and specific neutralizing antibodies in rabbits. These were active only between a narrow pH range of 6 to 8.5 and thermostable at 90 degrees C (1 min) but lost their activities on boiling. Trypsin and chymotrypsin enhanced their cytotoxicity, while pepsin, papain, protease, lipase and urea (5 M) had no appreciable effect on their cytotoxicity. Sodium carbonate (0.05 M) and formaldehyde (0.05%) had no effect on antigenicity of both the cytotoxic factors but rendered them nontoxic. Identification and characterization of cytotoxic moieties of S. Gallinarum not only reveals the important virulence factor but also indicates about the use of toxic factors as a candidate for toxoid vaccine and immunodiagnostics.

Production and charactization of toxins of bacillus cereus and its mutants

The crude toxin from three standard Bacillus cereus strains [NRRL 569, ATCC 11778 and KllS] was found to contain hemolysin, phospholipase C and mouse lethality factor. Mutant 88 which results from U.V. induction to the type strain B. cereus NRRL 569 could not produce hemolysin in its crude toxin[s]; it also failed in causing lethality to mice. Mutants 318, 431 and 486 failed in producing phospholipase C in their crude toxins. Gamma irradiation has not obvious effect on the properties of the crude toxin [s] up to 20 kGy. The most suitable temperature for storage of B. cereus crude toxin [s] was found to be 4 deg. Mouse lethal toxin was found to be inactivated by heat treatment/denaturation at 65C for 5 minutes

Effects of microcystin-LR in isolated perfused rat kidney

Microcystin is a hepatotoxic peptide which inhibits protein phosphatase types 1 and 2A. The objective of the present study was to evaluate the physiopathologic effects of microcystin-LR in isolated perfused rat kidney. Adult Wistar rats (N = 5) of both sexes (240-280 g) were utilized. Microcystin-LR (1 µg/ml) was perfused over a period of 120 min, during which samples of urine and perfusate were collected at 10-min intervals to determine the levels of inulin, sodium, potassium and osmolality. We observed a significant increase in urinary flow with a peak effect at 90 min (control (C) = 0.20 + or- 0.01 and treated (T) = 0.32 + or - 0.01 ml g-1 min(-1), P<0.05). At 90 min there was a significant increase in perfusate pressure (C = 129.7 + or - 4.81 and T = 175.0 + or - 1.15 mmHg) and glomerular filtration rate (C = 0.66 + or - 0.07 and T = 1.10 + or - 0.04 ml g-1 min(-1) and there was a significant reduction in fractional sodium tubular transport at 120 min (C = 78.6 + or - 0.98 and T = 73.9 + or - 0.95 percent). Histopathologic analysis of the perfused kidneys showed protein material in the urinary space, suggestive of renal toxicity. These data demonstrate renal vascular, glomerular and urinary effects of microcystin-LR, indicating that microcystin acts directly on the kidney by probable inhibition of protein phosphatases

Escherichia coli heat-labile toxin B subunit: Construction and evaluation of plasmids providing controlled high level production of the protein

With the plasmid DNA from a clinical isolate of enterotoxigenic Escherichia coli [ETEC] H10407 as template, PCR -mediated cloning of the sequence encoding the heat-labile toxin B subunit [L T -B] has been carried out Then this sequence was recloned into the pTrc 99A and pET23a expression vectors to give the plasmids pTRCLTB and pETLTB, respectively. After induction, the former plasmid provides for the production of rL T -Bin a yield of up to 15 mg per liter of bacterial culture. The recombinant protein was shown to be structurally and immunologically identical with the native L TB. High titer antibodies capable of neutralizing the native toxin were raised in mice by oral administration of the rL T - B. Hence the constructed plasmids provide the basis for an oral ETEC vaccine, as well as for genetic fusion of foreign antigens with the aim of developing polyvalent vaccines

Some studies on potato common scab disease. Pathological studies

Three streptomyces isolates causing potato common scab disease [i.e., S1, S2 and S3] were successfully isolated and identified from the growing areas at Menia. Pathogenicity tests, either in the laboratory or pots, revealed that potato cultivars Alpha, Diamont and Spunta could be infected by all three S. scabies isolates. The tested isolates caused lesions on the root tips of radish, software, soybean, squash, tomato, turnip and wheat seedlings. Only isolate S2 induced lesion on the root tips of cowpea, Nicotiana glutinosa, and sunflower seedlings. None of the S. scabies isolates infected maize seedlings or storage roots of carrot and sweet potato. However, storage roots of radish were infected by the highly pathogenic isolate S2. S. Scabies isolates produced phytotoxic substances with most produced after five days at 25C

Toxigenicity of Edwardsiella tarda isolates of fish and pig origin in experimental models.

Indian isolates of E. tarda from fish (7) and pigs (2) were examined for their enterotoxigenicity/cytotoxigenicity in rabbit ligated ileal loop (RLIL), suckling mouse, rabbit skin and Vero cell monolayers. Cell free culture filtrates (CFCF) of isolates from fish and pigs, induced blood tinged fluid accumulation in RLIL, increased vasopermeability in rabbit skin, and caused cytopathic effect in Vero cells but could not induce fluid accumulation in suckling mouse. CFCFs lost their activity on heating at 63 degrees C for 30 min or 72 degrees C for 15 sec, and also at pH < or = 4.5 or > or = 8.5. The toxic factor was released extracellularly and was nondializable.

Toxins of Moraxella bovis: effect on substrates and cells

Culturas totais em meio líquido e filtrados, de 12 cepas de Moraxella bovis, foram testados para determinar a presença de gelatinase, DNAse, lecitinase e dermonecrotoxinas. Foi também estudado seu efeito citotóxico sobre 5 culturas celulares de linhagem. Nas culturas totais demonstrou-se a presença de gelatinase e DNAse. Os filtrados produziram dermonecrose em cobaias brancas e efeito citotáxico em células BHK 21 (Cl.13), mas näo nas outras linhagens. A atividade tanto das culturas totais quanto dos filtrados foi eliminada por aquecimento a 100oC. Discute-se a participaçäo destas toxinas na patogênese e no controle da ceratoconjuntivite infecciosa bovina