Analysis of Serpulina hyodysenteriae strain variation and its molecular epidemiology using pulsed-field gel electrophoresis.
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Pulsed-field gel electrophoresis (PFGE) was applied as a molecular typing tool for the spirochaete Serpulina hyodysenteriae, the agent of swine dysentery. Analysis of a collection of 40 mainly Australian isolates, previously characterized by other methods, divided these into 23 PFGE types. This confirmed that there are many strains of the spirochaete in Australia. PFGE was more discriminatory for strain typing than both multilocus enzyme electrophoresis and serotyping. It had similar discriminatory power to restriction endonuclease analysis, but the results of PFGE were easier to interpret. When applied to 29 isolates collected from 4 farms over periods of up to 8 years, 2 PFGE patterns were found on 3 farms, and a single pattern on the other. In each case a new strain had apparently emerged as a variant of an original parent strain. PFGE was found to be a powerful technique for investigating the molecular epidemiology of swine dysentery outbreaks. (+info)
Isolation, oxygen sensitivity, and virulence of NADH oxidase mutants of the anaerobic spirochete Brachyspira (Serpulina) hyodysenteriae, etiologic agent of swine dysentery.
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Brachyspira (Serpulina) hyodysenteriae, the etiologic agent of swine dysentery, uses the enzyme NADH oxidase to consume oxygen. To investigate possible roles for NADH oxidase in the growth and virulence of this anaerobic spirochete, mutant strains deficient in oxidase activity were isolated and characterized. The cloned NADH oxidase gene (nox; GenBank accession no. U19610) on plasmid pER218 was inactivated by replacing 321 bp of coding sequence with either a gene for chloramphenicol resistance (cat) or a gene for kanamycin resistance (kan). The resulting plasmids, respectively, pCmDeltaNOX and pKmDeltaNOX, were used to transform wild-type B. hyodysenteriae B204 cells and generate the antibiotic-resistant strains Nox-Cm and Nox-Km. PCR and Southern hybridization analyses indicated that the chromosomal wild-type nox genes in these strains had been replaced, through allelic exchange, by the inactivated nox gene containing cat or kan. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western immunoblot analysis revealed that both nox mutant cell lysates were missing the 48-kDa Nox protein. Soluble NADH oxidase activity levels in cell lysates of Nox-Cm and Nox-Km were reduced 92 to 96% compared to the activity level in parent strain B204. In an aerotolerance test, cells of both nox mutants were at least 100-fold more sensitive to oxygen exposure than were cells of the wild-type parent strain B204. In swine experimental infections, both nox mutants were less virulent than strain B204 in that fewer animals were colonized by the mutant cells and infected animals displayed mild, transient signs of disease, with no deaths. These results provide evidence that NADH oxidase serves to protect B. hyodysenteriae cells against oxygen toxicity and that the enzyme, in that role, contributes to the pathogenic ability of the spirochete. (+info)
A descriptive study of the frequency and characteristics of proliferative enteropathy in swine in Ontario by analyzing routine animal health surveillance data.
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Routine surveillance data, collected on pathology submissions at the Animal Health Laboratory in Guelph between 1992 and 1997, were analyzed to determine demographic, clinical, and pathologic characteristics of cases of proliferative enteropathy and the frequency of this condition relative to other infectious enteric diseases in swine in Ontario. The most commonly reported disease was Escherichia coli enteritis (average cases/year = 70.0). Among infectious enteropathies that occur typically in neonatal pigs, coccidiosis (28.4 cases/year) and rotaviral enteritis (5.6 cases/year) were reported. Among infectious enteropathies generally associated with diarrhea in weaner and grower/finisher pigs, the most frequently reported was proliferative enteropathy (27.6 cases/year), followed by swine dysentery (23.3 cases/year), transmissible gastroenteritis (19.6 cases/year), and salmonellosis (8.4 cases/year). Diarrhea and bloody diarrhea were reported in 29% and 31%, respectively, of herds diagnosed with proliferative enteropathy. Important gross intestinal lesions included mucosal hypertrophy (62% of cases), hemorrhage (47%), and mucosal necrosis (34%). Histologic intestinal lesions included epithelial hyperplasia (90% of cases), mucosal necrosis (59%), and inflammation (49%). Our results suggest that proliferative enteropathy is a major infectious enteric disease in grower/finisher pigs in Ontario. (+info)
Prospective validation of a standardized questionnaire for estimating childhood mortality and morbidity due to pneumonia and diarrhoea.
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This paper reports the validation of a 'best-judgement' standardised questionnaire using guidelines and algorithms developed by an expert working group conducted in Nicaragua between 1995 and 1997. Prospective hospital data, including standardised medical recording of selected signs and symptoms, laboratory and radiographic test results and physician diagnoses were collected for children < 5 years admitted with any serious life-threatening condition in 3 study hospitals. The mothers or caregivers of the children were later traced and interviewed using the 'best-judgement' questionnaire. Interviews were completed 1-22 months after admission to hospital for 1115 children (400 who died during the stay in hospital and 715 who were discharged alive). The cause of death or admission to hospital was determined by an expert algorithm applied to hospital data. A similar procedure was used to derive the cause using the answers to questions from interviews. Hospital causes were compared with interview causes and sensitivity and specificity calculated, together with the estimated cause-specific fraction for diarrhoea and pneumonia. Multiple diagnoses were allowed; 378 children in the sample (104 deaths, 274 survivors) had a reference diagnosis of diarrhoeal illness, and 506 (168 deaths, 338 survivors) a reference diagnosis of pneumonia. When results for deaths and survivors in all age groups were combined, the expert algorithms had sensitivity between 86% and 88% and specificity between 81% and 83% for any diarrhoeal illness; and sensitivity between 74% and 87% and specificity between 37% and 72% for pneumonia. Algorithms tested in previous validation studies were also applied to data obtained in this study, and the results are compared. Despite less than perfect sensitivity and specificity, reasonably accurate estimates of the cause-specific mortality and morbidity fractions for diarrhoea were obtained, although the accuracy of estimates in other settings using the same instrument will depend on the true cause-specific fraction in those settings. The algorithms tested for pneumonia did not produce accurate estimates of the cause-specific fraction, and are not recommended for use in community settings. (+info)
Protection studies on winter dysentery caused by bovine coronavirus in cattle using antigens prepared from infected cell lysates.
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Cells infected with bovine coronavirus (BCV) were solubilized with Triton X-100 to yield a cell lysate (CL) antigen having high hemagglutinating (HA) titers. The antigen gave high HA titers using rat erythrocytes, suggesting that it contained large amounts of hemagglutinin esterase (HE) antigen. The CL antigen, combined with an oil adjuvant, was tested for protective and antibody-inducing activities in cattle. Four groups (2 cattle/group) of cattle were inoculated with CL antigen having HA titers of 16 000, 4000, 1000, and 250. Another group served as untreated controls. Two intramuscular inoculations were given at an interval of 3 wk. The animals were challenged with virus 1 wk after the second inoculation. The groups immunized with the CL antigen having an HA titer of 4000 or 16 000 produced hemagglutination inhibition (HI) antibody titers of > 320 and serum neutralizing (SN) antibody titers of > 1280. These groups of animals showed no clinical abnormalities after challenge. In the groups immunized with CL antigen at an HA titer of 1000 or 250, HI antibody titers were 40 to 160 and SN titers were 80 to 640. The cattle with HI antibody titers of > or = 160 and the SN titers of > or = 640 showed no clinical signs, but the cattle with the HI antibody titer < 80 and the SN antibody titer < 160 developed watery diarrhea and fever after challenge. These results indicate that CL antigen with high HA titer induces antibody production in cattle that provides effective protection against winter dysentery. (+info)
Changes in bacterial community structure in the colon of pigs fed different experimental diets and after infection with Brachyspira hyodysenteriae.
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Bacterial communities in the large intestines of pigs were compared using terminal restriction fragment length polymorphism (T-RFLP) analysis targeting the 16S ribosomal DNA. The pigs were fed different experimental diets based on either modified standard feed or cooked rice supplemented with dietary fibers. After feeding of the animals with the experimental diets for 2 weeks, differences in the bacterial community structure in the spiral colon were detected in the form of different profiles of terminal restriction fragments (T-RFs). Some of the T-RFs were universally distributed, i.e., they were found in all samples, while others varied in distribution and were related to specific diets. The reproducibility of the T-RFLP profiles between individual animals within the diet groups was high. In the control group, the profiles remained unchanged throughout the experiment and were similar between two independent but identical experiments. When the animals were experimentally infected with Brachyspira hyodysenteriae, causing swine dysentery, many of the T-RFs fluctuated, suggesting a destabilization of the microbial community. (+info)
Association between clinical type of diarrhoea and growth of children under 5 years in rural Bangladesh.
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BACKGROUND: The role of diarrhoea in the aetiology of growth retardation in young children remains controversial. To evaluate this, a population-based, longitudinal study of young children aged 6-48 months was conducted in Matlab, a rural area of Bangladesh, between May 1988 and April 1989. METHODS: Data obtained from 584 children were examined by one-year (n = 412) and 3-month (n = 1220) growth periods. Each growth period was analysed based on clinical types of diarrhoea, namely, non-diarrhoea, non-dysentery diarrhoea (diarrhoea without blood), and dysentery (diarrhoea with blood). Weight and height gains were compared among the study groups initially by one-way analysis of variance followed by multivariate analysis adjusting for potential confounding variables. RESULTS: Compared to non-diarrhoea and non-dysentery diarrhoea, dysentery was associated with significantly lower annual weight gain (1866 g [P < 0.01] and 1550 g [P < 0.05] versus 1350 g, respectively) and height gain (6.51 cm and 5.87 cm versus 5.27 cm [P < 0.01], respectively). Both 3-month dysentery and non-dysentery intervals were significantly associated with less weight gain compared to non-diarrhoea intervals (490 g and 522 g versus 637 g [P: < 0.05], respectively). Dysentery intervals were also associated with significantly poorer height gain compared to other intervals (2.19 cm versus 2.42 cm [P < 0.05] and 2.46 cm [P < 0.01], respectively). CONCLUSIONS: The growth of young children is strongly influenced by the clinical type of diarrhoea and the impact is dependent on the proportion of dysentery episodes in the total diarrhoeal burden. (+info)
Food supplementation with encouragement to feed it to infants from 4 to 12 months of age has a small impact on weight gain.
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It is unclear whether a substantial decline in malnutrition among infants in developing countries can be achieved by increasing food availability and nutrition counseling without concurrent morbidity-reducing interventions. The study was designed to determine whether provision of generous amounts of a micronutrient-fortified food supplement supported by counseling or nutritional counseling alone would significantly improve physical growth between 4 and 12 mo of age. In a controlled trial, 418 infants 4 mo of age were individually randomized to one of the four groups and followed until 12 mo of age. The first group received a milk-based cereal and nutritional counseling; the second group monthly nutritional counseling alone. To control for the effect of twice-weekly home visits for morbidity ascertainment, similar visits were made in one of the control groups (visitation group); the fourth group received no intervention. The median energy intake from nonbreast milk sources was higher in the food supplementation group than in the visitation group by 1212 kJ at 26 wk (P < 0.001), 1739 kJ at 38 wk (P < 0.001) and 2257 kJ at 52 wk (P < 0.001). The food supplementation infants gained 250 g (95% confidence interval: 20--480 g) more weight than did the visitation group. The difference in the mean increment in length during the study was 0.4 cm (95% confidence interval: -0.1--0.9 cm). The nutritional counseling group had higher energy intakes ranging from 280 to 752 kJ at different ages (P < 0.05 at all ages) but no significant benefit on weight and length increments. Methods to enhance the impact of these interventions need to be identified. (+info)