Biomedical subjects

D G Newell

Publications and source records attributed to D G Newell.

At least 37 records · Page 2Linked to original sources

PubMed2000

Roles of the surface layer proteins of Campylobacter fetus subsp. fetus in ovine abortion.

The role of the surface (S)-layer proteins of Campylobacter fetus subsp. fetus has been investigated using an ovine model of abortion. Wild-type strain 23D induced abortion in up to 90% of pregnant ewes challenged subcutaneously. Isolates recovered from both dams and fetuses expressed S-layer proteins with variable molecular masses. The spontaneous S-layer-negative variant, strain 23B, neither colonized nor caused abortions in pregnant ewes. A series of isogenic sapA and recA mutants, derived from 23D, also were investigated in this model. A mutant (501 [sapA recA(+)]) caused abortion in one of five challenged animals and was recovered from the placenta of a second animal. Another mutant (502 [sapA recA]) with no S-layer protein expression caused no colonization or abortions in challenged animals but caused abortion when administered intraplacentally. Mutants 600(2) and 600(4), both recA, had fixed expression of 97- and 127-kDa S-layer proteins, respectively. Two of the six animals challenged with mutant 600(4) were colonized, but there were no abortions. As expected, all five strains recovered expressed a 127-kDa S-layer protein. In contrast, mutant 600(2) was recovered from the placentas of all five challenged animals and caused abortion in two. Unexpectedly, one of the 16 isolates expressed a 127-kDa rather than a 97-kDa S-layer protein. Thus, these studies indicate that S-layer proteins appear essential for colonization and/or translocation to the placenta but are not required to mediate fetal injury and that S-layer variation may occur in a recA strain.

Abortion, Veterinary↗

PubMed2000

The galE gene of Campylobacter jejuni is involved in lipopolysaccharide synthesis and virulence.

Lipopolysaccharide (LPS) is one of the main virulence factors of gram-negative bacteria. The LPS from Campylobacter spp. has endotoxic properties and has been shown to play a role in adhesion. We previously cloned a gene cluster (wla) which is involved in the synthesis of the Campylobacter jejuni 81116 LPS molecule. Sequence alignment of the first gene in this cluster indicated similarity with galE genes. These genes encode a UDP-glucose 4-epimerase, which catalyzes the interconversion of UDP-galactose and UDP-glucose. A Salmonella galE mutant was transformed with the galE gene from C. jejuni. The LPS analysis of wild-type, galE, and complemented galE Salmonella strains showed that the C. jejuni galE gene could restore the smooth wild-type Salmonella LPS. A UDP-glucose 4-epimerase assay was used to demonstrate that the galE gene from C. jejuni encoded this epimerase. We constructed a C. jejuni galE mutant which expressed a lipid A-core molecule of reduced molecular weight that did not react with antiserum raised against the parental strain. These results show an essential role for the galE gene in the synthesis of C. jejuni LPS. The galE mutant also showed a reduction in its ability to adhere to and invade INT407 cells. However, it was still able to colonize chickens to the same level as the wild-type strain. The serum resistance and hemolytic activity of this mutant were not changed compared to the parent strain. The ability of the mutant to take up DNA and integrate it in its genome was reduced 20-fold. These results show that LPS of C. jejuni is an important virulence factor.

Amino Acid Sequence↗

PubMed1999

Generation of a superoxide dismutase (SOD)-deficient mutant of Campylobacter coli: evidence for the significance of SOD in Campylobacter survival and colonization.

The microaerophilic nature of Campylobacter species implies an inherent sensitivity towards oxygen and its reduction products, particularly the superoxide anion. The deleterious effects of exposure to superoxide radicals are counteracted by the activity of superoxide dismutase (SOD). We have shown previously that Campylobacter coli possesses an iron cofactored SOD. The sodB gene of C. coli UA585 was insertionally inactivated by the site-specific insertion of a tetO cassette. Organisms harboring the inactivated gene failed to produce a biologically functional form of the enzyme. While the ability of this mutant to grow in aerobic conditions was unchanged relative to the parental strain, its survival was severely compromised when nongrowing cells were exposed to air. Accordingly, the SOD-deficient mutant was unable to survive for prolonged periods in model foods. Furthermore, inactivation of the sodB gene decreased the colonization potential in an experimental infection of 1-day-old chicks. In contrast, strain CK100, which is deficient in catalase activity, showed the same survival and colonization characteristics as the parental strain. These results indicate that SOD, but not catalase, is an important determinant in the ability of C. coli to survive aerobically and for optimal colonization within the chicken gut.

Aerobiosis↗

PubMed1999

A novel Campylobacter jejuni two-component regulatory system important for temperature-dependent growth and colonization.

Campylobacter jejuni colonizes the intestines of domestic and wild animals and is a common cause of human diarrheal disease. We identified a two-component regulatory system, designated the RacR-RacS (reduced ability to colonize) system, that is involved in a temperature-dependent signalling pathway. A mutation of the response regulator gene racR reduced the organism's ability to colonize the chicken intestinal tract and resulted in temperature-dependent changes in its protein profile and growth characteristics.

Animals↗

PubMed1998

Evidence of genomic instability in Campylobacter jejuni isolated from poultry.

Poultry isolates of Campylobacter jejuni derived from a survey of meat processing batches were genotyped by pulsed-field gel electrophoresis (PFGE) of chromosomal DNA to establish the clonal relationships between single-colony isolates. In the majority of batches studied, one or two genotype patterns predominated. However, in one batch (batch A), 21 single-colony isolates gave 14 different PFGE genotypes. The banding patterns obtained with SmaI were sufficiently different to distinguish between genotypes, although the patterns also produced many common bands. The question of whether these isolates represented different clones or had a common clonal ancestry was addressed by additional genotypic and phenotypic methods. Restriction length polymorphism of PCR products obtained from the flagellin genes showed an identical flagellin genotype for all of these isolates. In contrast, unrelated control isolates resulted in different flagellin genotypes. Moreover, all 14 different PFGE genotypes of batch A had identical Penner serotypes and identical or similar biotypes and phage types. It was concluded that the isolates were of clonal origin and that the diversity in the PFGE banding patterns had most likely originated from genomic rearrangements. However, the PFGE genotypes were shown to be stable upon subculturing in vitro and after in vivo passage in chickens, and natural transformation between isogenic mutants carrying antibiotic markers did not occur in vivo in a chick colonization model. The possible mechanisms for the hypothesized genomic recombinations and the conditions that allow, induce, or select for such events are discussed.

Animals↗

PubMed1997

The kinetics of serum antibody responses to natural infections with Mycobacterium bovis in one badger social group.

Bovine tuberculosis remains a significant problem in some parts of Great Britain and Ireland largely because of a reservoir of infection in badgers. Little is currently known about the immunopathology of Mycobacterium bovis infection in the badger. Badgers, from 31 social groups, in a study area of the Cotswold escarpment, have been trapped and sampled from 1981 to 1995. Serum antibody responses directed against the 25 kDa antigen (MPB83) of M. bovis have been studied in detail in a selected social group (JM) which has endemic infection. Sequential sera from 44 badgers were studied and results compared with culture from faeces, urine, tracheal aspirates, bite wound swabs and at post mortem. The results indicate that some badgers (about 10%) remain uninfected despite exposure to endemic M. bovis infection within the social group. In culture-positive animals active excretion of organisms is not necessarily concomitant with seropositivity. Conversely, seropositivity is not an indicator that culture positivity is present or imminent. This is particularly true in cubs when a transient seropositivity can occur within the first 6-8 months of life but these animals can remain culture-negative for up to 5 years. Western blotting confirms that at least some of these antibodies, detectable by ELISA in the culture-negative cubs, are directed against the 25 kDa M. bovis antigen. In contrast antibodies detectable in the culture-positive animals do not Western blot prior to a positive culture. Thus, differential reactivity in Western blotting may distinguish between serum antibodies indicative of potentially culture-positive animals and animals which will remain culture-negative.

Animals↗

PubMed1997

Association of Helicobacter pylori infection with precancerous lesions and stomach cancer: a case-control study in Yangzhong County.

Previous study has raised H. pylori infection as a suspected biologic risk factor for gastric cancer. A comparative case-control study involving precancerous lesions and gastric cancer was conducted in Yanzhong county, an area with one of the highest rates of gastric cancer in China to study the relationship between the H. pylori infection and gastric cancer. Subjects in the study were all randomly selected participants of a screening program for gastric cancer sponsored by the Cancer Institute of CAMS in cooperation with Yangzhong county Hospital. Totally, 125 normal controls, 108 superficial gastritis, 111 atrophic gastritis and 110 gastric cancer patients were included in our study according to endoscopy and pathology result. Status of H. pylori infection was evaluated by measuring IgG antibody in plasma with ELISA assay. Our result showed Odds ratios of H. pylori infection were higher among gastritis and cancer groups, 4.5 (95% CI 2.5-7.9) for superficial gastritis, 6.3 (95% CI 3.4-12) for atrophic gastritis, 3.3 (95% CI 1.9-5.9) for gastric cancer. It was found in our study that consumption of pickled vegetables and drinking dirty water increased the relative risk of H. pylori infection for both precancerous lesions and gastric cancer and that H. pylori infection had higher risk of atrophic gastritis and gastric cancer for males and also higher risk of atrophic gastritis for olders. Our results strongly support the casual role played by H. pylori infection in the carcinogenic process of gastric mucosa.

Aged↗

PubMed1996

An apparent lack of association between Helicobacter pylori infection and risk of gastric cancer in China.

Several prospective studies have shown a significant association between Helicobacter pylori seropositivity and the risk of gastric cancer. Only a small proportion of H. pylori-infected individuals will, however, develop gastric cancer, and it is unclear what effects other factors, such as diet, might have on the risk of cancer. Eighty-seven subjects with gastric cancer were identified during the first 6 years of follow-up (mean 2.4 years) of a cohort of middle-aged men from Shanghai, China. They were matched with 261 cancer-free controls, and serum samples from all subjects, obtained at recruitment, were assayed for anti-H. pylori IgG antibodies. Questionnaire data provided information on a wide range of socio-demographic life-style and dietary variables. H. pylori seropositivity rates in the cases and controls were 54% and 56%, respectively. Neither the overall risk of developing gastric cancer nor the risk of developing non-cardia gastric cancer was significantly associated with prior M. pylori seropositivity. Adjustment for any of the other medical, dietary or life-style variables studied had little effect on the risk of developing non-cardia gastric cancer; simultaneous adjustment for all of these factors yielded an odds ratio of 1.17. The results do not support the hypothesis that H. pylori plays a role in the process of gastric carcinogenesis in China. It is possible that this is an artefact resulting from the relatively short follow-up period to date.

Antibodies, Bacterial↗

PubMed1996

Restriction fragment length polymorphism of polymerase chain reaction products applied to the differentiation of poultry campylobacters for epidemiological investigations.

A technique for subtyping Campylobacter jejuni isolates has been developed by using the restriction fragment length polymorphism (RFLP) of polymerase chain reaction (PCR) products of the flaA and flaB genes. The technique was validated by using strains representing 28 serotypes of C jejuni and it may also be applied to C coli. From these strains 12 distinct RFLP profiles were observed but there was no direct relationship between the RFLP profile and the serotype. One hundred and thirty-five campylobacter isolates from 15 geographically distinct broiler flocks were investigated. All the isolates could be subtyped by using the RFLP method. Isolates from most of the flocks had a single RFLP profile despite data indicating that several serotypes were involved. Although it is possible that further restriction analysis may have demonstrated profile variations in these strains, it is more likely that antigenic variation can occur within genotypically related campylobacters. As a result, serotyping may give conflicting information for veterinary epidemiological purposes. This RFLP typing scheme appears to provide a suitable tool for the investigation of the sources and routes of transmission of campylobacters in chickens.

Animals↗

PubMed1996

Increased colonization potential of Campylobacter jejuni strain 81116 after passage through chickens and its implication on the rate of transmission within flocks.

The mechanisms by which Campylobacter jejuni rapidly spreads through large broiler flocks are unknown. Recent evidence suggests that the minimum infective oral dose for 100% caecal colonization is about 10(4) cfu, which, with such a 'fragile' organism, may limit transmissibility. However, the colonization potential of laboratory-adapted strains may be anomalous compared with fresh isolates or those passaged in vivo. The colonization potential of two chicken and one human C. jejuni isolates, which were minimally passaged, have been investigated using a quantitative model of chicken colonization. There was no detectable difference between these strains but all were more efficient colonizers than a laboratory-adapted strain 81116. In addition, the colonization potential of C. jejuni strain 81116 following a passage in vivo was also determined. The results indicated this increased c. 10000 fold following a single passage in vivo, such that a dose of only 40 cfu caused maximal colonization. Enhanced colonization potential may, therefore, account for the rapid rate of transmission within large flocks.

Animals↗

PubMed1996

Is Helicobacter pylori transmitted from cats to humans?

BACKGROUND: Subsequent to the isolation of Helicobacter pylori from domestic cats, it has been suggested that the organism might be transmitted from cats to humans. This hypothesis has already gained considerable media attention. MATERIALS AND METHODS: In a previous study of risk factors for H. pylori infection, 447 factory workers from Stoke on Trent in the UK had provided blood samples for H. pylori serological workup. They had also completed a detailed questionnaire concerning their living conditions, including the possession of any household pets, in childhood. Logistic regression was used to assess the association between cat ownership in childhood and H. pylori seropositivity. RESULTS: After adjustment for potential confounders, it was found that subjects who had owned a pet as a child were slightly more likely to be H. pylori seropositive than subjects who had not. There was, however, no difference between subjects who had owned a cat and those with other pets. CONCLUSIONS: These data do not support the hypothesis that H. pylori infection might be transmitted from cats to humans.

Adolescent↗

PubMed1996

Helicobacter pylori transmission: evidence from a comparison with hepatitis A virus.

OBJECTIVE: To assess the possibility that faecal-oral contact might play a role in the transmission of Helicobacter pylori. DESIGN: A cross-sectional comparison of the patterns of hepatitis A and H. pylori seropositivity. METHODS: At interview, blood samples and questionnaire data were collected from a group of 467 male volunteers, aged 18-65, from Stoke-on-Trent, UK. Serum samples from each subject were then analysed for anti-H. pylori and anti-hepatitis A antibodies. RESULTS: Overall, 100 of 175 H. pylori seropositive subjects (57.1%) and 113 of 292 H. pylori seronegative subjects (38.7%) were hepatitis A seropositive (chi 2 = 15.0, P < 0.001). This difference was not statistically significant after adjustment for age group and father's occupation, as a surrogate for socioeconomic status in childhood (P = 0.15). The seroprevalence of hepatitis A increased with age at a rate of 2.3% per year, compared to only 1.0% per year for H. pylori (P = 0.015). CONCLUSION: These data suggest that the case for faecal-oral transmission of H. pylori, in a manner similar to the spread of hepatitis A, is not proven and that other modes of transmission, for instance through oral-oral contact, should also be considered.

Adult↗

PubMed1995

Control of bovine tuberculosis by vaccination.

The control of bovine tuberculosis remains a significant problem in the United Kingdom, especially in the south west of England where the rising prevalence of the disease is attributed to a reservoir of Mycobacterium bovis infection in badgers. The possibility of controlling the disease by the vaccination of cattle has been unpopular with veterinarians largely because of the potential compromise of existing diagnostic tests. However, the vaccination of badgers to reduce the risk of transmission to cattle is an attractive option and has now been adopted as a potential control strategy. Recent research has led to important advances in the molecular genetics of mycobacteria and in the understanding of protective immune responses. These advances mean that it may be feasible to design and develop effective mycobacterial vaccines. This review summarises the current understanding of protective immunity against M bovis infection and discusses the possible strategies for the development of vaccines.

Animals↗

PubMed1995

The speciation and subtyping of campylobacter isolates from sewage plants and waste water from a connected poultry abattoir using molecular techniques.

In this study the distribution of phenotypes of campylobacter strains in sewage and surface waters was investigated by subtyping and by speciation of isolates from various aquatic environments. These environments included two municipal sewage plants (SPA and SPB) and waste water from a poultry abattoir (WWA). Both the sewage plants SPA and SPB collected domestic and industrial waste, and SPA received drain water from WWA. SPB received no waste water from any meat-processing plant. The isolates were speciated by PCR and subtyped by PCR/RFLP based on the flagellin PCR products. From all three reservoirs, no Campylobacter lari was isolated, and approximately 80% of the isolates could be identified as C. jejuni and the rest belonged to the C. coli species. The PCR/RFLP typing technique has a high discrimination level and was reproducible between two separate laboratories. The 182 isolates tested yielded 22 distinct Dde I profiles. The results indicate that strains with profiles found in poultry are also detectable in waste water presumed to be solely from domestic and human sources. In addition some strains were unique to the known poultry-related sources, suggesting that avian-specific strains, non-pathogenic to man, may exist in the environment. In contrast some strains were unique to human waste indicating the potential importance of non-poultry sources of infection. No seasonality was observed in the profile distribution. So, at least in the Netherlands, it is unlikely that infections caused by contaminated surface waters contribute to the seasonality of human campylobacteriosis.

Abattoirs↗

PubMed1994

Serodiagnosis of Mycobacterium bovis infection in badgers: development of an indirect ELISA using a 25 kDa antigen.

A 25 kDa antigen of Mycobacterium bovis has previously been identified as immunodominant during badger infections. This 25 kDa antigen was partially purified from sonicated M bovis bacilli by using water precipitation and ion exchange chromatography, and its purification was monitored with a mouse monoclonal antibody, MBS43, which was specific for the antigen. The partly purified antigen was used to develop an ELISA for the assay of badger sera for the presence of specific antibodies. A presumed negative badger population was used to calculate the assay's threshold of seropositivity and using this value, its sensitivity (37 percent) and specificity (98 percent) were determined in a second population of known culture status. The results indicate that it may be possible to develop a specific and cost effective serological field assay for the diagnosis of M bovis infection in living badgers.

Animals↗

PubMed1994

Relation between infection with Helicobacter pylori and living conditions in childhood: evidence for person to person transmission in early life.

OBJECTIVES: To relate the prevalence of infection with Helicobacter pylori in adults to their living conditions in childhood to identify risk factors for infection. DESIGN: Prevalence study of IgG antibodies to H pylori (> 10 micrograms IgG/ml, determined by enzyme linked immunosorbent assay (ELISA)) and reported living conditions and other socioeconomic factors in childhood. SETTING: Three factories in Stoke on Trent. SUBJECTS: 471 male volunteers aged 18 to 65 years. MAIN OUTCOME MEASURES: Seroprevalence and variables in childhood. RESULTS: Seroprevalence of H pylori increased with age (22/74 (29.7%) at < 30 years v 29/46 (63%) at 55-65 years; P < 0.001 for trend) and was related to manual occupation (14/65 (21.5%) for non-manual v 162/406 (39.9%) for manual; P = 0.003). After data were adjusted for age and occupation subjects from large families, whose childhood homes were crowded or who regularly shared a bed in childhood, were significantly more likely to be seropositive (adjusted odds ratio (95% confidence interval) 2.15 (1.41 to 3.30) for crowding and 2.13 (1.38 to 3.30) for sharing a bed), but there was no relation with possession of a bathroom, inside toilet, refrigerator, or household pets in childhood. CONCLUSIONS: Close person to person contact in childhood is an important determinant of seroprevalence of H pylori in adulthood, suggesting that the infection is transmitted directly from one person to another and may be commonly acquired in early life.

Adolescent↗

PubMed1994

The epidemiology of low serum pepsinogen A levels and an international association with gastric cancer rates. EUROGAST Study Group.

BACKGROUND/AIMS: Low serum levels of pepsinogen A are indicative of chronic atrophy, a risk factor for gastric cancer. This study investigated the relationships between low pepsinogen A levels, Helicobacter pylori seropositivity, and gastric cancer rates in 17 populations worldwide. METHODS: In each center, about 200 randomly selected subjects (50 male and 50 female, aged 25-34 and 55-64 years) provided serum samples for pepsinogen analysis and H. pylori serology. RESULTS: Cumulative gastric cancer rates were associated with the prevalence of low pepsinogen A levels in men (coefficient, 0.15 [P = 0.06] for mortality; coefficient, 0.36 [P = 0.01] for incidence) but not women. The prevalence of low pepsinogen A levels was also correlated with H. pylori seropositivity in the older age group (r = 0.55; P = 0.02). Low pepsinogen A levels were significantly more common in the older group (7.5% vs. 2.1% in the younger group; P < 0.001), among women (5.5% vs. 4.1% in men; P = 0.04), and among nonsmokers (5.8% vs. 2.9% in current smokers; P = 0.001). CONCLUSIONS: Low pepsinogen A levels are more common in areas with a high seroprevalence of H. pylori and in men in areas with high rates of gastric cancer. The prevalence of low pepsinogen A levels increases with age, but the excess in women and nonsmokers could reflect factors other than gastric pathology.

Adult↗

PubMed1994

Production and characterization of a monoclonal badger anti-immunoglobulin G and its use in defining the specificity of Mycobacterium bovis infection in badgers by western blot.

A mouse monoclonal anti-badger IgG antibody was produced to investigate the specificity of the antibody response of badgers infected with Mycobacterium bovis. The monoclonal antibody generated was directed against badger IgG heavy chain and appeared to be species restricted, reacting only with badger and dog IgGs but not cat, rabbit, mouse, guinea pig, bovine or ferret IgGs. This monoclonal antibody detection system functioned well in both ELISA and Western blot analyses and was successfully used to investigate the humoral response of the badger to M. bovis infection. Sera from infected badgers detected a 25 kDa antigen which was not detected by sera from M. bovis culture-negative animals. This antigen was conserved in all field strains of M. bovis tested and seroconversion to it was detected during experimental infection. The immunodominance of this antigen in the badger during infection with M. bovis suggests that this 25 kDa polypeptide is a suitable candidate on which to base an antibody detection test for M. bovis infection.

Animals↗