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Biomedical subjects

P A Barrow

Publications and source records attributed to P A Barrow.

At least 73 records · Page 4Linked to original sources
PubMed1990

Reduction in faecal excretion of Salmonella typhimurium strain F98 in chickens vaccinated with live and killed S. typhimurium organisms.

Chickens given orally at 4 days of age a smooth spectinomycin resistant mutant (Spcr) of Salmonella typhimurium strain F98 excreted the organism in their faeces for approximately 4 weeks. Following oral administration of a nalidixic acid resistant (Nalr) mutant of the same strain 4 weeks later when the chickens had virtually cleared themselves of the first infection, these chickens excreted far fewer salmonella organisms and for a shorter time than did a previously uninfected control group of chickens which were infected at the same time with the Nalr mutant. Chickens inoculated intramuscularly at 4 days developed a similar immunity to challenge and also excreted the immunizing strain in their faeces. In contrast intramuscular inoculation or incorporation into the food of formalin-killed S. typhimurium organisms had little lasting effect on the faecal excretion of the challenge strain. Two attenuated mutants of strain F98 Nalr were produced: one was a rough strain produced by lytic bacteriophage and the other was an aro A auxotrophic mutant which had been cured of the 85 kilobase-pair virulence-associated plasmid. These mutants were avirulent for chickens, mice, calves and man and when ingested by human volunteers did not persist in the faeces. When inoculated intramuscularly into chickens they produced an early reduction in faecal excretion of the challenge strain (Spcr) which was not maintained. Oral administration of both strains produced reductions in faecal excretion of the challenge strain. This was much more noticeable with the rough strain which was itself excreted for a much longer period than the parent strain.

Agglutination Tests↗
PubMed1990

Further studies on the inhibition of colonization of the chicken alimentary tract with Salmonella typhimurium by pre-colonization with an avirulent mutant.

Oral administration to newly hatched chickens or to chicks up to 5 days of age with an avirulent, rough, spectinomycin-resistant mutant of Salmonella typhimurium strain F98 inhibited the colonization of a nalidixic acid-resistant mutant of the same strain administered by the same route 1 day later. The second strain passed rapidly through the alimentary tract and persisted in the caeca of only a few chickens. Resistance to colonization did not develop until 24 h after inoculation of the first strain but was still evident if the second strain was inoculated up to 7 days later. Resistance occurred in 5 different breeds of chicken and in chickens reared on 5 different diets. Protection was evident against a very high challenge dose and could be produced by the introduction of small numbers of the first strain. Pre-colonization of chicks with the first strain of F98 reduced faecal excretion of the second strain over many weeks, whether chickens were challenged directly or by contact with other infected chickens. The rough strain F98 produced protection against only a few S. typhimurium strains and not against other serotypes. However, strains of S. infantis and S. heidelberg, chosen because they colonized the chicken alimentary tract better than did F98, produced inhibition of a wider range of serotypes.

Animal Feed↗
PubMed1990

Immunity to experimental fowl typhoid in chickens induced by a virulence plasmid-cured derivative of Salmonella gallinarum.

Chickens were immunized by two intramuscular inoculations at 1 and 14 days of age with virulence plasmid-cured derivatives of Salmonella gallinarum and were challenged 14 days later by oral inoculation of ca. 50 50% lethal doses (LD50) of fully virulent S. gallinarum 9. Mortality in the nonimmunized and immunized groups were 36 and 3%, respectively. This difference was highly significant (P less than 0.01). A significant reduction in mortality was also produced following oral challenge with 5,000 LD50 doses. The LD50 values by intramuscular inoculation of the challenge organism into nonimmunized and immunized chickens were log10 (0.13 +/- 1.57) and (9.74 +/- 2.72), respectively. Immunization was effective whether chickens were immunized at 1 and 14 days of age or at 21 and 35 days of age. Serum agglutinins were present in immunized chickens. Immunization with plasmid-cured Salmonella pullorum gave less protection, and immunization with Escherichia coli K-12 possessing the virulence plasmid of S. gallinarum gave none. The plasmid-cured S. gallinarum was made both rough by virulent bacteriophage activity and nalidixic acid resistant (Nalr) to produce a strain designated 9VP-phi rNalr. It was compared with a Nalr mutant of the rough 9R vaccine strain designated 9 Nalr for virulence and immunogenicity. 9VP-phi rNalr was slightly less protective and less virulent than was the 9R vaccine strain.

Administration, Oral↗
PubMed1989

The virulence characteristics of strains of Escherichia coli isolated from cases of bovine mastitis in England and Wales.

Of 470 Gram-negative facultative anaerobes isolated from cases of bovine mastitis in England and Wales, 422 were identified as Escherichia coli. The characteristics of 237 of these were investigated. Guinea-pig red cell haemagglutinins were possessed by 86% of strains and 12% were resistant to D-mannose. None of the strains tested invaded Vero cells. Haemolysin, Vero toxin and enterotoxin were produced by 5, 0.5 and 1% of strains, respectively. Twenty-two percent were resistant to one or more antibiotics and 4% to sodium arsenate. Transfer ability was possessed by 41% and lysogenic phage by 27% of strains; 62% possessed either one or the other and 12% possessed both. Colicin production was detected in 18% of strains; 5% produced Colicin V. Ninety-nine percent of strains were serum-resistant, while only 6% were able to grow well in bovine serum. A microscopically visible capsule was seen in 75% of strains. All strains possessed at least one of the potential virulence factors or markers studied. Several strains which possessed one characteristic only (mannose-sensitive haemagglutination or serum resistance), possessed one or more large molecular weight plasmids. None of the strains was particularly virulent for chickens following intramuscular inoculation. Of the strains which possessed one virulence characteristic, only those which were serum-resistant were re-isolated from expressed milk following intramammary inoculation of lactating cows.

Animals↗
PubMed1989

Further observations on the effect of feeding diets containing avoparcin on the excretion of salmonellas by experimentally infected chickens.

Chickens which had been inoculated orally with a nalidixic acid-resistant strain of Salmonella typhimurium were reared on a diet containing different concentrations of avoparcin in an attempt to explain the variation in response to commercial levels of this antibiotic observed by different workers. In one experiment small increases in faecal excretion of the inoculated salmonella occurred at 2.5 and 5.0 mg kg-1, with greater increases between 7.5 and 20 mg kg-1. In a second experiment there was a significant increase in excretion at 7.5 mg kg-1 and in a third experiment in which generally higher excretion rates were detected in all groups, significant increases were observed at 10 and 12.5 mg kg-1 only. In addition avoparcin significantly increased the faecal excretion of S. cholerae-suis, S. dublin and S. arizonae, serotypes not usually associated with poultry-derived food-poisoning in the United Kingdom. It did not increase faecal excretion of S. pullorum. Avoparcin at 10 mg kg-1 appeared to have little effect on the normal intestinal flora of S. typhimurium infected chickens despite the fact that when tested in vitro individual organisms were susceptible to this drug concentration. At 100 mg kg-1 viable counts of intestinal enterococci and Gram-negative anaerobic bacteria were considerably reduced while those of S. typhimurium and Escherichia coli increased. Antibiotic activity due to avoparcin was detectable in the alimentary tract and there was some increase in concentration of the antibiotic in the more distal regions.

Animal Feed↗
PubMed1989

Invasion of Vero cells by Salmonella species.

The invasiveness of Salmonella strains for Vero cells was studied by quantitative bacteriology; the technique was more sensitive than phase contrast microscopy. All of 59 Salmonella strains, of 19 different serotypes, were more invasive than Escherichia coli K12. Three strains of Shigella were as invasive as most of the Salmonella strains whereas 29 strains of E. coli, two of Proteus, three of Klebsiella and one of Serratia were much less invasive. Two Citrobacter strains exhibited intermediate invasiveness. Eleven Salmonella strains were also shown to be invasive in HeLa, int 407, bovine kidney, chick kidney and chick embryonic fibroblast cells. The difference between invasive and non-invasive organisms was apparent irrespective of the numbers of bacteria in contact with Vero cells or the duration of bacteria-cell contact. There was little intracellular multiplication of S. typhimurium in Vero cells. Unlike the situation with Shigella, incubation of Salmonella or Salmonella-cell mixtures at 41 degrees C, 22 degrees C or 0 degree C had little effect on invasiveness. Non-viable Salmonella organisms were non-invasive. Incubation of Vero cells with cholera toxin, dinitrophenol, iodoacetic acid, cytochalasin B or D-mannose did not substantially reduce invasiveness. Virulence-associated plasmids were not essential to invasion by S. typhimurium, S. gallinarum or S. pullorum. Neither somatic antigens nor mannose-sensitive haemagglutinins were essential to the invasiveness of an S. infantis strain, but an additional factor, eliminated by N-methyl, N-nitro, N-nitrosoguanidine mutagenesis did contribute to invasiveness.

2,4-Dinitrophenol↗
PubMed1989

Functional homology of virulence plasmids in Salmonella gallinarum, S. pullorum, and S. typhimurium.

The virulence-associated plasmids of strains of Salmonella gallinarum and S. pullorum were transferred separately by mobilization with the F plasmid into virulence plasmid-cured derivatives of S. gallinarum, S. pullorum, and S. typhimurium and into a prototrophic Escherichia coli K-12 strain. The transconjugants were tested for virulence in chickens of different ages and in mice. The S. gallinarum and S. pullorum plasmids were able to restore full virulence in the three Salmonella strains, thus demonstrating functional homology in virulence plasmids from these Salmonella serotypes and biotypes. The virulence phenotypes of the transconjugants remained the same as that of the parent strain of the recipient. This, together with the fact that E. coli K-12 containing either of the virulence plasmids was avirulent for chickens, suggested that in addition to plasmid genes, chromosomal genes are important in determining virulence, particularly in determining the ability to survive and multiply in the cells of the reticuloendothelial system. The virulence plasmids were not self-transmissible and could not be transduced by temperate bacteriophages lysogenizing field strains of S. gallinarum. They were not in the same incompatibility group as F but were fi+.

Animals↗
PubMed1988

The effect of halofuginone on the excretion of Salmonella typhimurium by experimentally infected chickens.

The effect of feeding halofuginone at 3 and 6 ppm on the excretion of Salmonella typhimurium by experimentally infected chickens was studied. A standardized procedure was used involving the oral inoculation of 72-h-old specific pathogen-free chickens with 10(8) organisms of a nalidixic acid-resistant mutant of a strain of S. typhimurium. At weekly intervals, cloacal swabs were taken and a semi-quantitative assessment was made of the numbers of Salmonella organisms excreted. When compared with the control group of infected chickens fed unmedicated food, the group fed halofuginone at 3 ppm showed no significant increase in excretion rate. The group fed 6 ppm showed a slight increase in excretion which was statistically significant.

Animal Feed↗
PubMed1988

Genetics of resistance to Salmonella typhimurium in newly hatched chicks.

1. A survey of inbred and partially inbred lines of chickens showed pronounced differences in mortality following challenge of the newly hatched chicks with Salmonella typhimurium. Lines W, 6(1) and N were highly resistant to challenge, whereas lines C and 15I were highly susceptible. 2. This difference in susceptibility was observed with a range of 5 strains of S. typhimurium of different degrees of virulence and also following both oral and intramuscular challenge. 3. The inheritance of resistance was studied in detail by examining a series of crosses between the susceptible line C and resistant line W. The pattern of mortality in crosses and back-crosses between these lines indicated resistance is dominant and was consistent with the inheritance of a dominant autosomal resistance gene. 4. There was no evidence of maternal effects in these crosses, and no evidence of association with the major histocompatability complex.

Animals↗
PubMed1988

The association between a large molecular mass plasmid and virulence in a strain of Salmonella pullorum.

Eight strains of Salmonella pullorum isolated from epidemiologically independent cases of pullorum disease (bacillary white diarrhoea) in young chickens possessed at least one large molecular mass plasmid in addition to smaller molecular mass plasmids. The 85 kb large plasmid, designated pBL001, of one of these strains was 'tagged' with an ampicillin resistance marker by the insertion of transposon Tn3. The plasmid was eliminated by passage in nutrient broth containing acridine orange. It was reintroduced into the strain from which it had been eliminated by mobilization using the F plasmid. Following oral inoculation of newly hatched Rhode Island Red chickens, the parent strain produced a high level of mortality (71%) with characteristic signs of pullorum disease. Following intramuscular inoculation of chickens of the same age, the bacterial LD50 was (log10 c.f.u.) 3.38 +/- 0.43 (mean +/- SEM). The derivative lacking pBL001 produced no mortality or morbidity when inoculated orally and the bacterial LD50 value increased to (log10 c.f.u.) 5.54 +/- 0.28. This increase was statistically significant (chi 2 = 13.6, P less than 0.01). Reintroduction of pBL001 restored virulence as gauged by oral inoculation of chickens (62% mortality) and by the intramuscular bacterial LD50 value (log10 c.f.u. = 3.78 +/- 0.25). These values were not significantly different to those produced by the parent strain (chi 2 = 0.59, P = 0.4 and chi 2 = 0.66, P = 0.5, respectively). Following oral inoculation, the pBL001-cured derivative was less invasive than the parent strain and following intramuscular inoculation it persisted for a shorter period than the parent strain in the liver, spleen and the leg muscle into which it had been inoculated. In addition, the parent strain, but not the pBL001-cured derivative, localized in large numbers in the myocardium where it produced lesions typical of pullorum disease. Both the parent strain and the pBL001-cured derivative were serum resistant in the presence of rabbit serum and grew equally well in chick serum and broth.

Animals↗
PubMed1987

Inhibition of colonization of the chicken alimentary tract with Salmonella typhimurium gram-negative facultatively anaerobic bacteria.

Oral administration of strains of food poisoning salmonellas to day-old chickens produced a profound inhibition in the subsequent colonization of the caeca by a strain of Salmonella typhimurium given one day later. Closely related genera were unable to produce a similar inhibition. The inhibition was not the result of bacteriophages produced by the first strain. Neither was it the result of an immunological response by the host induced by the first strain. In additional experiments in day-old chickens, inhibition of an Escherichia coli Nalr strain and of a Citrobacter sp. Nalr strain was produced by the antibiotic-sensitive forms of the homologous strains while strains from other genera did not produce any inhibition. When an avirulent mutant of S. typhimurium was used for pre-treatment a statistically significant reduction in the excretion of the super-infecting S. typhimurium Nalr strain over several weeks was produced. A genus specific inhibition was reproduced in vitro by mixed culture experiments. Live cultures were necessary for in vitro inhibition. Killed cells or a culture supernatant produced no inhibition.

Animals↗
PubMed1987

Contribution of Salmonella gallinarum large plasmid toward virulence in fowl typhoid.

Four strains of Salmonella gallinarum isolated from independent cases of fowl typhoid all possessed both an 85-kilobase and a 2.5-kilobase plasmid. Each plasmid was eliminated in turn from one of the strains by transposon labeling and curing at 42 degrees C. Elimination of the small plasmid had no effect on the high virulence of the strain for newly hatched and 2-week-old chickens. Whereas oral inoculation of 2-week-old chickens with the parent strain produced 90% mortality with characteristic signs of fowl typhoid, inoculation of the large-plasmid-minus strain produced 0% mortality. A corresponding increase in the 50% lethal dose from log10 1.1 to greater than log10 7.3 was seen with the large-plasmid-minus strain after intramuscular inoculation. Reintroduction of the large plasmid completely restored virulence. A role for the plasmid-linked virulence genes in both invasion and growth in the reticuloendothelial system is suggested by the failure of the large-plasmid-minus strain to penetrate to the liver and spleen after oral inoculation and by its increased clearance from the reticuloendothelial system after intravenous inoculation. These results clearly demonstrate that the large plasmid of S. gallinarum contributes toward virulence in fowl typhoid of chickens.

Animals↗
PubMed1987

Observations on the pathogenesis of experimental Salmonella typhimurium infection in chickens.

The virulence of Salmonella typhimurium strains for day-old chickens was examined. The mortality following oral inoculation varied from 0 to 100 per cent. Some breeds were more susceptible than others. There was no correlation between oral and parenteral virulence. Pathogenesis studies associated with one of the most virulent strains suggested that, after invasion, organisms multiplied in the liver and spleen and spread to other organs producing a systemic infection. The cause of death was probably a combination of anorexia and dehydration resulting from general malaise and diarrhoea. A virulent strain studied in detail spread through the body faster, persisted for a longer period and was more invasive than an avirulent strain. In the system studied invasiveness was the virulence determinant of overriding importance.

Animals↗
PubMed1986

Inhibition of colonization of the chicken caecum with Salmonella typhimurium by pre-treatment with strains of Escherichia coli.

Simultaneous oral administration of broth cultures of three strains of Escherichia coli isolated from sewage and an abattoir strongly inhibited the colonization of a subsequently administered strain of Salmonella typhimurium. The three strains were protective against the S. typhimurium strain under a variety of conditions: in different breeds and in chickens fed different diets. The strains were not equally effective against other salmonella strains. Oral administration of the strains produced a statistically significant reduction in the excretion of the S. typhimurium strain over a period of 7 weeks.

Administration, Oral↗
PubMed1986

Physiological characteristics of the Mycobacterium tuberculosis-M. bovis group of organisms with particular reference to heterogeneity within M. bovis.

By examining the abilities of mycobacterial strains to remove amino acids from solution, differences were found between Mycobacterium tuberculosis and other closely related taxa. Heterogeneity was observed in most taxa. Strains of M. bovis were examined in greater detail. By using the amino acid typing method in combination with tests routinely used for differentiating mycobacterial species, and SDS-polyacrylamide gel electrophoresis of whole cell soluble proteins, a great degree of heterogeneity was observed in this taxon.

Amino Acids↗
PubMed1986

Bacteriophages mediating somatic antigenic conversion in Salmonella cholerae-suis: their isolation from sewage and other Salmonella serotypes possessing the somatic 6 antigen.

Bacteriophages which mediate the conversion of the O somatic antigen of Salmonella cholerae-suis from the 6(2)7 to the 6(1)7 phenotype have been isolated from two strains of S. newport and one of S. muenchen, and also from sewage collected from two areas where there have been no reports of S. cholerae-suis infection for several years. The phages differed from each other by cross-resistance tests.

Antigens, Bacterial↗
PubMed1984

The effect of feeding diets containing avoparcin on the excretion of salmonellas by chickens experimentally infected with natural sources of salmonella organisms.

Chickens were readily infected with salmonella organisms when fed diets containing unsterilized bone-meal or provided with drinking water containing a suspension of natural salmonella infected chicken faeces. When fed diets containing avoparcin at concentrations of 10 or 100 mg/kg chickens infected in these ways excreted larger numbers of salmonellas for longer periods than did chickens fed a nonmedicated diet.

Animal Feed↗