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Biomedical subjects

A C Ward

Publications and source records attributed to A C Ward.

At least 109 records · Page 6Linked to original sources
PubMed1990

Simultaneous conjugal transfer in Lactococcus to genes involved in bacteriocin production and reduced susceptibility to bacteriophages.

Conjugal matings were performed between Lactococcus lactis DRC1 (a lactose-fermenting (Lac+), bacteriocin-producing (Bac+) strain) and L. lactis HID113 (Lac- and Bac-). Transconjugant derivatives of HID113 were identified on the basis of lactose fermentation, resistance to the DRC1 bacteriocin (dricin) or reduced sensitivity to phage sk1. Regardless of how they were identified, all transconjugants gave fewer and smaller plaques with phages c2 and sk1 than did HID113. All but one of 275 transconjugants tested also produced dricin, suggesting some functional relationship or close genetic linkage between the reduced phage sensitivity and dricin production and resistance. Some transconjugants were also Lac+, but this property was unstable.

Bacteriocins↗
PubMed1990

Classification and identification of rhodococci.

Ninety-nine representative strains of Rhodococcus were compared through 129 unit characters and the data examined using the simple matching, Jaccard and pattern coefficients. Clustering was achieved using the unweighted pair group method with arithmetic averages algorithm. The numerical classification was not affected by the statistics used or by test error, estimated at 1.95%. Sixteen multimembered and 23 single member clusters were defined by the simple matching coefficient at or above the 89% similarity level. The numerical phenetic data support the taxonomic integrity of all 13 validly described species of Rhodococcus, including Rhodococcus aichiensis. Rapid enzymic tests based upon fluorophores 7-amino-4-methylcoumarin and 4-methylumbelliferone provide valuable data for rhodococcal systematics.

Bacterial Typing Techniques↗
PubMed1990

Isolation of a previously undescribed rickettsia from an aborted bovine fetus.

A previously undescribed obligate intracellular bacterium was isolated from an aborted bovine fetus. The organism was resistant to penicillin, replicated within cytoplasmic vacuoles, exhibited structural characteristics compatible with the rickettsias, and shared antigenic determinants with Cowdria ruminantium.

Abortion, Veterinary↗
PubMed1990

Isolation of Pasteurellaceae from bovine abortions.

A 2-year study was conducted to determine the incidence of Pasteurellaceae in abortion samples submitted for diagnostic evaluation. A total of 687 cases, including 623 with fetal tissues and/or stomach contents and 302 with placenta and/or uterine discharge, were evaluated. Pasteurellaceae were isolated on a nonselective medium from 9 (1.5%), 14 (2.8%), 13 (12.1%), and 42 (17.4%) of the fetal tissues, stomach contents, uterine discharges, and placentas, respectively. A total of 35 (19.9%) of 176 placental samples cultured on both a selective medium for Pasteurellaceae and a nonselective medium were positive for Pasteurellaceae. Fifteen (42.9%) of these isolates were detected only on the selective medium, whereas 5 (14.2%) were detected only on the nonselective medium and 15 (42.9%) grew on both media. Placentitis of different severity was evident in 13 (68.4%) of the 19 placentas from which Pasteurellaceae were isolated in the absence of other known abortifacient agents.

Abortion, Veterinary↗
PubMed1990

Isolation of Pasteurella haemolytica from tonsillar biopsies of Rocky Mountain bighorn sheep.

Isolations of Pasteurella haemolytica were compared from tonsillar biopsies versus nasal passages for 29 free-ranging Rocky Mountain bighorn sheep (Ovis canadensis canadensis) from central Idaho. Overall, P. haemolytica was isolated from 11 (38%) of 29 sheep. Two (18%) of the 11 positive samples were from only nasal passages compared to eight (73%) from tonsillar biopsies. Pasteurella haemolytica biotype T was isolated from tonsils of nine sheep and from nasal biopsies. Pasteurella haemolytica biotype T was isolated from tonsils of nine sheep and from nasal passages of only one sheep. Two sheep were positive for P. haemolytica biotype A from nasal passages. Culturing tonsillar biopsies as compared to nasal swab samples was a more reliable technique in detecting P. haemolytica, especially biotype T, in bighorn sheep.

Animals↗
PubMed1988

Epidemiologic survey of diarrhea in foals.

Epidemiologic and etiologic data about diarrhea in foals were collected under a planned prospective recording and monitoring study. The survey and monitoring procedures included a survey to obtain an overview of current horse management practices on participating farms, a daily health record survey to obtain information on mares and their foals, and collection of feces from 19 of 144 diarrheic foals and 10 age-matched nondiarrheic foals for electron microscopy, ELISA for rotavirus, and bacteriologic culture. Coronavirus was detected in the feces of diarrheic as well as clinically normal foals. Rotavirus was detected in the feces of diarrheic foals only. With regard to agents found in the feces, there was no significant (P less than 0.05) difference between diarrheic and nondiarrheic foals. Half of the 297 foals on which data were available developed diarrhea. Most foals that developed diarrhea lacked other clinical manifestations of disease. Basic cleanliness at foaling was associated with a lower percentage of foals developing diarrhea. Prophylactic use of antibiotics and vitamins in newborn foals was associated with a higher percentage of foals developing diarrhea. A higher percentage of foals born to visiting mares developed diarrhea, compared with foals born to resident mares.

Age Factors↗
PubMed1988

Relationships between days post partum, observed estrus and uterine microflora in commercial dairy cows.

This study was conducted to determine relationships between the uterine microflora and reproductive characteristics of dairy cows. Uterine lumina were swabbed during estrus immediately prior to artificial insemination (A I). Swabbings were cultured for bacteria and accessed for cytologic evidence of inflammation. The time of sampling averaged 104 d post partum. Bacteria in the uterus were cultured from 65% of the cows (n = 85). The number of cows with any given microbial genus ranged from 1 to 35 and the number of different genera per cow ranged from 0 to 8. There were on significant correlations between amount and type of uterine microflora, days post partum, numbers of observed estrus, conception rate and uterine inflammation. The number of observed estrus periods was not correlated with the presence of aerobic bacteria. No significant relationships were found between microbes and uterine inflammation or conception to the A.I. service at the time of sampling. A negative correlation between uterine inflammation and conception approached significance (r=-0.24, P > 0.10). Acquisition of uterine lumen samples by the technique utilized had no effect on conception to A I service.

Journal Article↗
PubMed1988

Teat skin normal flora and colonization with mastitis pathogen inhibitors.

Isolates of bacteria from normal teats were used to attempt colonization of teats of dry cows or neonatal calves. Isolates for inoculation were chosen on the basis of ability to inhibit mastitis pathogens in vitro, with the ultimate goal of in vivo inhibition of mastitis pathogens at the teat surface. Three bacterial normal flora isolates (Corynebacterium xerosis, Bacillus sp. and Aerococcus viridans) persisted less than 10 days on the teats of dry cows. The fourth isolate, Staphylococcus hominis 1, was studied in greatest detail because studies characterizing the normal teat flora showed staphylococci to be the predominant flora. The S. hominis 1 isolated used for inoculation was an inhibitor of Gram-positive mastitis pathogens. It was a biotype not found on these teats prior to inoculation, thus facilitating identification of the inoculated isolate on sequential sampling. Colonization of newborn calves, before other bacterial flora became established, resulted in recovery of inoculated S. hominis 1 for an average of 51 days or longer. On dry cow teats it was detected for up to 28 days. On several occasions the inoculated S. hominis 1 was found in pure culture. Since many new infections occur during the dry period, the colonization of dry cow teats with S. hominis 1 organisms inhibitory for Gram-positive pathogens should be tested as an adjunct to other methods of mastitis prevention.

Animals↗
PubMed1987

Serum susceptibility of bovine pasteurellas.

In this study, the serum sensitivity of 23 P. haemolytica isolates and 18 P. multocida isolates was determined by incubating dilutions of bacteria with equal volumes of fresh or heat-inactivated bovine serum for one, two, or three hours. Clinical isolates of both Pasteurella species were resistant to serum, whereas isolates from asymptomatic cattle varied in serum susceptibility. The classical pathway of complement appeared to be the principal means of complement mediated killing as detected by incubation in the presence or absence of EGTA-MgCl2. Lyzozyme and iron saturation of serum did not greatly affect serum susceptibility with either of the Pasteurella species.

Animals↗
PubMed1987

In vitro growth inhibition of mastitis pathogens by bovine teat skin normal flora.

One factor contributing to differences in the susceptibility of cows to mastitis may be differences in the teat skin normal flora, which could inhibit or enhance the growth of pathogenic bacteria. Using in vitro cross-streaking methods, we found that 25% of the isolates of teat normal flora of non-lactating heifers inhibited the growth of selected mastitis pathogens, but enhancers were not detected. Gram-positive pathogens were inhibited to a greater extent than Gram-negative pathogens. Inhibition was not a characteristic of specific genera or species of normal flora, but rather a property of certain variants within a species. This phenomenon of inhibition of mastitis pathogens in vitro by normal flora may be useful as an in vivo biological control method to reduce the incidence of mastitis.

Acinetobacter↗
PubMed1986

Isolation of piliated Escherichia coli from diarrheic foals.

Escherichia coli was isolated from the feces and intestines of foals with and without diarrhea. Piliation of isolates was demonstrated by electron microscopy and agglutination in antisera having specificity for K88, K99, P987 and F41 pili. Piliation was also demonstrated by electron microscopy on organisms which did not react with any of the antisera.

Agglutination Tests↗
PubMed1986

Detection of mink enteritis virus in mink feces, using enzyme-linked immunosorbent assay, hemagglutination, and electron microscopy.

Twenty-five mink were inoculated with mink enteritis virus (MEV). Fecal specimens were collected daily and were simultaneously evaluated for MEV antigen by use of a direct enzyme-linked immunosorbent assay (ELISA), hemagglutination (HA), and electron microscopy. Results of the evaluations indicated that MEV was shed in the feces on postinoculation days 5 and 6. The virus was not detectable by ELISA or HA after postinoculation day 6, although viruses were found in reduced numbers by use of electron microscopy. The ELISA was specific for MEV, and the sensitivity of the ELISA for MEV was comparable with that of HA.

Animals↗
PubMed1985

Transfer of transposable drug-resistance elements Tn5, Tn7, and Tn76 to Azotobacter beijerinckii: use of plasmid RP4::Tn76 as a suicide vector.

Transposable elements Tn5, Tn7, and Tn76 were transferred to Azotobacter beijerinckii. Evidence was obtained for the transposition of Tn5 but cells of the majority of presumptive transposition isolates had abnormal morphologies and rapidly lost viability when subcultured. Data are presented that indicate that plasmid RP4::Tn76 behaves as a suicide vector upon transfer to this host, allowing the isolation of A. beijerinckii::Tn76 isolates at a high frequency. Nitrogen-fixing mutants and leucine and adenine auxotrophs were isolated from cultures in which the transposition of Tn76 occurred.

Azotobacter↗
PubMed1985

Bacterial interactions in bovine respiratory and reproductive infections.

The ability of the aerobic bacterial flora from the normal bovine respiratory and reproductive tracts to enhance or inhibit the growth of Pasteurella haemolytica, P. multocida, and Haemophilus somnus was tested in vitro. Six strains of each of these pathogens were cross streaked with each isolate of bovine normal flora. Flora which enhanced the growth of these pathogenic bacteria outnumbered inhibitors four to one. An intermediate number of isolates produced no effect on pathogen growth. Most enhancers were gram positive (Micrococcus, Staphylococcus, Corynebacterium, or Rhodococcus isolates), although several isolates of Moraxella and Actinobacter were also good enhancers. For H. somnus, there were proportionally more organisms which produced marked enhancement among the preputial flora than among the nasal flora, which may account for the greater number of genital carriers than nasal carriers. Bacillus isolates were the most significant inhibitors among the nasal flora, whereas no genus or species from the reproductive tract was noted to produce appreciable inhibition. It is proposed that changes in ratios of inhibitors to enhancers may determine, in part, whether a carrier state or disease occurs. Also, suggestions are made for in vitro use of this phenomenon for diagnostic tests.

Animals↗
PubMed1985

Serum susceptibility of Haemophilus somnus from bovine clinical cases and carriers.

The serum susceptibility of 64 isolates of Haemophilus somnus from cattle was determined in a bactericidal assay with undiluted fresh or inactivated bovine serum with serial dilutions of bacterial suspension in RPMI 1640 medium. A total of 27 strains isolated from cattle with clinical disease (4 with thromboembolic meningoencephalitis, 13 with pneumonia, and 10 with reproductive failure) were compared with 35 strains from asymptomatic carriers (11 from the vagina and 24 from the prepuce). Essentially, all clinical isolates were serum resistant, whereas approximately 25% of preputial isolates were serum susceptible, as judged after 1 h of incubation in serum; a majority of vaginal isolates showed delayed serum susceptibility. Lysozyme played no role in serum killing, and the alternative complement pathway played only a minor role. Iron saturation, however, appeared to impart greater serum resistance to serum-susceptible strains from the vagina and prepuce. Perhaps the serum-susceptible strains from carriers would be useful vaccine candidates, but resistant strains from carriers may be pathogenic.

Animals↗
PubMed1985

Properties of a respiratory syncytial virus isolated from a sheep with rhinitis.

A virus isolated from a yearling cross-bred ewe was identified as respiratory syncytial virus (RSV) by indirect immunofluorescence and by virus neutralization with bovine RSV antisera. The virus caused a mild conjunctivitis in 3-month-old lambs when inoculated alone. Although clinical signs of pneumonia were not observed, there was gross and microscopic evidence of pulmonary inflammation in the lungs of lambs inoculated with either the sheep RSV isolate alone or in conjunction with Pasteurella haemolytica. Lung lesions in the dual infection were more severe, with approximately 10% of the total lung mass affected. Lavage fluids from lambs inoculated with virus and bacteria contained approximately 3 times more inflammatory cells than from control lambs or lambs inoculated with virus only. The sheep RSV isolate was classified as a mild respiratory pathogen in lambs of this age. Speculations on the potential importance of this virus in interspecies transmission to cattle and goats were discussed.

Animals↗
PubMed1984

The Ancillary Services Review Program in Massachusetts. Experience of the 1982 pilot project.

In 1982, a pilot program to review the use of ancillary services in 25 hospitals was implemented in Massachusetts. The program analyzed hospital claims data to generate statistical models of ancillary use. Hospitals where the model demonstrated substantially higher use were subjected to clinical review. For laboratory services, three of the four hospitals reviewed were found to have more than 30% inappropriate use of selected tests, compared with approximately 20% in other hospitals. For cardiac services, three hospitals were each found to have more than 30% inappropriate use of selected tests, compared with 16% in other hospitals. When informed of these results, five of the six hospitals used them to develop plans of corrective action. Based on the pilot program, a review of ancillary services began in all Massachusetts hospitals in 1983.

Ancillary Services, Hospital↗