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A C Wardlaw

Publications and source records attributed to A C Wardlaw.

At least 19 recordsLinked to original sources
PubMed2000

Bactericidal action of high-power Nd:YAG laser light on Escherichia coli in saline suspension.

Infra-red light (1064 nm) from a high-power Nd:YAG laser caused more than 90% loss of viability of Escherichia coli during exposures that raised the temperature of PBS suspensions of the bacteria to 50 C in a thermocouple-equipped cuvette. In contrast, there was minimal loss of viability after heating the same suspensions to 50 degrees C in a water-bath, or in a PCR thermal cycler. The mechanism of laser killing at 50 degrees C was explored by differential scanning calorimetry, by laser treatment of transparent and turbid bacterial suspensions, and by optical absorbency studies of E. coli suspensions at 1064 nm. Taken together, the data suggested that the bactericidal action of Nd:YAG laser light at 50 degrees C was due partly to thermal heating and partly to an additional, as yet undefined, mechanism. Scanning electron microscopy revealed localized areas of surface damage on laser-exposed E. coli cells.

Colony Count, Microbial↗
PubMed1999

Time-course of infection and responses in a coughing rat model of pertussis.

Adult female Sprague-Dawley rats were challenged intrabronchially with Bordetella pertussis strain 18-323 embedded in fine agarose beads and the time-course of infection and other events was determined. There was a steady decline in the numbers of B. pertussis recovered from the rat lungs, with clearance of the infection in most animals by day 12. Leucocytosis, lung inflammation and an increase in total serum IgE in the rats as a result of the challenge were highest around day 10, which was coincident with the highest incidence of coughing in such animals. IgG and IgA antibodies to the B. pertussis antigens pertussis toxin and filamentous haemagglutinin were not detected until after this period. The coughing rat model of pertussis resembles the human disease in the relationship between the time course of infection and cough production.

Animals↗
PubMed1999

Bactericidal activity of rat lung lavage fluid against Bordetella pertussis.

Cell-free lung lavage fluid (LLF) from healthy normal rats killed phase I (wild-type, virulent) Bordetella pertussis at 37 degrees C in vitro. B. parapertussis was also killed by the LLF, but phase IV (avirulent mutant) B. pertussis and some other common bacterial species, including B. bronchiseptica, were not. Transmission electron microscopy of thin sections of the phase I B. pertussis showed extensive structural damage and cell lysis. None of the other mammalian species tested had LLF with bactericidal activity against B. pertussis as high as that of the rat. Rats killed with halothane yielded LLF with higher bactericidal activity than when CO2 was used. Ultracentrifugation of LLF at 55,000 g gave a surfactant (pellet) fraction that had c. 95% of the bactericidal activity and which was biochemically distinct from the 5% of activity in the supernate fraction. Phospholipids and fatty acids appeared to be involved in LLF bactericidal activity, but not complement or lysozyme. Arachidonic acid was the most active of the fatty acids tested. Artificial surfactant, as used in premature infants, had no bactericidal effect on B. pertussis.

Anesthetics, Inhalation↗
PubMed1998

Responses to acellular pertussis vaccines and component antigens in a coughing-rat model of pertussis.

Two acellular pertussis vaccines (SmithKline Beecham 3-component and Connaught 5-component), and a whole-cell pertussis vaccine (Evans), were similarly protective against paroxysmal coughing and leukocytosis in a coughing-rat model of pertussis. A two-dose immunization schedule was followed by sublethal intrabronchial challenge with Bordetella pertussis strain 18-323, encased in fine agarose beads, and the coughing monitored by sound-activated tape recorders. Pertussis toxoid by itself gave some protection against coughing, but lower than that afforded by the vaccines, despite inducing a higher serum anti-PT titre. The other component antigens, given individually, failed to protect against coughing although inducing antibodies. Immunization with the whole-cell and acellular vaccines and with their component antigens, as well as challenge with B. pertussis, caused significant elevation of total serum IgE antibodies. Antigen-specific IgG and IgA were detected in tracheobronchial washings from rats recovering from B. pertussis challenge, but vaccination prior to challenge had little influence on these antibody levels. The coughing-rat model of pertussis may be useful for the comparative testing of different formulations of pertussis vaccines before trials in human infants.

Animals↗
PubMed1998

Induction of abnormal respiratory sounds by capsaicin in rats previously infected with Bordetella pertussis.

Sprague Dawley rats, previously infected with Phase-I Bordetella pertussis, developed more severe abnormal respiratory sounds than normal animals, but not coughing, when exposed to aerosolized capsaicin, one of several cough-inducing agents tested. Stethoscope examination suggested that greater production of pulmonary mucus might be occurring after capsaicin challenge of the infected animals, compared to the uninfected controls. Rats of three other strains gave characteristically different responses from the Sprague Dawleys. The administration of capsaicin to B. pertussis-infected rats may provide useful insights into the pathophysiology of excess mucus secretion in human pertussis.

Aerosols↗
PubMed1997

Differences in coughing and other responses to intrabronchial infection with Bordetella pertussis among strains of rats.

Four strains of rats were each infected intrabronchially with approximately 10(8) CFU of Bordetella pertussis 18-323 encased in fine agarose beads. After 8 days, Sprague-Dawley rats developed the highest incidence of coughing paroxysms, as monitored with voice-activated tape recorders; Brown Norway, Lewis, and Hooded Lister rats coughed significantly less frequently. Marked leukocytosis, with counts up to four times the normal levels, and retardation of normal weight gain occurred in all four rat strains. Both coughing and leukocytosis were greater in animals that were infected at 4 weeks of age than in those infected at 6 weeks of age. Total serum immunoglobulin E (IgE) rose in all four rat strains 9- to 244-fold by day 8 after infection and returned to near preinfection levels at 6 weeks. Sprague-Dawley and Lewis rats, which had the lowest basal levels of total IgE in serum, showed the greatest degrees of elevation. All four rat strains had IgG to B. pertussis whole-cell sonicate and to filamentous hemagglutinin in 6-week-postinfection sera. However, the strains differed in production of IgG to pertussis toxin, with Sprague-Dawley rats having the highest titers and Hooded Lister and Lewis rats being nonresponders. These studies highlight the importance of rat strain as a variable in the coughing-rat model of pertussis and validate the choice of the Sprague-Dawley rats in previous studies.

Age Factors↗
PubMed1996

Inactivation of bacteria and yeasts on agar surfaces with high power Nd:YAG laser light.

Near infrared light from a high-powered, 1064 nm, Neodymium:Yttrium Aluminium Garnet (Nd:YAG) laser killed a variety of Gram-positive and Gram-negative bacteria and two yeasts, lawned on nutrient agar plates. A beam (cross-sectional area, 1.65 cm2) of laser light was delivered in 10 J, 8 ms pulses at 10 Hz, in a series of exposure times. For each microbial species, a dose/response curve was obtained of area of inactivation vs energy density (J cm-2). The energy density that gave an inactivation area (IA) equal to 50% of the beam area was designated the IA50-value and was plotted together with its 95% confidence limits. Average IA50-values were all within a threefold range and varied from 1768 J cm-2 for Serratia marcescens to 4489 J cm-2 for vegetative cells of Bacillus stearothermophilus. There were no systematic differences in sensitivity attributable to cell shape, size, pigmentation or Gram reaction. At the lowest energy densities where inactivation was achieved for the majority of organisms (around 2000 J cm-2), no effect was observed on the nutrient agar surface, but as the energy density was increased, a depression in the agar surface was formed, followed by localized melting of the agar.

Agar↗
PubMed1994

Cough production, leucocytosis and serology of rats infected intrabronchially with Bordetella pertussis.

Adult Sprague-Dawley rats infected intrabronchially with Bordetella pertussis strain 18-323 encased in agarose beads (BP-beads), developed a paroxysmal cough and leucocytosis, both of which peaked at around day 10. When animals were exposed to ether for 2 min after delivery of the beads, there was an enhancement of the number of subsequent coughing episodes. Inclusion of carrageenan in the beads also enhanced coughing. Control rats, given sterile beads or left untreated, showed only a low level of coughing or no coughing, depending upon their source. Rats challenged by the same route with heat-killed B. pertussis in beads, or with live organisms in suspension (without beads) showed no cough induction or leucocytosis. However, intranasal delivery of B. pertussis suspension gave rise to a moderate amount of coughing and leucocytosis. Serum IgG responses to B. pertussis antigens were greatest in rats infected with BP-beads and antibodies against both pertussis toxin and filamentous haemagglutinin were detected. Since the rat is the only conveniently accessible laboratory animal species in which B. pertussis induces an intermittent paroxysmal cough, as in man, it merits further study for determining the mechanisms of pathogenesis and immunity in pertussis.

Animals↗
PubMed1994

Responses to Bordetella pertussis mutant strains and to vaccination in the coughing rat model of pertussis.

Phase I strains 18-323, Tohama and L-84 of Bordetella pertussis produced paroxysmal coughing when encased in agarose beads and administered intrabronchially to adult Sprague-Dawley rats. In contrast, the Phase IV variant of strain L-84 was inactive in cough induction, as was strain BP 357, a transposon-insertion mutant which is deficient only in pertussis toxin (PT). Strain BPM 1809, which lacks only the heat-labile toxin, was similar to the unmodified Phase I strains for cough induction, indicating that this toxin is not needed to induce coughing. B. parapertussis also was inactive as a cough inducer. These results indicate that PT, present in Phase I strains of B. pertussis, and absent from Phase IV strains, strain BP 357 and B. parapertussis, is essential for the induction of paroxysmal coughing in this rat model of whooping cough. Prior injection of DTP (whole-cell) vaccine greatly reduced the incidence of coughing in rats challenged subsequently with Phase I B. pertussis. Serological responses were monitored after intrabronchial infection with the various bacterial strains and after vaccination and challenge. The PT-positive or -negative status of the strains in vivo was confirmed by the appropriate presence or absence of anti-PT IgG in the convalescent sera.

Animals↗
PubMed1994

Bactericidal activity in the pig roundworm Ascaris suum.

A potent, humoral, bactericidal activity against Micrococcus luteus was discovered in pseudocoelomic fluid of the pig roundworm, Ascaris suum. The activity, which was not bacteriolytic, was not due to lysozyme or to a dietary antibiotic. It was not inactivated by exposure to 100 degrees C, to low or high pH, or to ethanol. Dialysis, electrophoresis and agar-diffusion experiments suggested that the main antibacterial activity in the fluid was associated with a basic substance of molecular weight somewhat less than 14,000 Da. Two other Gram-positive organisms, Bacillus megaterium and Staphylococcus aureus, were also killed by the Ascaris fluid, but the Gram-negative Escherichia coli, Proteus vulgaris and Bordetella bronchiseptica were insensitive.

Animals↗
PubMed1994

Tracheobronchial washings from seven vertebrate species as growth media for the four species of Bordetella.

The four species of Bordetella differed in their ability to grow at 37 degrees C in membrane-filtered tracheobronchial washings (TBW) from seven vertebrate species, including their natural hosts. From washed inocula of approximately 2 x 10(3) colony-forming units per ml (cfu ml-1), Bordetella bronchiseptica and B. avium grew much better than the other two bordetellae and yielded stationary-phase cultures containing 10(8)-10(9) cfu ml-1 in most of the TBW samples. These counts were only moderately lower than those attained in CL medium which contains about a 450-times higher concentration of amino acids. B. bronchiseptica and B. avium also grew to a limited extent in phosphate-buffered saline without nutrient supplements. B. parapertussis grew in TBW from man, sheep, rabbit, mouse and chicken, but not in TBW from a dog and a horse or in PBS. B. pertussis grew well in CL medium, but not in PBS or in any of 13 samples of TBW from the seven vertebrate species, which included three samples of lung lavage fluid from human patients. Analysis of the TBW samples for known Bordetella nutrients revealed concentrations of amino acids and nicotinic acid averaging 0.35 mM and 0.56 microgram ml-1 respectively.

Amino Acids↗
PubMed1994

Adjuvant effect of pertussis toxin on the production of anti-ovalbumin IgE in mice and lack of direct correlation between PCA and ELISA.

In studies designed to optimize the production and detection of anti-ovalbumin (anti-Oa) IgE in Ham/ICR mice, a range of doses of both Oa and pertussis toxin as the IgE adjuvant was explored. As determined by 48-hour passive cutaneous anaphylaxis (PCA) tests, the highest titre of anti-Oa IgE was obtained in a three-injection protocol with 0.1 micrograms Oa and 1 microgram pertussis toxin for the priming dose, followed by two further doses of 0.1 microgram Oa alone. In single-dose immunizations, the highest PCA responses were obtained in sera from mice given 20 micrograms Oa and 1 microgram pertussis toxin. These data confirm that murine IgE production to Oa depends on particular combinations of immunization variables. There was no direct correlation between the PCA and anti-IgE enzyme-linked immunosorbent assay (ELISA) titres of the PCA-positive sera; indeed there was a significant negative correlation. This relationship was not due to interference by IgG1, as there was no correlation between the anti-Oa IgG1 and anti-Oa IgE ELISA titres of the sera. These results highlight the need for caution in assuming that serum IgE levels as measured by ELISA will necessarily correlate positively with IgE biological activity as measured by allergen challenge in vivo.

Adjuvants, Immunologic↗
PubMed1993

Long-term survival of Bordetella bronchiseptica in lakewater and in buffered saline without added nutrients.

Bordetella bronchiseptica grew from small inocula, and retained viability for at least 24 weeks, in unsupplemented lakewater or phosphate-buffered saline. From washed inocula of around 10(3) colony-forming units/ml, there was growth at both 10 degrees C and 37 degrees C to give 10(6)-10(7) colony-forming units/ml. At 10 degrees C, these counts were maintained with little diminution up to week 24 when observations ceased. In the tests at 37 degrees C, two of three strains tested showed similar retention of viability. These results suggest that B. bronchiseptica may exist as hitherto unsuspected reservoirs of infection in freshwater habitats.

Bordetella bronchiseptica↗
PubMed1992

Multiple discontinuity as a remarkable feature of the development of acellular pertussis vaccines.

Development of the Japanese acellular pertussis vaccines (APVs) of the 1980s involved six procedural or conceptual features that were discontinuous with the then-accepted views of how pertussis vaccines should be made and tested. These discontinuities were: modification of the standard intracerebral mouse test for protective potency; use of culture supernates, rather than cells, of Bordetella pertussis as the feedstock for antigen purification; use of haemagglutination as a measure of protective antigen(s); identification of pertussis toxin (PT) as the main protective antigen; complete inactivation of the biological activities of PT by formalin; and the use of a single strain of B. pertussis. Several of these discontinuities had long precedence in the pertussis literature, but the original observations had not been incorporated into the mainstream of pertussis vaccinology and were therefore 'premature'. The APVs, purified from culture-supernates, emerged after a long period of unsuccessful research on the split-cell pertussis vaccines, i.e. those derived from the bacterial cells themselves. There is a brief discussion of why APVs have taken so long to obtain acceptance outside Japan, and of how the listed discontinuities may be explicable in terms of antigen processing by the immune system. General lessions, applicable to vaccines for other infectious diseases, may be learned from this account of how APVs have evolved from whole-cell pertussis vaccines.

Animals↗
PubMed1991

Assay of Bordetella pertussis heat-labile toxin with human embryonic lung cells.

An assay has been developed for Bordetella pertussis heat-labile toxin (HLT) based on morphological alterations in certain human embryonic lung (HEL) cell lines. Eighteen cell lines from human and other sources were tested but only two, MRC-5 and HELu2, were responsive to HLT. Confluent monolayers of the cells contracted within 24 h of exposure to the toxin, but without loss of viability during incubation for a further 3 days. The effect of HLT was quantitated by scoring the extent of morphological change, and by the decrease in Giemsa staining of the cell monolayers, as measured on an ELISA plate reader. This cell culture assay for HLT was more sensitive than lethality titration in mice but the dose-response curve had a lower slope. The specificity of the response was established by comparing unheated HLT with HLT heated at 56 degrees C, and with extracts from transposon-insertion mutants of B. pertussis which were deficient in HLT. Purified preparations of pertussis toxin and B. pertussis lipopolysaccharide gave no morphological response even at high doses.

Animals↗
PubMed1991

Growth and survival of Bordetella bronchiseptica in natural waters and in buffered saline without added nutrients.

Bordetella bronchiseptica showed increases in viable count when incubated in phosphate-buffered saline (PBS), in reagent-grade water, and in local lake and pond waters, all without added nutrients. Within 48 to 72 h at 37 degrees C in PBS and in lake and pond waters, stationary-phase populations of around 2.7 x 10(6) CFU/ml developed from washed B. bronchiseptica inocula of around 2 x 10(3) CFU/ml. Increases in CFU on the order of five- and eightfold, respectively, were observed in reagent-grade water and in seawater from the same sizes of inocula. The organisms remained viable for at least 3 weeks in PBS and in lake waters at 37 degrees C. The possibility that carry-over of nutrients was responsible for growth was discounted by showing serial transfer of B. bronchiseptica in PBS under conditions in which Escherichia coli tested in parallel rapidly died out.

Bordetella↗
PubMed1989

Effect of hyperreactivity to endotoxin on the toxicity of pertussis vaccine and pertussis toxin in mice.

In mice, greatly enhanced susceptibility to the lethal toxicity of whole-cell pertussis vaccine (PV) was produced by agents known to induce hypersusceptibility to endotoxin (LPS). The decreases in LD50 were 100-fold, 125-fold and 16-fold with galactosamine (GalN), actinomycin D (AcD) and lead acetate (PbAc) respectively and the animals died within 1-2 days. However, these decreases were less than those observed with extracted E. coli LPS, the LD50 of which was reduced approximately 500-fold, 800-fold and 50-fold respectively by these agents. In control mice, without drugs, the main lethal factor in the PV used here seemed to be pertussis toxin (PT), since deaths occurred at 3-5 days after injection, and heating the vaccine at 80 degrees C for 30 min raised the LD50 from 4 to greater than 6 single human doses (SHD) per mouse. In GalN and PbAc-treated mice, the toxicity of PV can be explained by its LPS content in view of the failure of heating at 80 degrees C to reduce toxicity. However, in AcD-treated mice, the 80 degrees C heated vaccine was threefold less toxic than the unheated material, suggesting a contribution of PT to vaccine toxicity in these animals. Indeed the toxicity of PT was increased by AcD. The possible bearing of these observations on children who appear to show serious adverse reactions to PV is discussed. Two acellular vaccines were devoid of lethal toxicity in either normal mice or in mice treated with any of the three drugs.

Animals↗