A magnetic massive star has experienced a stellar merger.

Massive stars (those ≥8 solar masses at formation) have radiative envelopes that cannot sustain a dynamo, the mechanism that produces magnetic fields in lower-mass stars. Despite this, approximately 7% of massive stars have observed magnetic fields, the origin of which is debated. We used multi-epoch interferometric and spectroscopic observations to characterize HD 148937, a binary system of two massive stars. We found that only one star is magnetic and that it appears younger than its companion. The system properties and a surrounding bipolar nebula can be reproduced with a model in which two stars merged (in a previous triple system) to produce the magnetic massive star. Our results provide observational evidence that magnetic fields form in at least some massive stars through stellar mergers.

D2R2: an evidence-based decision support tool to aid prioritisation of animal health issues for government funding.

An evidence-based decision support tool, 'D2R2', has been developed by Defra. It contains a wide range of standardised information about exotic and endemic diseases held in 'disease profiles'. Each profile includes 40 criteria used for scoring, enabling D2R2 to provide relative priority rankings for every disease profiled. D2R2 also provides a range of reports for each disease and the functionality to explore the impact of changes in any criterion or weighting on a disease's ranking. These outputs aid the prioritisation and management of animal diseases by government. D2R2 was developed with wide stakeholder engagement and its design was guided by clear specifications. It uses the weighted scores of a limited number of criteria to generate impact and risk scores for each disease, and relies on evidence drawn from published material wherever possible and maintained up to date. It allows efficient use of expertise, as maintained disease profiles reduce the need for on call, reactive, expert input for policy development and enables rapid simultaneous access to the same information by multiple parties, for example during exotic disease outbreaks. The experience in developing D2R2 has been shared internationally to assist others with their development of disease prioritisation and categorisation systems.

Rapid protection of gnotobiotic pigs against experimental salmonellosis following induction of polymorphonuclear leukocytes by avirulent Salmonella enterica.

Oral inoculation of 5-day-old gnotobiotic pigs with Salmonella enterica serovar Typhimurium strain F98 resulted in severe enteritis and invasive disease. Preinoculation 24 h earlier with an avirulent mutant of Salmonella enterica serovar Infantis (1326/28) completely prevented disease for up to 14 days (when the experiment was terminated). S. enterica serovar Infantis colonized the alimentary tract well, with high bacterial counts in the intestinal lumen but with almost no invasion into the tissues. Unprotected pigs had high S. enterica serovar Typhimurium counts in the intestines, blood, and major nonintestinal organs. Recovery of this strain from the blood and major organs in S. enterica serovar Infantis-protected pigs was substantially reduced despite the fact that intestinal counts were also very high. Protection against disease thus did not involve a colonization exclusion phenomenon. Significant (P < 0.05) infiltration of monocytes/macrophages was observed in the submucosal regions of the intestines of both S. enterica serovar Infantis-protected S. enterica serovar Typhimurium-challenged pigs and unprotected S. enterica serovar Typhimurium-challenged pigs. However, only polymorphonuclear neutrophils (PMNs) were observed throughout the villus, where significant (P < 0.05) numbers infiltrated the lamina propria and the subnuclear and supranuclear regions of the epithelia, indicating that PMN induction and positioning following S. enterica serovar Infantis inoculation was consistent with rapid protection against the challenge strain. Similarly, in vitro experiments using a human fetal intestinal epithelial cell line (INT 407) demonstrated that, although significantly (P < 0.05) fewer S. enterica serovar Infantis than S. enterica serovar Typhimurium organisms invaded the monolayers, S. enterica serovar Infantis induced an NF-kappaB response and significantly (P < 0.05) raised interleukin 8 levels and transmigration of porcine PMN. The results of this study suggest that attenuated Salmonella strains can protect the immature intestine against clinical salmonellosis by PMN induction. They also demonstrate that PMN induction is not necessarily associated with clinical symptoms and/or intestinal pathology.

Role of capsule in the pathogenesis of fowl cholera caused by Pasteurella multocida serogroup A.

We have constructed a defined acapsular mutant in Pasteurella multocida X-73 (serogroup A:1) by disrupting the hexA gene through the insertion of a tetracycline resistance cassette. The genotype of the hexA::tet(M) strain was confirmed by PCR and Southern hybridization, and the acapsular phenotype of this strain was confirmed by electron microscopy. The hexA::tet(M) strain was attenuated in both mice and chickens. Complementation of the mutant with an intact hexAB fragment restored lethality in mice but not in chickens. In contrast to the results described previously for P. multocida serogroup B (J. D. Boyce and B. Adler, Infect. Immun. 68:3463-3468, 2000), the hexA::tet(M) strain was sensitive to the bactericidal action of chicken serum, whereas the wild-type and complemented strains were both resistant. Following inoculation into chicken muscle, the bacterial count of the hexA::tet(M) strain decreased significantly, while the wild-type and complemented strains both grew rapidly over 4 h. The capsule is thus an essential virulence determinant in the pathogenesis of fowl cholera.

Genetic organization of Pasteurella multocida cap Loci and development of a multiplex capsular PCR typing system.

Current serotyping methods classify Pasteurella multocida into five capsular serogroups (serogroups A, B, D, E, and F) and 16 somatic serotypes (serotypes 1 to 16). In the present study, we have developed a multiplex PCR assay as a rapid alternative to the conventional capsular serotyping system. The serogroup-specific primers used in this assay were designed following identification, sequence determination, and analysis of the capsular biosynthetic loci of each capsular serogroup. The entire capsular biosynthetic loci of P. multocida A:1 (X-73) and B:2 (M1404) have been cloned and sequenced previously (J. Y. Chung, Y. M. Zhang, and B. Adler, FEMS Microbiol. Lett. 166:289-296, 1998; J. D. Boyce, J. Y. Chung, and B. Adler, Vet. Microbiol. 72:121-134, 2000). Nucleotide sequence analysis of the biosynthetic region (region 2) from each of the remaining three serogroups, serogroups D, E, and F, identified serogroup-specific regions and gave an indication of the capsular polysaccharide composition. The multiplex capsular PCR assay was highly specific, and its results, with the exception of those for some serogroup F strains, correlated well with conventional serotyping results. Sequence analysis of the strains that gave conflicting results confirmed the validity of the multiplex PCR and indicated that these strains were in fact capsular serogroup A. The multiplex PCR will clarify the distinction between closely related serogroups A and F and constitutes a rapid assay for the definitive classification of P. multocida capsular types.

Characteristics of a haemolytic extract from avian Pasteurella multocida.

In experimental fowl cholera, the intramuscular inoculation of Pasteurella multocida induces tissue damage that implies proteolytic or cytolytic activity of the bacteria. Such activity could not be demonstrated by conventional in vitro tests. The treatment of P. multocida strain VP21 with Tween-80 yielded an extract that lysed washed chicken red cells. Extracts were active to a maximum titre of 64. Haemolytic activity of the extract was neither affected by boiling nor by extremes of pH, indicating the active component was not a simple protein. Treatment with trypsin had no effect, but it was inactivated by Proteinase K. Yields were highest from bacteria grown in dextrose starch- or casein sucrose-yeast broths; were similar if cultured in air or anaerobically, but were reduced if the bacteria were grown in 5% CO(2). Haemolytic activity was eliminated on exposure to serum or serum albumen. The extract from strain VP21 haemolysed red cells from the chicken, rabbit, sheep, horse, bovine and human, with the highest titres observed on chicken cells. Six other avian strains and seven out of 10 strains of P. multocida from other species yielded an extract which haemolysed chicken red cells. The elaboration of this cytotoxic substance in vivo and its role in pathogenesis remains to be determined.

The demonstration of Pasteurella multocida in the alimentary tract of chickens after experimental oral infection.

A selective medium containing polymyxin B, crystal violet, thallous acetate, bacitracin and cycloheximide in 10% sheep blood dextrose starch agar, and a modified Pasteurella multocida-specific polymerase chain reaction (PCR) assay were developed for the respective isolation and detection of P. multocida from chicken alimentary tract. The selective medium and the PCR assay were highly sensitive, detecting 100 cfu from colon contents. These techniques were used to follow the localisation of an orally administered virulent P. multocida in chickens. Pasteurellae could be isolated from the crop of some birds up to 30 h, occasionally from other sites after 28 h. It was concluded that the crop was a likely site for colonisation and that infection was most likely to occur through the mucosa of the jejunum or ileum.

The virulence and protective efficacy for chickens of pasteurella multocida administered by different routes.

The relative virulence for chickens of five strains of Pasteurella multocida was evaluated. Twenty groups, each of ten chickens, were inoculated with a standard dose of 10(5) of each of five strains by the intramuscular (I.m.), intravenous (I.v.), intratracheal (I.tr.) or conjunctival (Co) routes. The highest mortality occurred in the groups dosed I.m. and I.v., followed by I.tr. inoculation. The relative virulence of each strain did not change when inoculated by the different routes. The most virulent strain, VP161, caused 100% mortality by all except the Co route. The least virulent strain, VP17, caused a single mortality by the I.v. route, but gave a high level of protection to birds inoculated by both the I.m. and I.v. routes, when challenged by intramuscular injection with (VP161). There was no protection against I.m. challenge in the birds inoculated by the I.tr. or Co routes. Serum antibody levels measured by ELISA correlated with the level of protection against virulent challenge for groups inoculated I.m. or I.v., but not I.tr. Western blots of pooled sera from each group did not show any specific antigen recognition that might explain the observed differences in protection. Inoculation with strain VP17, (both I.m. and I.tr.) also gave a high level of protection to birds challenged with strain VP161 by intratracheal instillation.

PCR detection and analysis of Pasteurella multocida from the tonsils of slaughtered pigs in Vietnam.

A total of 36 tonsil swab samples were collected from healthy swine prior to slaughter at the abattoirs in Can tho and Tien giang provinces of Southern Vietnam. The presence of Pasteurella multocida in these samples was detected by the combination of direct cultivation and isolation, mouse inoculation and the polymerase chain reaction (PM-PCR). P. multocida was detected in 16 samples by PCR, with 17 strains ultimately isolated. All samples were negative for serogroup B by HSB-PCR and conventional serotyping, with isolates identified as A:3, D:1 or D:3. In addition, all samples were determined to be negative for the P. multocida toxin (PMT). Characterisation of isolated P. multocida by REP-PCR and biotyping revealed nine distinct REP profiles and seven biotypes among the 17 isolates. Some correlation was seen with P. multocida isolated from a previous Australian outbreak of acute swine pasteurellosis, and those isolated from fowl cholera outbreaks in Vietnamese poultry.

Molecular characterisation of avian Pasteurella multocida isolates from Australia and Vietnam by REP-PCR and PFGE.

A total of 95 isolates of Pasteurella multocida were analysed by pulsed field gel electrophoresis (PFGE) using the enzyme ApaI, including 73 avian isolates from Australia and 22 from Vietnam. The majority of field isolates were capsular Type A, with the predominant somatic serovars of 1, 3, 4 and 3,4. Twenty-one distinct profiles were evident among the Australian isolates, with only 3 profiles observed among the 22 P. multocida strains isolated from Vietnam. Within the Australian isolates, related and unrelated outbreaks could be identified by PFGE. These results correlated well with previously published studies, with greater discrimination shown by PFGE. Repetitive extragenic palindromic sequence PCR (REP-PCR) analysis of representative isolates from PFGE classifications yielded 21 profiles, with most of the subgroups in accordance with PFGE analysis. While REP-PCR was shown to be less discriminating than PFGE, the epidemiological relatedness of strains compared favourably between the techniques. Thus, the ease and rapidity of REP-PCR while maintaining a high level of differentiation, supports the use of REP-PCR as a competent alternative to the more labour-intensive PFGE system for strain identification and epidemiological studies of avian P. multocida.

The molecular epidemiology of four outbreaks of porcine pasteurellosis.

Biochemical profiles, restriction endonuclease analysis (REA) and ribotyping were used to investigate a total of 38 Pasteurella multocida isolates from four separate outbreaks of pasteurellosis in Australian piggeries. Six isolates were obtained from Outbreak 1, 16 from Outbreak 2 and eight each from outbreaks 3 and 4. Outbreaks 1 and 2 were cases of pneumonic pasteurellosis while outbreaks 3 and 4 involved systemic pasteurellosis. Biochemical characterisation established that a number of different types of P. multocida were present in outbreaks 1 and 3 while outbreaks 2 and 4 were associated with a single type of P. multocida. Outbreaks 1 and 3 yielded isolates of P. multocida that belonged to the subspecies multocida and gallicida, with the subspecies multocida isolates being identified as biovar 3 (6 in total) or 12 (1 in total) and the subspecies gallicida isolates (7 in total) being identified as biovar 8. All 24 isolates from outbreaks 2 and 4 belonged to the subspecies multocida and were all biovar 3. REA and ribotyping showed that, in outbreaks 1 and 3, there were three different types of P. multocida in each outbreak with no common strains between the outbreaks. The molecular methods showed that only a single strain of P. multocida was associated with outbreaks 2 and 4, although the outbreaks were associated with strains that differed in REA profiles but shared a ribotype profile. This study has shown that both, systemic and pneumonic pasteurellosis can be associated with either a single strain or multiple strains of P. multocida. The results also indicate that the molecular typing methods of REA and ribotyping are superior to biochemical characterisation for epidemiological investigation of porcine pasteurellosis.

Survival of avian strains of Pasteurella multocida in chicken serum.

The ability of bacteria to survive in serum is considered a likely virulence determinant in diseases where the infective bacteria become septicaemic. Optimal conditions were established to test the survival of Pasteurella multocida in chicken serum. Serum was used at 90%, the inoculum was 10(3)-10(4)cfu in phosphate buffered saline pH 7.4. Survival was measured after incubation for 2-4 h; if survival was <50% the strain was considered serum susceptible. Susceptible strains were either killed or their growth was inhibited. Some resistant strains not only survived but grew rapidly in unheated serum. Thirty-five strains, all originally isolated from clinical fowl cholera, were tested; eight were susceptible, of which three were killed and five inhibited, and the remainder (27) were resistant. Ten serum-resistant P. multocida serogroup A strains were grown in hyaluronidase to remove the capsule and survival in chicken serum was re-tested. Three strains became susceptible, while seven strains remained resistant. Three serum susceptible strains were then tested in the presence of cytidine monophosphate-N-acetylneuraminic acid (CMP-NANA). This substance is present in the human serum, and is known to mask the effect of complement on Neisseria gonorrhoeae rendering susceptible strains resistant. Two of the three serum susceptible strains became resistant in the presence of CMP-NANA. Serum susceptibility/resistance was more complex than that of Escherichia coli, and the role of resistance to avian complement in the pathogenesis of fowl cholera remains to be determined.

Effects of dry cow intramammary therapy on quarter infections in the dry period.

Quarter milk samples were taken from 150 cows from three dairy farms in south-east Queensland at drying off, two, four and six weeks after drying off, at calving, and one, two and three weeks after calving. In each of the herds, the cows were randomly allocated to three groups of approximately equal size. One group had all the quarters of all the cows treated at drying off with a dry cow antibiotic infusion containing cloxacillin; the second group was given no treatment, and the third group had selected quarters treated on the basis of their high activity of N-acetyl-beta-D-glucosaminidase at drying off. Dry cow treatment resulted in a marked reduction in the number of infected quarters at two and four weeks after drying off, so that the comprehensively treated group had significantly less infected quarters at these times (P<0.02). Twelve dinical cases of mastitis were detected two weeks after drying off in the untreated groups, 10 in the untreated quarters of the selectively treated groups, and no cases in the comprehensively treated groups. These cases were due mainly to Streptococcus uberis and Streptococcus dysgalactiae. The number of infected untreated quarters increased markedly between drying off and two weeks later, but in all three groups there was a marked decrease in the number of infected quarters between six weeks after drying off and calving, suggesting that the mammary glands were more able to overcome infections at this time.

Acute septicaemic pasteurellosis in Vietnamese pigs.

Sixteen isolates of Pasteurella multocida were cultured from cases diagnosed as acute septicaemic pasteurellosis in Vietnamese pigs. The HSB-PCR assay provided rapid presumptive determination of 10 isolates of P. multocida identified as haemorrhagic septicaemia (HS) causing type B cultures (B:2, B:5, B:2,5). Serological designation using the Carter and Heddleston typing systems confirmed these findings, and identified the six HSB-PCR negative cultures as either A:1, A:3 or D:3,4. Biochemical fermentation and REP-PCR revealed phenotypic and genotypic identity between P. multocida type A:1 isolated from Vietnamese pigs and poultry. Marked homogeneity was also demonstrated among HSB-PCR positive swine isolates, which were shown to possess genotypic identity with P. multocida type B:2 from buffaloes diagnosed with HS.

Antibiotics for the preservation of koala (Phascolarctos cinereus) semen.

AIM: To determine the normal microbial flora of the koala ejaculate and prepuce in order to select appropriate antibiotics for addition into diluents designed for the preservation of semen. PROCEDURE: Bacteriological samples of the koala prepuce (n = 12) and ejaculate (n = 20) were submitted for microbial culture and sensitivity testing. Microbial flora of ejaculates collected by electroejaculation and artificial vagina were compared. The effects of varying concentrations of penicillin G and gentamicin on sperm motility and on the growth of bacteria in diluted semen stored at room temperature and 16 degrees C over a 24 h period were investigated. RESULTS: A range of bacteria was isolated from the koala prepuce and ejaculate. The predominant organisms in semen collected by electroejaculation and artificial vagina were Corynebacterium spp, none of which could be assigned to any recognised species. The addition of penicillin G and gentamicin to a PBS-based diluent at dose rates of 1000 to 2000 IU/mL and 100 to 200 micrograms/mL respectively, resulted in no adverse effect on sperm motility over a 24 h incubation period. Penicillin G (1000 IU/mL) and gentamicin (100 micrograms/mL) prevented growth of bacterial contaminants in diluted koala semen. CONCLUSION: By controlling the growth of bacteria in extended koala semen, penicillin G and gentamicin are likely to lengthen the period by which spermatozoa can be stored at 16 degrees C and reduce the possibility of disease transmission during artificial insemination procedures.

Development of PCR assays for species- and type-specific identification of Pasteurella multocida isolates.

Genomic subtractive hybridization of closely related Pasteurella multocida isolates has generated clones useful in distinguishing hemorrhagic septicemia-causing type B strains from other P. multocida serotypes. Oligonucleotide primers designed during the sequencing of these clones have proved valuable in the development of PCR assays for rapid species- and type-specific detection of P. multocida and of type B:2 in particular. This study demonstrated that the primer pair designed from the sequence of the clone 6b (KTT72 and KTSP61) specifically amplified a DNA fragment from types B:2, B:5, and B:2,5 P. multocida and that the primers KMT1T7 and KMT1SP6 produced an amplification product unique to all P. multocida isolates analyzed. It was also shown that PCR amplification performed directly on bacterial colonies or cultures represents an extremely rapid, sensitive method of P. multocida identification.

The early dynamic response of the calf ileal epithelium to Salmonella typhimurium.

Ileal loops including Peyer's patch were prepared in five 28-day-old calves and infused Salmonella typhimurium strain ST4/74. Loops were fixed 5 minutes to 2 hours after inoculation, and the mucosa was examined by light and electron microscopy. Within 5 minutes, the bacteria were interacting with the follicle-associated epithelium (FAE); the surface of M cells changed to lamellipodia, engulfing many bacteria. This process proceeded rapidly to 30 minutes, involving most M cells above crypt level. Most cells were exfoliated, and many were packed with bacteria, and the domed villi became stunted. There was a rapid migration of neutrophils through the FAE into the lumen by 15 minutes. By 60 minutes, there was no further interaction between the bacteria and the FAE; at this time bacteria were present in macrophages in the lamina propria. Restitution of the FAE was complete by 2 hours in spite of the many bacteria in the cell debris overlying the epithelium. Interaction of bacteria with the absorptive villi was delayed compared with interaction with the FAE. After 15 minutes, bacteria were seen adhering to some enterocytes of the upper third of the villi; many bacteria were adhering to the surface of the enterocytes at 20 and 30 minutes, but few were seen thereafter. Adherence was patchy and largely confined to cells whose surfaces were depressed relative to others. The microvillous surface of these enterocytes was extensively remodelled. Tissue response, with uptake of bacteria into vacuoles, exfoliation of enterocytes containing bacteria, and subsequent stunting of the villi, began at 30 minutes and was severe and progressive to 2 hours. Following the initial attachment and uptake of the bacteria loss of enterocytes progressed from these initial sites; bacteria were associated with the lateral cell membrane of cells adjacent to cells being extruded and not with the microvilli of cells at new sites. In a calf 4 hours after dosing orally with the same strain, M cells were engulfing bacteria and their cell surface was changed as seen in the inoculated loops; absorptive enterocytes were also taking up bacteria as seen in the ileal loops, indicating the process seen in the loops and after oral dosage was similar. For this strain of S typhimurium, there was an initial concentration of bacilli around the domed villus epithelium. This distribution was not random but may have resulted from a specific attraction to the FAE.