David Hampson | Murdoch University (original) (raw)

Papers by David Hampson

BMC Veterinary Research, 2012

Background: Swine dysentery (SD), a mucohaemorrhagic diarrhoeal disease of pigs, results from inf... more Background: Swine dysentery (SD), a mucohaemorrhagic diarrhoeal disease of pigs, results from infection of the large intestine with the spirochaete Brachyspira hyodysenteriae. ELISA systems using whole spirochaete cells (WC) and the B. hyodysenteriae outer membrane lipoprotein Bhlp29.7 previously have been established as potential diagnostic tools for SD. However, their true value in identifying infected herds remains unclear. The present study aimed to compare the performance of whole-cell and Bhlp29.7 based ELISAs in detecting specific immunoglobulin class IgG and IgM to B. hyodysenteriae in growing pigs, and additionally evaluated whether meat juice could serve as a source of specific antibodies. Results: Levels of circulating IgG and IgM reacting with WC spirochaete preparations and recombinant Bhlp29.7 peaked 4-6 weeks post-infection in the experimentally challenged pigs, and remained elevated in the present study. In a cohort of pigs on an infected farm levels of antibody directed against both antigens showed a progressive increase with time. However, other than for the level of IgG against WC antigen, a significant increase in antibody levels also was observed in a cohort of pigs on a non-infected farm. In addition, assays using meat juice had 100% specificity and equivalent sensitivity to those based on serum, and likewise the best performance was achieved using the WC IgG ELISA. Conclusions: IgG ELISAs using either WC or Bhlp29.7 as plate-coating antigens were shown to be useful for monitoring the dynamics of B. hyodysenteriae infection in grower pigs. Of the two antigens, the WC preparation tended to give better discrimination between pigs from infected and non-infected farms. Testing of meat juice was shown to have potential for identifying infected herds.

Journal of Clinical Microbiology, Sep 1, 2003

Journal of Medical Microbiology, Jun 1, 2003

The purposes of this study were to identify a solid medium that supports improved growth of the a... more The purposes of this study were to identify a solid medium that supports improved growth of the anaerobic intestinal spirochaete Brachyspira aalborgi, to modify this for use as a selective isolation medium and then to test the medium for its effectiveness in isolating B. aalborgi from patients' faeces. Of the media evaluated, brain heart infusion agar (BHIA) with 10 % bovine blood (BB) was the most effective base-supplement combination for growth, with colonies attaining 1•2 mm in diameter by 21 days. Incubation in an anaerobic jar (94 % H 2 , 6 % CO 2) permitted growth of larger colonies than incubation in an anaerobic chamber (80 % N 2 , 10 % H 2 , 10 % CO 2). Growth was improved only slightly at 38•5 8C compared with 37 8C. Selection of B. aalborgi from artificially seeded faeces was achieved equally well on eight different solid media containing spectinomycin (400 ìg ml À1) alone or in combinations with polymyxin B (5 ìg ml À1), colistin (25 ìg ml À1) and rifampicin (12•5 ìg ml À1). By using BHIA 10 % BB with spectinomycin plus polymyxin B, B. aalborgi was isolated from one of five human faecal samples that were positive for B. aalborgi by PCR amplification. This is the first report of the isolation of B. aalborgi from human faeces.

Epidemiology and Infection, Aug 1, 1991

Streptococcus suis types 1 and 2 were detected in nasal swabs taken from five litters of piglets ... more Streptococcus suis types 1 and 2 were detected in nasal swabs taken from five litters of piglets sampled twice weekly from birth. The two types had been detected in all pigs by the time they were 38 and 25 days old respectively with mean ages of first detectable infection being 13-5 and 8-5 days. The prevalence of infection was not affected by housing conditions or the population density of pigs. Piglets originating from a sow with vaginal swabs positive for S. suis type 2 were infected earlier than piglets from non-vaginal carriers. It is concluded that infection of piglets with S. suis type 2 may occur during the birth process.

Microbiology, 2010

The anaerobic intestinal spirochaete Brachyspira pilosicoli colonizes the large intestine of vari... more The anaerobic intestinal spirochaete Brachyspira pilosicoli colonizes the large intestine of various species, including humans. In the colon this spirochaete can penetrate the overlying mucus layer, attach by one cell end to the underlying enterocytes, and initiate localized colitis and diarrhoea. The aim of this study was to investigate whether, as part of the colonization process, B. pilosicoli is attracted to mucin. Fifteen B. pilosicoli strains isolated from humans, pigs, chickens and dogs, and a control strain of Brachyspira hyodysenteriae, were analysed for their ability to enter solutions of hog gastric mucin in an in vitro capillary tube assay. No significant attraction was detected with 1 % mucin, but some strains started to enter a 2 % solution, and attraction then increased with increasing concentrations to peak at around 6-8 % mucin. A similar increase was seen with B. hyodysenteriae, although this activity peaked at 6 % mucin and then declined, suggesting that the two species have different affinities for mucin. These mucin concentrations were much higher than those used in previous experimental studies with Brachyspira species. The viscosities of the 6-8 % mucin solutions were around 7-12 mPa s, which were similar to the measured viscosities of the mucus layer overlying the epithelium in the caecum and colon of experimental pigs. The strains varied in their motility, as assessed by their ability to enter tubes containing chemotaxis buffer, but there was no significant relationship between this motility and the extent of their ability to enter the mucin solutions. Different strains also had different propensities to enter the mucin solutions, but there were no consistent differences according to the host species of origin. B. pilosicoli strain 95/1000 was attracted towards a solution of Dserine, suggesting that chemotaxis was involved in the attraction to mucin; however, 95/1000 was also attracted to viscous solutions of polyvinylpyrrolidone (PVP), in a manner mirroring the response to mucin, and hence suggesting the involvement of viscotaxis in the attraction to mucin. B. hyodysenteriae B204 showed a similar viscotaxis to PVP. Further studies are required to determine whether the in vitro interaction of a given strain with mucin is a useful indicator of its in vivo colonization ability, and hence could be used as a potential marker for virulence.

Antimicrobial Agents and Chemotherapy, Jul 1, 2003

The in vitro antimicrobial susceptibility of the anaerobic intestinal spirochete Brachyspira pilo... more The in vitro antimicrobial susceptibility of the anaerobic intestinal spirochete Brachyspira pilosicoli was investigated by an agar dilution method. Human (n ‫؍‬ 123) and porcine (n ‫؍‬ 16) isolates were susceptible to metronidazole, ceftriaxone, meropenem, tetracycline, moxifloxacin, and chloramphenicol; erythromycin and ciprofloxacin were not active. Resistance to amoxicillin and clindamycin varied. Amoxicillin susceptibility was restored by clavulanic acid.

PLOS ONE, Dec 17, 2009

Background: Brachyspira pilosicoli is an anaerobic spirochete that has received relatively little... more Background: Brachyspira pilosicoli is an anaerobic spirochete that has received relatively little study, partly due to its specialized culture requirements and slow growth. This bacterium colonizes the large intestine of various species, including humans; typically, a dense layer of spirochete cells may be found intimately attached by one cell end to the surface of colonic enterocytes. Colonized individuals may develop colitis, but the mechanisms involved are not understood. The current study aimed to develop an in vitro model to investigate this process. Methodology/Principal Findings: Four strains of B. pilosicoli were incubated at a high multiplicity of infection with monolayers of a human colonic adenocarcinoma cell line (Caco-2 cells). One strain isolated from a pig (95/1000) and one from a human (WesB) attached to the monolayers. Colonization increased with time, with the Caco-2 cell junctions being the initial targets of attachment. By electron microscopy, individual spirochete cells could be seen to have one cell end invaginated into the Caco-2 cell membranes, with the rest of the spirochete draped over the Caco-2 cell surface. After 6 h incubation, the monolayer was covered with a layer of spirochetes. Colonized monolayers demonstrated a time-dependent series of changes: staining with labelled phalloidin identified accumulation of actin at the cell junctions; ZO-1 staining revealed a loss of Caco-2 tight junction integrity; and Hoechst staining showed condensation and fragmentation of nuclear material consistent with apoptosis. Using quantitative reverse transcription PCR, the colonized monolayers demonstrated a significant up-regulation of interleukin-1b (IL-1b) and IL-8 expression. B. pilosicoli sonicates caused significant up-regulation of IL-1b, TNF-a, and IL-6, but culture supernatants and non-pathogenic Brachyspira innocens did not alter cytokine expression. Conclusions/Significance: The changes induced in the Caco-2 cells provide evidence that B. pilosicoli has pathogenic potential, and give insights into the likely in vivo pathogenesis.

Epidemiology and Infection, Feb 1, 1993

An indirect fluorescent antibody test was used to detect the presence of Streptococcus suis type ... more An indirect fluorescent antibody test was used to detect the presence of Streptococcus suis type 2 in nasal and pharyngeal swabs taken from pigs in Papua New Guinea. The rate of carriage for the two sites in domesticated indigenous village pigs was 05 and 2-5 % respectively, compared to 39 and 43 % for intensively reared pigs. These findings were supported by the results of a serological survey, using an enzyme linked immunosorbent assay, in which 87 % of intensively reared pigs but only 8 % of village pigs were seropositive to S. suis type 2. It is proposed that in intensive piggeries S. suis type 2 is continually cycled between pigs. In village pigs, the low population density and harsh environmental conditions prevents this cycle of infection.

Clinical Microbiology Reviews, 2018

Controlling the use of the most critically important antimicrobials (CIAs) in food animals has be... more Controlling the use of the most critically important antimicrobials (CIAs) in food animals has been identified as one of the key measures required to curb the transmission of antimicrobial resistant bacteria from animals to humans. Expanding the evidence demonstrating the effectiveness of restricting CIA usage for preventing the emergence of resistance to key drugs amongst commensal organisms in animal production would do much to strengthen international efforts to control antimicrobial resistance (AMR). As Australia has strict controls on antimicrobial use in layer hens, and internationally comparatively low levels of poultry disease due to strict national biosecurity measures, we investigated whether these circumstances have resulted in curtailing development of critical forms of AMR. The work comprised a cross-sectional national survey of 62 commercial layer farms with each assessed for AMR inEscherichia coliisolates recovered from faeces. Minimum inhibitory concentration analysi...

Animal Health Research Reviews, Jun 1, 2001

Emerging Infectious Diseases, May 1, 2006

PLOS ONE, Aug 4, 2016

Swine dysentery (SD) is a mucohaemorrhagic colitis of grower/finisher pigs classically resulting ... more Swine dysentery (SD) is a mucohaemorrhagic colitis of grower/finisher pigs classically resulting from infection by the anaerobic intestinal spirochaete Brachyspira hyodysenteriae. This study aimed to determine whether B. hyodysenteriae isolates from pigs in three healthy German multiplier herds supplying gilts to other farms differed from isolates from nine German production herds with SD. Isolates were subjected to whole genomic sequencing, and in silico multilocus sequence typing showed that those from the three multiplier herds were of previously undescribed sequence types (ST132, ST133 and ST134), with all isolates from the same herd having the same ST. All isolates were examined for the presence of 332 genes encoding predicted virulence or virulence lifestyle associated factors, and these were well conserved. Isolates from one multiplier herd were atypical in being weakly haemolytic: they had 10 amino acid substitutions in the haemolysin III protein and five in the haemolysin activation protein compared to reference strain WA1, and had a disruption in the promoter site of the hlyA gene. These changes likely contribute to the weakly haemolytic phenotype and putative lack of virulence. These same isolates also had nine base pair insertions in the iron metabolism genes bitB and bitC and lacked five of six plasmid genes that previously have been associated with colonisation. Other overall differences between isolates from the different herds were in genes from three of five outer membrane proteins, which were not found in all the isolates, and in members of a block of six plasmid genes. Isolates from three herds with SD had all six plasmid genes, while isolates lacking some of these genes were found in the three healthy herds-but also in isolates from six herds with SD. Other differences in genes of unknown function or in gene expression may contribute to variation in virulence; alternatively, superior husbandry and better general health may have made pigs in the two multiplier herds colonised by "typical" strongly haemolytic isolates less susceptible to disease expression.

Anaerobe, Oct 1, 2019

Brachyspira catarrhinii sp. nov., an anaerobic intestinal spirochaete isolated from vervet monkey... more Brachyspira catarrhinii sp. nov., an anaerobic intestinal spirochaete isolated from vervet monkeys may have been misidentified as Brachyspira aalborgi in previous studies. Anaerobe

Veterinary Microbiology, May 1, 2013

Multiple locus variable number tandem repeat analysis (MLVA) of the pathogenic intestinal spiroch... more Multiple locus variable number tandem repeat analysis (MLVA) of the pathogenic intestinal spirochaete Brachyspira pilosicoli

Veterinary Microbiology, Feb 1, 2019

Across all bacterial species the continuing reduction in susceptibility to antimicrobial agents i... more Across all bacterial species the continuing reduction in susceptibility to antimicrobial agents is a critical and increasing threat for disease control. This mini-review outlines the extent of this problem amongst anaerobic intestinal spirochaetes of the genus Brachyspira, of which there are currently nine officially recognised species. These include some important pathogens that may cause colitis with diarrhoea and/or dysentery in various mammalian and avian species, but most notably in pigs and in adult chickens. The most economically significant pathogen is Brachyspira hyodysenteriae, the spirochaete which causes swine dysentery in countries throughout the world. Control of infections with Brachyspira species has long relied on the prophylactic or therapeutic use of antimicrobials, but increasingly strains with reduced susceptibility and sometimes multidrug resistance to previously effective antimicrobial agents are being encountered. In this mini-review we outline these problems and explain the extent and molecular basis of the emerging resistance. Future control will rely on developing and applying standardised methods for measuring antimicrobial susceptibility; improving surveillance of resistance using traditional phenotypic as well as genomic analysis of known resistance determinants; improving understanding of the molecular basis of resistance to different drug classes; improving farmer and veterinarian education about prudent antimicrobial use so as to reduce selective pressure on the emergence of resistance; and developing alternatives to antimicrobials as a means to control these infections. 1. The genus Brachyspira The genus Brachyspira comprises a diverse group of oxygen-tolerant anaerobic spirochaetes that inhabit the large intestines of a variety of mammalian and avian hosts. The genus currently includes nine species on the list of officially approved names (Table 1), as well as several unofficially suggested species, most of which appear to be commensals. Many but not all of the official species are confirmed pathogens of animals based on fulfilment of Koch's postulates, although the species and individual strains vary widely in their pathogenic potential in susceptible hosts. An update on the Brachyspira species and associated diseases recently has been presented by Looft and Stanton (2018). Briefly, the most common and important pathogenic species include Brachyspira hyodysenteriae, the originally-described agent of swine dysentery (SD); Brachyspira pilosicoli, the agent of intestinal spirochaetosis in pigs, poultry, dogs, horses and other species-including human beings; Brachyspira intermedia and Brachyspira alvinipulli, both of which are agents of avian intestinal spirochaetosis; and the newly recognized species Brachyspira suanatina and Brachyspira hampsonii that can cause similar clinical signs and lesions to B. hyodysenteriae in pigs. This article places most emphasis on B. hyodysenteriae and B. pilosicoli, since the bulk of available data about antimicrobial susceptibility relates to these two species, and they can cause significant clinical problems and economic loss in pigs and/or adult poultry. 2. Prevention and control of Brachyspira infections The main source of new infections with Brachyspira species comes

Animal Production Science, 2015

Veterinary Research, Dec 1, 2014

The gene content of 14 strains of the intestinal spirochaete Brachyspira hyodysenteriae was compa... more The gene content of 14 strains of the intestinal spirochaete Brachyspira hyodysenteriae was compared using a DNA microarray. A consistent difference occurred in a block of four genes on the~36 Kb plasmid, with these being present in six virulent strains and absent in eight strains with reduced pathogenic potential. These genes encoded a predicted radical S-adenosylmethionine domain protein, a glycosyl transferase group 1-like protein, an NAD dependant epimerase and a dTDP-4-dehydrorhamnose 2-5 epimerase: they may be involved in rhamnose biosynthesis and glycosylation. The absence of these plasmid genes in B. hyodysenteriae isolates is predictive of reduced pathogenic potential.

Epidemiology and Infection, Aug 1, 1990

Two Australian isolates of Treponema hyodysenteriae which did not fit within the current serologi... more Two Australian isolates of Treponema hyodysenteriae which did not fit within the current serological grouping system for these bacteria w r ere examined by agarose gel double immunodiffusion tests (AGDP). Isolate Vicl was serologically unique, and we propose that it becomes the type organism for a new sixth serological group of T. hyodysenteriae (Group F). Isolate Ql was unusual in that lipopolysaccharide (LPS) extracted from it reacted strongly in AGDP with serum raised against the type organism for serogroup D (Al), and also weakly with serum raised against the type organism for serogroup B (WAI). The nature of this crossreactivity was examined by using cross-absorbed antisera in AGDP, and by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis. The pattern of serological cross-reactivity between Ql, Al and WAI was complex and was not fully defined, but the isolate Ql apparently shared low molecular weight 'serogroup' LPS antigens with Al, and shared higher molecular weight LPS antigens with WAI. On this basis Ql was designated as belonging to serogroup D, although it was recommended that this be qualified as D (B) to indicate the presence of weak cross-reactivity with serogroup B. Such serological cross-reactivity may have significance in relation to the development of immunity to T. hyodysenteriae. Isolate Ql may be a potentially useful organism for vaccine development because of its ability to induce a good serological response to LPS of treponemes from both serogroups D and B.

Frontiers in Veterinary Science, 2022

Colistin-resistant bacteria harboring plasmid-mediated mcr genes are of concern as they may be a ... more Colistin-resistant bacteria harboring plasmid-mediated mcr genes are of concern as they may be a cause of serious nosocomial infections. It is hypothesized that cessation of colistin use as a feed additive for pigs will reduce the occurrence and distribution of mcr genes in farms. The aim of this study was to investigate this hypothesis by longitudinal monitoring and characterizing of mcr positive Escherichia coli (MCRPE) isolates after colistin was withdrawn on a central Thailand pig farm that previously had a high frequency of MCRPE. Colistin use ceased at the beginning of 2017, and subsequently 170 samples were collected from farrowing sows and suckling piglets (n = 70), wastewater (n = 50) and farm workers (n = 50) over a 3.5-year period. Bacteria were identified by MALDI-TOF mass spectrometry and minimal inhibitory concentrations were determined by broth microdilution. The antibiogram of mcr positive E. coli isolates was determined using the Vitek2 automated susceptibility mach...