The role of maternal antibodies in the lag phase of Campylobacter positivity, widely observed in commercial broiler flocks, was investigated. The results indicate that 3-wk-old birds derived from a ...commercial flock are more susceptible to colonization with Campylobacter jejuni than 1-to-2-wk-old birds. This increasing susceptibility parallels the loss of maternally derived, circulating, anti-Campylobacter, immunoglobulin Y antibodies as detected by enzyme-linked immunosorbent assay. The role of these antibodies in resistance to colonization was further investigated using progeny from breeder flocks of known Campylobacter status. These results confirmed that maternal antibodies confer partial protection against Campylobacter colonization on young chickens (1–2 wk old). This protection was directed against challenge with both homologous and heterologous strains of C. jejuni and even against strains with a high colonization potential. However, evidence presented indicates that newly hatched chicks, with the highest levels of maternal antibodies, were as susceptible to Campylobacter challenge as 3-wk-old birds. This conundrum was investigated further, and an increase in resistance was detected from 1 to 3 days of age. The reasons for this are, as yet, unknown, but the observation validates the use of newly hatched chicks in models of Campylobacter colonization. Moreover, this high susceptibility in the first few days of life may explain the occasional early flock colonization observed, especially when environmental exposure to Campylobacter is high, for example, in free-range birds.
•Significant increase in fully susceptible E. coli after reduced antimicrobial use.•Multidrug resistant E. coli decline significantly after withdrawing group treatment.•However, resistant commensal ...E. coli remain after withdrawal of group treatment.•Resistant E. coli survived pen cleaning and could be detected on farm equipment.•Plasmids have an important role for the maintenance and dissemination of resistance.
An important element in the control of antimicrobial resistance (AMR) is reduction in antimicrobial usage. In the veterinary sector individual antimicrobial treatment of livestock, rather than the use of group treatment, can help achieve this goal. The aim of this study was to investigate how cessation of group antimicrobial treatment impacted the prevalence of AMR in commensal Escherichia coli in pigs at one farm over an 11-month period. Minimum inhibitory concentrations of eight antimicrobials were determined for 259 E. coli isolates collected during the study. A significant reduction in the prevalence of multidrug resistance and a significant increase in the proportion of full susceptibility to the panel of nine antimicrobials tested was seen after 11 months. Whole genome sequencing of 48 multidrug resistant isolates revealed E. coli clones that persisted across multiple visits and provided evidence for the presence of plasmids harbouring AMR genes shared across multiple E. coli lineages. E. coli were also isolated from on-farm environmental samples. Whole genome sequencing of one multidrug resistant isolate obtained from cleaning tools showed it was clonal to pig-derived E. coli that persisted on the farm for 11 months. In this study we provide evidence that withdrawal of group antimicrobial use leads to significant reductions in key indicators for AMR prevalence and the importance of the farm environment as a reservoir of resistant bacteria. These findings support policy makers and producers in the implementation of measures to control AMR and reduce antimicrobial use.
A panel of pulsed field gel electrophoresis (PFGE) type variants of Campylobacter jejuni, previously identified as of clonal origin, were investigated to determine whether genomic instability could ...be observed during competitive growth. Upon recovery from frozen storage, some variants had undergone alterations in PFGE profiles, but subsequent culture produced constant genotypes. Individual variants did not display differences in colonization potential when tested in orally challenged 1-day-old chickens. However, competitive colonization using mixtures of two or three PFGE types generally resulted, by 4 weeks postchallenge, in one predominant PFGE type in all birds. For some variant mixtures, a minor population of novel PFGE types was detected in individual birds. The creation of new variants appeared to be dependent on the extent of competition and of the individual host. Genomic rearrangements most likely explain this increase in genetic diversity, apparently without the involvement of natural transformation or plasmid acquisition. In vitro cultivation of mixed inoculations were again selected for particular variants; but genetic diversity was not generated, suggesting that the selection pressures in vitro differed from those active in vivo. These observations support the hypothesis that by generating genetic diversity, C. jejuni can improve its phenotypic fitness to survive and colonize subsequent hosts. The consequences of such observations for the development of campylobacter control strategies for poultry may be substantial.
Great Britain and elsewhere have detected atypical scrapie infection in sheep with PrP genotypes thought to be genetically resistant to the classical form of scrapie. DNA sequencing of the PrP gene ...of British atypical scrapie cases (n=69), classical scrapie cases (n=59) and scrapie-free controls (n=138) was undertaken to identify whether PrP variants, other than the three well-characterized polymorphic codons, influenced susceptibility to atypical scrapie infection. Four non-synonymous changes, M112T, M137T, L141F and P241S, were detected that are most probably associated with the A136R154Q171 haplotype. Only the PrP variant containing a phenylalanine residue at amino acid position 141 was found to be associated more commonly with the atypical scrapie cases. In addition to the single nucleotide polymorphisms associated with the ARQ allele, two out of nine atypical scrapie cases with the ARR/ARR genotype were found to contain a 24 bp insertion, leading to an additional octapeptide repeat. In terms of PrP genetics, one classification of the GB scrapie cases examined in this study would place animals carrying any homozygous or heterozygous combination of ARR, AHQ or AF141RQ alleles, or any one of these alleles when paired with ARQ, as being susceptible to atypical scrapie infection, and animals heterozygous or homozygous for VRQ or homozygous for ARQ as being susceptible to classical scrapie disease. The AHQ PrP allele was associated with the highest incidence of atypical scrapie (263 per 100 000 alleles), whilst VRQ was associated with the lowest incidence (10 per 100 000 alleles).
Aim
Shiga toxin‐producing Escherichia coli (STEC) cause bloody diarrhoea, kidney failure and occasionally death. However, identifying the source of infection caused by STEC other than serogroup O157 ...is hampered by the availability of sensitive methods for detecting these pathogens. In this study, we developed novel tools for detecting E. coli O55 that is potentially associated with human outbreaks.
Methods and Results
Overall specificity of immuno‐magnetic separation (IMS) beads coated with anti‐O55 serum was good with exception of cross‐reactivity with E. coli O22 and O23, which was eliminated using an O55‐specific PCR. Limit of detection for E. coli O55 using O55‐IMS beads in spiked cattle faeces was on average 50 CFU per ml (range 1–90), and improved to <10 CFU per ml using the O55‐specific PCR, following IMS on samples enriched for 2 h with E. coli O55. Application of these tools to test cattle faeces collected on‐farm allowed the isolation of O55:H19, which through whole genome sequencing was compared to STEC O55:H7 human outbreak strains.
Conclusion
These tools provide a sensitive method which could be used to screen samples for STEC O55, whether environmental or human clinical.
Significance and Impact of the Study
Several human outbreaks reported in England were caused by STEC O55:H7. Tools developed here could assist in identification of the environmental source for these isolates, which has not yet been established.
Aims: To test the efficacy of enhanced biosecurity measures on poultry farms for reducing environmental contamination with Campylobacter during partial depopulation of broiler flocks prior to normal ...slaughter age. The study has also evaluated the risk of infection from live‐bird transport crates that are routinely cleaned at the slaughterhouse, but may remain contaminated.
Methods and Results: On‐farm sampling and Campylobacter isolation was undertaken to compare the prevalence of contamination on vehicles, equipment and catching personnel during farm visits that took place under normal or enhanced biosecurity. Campylobacters were found in almost all types of sample examined and enhanced biosecurity reduced the prevalence. However, the additional measures failed to prevent colonisation of the flocks. For transport crates, challenge trials involved exposure of broilers to commercially cleaned crates and genotyping of any campylobacters isolated. The birds were rapidly colonised with the same genotypes as those isolated from the cleaned crates.
Conclusions: The enhanced biosecurity measures were insufficient to prevent flock colonisation, and the problem was exacerbated by inadequate cleaning of transport crates at the slaughterhouse.
Significance and Impact of the Study: Current commercial practices in the United Kingdom facilitate the spread of campylobacters among broiler chicken flocks. Prevention of flock infection appears to require more stringent biosecurity than that studied here.
Abstract
Objectives
To assess stability and contribution of a large ESBL-encoding IncI1 plasmid to intestinal colonization by Escherichia coli O104:H4 in two different mammalian hosts.
Methods
...Specific-pathogen-free 3–4-day-old New Zealand White rabbits and conventionally reared 6-week-old weaned lambs were orally infected with WT E. coli O104:H4 or the ESBL-plasmid-cured derivative, and the recovery of bacteria in intestinal homogenates and faeces monitored over time.
Results
Carriage of the ESBL plasmid had differing impacts on E. coli O104:H4 colonization of the two experimental hosts. The plasmid-cured strain was recovered at significantly higher levels than WT during late-stage colonization of rabbits, but at lower levels than WT in sheep. Regardless of the animal host, the ESBL plasmid was stably maintained in virtually all in vivo passaged bacteria that were examined.
Conclusions
These findings suggest that carriage of ESBL plasmids has distinct effects on the host bacterium depending upon the animal species it encounters and demonstrates that, as for E. coli O157:H7, ruminants could represent a potential transmission reservoir.
It has recently been shown that the enteropathogen Campylobacter jejuni has an N-linked general protein glycosylation pathway (Pgl) that modifies many of the organism's proteins. To determine the ...role of the N-linked general glycosylation in C jejuni, the authors studied the pglH gene, which shows high similarity to a family of sugar transferases. pglH mutants were constructed in strains 81116 and 11168H. Both mutants were shown to be deficient in their ability to glycosylate a number of C. jejuni proteins, but their lipooligosaccharide and capsule were unaffected. The pglH mutants had significantly reduced ability to adhere to and invade human epithelial Caco-2 cells. Additionally, the 81116 pglH mutant was severely affected in its ability to colonize chicks. These results suggest that glycosylation is important for the attachment of C. jejuni to human and chicken host cells and imply a role for glycoproteins in the pathogenesis of C. jejuni.
To determine the effect of various enrofloxacin dose regimes on the colonization and selection of resistance in Campylobacter jejuni strain 81116P in experimentally colonized chickens. Two ...experiments were undertaken, in which 14-day-old chickens were colonized with 1 x 10⁷-1 x 10⁹ CFU g⁻¹Camp. jejuni strain 81116P and then treated with enrofloxacin at 12-500 ppm in drinking water for various times. Caecal colonization levels were determined at various time-points after start-of-treatment, and the susceptibility of recovered isolates to ciprofloxacin was monitored. Resistance was indicated by growth on agar containing 4 μg ml⁻¹ ciprofloxacin, MICs of 16 μg ml⁻¹ and the Thr86Ile mutation in gyrA. Enrofloxacin at doses of 12-250 ppm reduced Camp. jejuni colonization over the first 48-72 h after start-of-treatment. The degree of reduction in colonization was dose, but not treatment time, dependent. In all cases, maximal colonization was re-established within 4-6 days. Fluoroquinolone-resistant organisms were recoverable within 48 h of start-of-treatment; after a further 24 h all recovered isolates were resistant. In contrast, a dose of 500 ppm enrofloxacin reduced colonization to undetectable levels within 48 h, and the treated birds remained Campylobacter negative throughout the remaining experimental period. By high pressure liquid chromatography, for all doses, the maximum concentrations of enrofloxacin and ciprofloxacin in the caecal contents were detected at the point of treatment completion. Thereafter, levels declined to undetectable by 7 days post-treatment withdrawal. In a model using chickens maximally colonized with Camp. jejuni 81116P, treatment with enrofloxacin, at doses of 12-250 ppm in drinking water, enables the selection, and clonal expansion, of fluoroquinolone-resistant organisms. However, this is preventable by treatment with 500 ppm of enrofloxacin. Treatment of chickens with enrofloxacin selects for resistance in Camp. jejuni in highly pre-colonized birds. However, a dose of 500 ppm enrofloxacin prevented the selection of resistant campylobacters.
First identified in Great Britain in 1986 ( Wells and others 1987 ), bovine spongiform encephalopathy (BSE) was subsequently detected in many other countries worldwide. All three H-type BSE cases ...detected to date have been aged fallen stock born before Great Britain reinforced the ban on feeding ruminant protein to ruminants in 1996. Since the beginning of 2005 a total of 290,182 cattle aged eight years and over from the fallen stock category have been tested (30,400 in 2005, 69,928 in 2006, 70,133 in 2007, 79,803 in 2008 and 39,916 to the end of July 2009).
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