Herd-level risk factors associated with the presence of Phage type 21/28 E. coli O157 on Scottish cattle farms

Background  

E. coli O157 is a bacterial pathogen that is shed by cattle and can cause severe disease in humans. Phage type (PT) 21/28 is a subtype of E. coli O157 that is found across Scotland and is associated with particularly severe human morbidity.     

Immune responses in pigs vaccinated with adjuvanted and non-adjuvanted A(H1N1)pdm/09 influenza vaccines used in human immunization programmes

Following the emergence and global spread of a novel H1N1 influenza virus in 2009, two A(H1N1)pdm/09 influenza vaccines produced from the A/California/07/09 H1N1 strain were selected and used for the national immunisation programme in the United Kingdom: an adjuvanted split virion vaccine and a non-adjuvanted whole virion vaccine. In this study, we assessed the immune responses generated in inbred large white pigs (Babraham line) following vaccination with these vaccines and after challenge with A(H1N1)pdm/09 virus three months post-vaccination. Both vaccines elicited strong antibody responses, which included high levels of influenza-specific IgG1 and haemagglutination inhibition titres to H1 virus. Immunisation with the adjuvanted split vaccine induced significantly higher interferon gamma production, increased frequency of interferon gamma-producing cells and proliferation of CD4(-)CD8(+) (cytotoxic) and CD4(+)CD8(+) (helper) T cells, after in vitro re-stimulation. Despite significant differences in the magnitude and breadth of immune responses in the two vaccinated and mock treated groups, similar quantities of viral RNA were detected from the nasal cavity in all pigs after live virus challenge. The present study provides support for the use of the pig as a valid experimental model for influenza infections in humans, including the assessment of protective efficacy of therapeutic interventions.     

Quantifying the Risk of Localised Animal Movement Bans for Foot-and-Mouth Disease

The maintenance of disease-free status from Foot-and-Mouth Disease is of significant socio-economic importance to countries such as the UK. The imposition of bans on the movement of susceptible livestock following the discovery of an outbreak is deemed necessary to prevent the spread of what is a highly contagious disease, but has a significant economic impact on the agricultural community in itself. Here we consider the risk of applying movement restrictions only in localised zones around outbreaks in order to help evaluate how quickly nation-wide restrictions could be lifted after notification. We show, with reference to the 2001 and 2007 UK outbreaks, that it would be practical to implement such a policy provided the basic reproduction ratio of known infected premises can be estimated. It is ultimately up to policy makers and stakeholders to determine the acceptable level of risk, involving a cost benefit analysis of the potential outcomes, but quantifying the risk of spread from different sized zones is a prerequisite for this. The approach outlined is relevant to the determination of control zones and vaccination policies and has the potential to be applied to future outbreaks of other diseases.     

F factor conjugation is a true type IV secretion system

The F sex factor of Escherichia coli is a paradigm for bacterial conjugation and its transfer (tra) region represents a subset of the type IV secretion system (T4SS) family. The F tra region encodes eight of the 10 highly conserved (core) gene products of T4SS including TraAF (pilin), the TraBF, -KF (secretin-like), -VF (lipoprotein) and TraCF (NTPase), -EF, -LF and TraGF (N-terminal region) which correspond to TrbCP, -IP, -GP, -HP, -EP, -JP, DP and TrbLP, respectively, of the P-type T4SS exemplified by the IncP plasmid RP4. F lacks homologs of TrbBP (NTPase) and TrbFP but contains a cluster of genes encoding proteins essential for F conjugation (TraFF, -HF, -UF, -WF, the C-terminal region of TraGF, and TrbCF) that are hallmarks of F-like T4SS. These extra genes have been implicated in phenotypes that are characteristic of F-like systems including pilus retraction and mating pair stabilization. F-like T4SS systems have been found on many conjugative plasmids and in genetic islands on bacterial chromosomes. Although few systems have been studied in detail, F-like T4SS appear to be involved in the transfer of DNA only whereas P- and I-type systems appear to transport protein or nucleoprotein complexes. This review examines the similarities and differences among the T4SS, especially F- and P-like systems, and summarizes the properties of the F transfer region gene products.     

Population dynamics of plant-parasite interactions: thresholds for invasion

Thresholds are derived for the invasion of plant populations by parasites. The theory is developed for a generic model that takes into account two features characteristic of plant-parasite interactions: a dual source of inoculum (infection from primary or externally introduced inoculum and secondary infection from contact between susceptible and infected host tissue) and a host response to infection load. Each of the threshold criteria is shown to be the sum of the individual components for primary and secondary infection. This indicates that if parasite invasion is not possible through primary or secondary infection alone, when the two modes of transmission are combined, the parasite may be able to invade. The invasion criteria demonstrate that there is a threshold population of susceptible hosts below which the parasite is unable to invade. If there are nonlinearities in the population dynamics (arising through either the transmission process or the host response), there are also threshold densities for the infected hosts and parasite populations below which invasion does not occur. The implications of the results for the control of plant disease are discussed.     

Characterizing the structural features of RNA/RNA interactions of the F-plasmid FinOP fertility inhibition system

F-like plasmid transfer is mediated by the FinOP fertility inhibition system. Expression of the F positive regulatory protein, TraJ, is controlled by the action of the antisense RNA, FinP, and the RNA-binding protein FinO. FinO binds to and protects FinP from degradation and promotes duplex formation between FinP and traJ mRNA, leading to repression of both traJ expression and conjugative F transfer. FinP antisense RNA secondary structure is composed of two stem-loops separated by a 4-base single-stranded spacer and flanked on each side by single-stranded tails. Here we show that disruption of the expected Watson-Crick base pairing between the loops of FinP stem-loop I and its cognate RNA binding partner, traJ mRNA stem-loop Ic, led to a moderate reduction in the rate of duplex formation in vitro. In vivo, alterations of the anti-ribosome binding site region in the loop of FinP stem-loop I reduced the ability of the mutant FinP to mediate fertility inhibition and to inhibit TraJ expression when expressed in trans at an elevated copy number. Alterations of intermolecular complementarity between the stems of these RNAs reduced the rate of duplex formation. Our results suggest that successful interaction between stem-loop I of FinP and stem-loop Ic of traJ mRNA requires that base pairing must proceed from an initial loop-loop interaction through the top portion of the stems for stable duplex formation to occur.     

Waist Circumference as a Screening Tool for Cardiovascular Risk Factors: Evaluation of Receiver Operating Characteristics (ROC)

To evaluate the receiver operating characteristics (ROC) to determine the cutoffs of waist circumference as a potential population directed screening tool for hypercholesterolaemia (≥6.5 mmol/L), low high density lipoprotein cholesterol (<0.9 mmol/L), and hypertension (treated and/or systolic ≥160 and/or diastolic blood pressure ≥95 mmHg), in 2183 men and 2698 women aged 20 to 59 years selected at random from Dutch civil registries. Main outcome measures: Height, weight, body mass index (BMI), waist circumference, total plasma cholesterol and high density lipoprotein cholesterol concentrations, and blood pressure. Results: ROC curves showed that sensitivity equalled specificity at waist circumferences between 93–95 cm in men and 81–84 cm in women for identifying individual risk factors, and 92 cm in men and 81 cm in women for identifying those with at least one risk factor. Sensitivity and specificity were equal at levels between 61% to 69% for identifying individual risk factors, with positive predictions (56.8% in men and 37.8% in women) within 2% of those using previously defined ‘Action Level 1’ of waist circumference 94 cm in men and 80 cm in women (58.8% in men and 37.4% in women). Risk prediction by anthropometric methods was relatively low: ROC areas for identifying each risk factor by waist varied from 55% to 60%, and reached about 65% for identifying at least one risk factor. Height accounted for less than 03% of variance in waist circumference. Using BMI at 25 kg/m² gave similar prediction to waist, but its combination with waist did not improve predictive values. Conclusions: Measurement of waist circumference ‘Action Level 1’ at 94 cm (37 inches) in men and 80 cm (32 inches) in women could be adopted as a simpler valid alternative to BMI for health promotion, to alert those at risk of cardiovascular disease, and as a guide to risk avoidance by self-weight management