Analysis of Campylobacter jejuni infection in the gnotobiotic piglet and genome-wide identification of bacterial factors required for infection.

To investigate how Campylobacter jejuni causes the clinical symptoms of diarrhoeal disease in humans, use of a relevant animal model is essential. Such a model should mimic the human disease closely in terms of host physiology, incubation period before onset of disease, clinical signs and a comparable outcome of disease. In this study, we used a gnotobiotic piglet model to study determinants of pathogenicity of C. jejuni. In this model, C. jejuni successfully established infection and piglets developed an increased temperature with watery diarrhoea, which was caused by a leaky epithelium and reduced bile re-absorption in the intestines. Further, we assessed the C. jejuni genes required for infection of the porcine gastrointestinal tract utilising a transposon (Tn) mutant library screen. A total of 123 genes of which Tn mutants showed attenuated piglet infection were identified. Our screen highlighted a crucial role for motility and chemotaxis, as well as central metabolism. In addition, Tn mutants of 14 genes displayed enhanced piglet infection. This study gives a unique insight into the mechanisms of C. jejuni disease in terms of host physiology and contributing bacterial factors.

Characterisation of proteins extracted from the surface of Salmonella Typhimurium grown under SPI-2-inducing conditions by LC-ESI/MS/MS sequencing.

Salmonella enterica has two pathogenicity islands encoding separate type three secretion systems (T3SS). Proteins secreted through these systems facilitate invasion and survival. After entry, Salmonella reside within a membrane bound vacuole, the Salmonella containing vacuole (SCV), where translocation of a second set of effectors by the Salmonella pathogenicity island 2 (SPI-2) T3SS is initiated. SPI-2 secretion in vitro can be induced by conditions that mimic the Salmonella containing vacuole. Utilising high-throughput mass spectrometry, we mapped the surface-attached proteome of S. Typhimurium SL1344 grown in vitro under SPI-2-inducing conditions and identified 108 proteins; using secretion signal prediction software, 43% of proteins identified contained a signal sequence. Of these proteins, 13 were known secreted effector proteins including SPI-2 effector proteins SseB, SseC, SseD, SseL, PipB2 and SteC, although surprisingly five were SPI-1 proteins, SipA, SipB, SipC, SipD and SopD, while 2 proteins SteA and SlrP are secreted by both T3SSs. This is the first in vitro study to demonstrate dual secretion of SPI-1 and SPI-2 proteins by S. Typhimurium and demonstrates the potential of high-throughput LC-ESI/MS/MS sequencing for the identification of novel proteins, providing a platform for subsequent comparative proteomic analysis, which should greatly assist understanding of the pathogenesis and inherent variation between serovars of Salmonella and ultimately help towards development of novel control strategies.

Social physique anxiety and physical self-esteem: gender and age effects.

The aim of this study was to test the generalisability of the factor pattern, structural parameters, factor correlations and latent mean structure of social physique anxiety and physical self-esteem across gender, age and gender x age. The social physique anxiety scale and general physical self-esteem scale from the physical self-perception profile was administered to high school and university students aged 11-24 years (N = 2334). Confirmatory factor analysis (CFA) was used to test the adequacy of a two-factor correlated model in the full sample, and separately by gender, age and gender x age sub-samples. The CFA model satisfied criteria for goodness-of-fit with the data in all sub-samples, the only exception was for females aged 21 and over. Tests of invariance of the factor pattern, structural parameters and correlations across age, gender and age x gender revealed few decrements in goodness-of-fit. Latent means analysis revealed that females had consistently higher levels of social physique anxiety and lower levels of physical self-esteem than males, with the exception of the 11-12 age group. Results extend previous findings that females tend to report higher levels of social physique anxiety and lower levels of physical self-esteem than males by demonstrating that these differences are consistent across age group.