Diarrhea-associated biofilm formed by enteroaggregative <Emphasis Type="Italic">Escherichia coli</Emphasis> and aggregative <Emphasis Type="Italic">Citrobacter freundii</Emphasis>: a consortium mediated by putative F pili

Background  

Enteroaggregative Escherichia coli (EAEC) are enteropathogenic strains identified by the aggregative adhesion (AA) pattern that share the capability to form biofilms. Citrobacter freundii is classically considered as an indigenous intestinal species that is sporadically associated with diarrhea.     

IFN-gamma enhances production of nitric oxide from macrophages via a mechanism that depends on nucleotide oligomerization domain-2

Pattern recognition receptors are central to the responsiveness of various eukaryotic cell types when they encounter pathogen-associated molecular patterns. IFN-gamma is a cytokine that is elevated in humans and other animals with bacterial infection and enhances the LPS-induced production of antibacterial mediators by macrophages. Mice lacking the pattern recognition receptor, TLR4, respond very poorly to stimulation by LPS, but administration of IFN-gamma has been described as restoring apparent sensitivity to this stimulatory ligand. In this study, we show that IFN-gamma primes murine macrophages stimulated by crude LPS preparations to produce the antibacterial mediator NO, a proportion of which is independent of TLRs 2 and 4. This response is lost in tlr4-/- IFN-gamma-primed murine macrophages when the LPS preparation is highly purified. NO is also induced if chemically synthesized muramyl dipeptide, an intermediate in the biosynthesis of peptidoglycan, is used to stimulate macrophages primed with IFN-gamma. This is absolutely dependent on the presence of a functional nucleotide oligomerization domain-2 (NOD-2) protein. IFN-gamma increases NOD-2 expression and dissociates this protein from the actin cytoskeleton within the cell. IFN-gamma priming of macrophages therefore reveals a key proinflammatory role for NOD-2. This study also shows that the effect of IFN-gamma in restoring inflammatory responses to gram-negative bacteria or bacterial products in mice with defective TLR4 signaling is likely to be due to a response to peptidoglycan, not LPS.     

Evaluation of Silicone as an Artificial Lubricant in Osteoarthrotic Joints

Silicone 300 has been evaluated as an artificial lubricant in osteoarthrotic joints by means of a pilot study in five inpatients and a control trial of 25 outpatients with 40 osteoarthrotic knees. Sequential analysis showed a significant benefit from saline compared with silicone at one week follow-up and no significant difference at one month.Measurement of stiffness with a knee arthrograph showed no difference in reduction of stiffness between the two substances. In a study of 18 rabbits there was no evidence that silicone was retained in the joint cavity for longer than 48 hours. There was a failure of clearance of iodinated serum albumin for as long as three to four days after the injection of silicone, suggesting some obstruction to lymphatic outflow. Experimentally produced cartilaginous defects did not heal quicker with the injection of silicone into the joint.     

Burkholderia cepacia complex bacteria: opportunistic pathogens with important natural biology

Interaction with plants around their roots and foliage forms the natural habitat for a wide range of gram-negative bacteria such as Burkholderia, Pseudomonas and Ralstonia. During these interactions many of these bacteria facilitate highly beneficial processes such as the breakdown of pollutants or enhancement of crop growth. All these bacterial species are also capable of causing opportunistic infections in vulnerable individuals, especially people with cystic fibrosis (CF). Here we will review the current understanding of the Burkholderia cepacia complex (Bcc) as a group of model opportunistic pathogens, contrasting their clinical epidemiology with their ecological importance. Currently, the B. cepacia complex is composed of nine formally named species groups which are all difficult to identify using phenotypic methods. Genetic methods such as 16S rRNA and recA gene sequence analysis have proven useful for Bcc species identification. Multilocus sequence typing (MLST) is also emerging as a very useful tool for both Bcc strain and species identification. Historically, Burkholderia cenocepacia was the most dominant Bcc pathogen in CF, however, probably as a result of strict infection control practices introduced to control the spread of this species, its prevalence has been reduced. Burkholderia multivorans is the now the most dominant Bcc infection encountered in the UK CF population, a changing epidemiology that also appears to be occurring in the US CF population. The distribution of Bcc species residing in the natural environment may vary considerably with the type of environment examined. Clonally identical Bcc strains have been found to occur in the natural environment and cause infection. The contamination of medical devices, disinfectants and pharmaceutical formulations has also been directly linked to several outbreaks of infection. In the last 10 years considerable progress has been made in understanding the natural biology and clinical infections caused by this fascinating group of bacteria.     

Prediction of lubricating film thickness in UHMWPE hip joint replacements

An elastohydrodynamic lubrication model developed for a ball-in-socket configuration in a previous studies by the present authors (Jalali-Vahid et al., Thinning films and tribological interfaces, 26th Leeds-Lyon Symposium on Tribology, 2000, pp. 329-339) was applied to analyse the lubrication problem of a typical artificial hip joint replacement, consisting of an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup against a metallic or ceramic femoral head. The cup was assumed to be stationary whilst the ball was assumed to rotate at a steady angular velocity and under a constant load. A wide range of main design parameters were considered. It has been found that the predicted lubricating film thickness increases with a decrease in the radial clearance, an increase in the femoral head radius, an increase in UHMWPE thickness and a decrease in UHMWPE modulus. However, the predicted lubricating film thicknesses are not found to be sufficiently large in relation to the surface roughness of the cup and head to indicate separation of the two articulating surfaces. It should also be noted that if the design features are unable to secure full fluid film lubrication, it may be preferable to select them for minimum wear rather than maximum film thickness. For example, an increase in head radius will enhance the film thickness, but it will also increase the sliding distance and hence wear in mixed or boundary lubrication conditions. Furthermore, it is pointed out that an increase in the predicted lubricant film thickness is usually associated with an increase in the contact area, and this may cause lubricant starvation and stress concentration at the edge of the cup, and adversely affect the tribological performance of the implant. The effect of running-in process on the lubrication in UHMWPE hip joint replacements is also discussed.     

Multilocus sequence typing for comparison of veterinary and human isolates of Campylobacter jejuni

Multilocus sequence typing (MLST) has been applied to 266 Campylobacter jejuni isolates, mainly from veterinary sources, including cattle, sheep, poultry, pigs, pets, and the environment, as well as isolates from human cases of campylobacteriosis. The populations of veterinary and human isolates overlap, suggesting that most veterinary sources should be considered reservoirs of pathogenic campylobacters. There were some associations between source and sequence type complex, indicating that host or source adaptation may exist. The pig isolates formed a distinct group by MLST and may well represent a potential pig-adapted clone of C. jejuni. A subset (n = 82) of isolates was reanalyzed with a second MLST scheme which provided a unique set of isolates that had been analyzed at a total of 12 loci. The distribution of isolates among the complexes in each of the two schemes was similar but not identical. In addition to isolates from human outbreaks, one group of isolates that were not epidemiologically linked was also identical at all 12 loci. This group of isolates is believed to represent another stable strain of C. jejuni.     

The innate immune repertoire in Cnidaria - ancestral complexity and stochastic gene loss

Background  

Characterization of the innate immune repertoire of extant cnidarians is of both fundamental and applied interest - it not only provides insights into the basic immunological 'tool kit' of the common ancestor of all animals, but is also likely to be important in understanding the global decline of coral reefs that is presently occurring. Recently, whole genome sequences became available for two cnidarians, Hydra magnipapillata and Nematostella vectensis, and large expressed sequence tag (EST) datasets are available for these and for the coral Acropora millepora.     

PiuA and PiaA, iron uptake lipoproteins of Streptococcus pneumoniae, elicit serotype independent antibody responses following human pneumococcal septicaemia

Streptococcus pneumoniae causes considerable morbidity and mortality worldwide. The need for a cheap and effective pneumococcal vaccine has necessitated the evaluation of common virulence-associated proteins as potential vaccine antigens. PiuA and PiaA are the lipoprotein components of two pneumococcal iron ABC transporters. Here, we show that patients with culture confirmed pneumococcal septicaemia have elevated levels of antibody to PiuA and PiaA in convalescent-phase, compared with acute-phase serum. Additionally, sera from septicaemic patients infected with 13 pneumococcal strains covering eight different serotypes, cross-reacted with recombinant PiuA-His(6) and PiaA-His(6) from a single pneumococcal strain, indicating that this immune response is serotype independent. Anti-PiuA and anti-PiaA antibodies were also found in healthy seven-month-old infants, indicating that they are immunogenic at a very early age.