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It is rapidly becoming apparent that many E. coli pathotypes cause a considerable burden of human disease. Surveillance of these organisms is difficult because there are few or no simple, rapid methods for detecting and differentiating the different pathotypes. MALDI-TOF mass spectroscopy has recently been rapidly and enthusiastically adopted by many clinical laboratories as a diagnostic method because of its high throughput, relatively low cost, and adaptability to the laboratory workflow. To determine whether the method could be adapted for E. coli pathotype differentiation the Bruker Biotyper methodology and a second methodology adapted from the scientific literature were tested on isolates representing eight distinct pathotypes and two other groups of E. coli. A total of 136 isolates was used for this study. Results confirmed that the Bruker Biotyper methodology that included extraction of proteins from bacterial cells was capable of identifying E. coli isolates from all pathotypes to the species level and, furthermore, that the Bruker extraction and MALDI-TOF MS with the evaluation criteria developed in this work was effective for differentiating most pathotypes.

A Chlamydia trachomatis strain (L2/CPEC) resistant to the cytotoxic effects of cyclopentenyl cytosine (CPEC) was isolated by a stepwise selection procedure. This strain showed an approximate 350-fold increase in resistance to CPEC. Sequencing of the gene encoding CTP synthetase from this resistant strain revealed a single point mutation, resulting in a change of amino acid 149 from Asp to Glu. This appeared to be the only mutation in L2/CPEC, because no changes in CTP transport, CTP synthetase expression, or incorporation of CPEC into DNA or RNA could be detected. The mutation in the chlamydial CTP synthetase resulted in a loss of CTP feedback inhibition. This was demonstrated both in vivo using Escherichia coli cells carrying the cloned gene, and an in vitro assay using partially purified preparations of CTP synthetase. As a result of the loss of feedback inhibition, E. coli cells carrying the CPECR CTP synthetase showed a 22-fold increase in their CTP pools. However, examination of the CTP pools of L2/CPEC revealed no change in CTP levels when compared with wild type C. trachomatis.

Background Previously we studied the antibiotic susceptibility of invasive Haemophilus influenzae collected in Canada from 1990 to 2006 and characterized isolates by serotype, MLST and ftsI gene sequencing for significant PBP3 mutations. Objectives To provide an update based on isolates collected from 2007 to 2014. Methods A total of 882 case isolates were characterized by serotype using slide agglutination and PCR. MLST was carried out to determine ST. Isolates were tested for β-lactamase production, presence of significant PBP3 mutations and antibiotic susceptibility by disc diffusion against 14 antibiotics. MIC values of three antibiotics were determined for 316 isolates using microbroth dilution. Results Non-typeable H. influenzae accounted for 54.6% of the isolates and 45.4% were serotypeable, predominantly type a (23.1%), type b (8.3%) and type f (10.8%). The overall rate of ampicillin resistance due to β-lactamase production was 16.4% and increased from 13.5% in 2007-10 to 19% in 2011-14. Significant PBP3 mutations were identified in 129 isolates (14.6%) with 23 (2.6%) also producing β-lactamase. MLST identified related STs (ST-136, ST-14 and ST-367) associated exclusively with genetically β-lactamase-negative, ampicillin-resistant isolates and confirmed previously reported associations between significant PBP3 mutations and ST. Conclusions A significant increase in β-lactamase-producing isolates was observed from 2007 to 2014; the rate of significant PBP3 mutations has increased since previously reported and 52.5% of non-typeable H. influenzae now show resistance markers. Resistance to trimethoprim/sulfamethoxazole was common and no resistance to fluoroquinolones or third-generation cephalosporins was found.

Social networks are natural social units of people (nodes, actors) linked directly or indirectly to others by interaction, affections, associations or relationships and, for the purposes of this chapter, sexual intercourse. Sexual networks through which sexually transmitted pathogens are transmitted form the centre of this review of sexual networks. The fundamental concept of a social network is that the collection of links (paths or edges) and nodes forms an entity far greater than the sum of its parts [1], including interdependent norms, members, organisation and culture.

The objective of the current study was to determine whether the antimicrobial susceptibility profile or genotype of hospital-acquired isolates of Clostridium difficile differed from isolates causing community-acquired disease. Five hundred diarrhoeal stool samples (one >2 ml sample per patient) from patients across Manitoba, Canada, in 2006–2007 that were reported as C. difficile toxin positive were cultured, resulting in 432 isolates of toxin-positive C. difficile for analysis. Of these 432 isolates, acquisition status could be determined for 235 (54.4 %); 182 (77.4 %) isolates were hospital acquired and 53 (22.6 %) were community acquired. North American pulsotype (NAP) designations based on SmaI PFGE could be defined for 52.3 % of the 432 isolates, with NAP2 (n = 122) being the most common. Ninety-one per cent (71/78) of NAP2 isolates were recovered from patients with hospital-acquired C. difficile disease. Other NAP types and isolates with non-NAP-type PFGE patterns were less frequently associated with hospital-acquired disease. Community-acquired disease (35.3 % of isolates) was associated with a wide variety of NAP types. NAP2 isolates were homogeneous (85.5 % had SmaI PFGE pattern 0003) and demonstrated low susceptibility to moxifloxacin (6.6 %) and clindamycin (1.6 %) compared with non-NAP2 isolates (64.1–93.2 % moxifloxacin susceptible; 14.1–28.2 % clindamycin susceptible). All isolates of C. difficile in Manitoba were susceptible to metronidazole, piperacillin–tazobactam, amoxicillin–clavulanate and meropenem. NAP2 isolates of toxigenic C. difficile were approximately three times more common than NAP1 isolates (28.2 vs 9.1 %) in Manitoba in 2006–2007, and these isolates demonstrated high levels of clonality and multidrug resistance, and were associated with hospital acquisition.

OprB is a glucose-selective porin known to be produced by Pseudomonas aeruginosa and Pseudomonas putida. We have cloned and sequenced the oprB gene of P. aeruginosa and obtained expression of OprB in Escherichia coli. The mature protein consists of 423 amino acid residues with a deduced molecular mass of 47597 Da. Several clusters of amino acid residues, potentially involved in the structure or function of the protein, were identified. An area of regional homology with E. coli LamB was also identified. Carbohydrate-inducible proteins, potentially homologous to OprB, were identified in several rRNA homology-group-I pseudomonads by sodium dodecyl sulfate/polyacrylamide gel electrophoresis analysis, Western immunoblotting and N-terminal amino acid sequencing. These species also contained DNA that hybridized to a P. aeruginosa oprB gene probe.

The vanE operon was characterized from Enterococcus faecalis N00-410 (MIC of vancomycin = 24 μg/ml). The organization of the vanE operon was identical to that of the vanC1 operon from Enterococcus gallinarum , with protein identities ranging from 46 to 63%. An open reading frame located downstream of the vanE operon showed significant homology to a number of integrase genes, all of which are located downstream of the chromosomal GMP synthase gene guaA .

OprB, a glucose-inducible porin of P. aeruginosa, was characterized by black lipid bilayer analysis and circular dichroism spectroscopy. Black lipid bilayer analysis of OprB revealed a single-channel conductance of 25 pS, the presence of a glucose binding site with a Ks for glucose of 380 +/- 40 mM, and the formation of channels with a strong selection for anions. Analysis of P. aeruginosa OprB circular dichroism spectra revealed a high beta sheet content (40%) which is within the range of that determined for other porins. Values obtained from black lipid bilayer analysis were compared to those previously obtained for OprB of P. putida [Saravolac et al. (1991). J. Bacteriol. 173, 4970-4976] and indicated extensive similarities in the single-channel conductance and glucose-binding properties of these two porins. Immunological and amino terminal sequence analysis revealed a high degree of homology. Of the first 14 amino terminal residues, 12 were identical. A major difference between the two porins was found in their ion selectivity. Whereas P. aeruginosa OprB is anion selective, P. putida OprB and other carbohydrate selective porins are known to be cation selective.

Using the terrestrial, non-volant mammalian faunas of land-bridge islands worldwide, we investigated the roles of area and ambient environmental energy in determining species richness. Earlier studies showed that consideration of total island energy (i.e. area times energy per unit area) allows one to formulate a single model applicable to island faunas in different regions. However, we found that variation in ambient energy has a much more pronounced effect on richness than does variation in area. Incorporation of this fact into predictive models eliminates the latitudinal bias in earlier models' prediction of bird and angiosperm species richness. However, latitude was a better predictor of mammalian richness than the energy measures used in our analysis.

We used an island-based model to estimate mammal species richness in reserves following isolation of the reserve from surrounding habitat. Model predictions were compared to observed species richness in isolated reserves in the Australian wheatbelt. Our global, island-based model underestimates the total richness in the Australian reserves. However, the model accurately predicts the number of species that forage exclusively on the reserves and not on surrounding farmland. We tentatively conclude that general, island-based models may be useful tools to predict richness on reserves.

Introduction Research on the HIV vulnerability of men who have sex with men (MSM) in India has tended to focus on aggregates of individual risk behaviours. However, such an approach often overlooks the complexities in the sexual networks that ultimately underpin patterns of spread. This paper analyses a set of sexual contact network (SCN) snapshots in relation to ethnographic findings to reorientate individual-level explanations of risk behaviour in terms of more complex systems. Methods Fifteen community researchers conducted a 2-month ethnographic study in three cities in Karnataka to generate descriptions of the risk environments inhabited by MSM. SCNs were reconstructed by two methods. First, initial participants, defined as nodes of various sexual networks, were purposively sampled. In each site, six nodes brought in three sexual partners separately as participants. In all sites, 72 participants completed 431 surveys for their 7-day sexual partners. Second, each site determined four groups representing various sexual networks, each group containing four individuals. In all sites, 48 participants completed 334 surveys for their regular sexual partner. Results Considerable differences were observed between sites for practically all included behavioural variables. On their own, these characteristics yielded contradictory interpretations with respect to understanding contrasts in HIV prevalence at each site. However, viewing these variables in relation to SCNs and ethnographic data produced non-linear interpretations of HIV vulnerability which suggested importance to local interventions. Conclusion SCN data may be used with existing data on risk behaviour and the structural determinants of vulnerability to re-tailor more tightly focused interventions.

Recent emergence of infections resulting from this strain is of public health concern., Rates of colonization with livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) sequence type 398 have been high for pigs and pig farmers in Canada, but prevalence rates for the general human population are unknown. In this study, 5 LA-MRSA isolates, 4 of which were obtained from skin and soft tissue infections, were identified from 3,687 tested MRSA isolates from persons in Manitoba and Saskatchewan, Canada. Further molecular characterization determined that these isolates all contained staphylococcal cassette chromosome (SCC) mecV, were negative for Panton-Valentine leukocidin, and were closely related by macrorestriction analysis with the restriction enzyme Cfr91. The complete DNA sequence of the SCCmec region from the isolate showed a novel subtype of SCCmecV harboring clustered regularly interspaced short palindromic repeats and associated genes. Although prevalence of livestock-associated MRSA seems to be low for the general population in Canada, recent emergence of infections resulting from this strain is of public health concern.

With the introduction of the Haemophilus influenzae serotype b (Hib) vaccine, invasive Hib disease has decreased substantially, but nontypeable H. influenzae (NT Hi) disease appears to be increasing. In order to understand the origin of NT Hi strains and their relationship with serotypeable strains, we analysed 125 NT Hi isolates collected from individual patients with either invasive disease (70 isolates) or respiratory tract infections (55 isolates). Serotype-specific and capsular transport genes were absent by PCR analysis, confirming their nonencapsulated status, which also suggested the NT Hi isolates were not encapsulated strains that shed their capsules. Multilocus sequence typing confirmed the NT Hi isolates did not have the same genetic background as serotypeable strains, including Hib. Despite the genetic heterogeneity found, two major genetic clusters were identified, both containing invasive and respiratory isolates. Fourteen invasive isolates and nine respiratory isolates produced beta-lactamase and were ampicillin resistant. More invasive (26.8%) than respiratory isolates (10.9%) showed decreased susceptibility towards ampicillin by a mechanism unrelated to beta-lactamase production. Besides a change in the capsule status of invasive Hi strains, the burden of invasive Hi disease, which used to be mainly a childhood disease, has now shifted to involve both adults and infants.

There is increasing evidence that the main role of the microbial loop in aquatic food webs is rapid remineralization of organic nutrients with little C being transferred to higher trophic levels. There is also evidence, however, that the transfer of C from algae to crustaceans is equally inefficient. This finding suggests that simultaneous determination of C flow from both bacteria and algae to crustaceans is necessary to determine if bacteria might represent an important source of C for higher trophic levels. Our data suggest that when copepods dominate a crustacean community bacteria and picoplankton contribute insignificant amounts of C to crustaceans. When cladocerans predominate, the significance of these trophic links increases. At our study site, up to 16–21% of the C input to crustaceans may have originated from bacteria and picoplankton when cladocerans were present in large numbers. For some of our analyses, percentage of algal or heterotrophic bacterial C transferred per hour to crustaceans was of a similar magnitude, which suggests that if bacterial and algal biomass is similar much of the C flow to crustaceans could originate from bacteria.

Objectives. We used cluster analysis to subdivide a population of injection drug users and identify previously unknown behavioral heterogeneity within that population. Methods. We applied cluster analysis techniques to data collected in a cross-sectional survey of injection drug users in Winnipeg, Manitoba. The clustering variables we used were based on receptive syringe sharing, ethnicity, and types of drugs injected. Results. Seven clusters were identified for both male and female injection drug users. Some relationships previously revealed in our study setting, such as the known relationship between Talwin (pentazocine) and Ritalin (methylphenidate) use, injection in hotels, and hepatitis C virus prevalence, were confirmed through our cluster analysis approach. Also, relationships between drug use and infection risk not previously observed in our study setting were identified, an example being a cluster of female crystal methamphetamine users who exhibited high-risk behaviors but an absence or low prevalence of blood-borne pathogens. Conclusions. Cluster analysis was useful in both confirming relationships previously identified and identifying new ones relevant to public health research and interventions.

Increases in the rates of sexually transmitted infections (STIs) suggest that control programmes may not be effectively targeting diverse subpopulations. The objective of this investigation was to examine STI transmission within different groups, using both social network analysis and cluster analysis. Routine partner notification data were analysed from individuals diagnosed with, or exposed to an STI in Manitoba. Groups were identified and characterized. Three different clusters of groups were identified, comprised of demographically and clinically distinct individuals. A greater understanding of disease transmission patterns within these groups will aid in the development of targeted education and prevention programmes for all STIs.

In addition to the proportional increase in cases of non-type b Haemophilus influenzae disease in the post-H. influenzae type b vaccine era, the incidence of invasive H. influenzae disease was found to be approaching the rates of H. influenzae type b disease that were documented in the prevaccine period. Fifty-six percent of invasive disease now occurs in individuals aged >10 years.

Background Previous studies have used social network variables to improve our understanding of HIV transmission. Similar analytic approaches have not been undertaken for hepatitis C (HCV) or B (HBV), nor used to conduct comparative studies on these pathogens within a single setting. Methods A cross-sectional survey consisting of a questionnaire and blood sample was conducted on injection drug users in Winnipeg between December 2003 and September 2004. Logistic regression analyses were used to correlate respondent and personal network data with HCV, HBV and HIV prevalence. Results At the multivariate level, pathogen prevalence was correlated with both respondent and IDU risk network variables. Pathogen transmission was associated with several distinct types of high-risk networks formed around specific venues (shooting galleries, hotels) or within users who are linked by their drug use preferences. Smaller, isolated pockets of IDUs also appear to exist within the larger population where behavioural patterns pose a lesser risk, unless or until, a given pathogen enters those networks. Conclusion The findings suggest that consideration of both respondent and personal network variables can assist in understanding the transmission patterns of HCV, HBV, and HIV. It is important to assess these effects for multiple pathogens within one setting as the associations identified and the direction of those associations can differ between pathogens.

Using social network analysis, we investigated how communal meeting places can link injection drug user (IDU) populations and create opportunities for the transmission of bloodborne pathogens. In our locale, specific hotels played a key role in the injection drug scene. Within this hotel network some IDU injected at only one hotel while others injected at multiple hotels; this latter group potentially acted as spatial bridges linking relatively distinct hotel networks. Pathogen prevalence showed a gradation with the highest prevalence occurring at the centre of the network. Consistent with pathogen prevalence, people most central to the network were more likely to engage in risky injection practices. Incorporating geographic place into analyses involving IDU can contribute to an understanding of pathogen transmission patterns in an area and assist public health efforts to develop targeted intervention programs.

Multilocus sequence typing of 31 stx -carrying Escherichia coli O26:H11 strains isolated in Canada between 1999 and 2003 revealed a high degree of genetic relatedness at 10 loci, suggesting either that this is a clonal serotype (similar to O157:H7) or that additional genetic loci need to be examined.

Background. Despite widespread efforts to control it, Chlamydia trachomatis remains the most frequently diagnosed bacterial sexually transmitted infection (STI). Analysis of sexual networks has been proposed as a novel tool for control of and research into STI. In the present study, we combine molecular genotype data, analysis of geographic clusters, and sociodemographic descriptors to facilitate analysis of large sexual networks. Methods. Individual chlamydia genotypes found in Manitoba, Canada, were analyzed to identify geographic clusters, and the identified clusters were further characterized by statistical analysis of sociodemographic variables. Results. A total of 10 geographic clusters of chlamydia-genotype infection were identified. Clusters in Winnipeg showed no or little geographic overlap and could be further differentiated on the basis of the sociodemographic characteristics of the individuals within a cluster. Several clusters in northern Manitoba overlapped geographically but, nonetheless, could be differentiated on the basis of the sociodemographic characteristics of the infected individuals. Conclusions. On the basis of results of the combined analyses, each geographic cluster appeared to represent a relatively distinct transmission network within the larger sexual network. The geographic analysis of the molecular data provided a basis for establishment of potential epidemiological connections between small groups of unlinked individuals. Analytic approaches of the type described here would help to decipher the patterns that exist within large social network data sets and would be applicable to many types of infectious agents.

Background Sexually transmitted and bloodborne infection (STBBI) risk is multifaceted and can involve a complex interplay between sexual behaviours, substance abuse and mental health conditions. In Winnipeg, Manitoba Canada we conducted a study to better understand the interconnectedness and overlap of these conditions and behaviours. Methods Data from the Social Network study phase III (SNS III) were collected in the fall and winter of 2009 using semi-structured in-person interviews (n=600). Sampling was by respondent driven sampling and targeted street populations. The average mean age was 37 (SD=14.8) and the gender distribution was relatively equal (males constituted 53%). Latent class analysis was used to identify unobserved or latent subgroups (ie, risk profiles) to explore the extent of overlap between risky sexual behaviours, substance use choice (crack, alcohol, solvents, injection drug use), and mental health conditions. Six individual level items constituting risky behaviours and five network or environmental level risk behaviours were used in the latent class analysis. Individual items included: Ever diagnosed with a mental health condition, ever used crack, daily binge drinking, ever used solvents, ever injected drugs and knowing your sex partner has multiple other sex partners while social network items included: the proportion of your social network members who drink alcohol, use crack, sniff solvents, inject drugs, or are sex partners. Fit indices of G2, AIC, and BIC were used in assessing model fit. Additionally, the model fit was assessed by examining the relationship between items and their conditional latent class by strength of homogeneity (closeness to 0 or 1) and by whether there was evidence of good separation of latent classes. Results The 2-, 3-, 4-, and 5-class LCA models were compared. Goodness of fit indices favoured the 4-class model. For the 4-class model indices were: G2=1115, df=2000, AIC=1209, BIC=1415. Class prevalence of the 4 latent classes were: 31% were at high risk for all individual and network items, 25% constituted another latent class labelled as low-risk, 21% constituted a subgroup who were labelled as “loners” and exhibited high risk for mental health issues as well as individual crack, solvent use, and injection use but no network level correlates while the fourth latent class (23%) was distinguished for engaging in risky sexual behaviours and having these risky behaviours be supported at the social network level. Conclusions Latent class analysis demonstrated that there are indeed subgroups of vulnerable populations who warrant targeted interventions given their different risk profiles. This type of investigation offers a public health population segmentation strategy to plan for future targeted prevention efforts that can more effectively address the special needs of these subgroups of vulnerable populations.

Background The use of sexual network analysis has the potential to further our understanding of sexually tranmitted disease (STD) epidemics and contribute to the development of more effective targeted control strategies. Goal To use sexual network analysis to study transmission patterns of chlamydia and gonorrhea in Manitoba, Canada. Study Design Routinely collected case/contact information gathered by public health nurses was used to construct the sexual network. Results Components within the sexual network ranged in size from 2 to 82 people. Two types of components, designated radial and linear, were described. Large linear components resembled the theoretical structure of STD core groups. Geographic analysis of the largest components demonstrated the potential for STD transmission between isolated rural communities and within different areas of an urban center. Conclusions The application of sexual network analysis on a provincial basis demonstrated the importance of a centralized, coordinated approach to STD control. The analysis highlights the need for a greater understanding of the causative factors promoting the formation of different component types, the homogeneity and heterogeneity of behaviors within and between components, and the temporal stability of these patterns.

We conducted a comparative evaluation of the Chlamydiazyme (Abbott Laboratories), PACE 2 (Gen-Probe), and AMP-CT (Gen-Probe) assays for the detection of Chlamydia trachomatis in endocervical samples. Specimens from 787 females were included in the study. The sensitivities of the PACE 2 and Chlamydiazyme assays in comparison to the results of the AMP-CT assay were 79.3 and 63.4%, respectively. The specificities of the Chlamydiazyme and PACE 2 assays were 100%. All of the positive specimens detected in this study were positive by the AMP-CT assay. On the basis of the final results of the comparison, the prevalence of C. trachomatis in the population was 10.4%. Retesting of specimens whose results were in the intermediate zone by the PACE 2 assay by a probe competition assay identified some additional true-positive specimens. Amplification assay testing of such specimens did not significantly increase the yield. The majority of specimens which tested positive by the AMP-CT assay only were not in the intermediate zone by the PACE 2 assay. We were unable to identify demographic or clinical factors which could predict those individuals who tested positive by amplified tests but not by nonamplified tests. The Gen-Probe PACE 2 assay proved to be superior to the Chlamydiazyme assay for the screening and diagnosis of C. trachomatis infections in female endocervical specimens.

There is little information on the trafficking of eukaryotic lipids from a host cell to either the cytoplasmic membrane of or the vacuolar membrane surrounding intracellular pathogens. Purified Chlamydia trachomatis, an obligate intracellular bacterial parasite, contains several eukaryotic glycerophospholipids, yet attempts to demonstrate transfer of these lipids to the chlamydial cell membrane have not been successful. In this report, we demonstrate that eukaryotic glycerophospholipids are trafficked from the host cell to C. trachomatis. Phospholipid trafficking was assessed by monitoring the incorporation of radiolabelled isoleucine, a precursor of C. trachomatis specific branched-chain fatty acids, into host-derived glycerophospholipids and by monitoring the transfer of host phosphatidylserine to chlamydiae and its subsequent decarboxylation to form phosphatidylethanolamine. Phospholipid trafficking to chlamydiae was unaffected by brefeldin A, an inhibitor of Golgi function. Furthermore, no changes in trafficking were observed when C. trachomatis was grown in a mutant cell line with a nonfunctional, nonspecific phospholipid transfer protein. Host glycerophospholipids are modified by C. trachomatis, such that a host-synthesized straight-chain fatty acid is replaced with a chlamydia-synthesized branched-chain fatty acid. We also demonstrate that despite the acquisition of host-derived phospholipids, C. trachomatis is capable of de novo synthesis of phospholipids typically synthesized by prokaryotic cells. Our results provide novel information on chlamydial phospholipid metabolism and eukaryotic cell lipid trafficking, and they increase our understanding of the evolutionary steps leading to the establishment of an intimate metabolic association between an obligate intracellular bacterial parasite and a eukaryotic host cell.

Chlamydia trachomatis is a nucleotide parasite, being entirely dependent on its host eukaryotic cell for a supply of ATP, GTP, and UTP. Chlamydiae are not, however, auxotrophic for CTP, as they are able both to transport CTP from the host and synthesize CTP de novo via a chlamydial CTP synthetase. This study addresses the developmental regulation of CTP synthetase over the course of the C. trachomatis life cycle. Given the distinct life stages of C. trachomatis, analysis of temporal changes in gene expression and regulation of protein activity is the key to unravelling the mechanism of pathogenesis of this bacterium. The results of immunodetection analysis indicate that CTP synthetase is present in C. trachomatis elementary bodies and reticulate bodies and that it is widespread in other chlamydial strains. Reverse transcriptase-polymerase chain reaction (RT-PCR) and metabolic labelling experiments show that CTP synthetase is transcribed and translated primarily during the mid- and late stages of the chlamydial growth cycle. In addition, C. trachomatis CTP synthetase was transcribed with the CTP utilizing enzyme CMP-2-keto-3-deoxy-octanoic acid synthetase (CMP-KDO synthetase) as part of a polycistronic mRNA. The co-expression of these two enzymes suggests a role for CTP synthetase in lipopolysaccharide biosynthesis, potentially channelling CTP directly to CMP-KDO synthetase. The ability of the intact operon to complement CTP synthetase and CMP-KDO deficiencies in mutant Escherichia coli strains indicates that both enzymes are efficiently translated from a single messenger RNA. Kinetic analysis revealed that the C. trachomatis CTP synthetase possessed co-operativity patterns typical of both prokaryotic and eukaryotic CTP synthetases. However, the K(m) of the enzyme for UTP was lower than that of E. coli CTP synthetase, presumably in response to the low intracellular concentration of this nucleotide in C. trachomatis.

Using interposon mutagenesis, we have generated strains of Pseudomonas aeruginosa which lack or overexpress the substrate-selective OprB porin of this species. A marked decrease or increase in the initial uptake of glucose by these strains verified the role of OprB in facilitating the diffusion of glucose across the outer membrane of P. aeruginosa. However, we also demonstrated that the loss or overexpression of OprB had a similar effect on the uptake of three other sugars able to support the growth of this bacterium (mannitol, glycerol, and fructose). This effect was restricted to carbohydrate transport; arginine uptake was identical in mutant and wild-type strains. These results indicated that OprB cannot be considered strictly a glucose-selective porin; rather, it acts as a central component of carbohydrate transport and is more accurately described as a carbohydrate-selective porin.

Background The risk-related behaviours and practices associated with injection drug use remain a driver of HIV and hepatitis C virus (HCV) transmission throughout the world. Here we evaluated HIV and HCV transmission patterns in the context of social networks of injection drug users (IDU) recruited from a higher incidence region in order to better understand factors that contribute to ongoing transmission among IDU. Methods IDU recruited through a chain-referral method provided biological specimens for analysis. HIV and HCV positive specimens were sequenced and analyzed using phylogenetic methods (Neighbour-joining and Bayesian) and transmission patterns of HIV and HCV evaluated in the context of the recruitment networks. Results Among the 407 recruited IDU, HCV and HIV prevalence were 60.6% and 10.1%, respectively; 98% of HIV positive individuals were co-infected with HCV. Thirty-six percent of HCV sequences were associated with clusters, compared to 67% of HIV sequences. Four (16.7%) of the 24 HCV clusters contained membership separated by 2 or fewer recruitment cycles, compared to 10 (41.6%) derived from more than one recruitment component. Two (28.6%) of the 7 HIV clusters contained membership separated by 2 or fewer recruitment cycles while 6 (85.7%) were composed of inter component membership. Conclusions Few HIV and HCV transmissions coincided with the recruitment networks, suggesting that they occurred in a different social context or a context not captured by the recruitment network. However, among the complete cohort, a higher degree of HIV clustering indicates many are recent infections originating from within current social networks, whereas a larger proportion of HCV infections may have occurred earlier in injecting history and in the context of a different social environment.

Introduction Globally, substantial heterogeneity in the prevalence of HIV and other sexually transmitted infections (STIs) among most at-risk populations (MARPs) has been demonstrated. Examining factors related to heterogeneity can inform targeted programming. In Winnipeg, Canada, particularly high risk for HIV and hepatitis C (HCV) has been observed in injection drug users (IDUs) with a history of solvent use (S-IDUs). However, comparisons to other MARPs have been limited. Thus this study examined the association between HIV/STIs and S-IDUs in comparison to IDUs and other MARPs. Methods Data were from a 2008 to 2009 cross-sectional study of Winnipeg MARPs (IDUs, sex work- and street-involved individuals); subjects were recruited through respondent-driven sampling (RDS) methods. Adjusted ORs (AORs) from multivariable logistic regression models were estimated, examining the risk of HIV, HCV and HIV/HCV co-infection, and corrected for RDS-chain clustering using generalised estimating equations. Results Total sample was 499, of which 13% recently injected drugs (ie, last 6 months), 5% recently inhaled solvents, 6% were recent S-IDUs, and 76% did not inject drugs or inhale solvents. HIV and HCV prevalence among recent S-IDU was 21% and 79%, respectively; HIV/HCV co-infection was 18%. In multivariable models, S-IDUs were at highest risk of HIV (AOR: 3.6, 95% CI: 1.6% to 7.9%; p Conclusions Solvent use occurs among the most marginalised of MARPs, representing unique and complicated drug use trajectories. As the HIV epidemic in Canada becomes increasingly complex, examination of outlier populations such as S-IDU can inform public health by elucidating important pathways by which structural, environmental and individual factors interact to create the highest risk for HIV/STIs and other bloodborne pathogens.

Specificity of the high-affinity glucose transport system of Pseudomonas aeruginosa was examined. At a concentration of [14C]glucose near the Vmax of the system, inhibition by maltose, galactose, and xylose was detected. This inhibition is similar to that detected in earlier in vivo studies and correlates with the known specificity of OprB, a glucose-specific porin of P. aeruginosa. At a level of [14C]glucose 100 times lower, only unlabelled glucose inhibited uptake to any extent. This matches the known in vitro specificity of the periplasmic glucose binding protein. These findings were used to explain the discrepancy between earlier in vivo and in vitro results reported in the literature.Key words: Pseudomonas aeruginosa, glucose transport, OprB, glucose binding protein.

Background The study describes population level variations in campylobacter incidence within the Canadian province of Manitoba, and the relationship to sociodemographic and landscape related characteristics. Using data derived from the Manitoba Health Public Health Branch communicable disease surveillance database, the study applied a number of spatial and ecological techniques to visualize, explore and model campylobacter incidence for the years 1996 to 2004. Analytical techniques used in the study included spatial smoothing, the spatial scan statistic, the Gini coefficient, and Poisson regression analysis. Results The study demonstrated marked and statistically significant geographic variability in the rates of campylobacter incidence in Manitoba.. The incidence of campylobacter was observed to be significantly higher in populations living in rural and agricultural areas of the province, with the highest rates occurring in populations living in proximity to high densities of farm animals (cows, pigs, chickens). The study also observed that the age specific pattern of campylobacter incidence in rural Manitoba was very different than the urban pattern, with the incidence rate in the 0–4 year age group seven times higher in rural Manitoba than in the City of Winnipeg. Conclusion The study demonstrates the value of a deploying a diverse set of spatial techniques to better understand the dynamics of an enteric disease such as campylobacter infection. The study concludes that there may be three distinct mechanisms for the transmission of campylobacter in Manitoba which are operating simultaneously. These include broad population exposure to a centralized food system endemically infected with the campylobacter organism, exposure to local level factors such as farm animals or contaminated water, and exposure to campylobacter infection through foreign travel.

Background Solvent abuse is a particularly serious issue affecting Aboriginal people. Here we examine the association between solvent use and socio-demographic variables, drug-related risk factors, and pathogen prevalence in Aboriginal injection drug users (IDU) in Manitoba, Canada. Methods Data originated from a cross-sectional survey of IDU from December 2003 to September 2004. Associations between solvent use and variables of interest were assessed by multiple logistic regression. Results A total of 266 Aboriginal IDU were included in the analysis of which 44 self-reported recent solvent use. Hepatitis C infection was 81% in solvent-users, compared to 55% in those reporting no solvent use. In multivariable models, solvent-users were younger and more likely to be infected with hepatitis C (AOR: 3.5; 95%CI: 1.3,14.7), to have shared needles in the last six months (AOR: 2.6; 95%CI:1.0,6.8), and to have injected talwin & Ritalin (AOR: 10.0; 95%CI: 3.8,26.3). Interpretation High hepatitis C prevalence, even after controlling for risky injection practices, suggests that solvent users may form closed networks of higher risk even amongst an already high-risk IDU population. Understanding the social-epidemiological context of initiation and maintenance of solvent use is necessary to address the inherent inequalities encountered by this subpopulation of substance users, and may inform prevention strategies for other marginalized populations.