Moraxella osloensis Gene Expression in the Slug Host Deroceras reticulatum

<p>Abstract</p> <p>Background</p> <p>The bacterium <it>Moraxella osloensis </it>is a mutualistic symbiont of the slug-parasitic nematode <it>Phasmarhabditis hermaphrodita</it>. In nature, <it>P. hermaphrodita </it>vectors <it>M. osloensis </it>into the shell cavity of the slug host <it>Deroceras reticulatum </it>in which the bacteria multiply and kill the slug. As <it>M. osloensis </it>is the main killing agent, genes expressed by <it>M. osloensis </it>in the slug are likely to play important roles in virulence. Studies on pathogenic interactions between bacteria and lower order hosts are few, but such studies have the potential to shed light on the evolution of bacterial virulence. Therefore, we investigated such an interaction by determining gene expression of <it>M. osloensis </it>in its slug host <it>D. reticulatum </it>by selectively capturing transcribed sequences.</p> <p>Results</p> <p>Thirteen <it>M. osloensis </it>genes were identified to be up-regulated post infection in <it>D. reticulatum</it>. Compared to the <it>in vitro </it>expressed genes in the stationary phase, we found that genes of ubiquinone synthetase (<it>ubiS</it>) and acyl-coA synthetase (<it>acs</it>) were up-regulated in both <it>D. reticulatum </it>and stationary phase <it>in vitro </it>cultures, but the remaining 11 genes were exclusively expressed in <it>D. reticulatum </it>and are hence infection specific. Mutational analysis on genes of protein-disulfide isomerase (<it>dsbC</it>) and <it>ubiS </it>showed that the virulence of both mutants to slugs was markedly reduced and could be complemented. Further, compared to the growth rate of wild-type <it>M. osloensis</it>, the <it>dsbC </it>and <it>ubiS </it>mutants showed normal and reduced growth rate <it>in vitro</it>, respectively.</p> <p>Conclusion</p> <p>We conclude that 11 out of the 13 up-regulated <it>M. osloensis </it>genes are infection specific. Distribution of these identified genes in various bacterial pathogens indicates that the virulence genes are conserved among different pathogen-host interactions. Mutagenesis, growth rate and virulence bioassays further confirmed that <it>ubiS </it>and <it>dsbC </it>genes play important roles in <it>M. osloensis </it>survival and virulence, respectively in <it>D. reticulatum</it>.</p

Effect of age and anatomic site on likelihood of detecting S. aureus in pigs

Intensive sampling of two swine farms in Minnesota was conducted to obtain basic information about the ecology and epidemiology of S. aureus in modern multiple site swine production. The farms were selected by convenience, and two cohorts of animals were sampled in each system

Longitudinal study of Staphylococcus aureus and MRSA colonization of US swine veterinarians

Patterns of detection of S. aureus are being evaluated in a longitudinal study of a cohort of 67 swine veterinarians in the USA. This report presents interim data from the initial period of the study. Overall, approximately 70% of sampling events yielded S. aureus in nasal swabs from veterinarians, and 8% yielded MRSA isolates

embCAB Sequence Variation Among Ethambutol-Resistant Mycobacterium Tuberculosis Isolates Without embB306 Mutation

Mechanisms of resistance to ethambutol in Mycobacterium tuberculosis remain inadequately described. Although there is mounting evidence that mutations of codon 306 in embB play a key role, a significant number of phenotypically ethambutol-resistant strains do not carry mutations in this codon. Here, other mutations in the embCAB operon are suggested to be involved in resistance development

Methicillin resistantS. au reus in market hogs, retail pork, and swine veterinarians in the USA

Cross-sectional studies were conducted to obtain preliminary data on the prevalence of MRSA in swine veterinarians and market hogs, and S. aureus in retail pork in the USA. Convenience sampling was employed, but samples were broadly sourced across the country. Nasal swabs were collected from 111 swine veterinarians at a national swine veterinary meeting, and from 539 market hogs slaughtered at large US packing plants. Fresh pork products (chops or ground pork) were obtained from retail stores in 15 states. Samples were cultured using double enrichment methods and selective plating

Genome Analysis of Multi- and Extensively-Drug-Resistant Tuberculosis from KwaZulu-Natal, South Africa

The KZN strain family of Mycobacterium tuberculosis is a highly virulent strain endemic to the KwaZulu-Natal region of South Africa, which has recently experienced an outbreak of extensively-drug resistant tuberculosis. To investigate the causes and evolution of drug-resistance, we determined the DNA sequences of several clinical isolates - one drug-susceptible, one multi-drug resistant, and nine extensively drug-resistant - using whole-genome sequencing. Analysis of polymorphisms among the strains is consistent with the drug-susceptibility profiles, in that well-known mutations are observed that are correlated with resistance to isoniazid, rifampicin, kanamycin, ofloxacin, ethambutol, and pyrazinamide. However, the mutations responsible for rifampicin resistance in rpoB and pyrazinamide in pncA are in different nucleotide positions in the multi-drug-resistant and extensively drug-resistant strains, clearly showing that they acquired these mutations independently, and that the XDR strain could not have evolved directly from the MDR strain (though it could have arisen from another similar MDR strain). Sequencing of eight additional XDR strains from other areas of KwaZulu-Natal shows that they have identical drug resistant mutations to the first one sequenced, including the same polymorphisms at sites associated with drug resistance, supporting the theory that this represents a case of clonal expansion

First insights into the phylogenetic diversity of Mycobacterium tuberculosis in Nepal

BACKGROUND: Tuberculosis (TB) is a major public health problem in Nepal. Strain variation in Mycobacterium tuberculosis may influence the outcome of TB infection and disease. To date, the phylogenetic diversity of M. tuberculosis in Nepal is unknown. METHODS AND FINDINGS: We analyzed 261 M. tuberculosis isolates recovered from pulmonary TB patients recruited between August 2009 and August 2010 in Nepal. M. tuberculosis lineages were determined by single nucleotide polymorphisms (SNP) typing and spoligotyping. Drug resistance was determined by sequencing the hot spot regions of the relevant target genes. Overall, 164 (62.8%) TB patients were new, and 97 (37.2%) were previously treated. Any drug resistance was detected in 50 (19.2%) isolates, and 16 (6.1%) were multidrug-resistant. The most frequent M. tuberculosis lineage was Lineage 3 (CAS/Delhi) with 106 isolates (40.6%), followed by Lineage 2 (East-Asian lineage, includes Beijing genotype) with 84 isolates (32.2%), Lineage 4 (Euro-American lineage) with 41 (15.7%) isolates, and Lineage 1 (Indo-Oceanic lineage) with 30 isolates (11.5%). Based on spoligotyping, we found 45 different spoligotyping patterns that were previously described. The Beijing (83 isolates, 31.8%) and CAS spoligotype (52, 19.9%) were the dominant spoligotypes. A total of 36 (13.8%) isolates could not be assigned to any known spoligotyping pattern. Lineage 2 was associated with female sex (adjusted odds ratio [aOR] 2.58, 95% confidence interval [95% CI] 1.42-4.67, p = 0.002), and any drug resistance (aOR 2.79; 95% CI 1.43-5.45; p = 0.002). We found no evidence for an association of Lineage 2 with age or BCG vaccination status. CONCLUSIONS: We found a large genetic diversity of M. tuberculosis in Nepal with representation of all four major lineages. Lineages 3 and 2 were dominating. Lineage 2 was associated with clinical characteristics. This study fills an important gap on the map of the M. tuberculosis genetic diversity in the Asian reg

Microevolution of Helicobacter pylori during prolonged infection of single hosts and within families

Our understanding of basic evolutionary processes in bacteria is still very limited. For example, multiple recent dating estimates are based on a universal inter-species molecular clock rate, but that rate was calibrated using estimates of geological dates that are no longer accepted. We therefore estimated the short-term rates of mutation and recombination in Helicobacter pylori by sequencing an average of 39,300 bp in 78 gene fragments from 97 isolates. These isolates included 34 pairs of sequential samples, which were sampled at intervals of 0.25 to 10.2 years. They also included single isolates from 29 individuals (average age: 45 years) from 10 families. The accumulation of sequence diversity increased with time of separation in a clock-like manner in the sequential isolates. We used Approximate Bayesian Computation to estimate the rates of mutation, recombination, mean length of recombination tracts, and average diversity in those tracts. The estimates indicate that the short-term mutation rate is 1.4×10−6 (serial isolates) to 4.5×10−6 (family isolates) per nucleotide per year and that three times as many substitutions are introduced by recombination as by mutation. The long-term mutation rate over millennia is 5–17-fold lower, partly due to the removal of non-synonymous mutations due to purifying selection. Comparisons with the recent literature show that short-term mutation rates vary dramatically in different bacterial species and can span a range of several orders of magnitude

The non-clonality of drug resistance in Beijing-genotype isolates of Mycobacterium tuberculosis from the Western Cape of South Africa

Background. The Beijing genotype of M. tuberculosis is a virulent strain that is disseminating worldwide and has a strong association with drug resistance. In the Western Cape of South Africa, epidemiological studies have identified the R220 cluster of the Beijing genotype as a major contributor to a recent outbreak of drug-resistant tuberculosis. Although the outbreak is considered to be due to clonal transmission, the relationship among drug resistant isolates has not yet been established. Results. To better understand the evolution of drug resistance among these strains, 14 drug-resistant clinical isolates of the Beijing genotype were sequenced by whole-genome sequencing, including eight from R220 and six from a more ancestral Beijing cluster, R86, for comparison. While each cluster shares a distinct resistance mutation for isoniazid, mapping of other drug-resistance mutations onto a phylogenetic tree constructed from single nucleotide polymorphisms shows that resistance mutations to many drugs have arisen multiple times independently within each cluster of isolates. Thus, drug resistance among these isolates appears to be acquired, not clonally derived. This observation suggests that, although the Beijing genotype as a whole might have selective advantages enabling its rapid dissemination, the XDR isolates are relatively less fit and do not propagate well. Although it has been hypothesized that the increased frequency of drug resistance in some Beijing lineages might be caused by a mutator phenotype, no significant shift in synonymous substitution patterns is observed in the genomes. Conclusion. While MDR-TB is spreading by transmission in the Western Cape, our data suggests that further drug resistance (i.e. XDR-TB) at this stage is acquired.Peer Reviewe