Mapping the pathways to staphylococcal pathogenesis by comparative secretomics.

The gram-positive bacterium Staphylococcus aureus is a frequent component of the human microbial flora that can turn into a dangerous pathogen. As such, this organism is capable of infecting almost every tissue and organ system in the human body. It does so by actively exporting a variety of virulence factors to the cell surface and extracellular milieu. Upon reaching their respective destinations, these virulence factors have pivotal roles in the colonization and subversion of the human host. It is therefore of major importance to obtain a clear understanding of the protein transport pathways that are active in S. aureus. The present review aims to provide a state-of-the-art roadmap of staphylococcal secretomes, which include both protein transport pathways and the extracytoplasmic proteins of these organisms. Specifically, an overview is presented of the exported virulence factors, pathways for protein transport, signals for cellular protein retention or secretion, and the exoproteomes of different S. aureus isolates. The focus is on S. aureus, but comparisons with Staphylococcus epidermidis and other gram-positive bacteria, such as Bacillus subtilis, are included where appropriate. Importantly, the results of genomic and proteomic studies on S. aureus secretomes are integrated through a comparative "secretomics" approach, resulting in the first definition of the core and variant secretomes of this bacterium. While the core secretome seems to be largely employed for general housekeeping functions which are necessary to thrive in particular niches provided by the human host, the variant secretome seems to contain the "gadgets" that S. aureus needs to conquer these well-protected niches.

Secretory ribonucleases in the primitive ruminant chevrotain (Tragulus javanicus).

Phylogenetic analyses of secretory ribonucleases or RNases 1 have shown that gene duplication events, giving rise to three paralogous genes (pancreatic, seminal and brain RNase), occurred during the evolution of ancestral ruminants. A higher number of paralogous sequences are present in chevrotain (Tragulus javanicus), the earliest diverged taxon within the ruminants. Two pancreatic RNase sequences were identified, one encoding the pancreatic enzyme, the other encoding a pseudogene. The identity of the pancreatic enzyme was confirmed by isolation of the protein and N-terminal sequence analysis. It is the most acidic pancreatic ribonuclease identified so far. Formation of the mature enzyme requires cleavage by signal peptidase of a peptide bond between two glutamic acid residues. The seminal-type RNase gene shows features of a pseudogene, like orthologous genes in other ruminants investigated with the exception of the bovine species. The brain-type RNase gene of chevrotain is expressed in brain tissue. A hybrid gene with a pancreatic-type N-terminal and a brain-type C-terminal sequence has been identified but nothing is known about its expression. Phylogenetic analysis of RNase 1 sequences of six ruminant, three other artiodactyl and two whale species support previous findings that two gene duplications occurred in a ruminant ancestor. Three distinct groups of pancreatic, seminal-type and brain-type RNases have been identified and within each group the chevrotain sequence it the first to diverge. In taxa with duplications of the RNase gene (ruminants and camels) the gene evolved at twice as fast than in taxa in which only one gene could be demonstrated; in ruminants there was an approximately fourfold increase directly after the duplications and then a slowing in evolutionary rate.

Distinction between major and minor Bacillus signal peptidases based on phylogenetic and structural criteria.

The processing of secretory preproteins by signal peptidases (SPases) is essential for cell viability. As previously shown for Bacillus subtilis, only certain SPases of organisms containing multiple paralogous SPases are essential. This allows a distinction between SPases that are of major and minor importance for cell viability. Notably, the functional difference between major and minor SPases is not reflected clearly in sequence alignments. Here, we have successfully used molecular phylogeny to predict major and minor SPases. The results were verified with SPases from various bacilli. As predicted, the latter enzymes behaved as major or minor SPases when expressed in B. subtilis. Strikingly, molecular modeling indicated that the active site geometry is not a critical parameter for the classification of major and minor Bacillus SPases. Even though the substrate binding site of the minor SPase SipV is smaller than that of other known SPases, SipV could be converted into a major SPase without changing this site. Instead, replacement of amino-terminal residues of SipV with corresponding residues of the major SPase SipS was sufficient for conversion of SipV into a major SPase. This suggests that differences between major and minor SPases are based on activities other than substrate cleavage site selection.

The phylogenetic position of "Acomyinae" (Rodentia, Mammalia) as sister group of a Murinae + Gerbillinae clade: evidence from the nuclear ribonuclease gene.

The phylogenetic relationships of Acomys and Uranomys within Muridae were investigated using nuclear pancreatic ribonuclease A gene sequences. The various kinds of substitutions in the data matrix (15 taxa x 375 nucleotides) were examined for saturation, in order to apply a weighted parsimony approach. Phylogenies were derived by maximum parsimony (weighted and unweighted) and maximum likelihood procedures, using a dormouse (Gliridae) as outgroup. Maximum likelihood gave the most robust results. All analyses cluster some traditional taxa with a strong robustness, such as three species of the genus Mus, two South-East Asian rats, and two genera in each of the gerbil and vole families. When analyzed with those of other murid rodents representing Murinae, Gerbillinae, Arvicolinae, Cricetinae, and Sigmodontinae, sequences of the ribonuclease gene suggest that Acomys and Uranomys constitute a monophyletic clade at the subfamily level, denoted "Acomyinae." The relationships between the six subfamilies of Muridae appear poorly resolved, except for a clade uniting Murinae, Acomyinae, and Gerbillinae. Within this clade, the sister group of Acomyinae could not be identified, as the branch length defining a Gerbillinae + Murinae cluster is extremely short. The poor resolution of our phylogenetic inferences is probably the result of two confounding factors, namely the limited size of the pancreatic ribonuclease sequence and the probable short time intervals during the radiation of the six murid subfamilies involved in this study.

Follow-up of occupational asthma caused by crab and various agents.

Sixty-three subjects with occupational asthma caused by crab (n = 31) and various other agents (n = 32) were studied after cessation of exposure at work for mean +/- SD intervals of 12.3 +/- 5.5 and 24.5 +/- 18.7 months (greater than 6 months in every subject), respectively. Nineteen of the subjects with asthma caused by crab and 30 of the subjects with asthma caused by various agents were still symptomatic of asthma, nine subjects of the latter group requiring bronchodilators (with inhaled beclomethasone in five) regularly. No significant changes in baseline spirometry were observed at the time of follow-up as compared with initial assessment, nine subjects (all in the asthma group caused by various agents) demonstrating significant bronchial obstruction. Improvement in bronchial responsiveness to histamine was significant (p less than 0.01) in the group with asthma caused by crab but not in the other group. Forty-eight of 52 subjects still had significant airway hyperexcitability. Subjects with asthma caused by crab who were asymptomatic and those subjects with asthma caused by various agents who used bronchodilators only if they were needed had worked for shorter intervals after onset of symptoms (p less than 0.01 and p less than 0.05, respectively). It is concluded that subjects with occupational asthma caused by various agents can remain symptomatic of asthma and demonstrate a persistence of bronchial obstruction and hyperexcitability for prolonged intervals after cessation of exposure.

Occupational asthma in snow crab-processing workers.

The prevalence of occupational asthma was studied in two snow crab-processing industries in operation since 1980. Before the 1982 season, all except 10 of the 313 employees were investigated by a questionnaire, prick skin tests with common allergens, crab n and crab-boiling water extracts, and spirometry. The diagnosis was confirmed in 46 (15.6%) workers (including 33 of 64 subjects with a history highly suggestive of occupational asthma in the previous seasons) by (1) specific inhalation challenges in 33 subjects (one immediate, nine dual, and 23 late asthmatic responses) and/or (2) a combination of monitoring of peak expiratory flow rates (n = 12) and significant changes in bronchial responsiveness to histamine (n = 16) as well as in spirometry (n = 18) after reappearance of symptoms on return to work. Positive skin tests to crab (p less than 0.001) and, to a lesser degree, smoking history (p = 0.03) but not atopy (p greater than 0.05) were related to the presence of occupational asthma. A high prevalence of rhinoconjunctivitis (35 of 46) and urticaria (16 of 46) was also documented in the affected individuals.

[Not Available]. / L'Examen Médical Périodique de L'Adulte: Une Approche Préventive Systématique.

Following the Task Force on the Periodic Health Examination, the authors review the chief preventable pathology and outline norms for the nature and frequency of preventive procedures. They propose a systematic program of prevention and screening of the adult. In order to accomplish this, the initial evaluation of the patient must include the search for risk factors and these are included in the problem list. Finally, tables provide simple and efficient modes of applying this program, which also constitutes a useful research tool.