Phage Paride can kill dormant, antibiotic-tolerant cells of Pseudomonas aeruginosa by direct lytic replication

Bacteriophages are ubiquitous viral predators that have primarily been studied using fast-growing laboratory cultures of their bacterial hosts. However, microbial life in nature is mostly in a slow- or non-growing, dormant state. Here, we show that diverse phages can infect deep-dormant bacteria and suspend their replication until the host resuscitates ("hibernation"). However, a newly isolated Pseudomonas aeruginosa phage, named Paride, can directly replicate and induce the lysis of deep-dormant hosts. While non-growing bacteria are notoriously tolerant to antibiotic drugs, the combination with Paride enables the carbapenem meropenem to eradicate deep-dormant cultures in vitro and to reduce a resilient bacterial infection of a tissue cage implant in mice. Our work might inspire new treatments for persistent bacterial infections and, more broadly, highlights two viral strategies to infect dormant bacteria (hibernation and direct replication) that will guide future studies on phage-host interactions.

Pareto optimality between growth-rate and lag-time couples metabolic noise to phenotypic heterogeneity in Escherichia coli

Despite mounting evidence that in clonal bacterial populations, phenotypic variability originates from stochasticity in gene expression, little is known about noise-shaping evolutionary forces and how expression noise translates to phenotypic differences. Here we developed a high-throughput assay that uses a redox-sensitive dye to couple growth of thousands of bacterial colonies to their respiratory activity and show that in Escherichia coli, noisy regulation of lower glycolysis and citric acid cycle is responsible for large variations in respiratory metabolism. We found that these variations are Pareto optimal to maximization of growth rate and minimization of lag time, two objectives competing between fermentative and respiratory metabolism. Metabolome-based analysis revealed the role of respiratory metabolism in preventing the accumulation of toxic intermediates of branched chain amino acid biosynthesis, thereby supporting early onset of cell growth after carbon starvation. We propose that optimal metabolic tradeoffs play a key role in shaping and preserving phenotypic heterogeneity and adaptation to fluctuating environments.

A Surface-Induced Asymmetric Program Promotes Tissue Colonization by Pseudomonas aeruginosa

The opportunistic human pathogen Pseudomonas aeruginosa effectively colonizes host epithelia using pili as primary adhesins. Here we uncover a surface-specific asymmetric virulence program that enhances P. aeruginosa host colonization. We show that when P. aeruginosa encounters surfaces, the concentration of the second messenger c-di-GMP increases within a few seconds. This leads to surface adherence and virulence induction by stimulating pili assembly through activation of the c-di-GMP receptor FimW. Surface-attached bacteria divide asymmetrically to generate a piliated, surface-committed progeny (striker) and a flagellated, motile offspring that leaves the surface to colonize distant sites (spreader). Cell differentiation is driven by a phosphodiesterase that asymmetrically positions to the flagellated pole, thereby maintaining c-di-GMP levels low in the motile offspring. Infection experiments demonstrate that cellular asymmetry strongly boosts infection spread and tissue damage. Thus, P. aeruginosa promotes surface colonization and infection transmission through a cooperative virulence program that we termed Touch-Seed-and-Go.

Cyclic di-GMP differentially tunes a bacterial flagellar motor through a novel class of CheY-like regulators

The flagellar motor is a sophisticated rotary machine facilitating locomotion and signal transduction. Owing to its important role in bacterial behavior, its assembly and activity are tightly regulated. For example, chemotaxis relies on a sensory pathway coupling chemical information to rotational bias of the motor through phosphorylation of the motor switch protein CheY. Using a chemical proteomics approach, we identified a novel family of CheY-like (Cle) proteins in Caulobacter crescentus, which tune flagellar activity in response to binding of the second messenger c-di-GMP to a C-terminal extension. In their c-di-GMP bound conformation Cle proteins interact with the flagellar switch to control motor activity. We show that individual Cle proteins have adopted discrete cellular functions by interfering with chemotaxis and by promoting rapid surface attachment of motile cells. This study broadens the regulatory versatility of bacterial motors and unfolds mechanisms that tie motor activity to mechanical cues and bacterial surface adaptation.

Evolutionary Dynamics of Pathoadaptation Revealed by Three Independent Acquisitions of the VirB/D4 Type IV Secretion System in Bartonella

The α-proteobacterial genus Bartonella comprises a group of ubiquitous mammalian pathogens that are studied as a model for the evolution of bacterial pathogenesis. Vast abundance of two particular phylogenetic lineages of Bartonella had been linked to enhanced host adaptability enabled by lineage-specific acquisition of a VirB/D4 type IV secretion system (T4SS) and parallel evolution of complex effector repertoires. However, the limited availability of genome sequences from one of those lineages as well as other, remote branches of Bartonella has so far hampered comprehensive understanding of how the VirB/D4 T4SS and its effectors called Beps have shaped Bartonella evolution. Here, we report the discovery of a third repertoire of Beps associated with the VirB/D4 T4SS of B. ancashensis, a novel human pathogen that lacks any signs of host adaptability and is only distantly related to the two species-rich lineages encoding a VirB/D4 T4SS. Furthermore, sequencing of ten new Bartonella isolates from under-sampled lineages enabled combined in silico analyses and wet lab experiments that suggest several parallel layers of functional diversification during evolution of the three Bep repertoires from a single ancestral effector. Our analyses show that the Beps of B. ancashensis share many features with the two other repertoires, but may represent a more ancestral state that has not yet unleashed the adaptive potential of such an effector set. We anticipate that the effectors of B. ancashensis will enable future studies to dissect the evolutionary history of Bartonella effectors and help unraveling the evolutionary forces underlying bacterial host adaptation.

Bacteria in the CF Lung: Isolation Drives Diversity

In-host pathogen evolution influences disease progression and chronicity, but forces that shape this remain poorly understood. In this issue of Cell Host & Microbe, Jorth et al. (2015) describe regional subpopulations of Pseudomonas aeruginosa in lungs from cyctic fibrosis patients and provide support for compartmentalization-driven evolution of this bacterium.

Activation and polar sequestration of PopA, a c-di-GMP effector protein involved in Caulobacter crescentus cell cycle control

When Caulobacter crescentus enters S-phase the replication initiation inhibitor CtrA dynamically positions to the old cell pole to be degraded by the polar ClpXP protease. Polar delivery of CtrA requires PopA and the diguanylate cyclase PleD that positions to the same pole. Here we present evidence that PopA originated through gene duplication from its paralogue response regulator PleD and subsequent co-option as c-di-GMP effector protein. While the C-terminal catalytic domain (GGDEF) of PleD is activated by phosphorylation of the N-terminal receiver domain, functional adaptation has reversed signal transduction in PopA with the GGDEF domain adopting input function and the receiver domain serving as regulatory output. We show that the N-terminal receiver domain of PopA specifically interacts with RcdA, a component required for CtrA degradation. In contrast, the GGDEF domain serves to target PopA to the cell pole in response to c-di-GMP binding. In agreement with the divergent activation and targeting mechanisms, distinct markers sequester PleD and PopA to the old cell pole upon S-phase entry. Together these data indicate that PopA adopted a novel role as topology specificity factor to help recruit components of the CtrA degradation pathway to the protease specific old cell pole of C. crescentus.

The lipopolysaccharide from Capnocytophaga canimorsus reveals an unexpected role of the core-oligosaccharide in MD-2 binding

Capnocytophaga canimorsus is a usual member of dog's mouths flora that causes rare but dramatic human infections after dog bites. We determined the structure of C. canimorsus lipid A. The main features are that it is penta-acylated and composed of a “hybrid backbone” lacking the 4′ phosphate and having a 1 phosphoethanolamine (P-Etn) at 2-amino-2-deoxy-d-glucose (GlcN). C. canimorsus LPS was 100 fold less endotoxic than Escherichia coli LPS. Surprisingly, C. canimorsus lipid A was 20,000 fold less endotoxic than the C. canimorsus lipid A-core. This represents the first example in which the core-oligosaccharide dramatically increases endotoxicity of a low endotoxic lipid A. The binding to human myeloid differentiation factor 2 (MD-2) was dramatically increased upon presence of the LPS core on the lipid A, explaining the difference in endotoxicity. Interaction of MD-2, cluster of differentiation antigen 14 (CD14) or LPS-binding protein (LBP) with the negative charge in the 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) of the core might be needed to form the MD-2 – lipid A complex in case the 4′ phosphate is not present.

Capnocytophaga canimorsus, a commensal bacterium in dog's mouths, causes rare but dramatic infections in humans that have been bitten by dogs. The disease often begins with mild symptoms but progresses to severe septicemia. The lipopolysaccharide (LPS), composed of lipid A, core and O-antigen, is one of the most pro-inflammatory bacterial compounds. The activity of the LPS has so far been attributed to the lipid A moiety. We present here the structure of C. canimorsus lipid A, which shows several features typical for low-inflammatory lipid A. Surprisingly, this lipid A, when attached to the core-oligosaccharide was far more pro-inflammatory than lipid A alone, indicating that in this case the core-oligosaccharide is able to contribute significantly to endotoxicity. Our further work suggests that a negative charge in the LPS-core can compensate the lack of such a charge in the lipid A and that this charge is needed not for stabilization of the final complex with its receptor but in the process of forming it. Overall the properties of the lipid A-core may explain how this bacterium first escapes the innate immune system, but nevertheless can cause a shock at the septic stage.

The N-glycan glycoprotein deglycosylation complex (Gpd) from Capnocytophaga canimorsus deglycosylates human IgG

C. canimorsus 5 has the capacity to grow at the expenses of glycan moieties from host cells N-glycoproteins. Here, we show that C. canimorsus 5 also has the capacity to deglycosylate human IgG and we analyze the deglycosylation mechanism. We show that deglycosylation is achieved by a large complex spanning the outer membrane and consisting of the Gpd proteins and sialidase SiaC. GpdD, -G, -E and -F are surface-exposed outer membrane lipoproteins. GpdDEF could contribute to the binding of glycoproteins at the bacterial surface while GpdG is a endo-β-N-acetylglucosaminidase cleaving the N-linked oligosaccharide after the first N-linked GlcNAc residue. GpdC, resembling a TonB-dependent OM transporter is presumed to import the oligosaccharide into the periplasm after its cleavage from the glycoprotein. The terminal sialic acid residue of the oligosaccharide is then removed by SiaC, a periplasm-exposed lipoprotein in direct contact with GpdC. Finally, most likely degradation of the oligosaccharide proceeds sequentially from the desialylated non reducing end by the action of periplasmic exoglycosidases, including β-galactosidases, β-N-Acetylhexosaminidases and α-mannosidases.

Measures of disassortativeness and their application to directly transmitted infections

We propose a measure of disassortativeness to summarize contact patterns relevant to the transmission of directly transmitted infections. We discuss the properties of this measure, describe standardization relative to homogeneous mixing, and generalize it to multivariate contact structures. We explore some of its properties and apply our methods to serological surveys of close contact infections and surveys of self-reported social contacts obtained in several European countries.

Seroprevalence of bactericidal antibody against Neisseria meningitidis serogroup C in pre-vaccinal era: the Italian epidemiological scenario

Meningococcal disease is particularly severe. The case-fatality rate is 7.78% in Europe and 10-14% in the USA. This paper reports the results of a sero-epidemiological study in Italy on meningitis due to Meningococcus C before the introduction of the monovalent conjugate vaccine. In 2003-2004, a total of 577 sera were collected in 17 of the 20 Italian Regions. Serum Bactericidal Assay (SBA) was performed by using rabbit complement serum according to standardized SBA. The results showed that the percentages of protected subjects decreased from 6 to 12 months of age, increased from 1 to 4 years, decreased again until the age of 8 years and from 13 to 16 years, and were particularly high in 9- and 17-year-old subjects. The geometric mean titre of bactericidal antibodies (SBAbs GMT) was low in subjects under 1 year of age, significantly increased in 1-9-year-old children and decreased in adolescents and young adults. Finally, in each one-year age-group, low levels of antibodies were observed in subjects under 1 year of age, in 10-year-old subjects and in 14-16-year-old adolescents. High titres were observed in 3-, 8-, 9- and 17-year-old subjects. Our results therefore indicate that meningococcus C has the highest probability of spreading among 1-4, 8-10 and 14-17-year-old subjects in Italy.

Two unusual cases of pharyngeal hairy polyp causing intermittent neonatal airway obstruction

Hairy polyp of the pharynx is an uncommon developmental malformation that is most frequently seen as a penduculated tumour in the neonate. The clinical presentation is characterized by the presence of a polypoid mass protruding through the mouth as 'a second tongue' causing respiratory distress. Two patients are presented with this condition.

Retinal dysfunction in patients with chronic Chagas' disease is associated to anti‐Trypanosoma cruziantibodies that cross‐react with rhodopsin

To investigate retinal involvement in chronic Chagas' disease, we performed electroretinography and retinal fluorescein angiography studies in chagasic patients. Our results demonstrated a dissociated electrophysiological response characterized by both an abnormal reduction of the electroretinographic b-wave amplitude and a delayed latency, under the dark-adaptated condition. These alterations are compatible with a selective dysfunction of the rods. Antibodies raised against Trypanosoma cruzi that also interact with beta1-adrenergic receptor blocked light stimulation of cGMP-phosphodiesterase in bovine rod membranes. The specificity from the antibody-rhodopsin interaction was confirmed by Western blot analysis and antigenic competition experiments. Our results suggest an immunomediated rhodopsin blockade. T. cruzi infection probably induces an autoimmune response against rhodopsin in the chronic phase of Chagas' disease through a molecular mimicry mechanism similar to that described previously on cardiac human beta1-adrenergic and M2-cholinergic receptors, all related to the same subfamily of G-protein-coupled receptors.

Measles elimination in Italy: projected impact of the National Elimination Plan

A mathematical model was used to evaluate the impact of the Italian Measles National Elimination Plan (NEP), and possible sources of failure in achieving its targets. The model considered two different estimates of force of infection, and the possible effect on measles transmission of the current Italian demographic situation, characterized by a below-replacement fertility. Results suggest that reaching all NEP targets will allow measles elimination to be achieved. In addition, the model suggests that achieving elimination by reaching a 95 % first-dose coverage appears unlikely; and that conducting catch-up activities, reaching high vaccination coverage, could interrupt virus circulation, but could not prevent the infection re-emerging before 2020. Also, the introduction of the second dose of measles vaccine seems necessary for achieving and maintaining elimination. Furthermore, current Italian demography appears to be favourable for reaching elimination.

[Research on Pisa University student's life style and health]

Surveys on life and health conditions of university students besides providing useful epidemiologic data partly related to the young population. They are potentially useful for the intervention planning aimed to remove possible environmental or behavioural risk factors. Following these purpose a survey sample about 1200 student attending the University of Pisa was carried out through an anonymous questionnaire about 41 questions focused on behaviours and lifestyles of young people, possible health problems, self-perception of the health state, the use of public health services, and the more commonly used (or preferred) sources of information on health topics. The results suggest that although the self perception of the state of health is broadly positive for the majority of students, there is also a significant frequency of individuals declaring significant at risk behaviours (persistence of sexual practices at risk, drug use, alcohol and smoke abuse). The consumption, also sporadic, of psicoattive substances has been declared gives beyond 40% of the students, in particular 37% asserts to have tried drugs. The habit to smoke appeared diffused much between the students; the percentage of smokers turns out equal to 41% in total (40% females, 42% males). 76% of the interviewed ones has declared to be sexually active, the percentage of those who have declared multiple relations or occasional is elevated (12%), and 47% of the students asserts to use the condom with fixed partner and 77% with occasional partner. Moreover there seems to be a significant association between the changes in the diet and other lifestyles that are due to the "university lifestyle" (as a consequence of leaving the family or increased commuting) and the insurgence of several types of sickness, e.g. gastroenteric disturbances and fever attacks. Finally, the present investigation suggests that few interventions on services offered to students (such as accommodation, teaching structures and especially the creation of a "health office" where students can acquire information on health and other topics related to their condition) could have a significantly beneficial impact on the general state of health of the university population.

Prevalence of tic disorders among primary school students in the city of Pavia, Italy

BACKGROUND

The prevalence of tic disorders in children varies from 1% to 29% depending on the characteristics of the study population, the diagnostic criteria, and the study design and methods.

AIMS

To calculate the prevalence of tic disorders among primary school children in Italy.

METHODS

The study population comprised 2347 primary school children from the city of Pavia (pop. 80 073), Northern Italy. Using trained school teachers as the source of cases, all children with motor or vocal tics occurring intermittently and unpredictably out of a background of normal motor activity were accepted. The type, frequency, and circumstances of tic disorders were noted. School performance was correlated to the presence of tics.

RESULTS

A total of 68 children (56 boys, 12 girls) aged 6-11 years were identified with tic disorders. The period prevalence was 2.9% (95% CI 2.3 to 3.7). The prevalence was 4.4% in boys and 1.1% in girls, with no detectable trends at age 6-11. Motor tics were present in 46 cases, vocal tics in 6, and motor and vocal tics in 16. Situation related tics were noted in 37 cases. A significant correlation was found between the presence of tic disorders and impaired school performance.

DISCUSSIONS

Tic disorders are a fairly uncommon but disabling clinical disorder among primary school children from an urban community. The fairly low prevalence of this clinical condition, as compared to other reports, can be explained by the choice of stringent diagnostic criteria and the exclusion of patients with other movement disorders.

Intravenous methadone in the management of chronic cancer pain: safe and effective starting doses when substituting methadone for fentanyl

BACKGROUND

Patients often are rotated from other opioids to methadone when side effects occur before satisfactory analgesia is achieved. Various strategies have been proposed to estimate safe and effective starting doses of methadone when rotating from morphine and hydromorphone; however, there are no guidelines for estimating safe and effective starting doses of methadone when rotating from fentanyl.

METHODS

The authors prospectively observed 18 consecutive patients experiencing chronic pain from cancer who underwent opioid rotation from intravenous patient-controlled analgesia (PCA) with fentanyl to intravenous PCA with methadone. Patients were switched from fentanyl to methadone because of uncontrolled pain associated with sedation or confusion. A conversion ratio of 25 microg/hour of fentanyl to 0.1 mg/hour of methadone was used to calculate the initial dose of methadone in all patients.

RESULTS

Mean pain scores decreased from 8.1 to 4.8 on Day 1 after the switch and to 3.22 on Day 4 after the switch. Mean sedation scores were 1.5 before the switch and 0.44 and 0.16 on Days 1 and 4, respectively. Among the 6 patients who experienced confusion while on fentanyl before the switch, 5 improved within 2 days of the switch. None of the patients experienced toxicity from methadone.

CONCLUSIONS

On the basis of this preliminary study, the authors suggest that when switching from intravenous fentanyl to methadone a conversion ratio of 25 microg/hour of fentanyl to 0.1 mg/hour of methadone may be safe and effective.

Synthesis and expression of genes encoding putative insect neuropeptide precursors in tobacco

Neuropeptides are the key molecules in a multiplicity of physiological processes and their use in pest control has recently been suggested. Most neuropeptides are produced in the form of a precursor that is cleaved by proteolysis to yield various biologically active peptides. To mimic this structure, a method has been developed for synthesizing genes that code for putative polyneuropeptide precursors. As a model neuropeptide, the 5-amino-acid proctolin, one of the best studied invertebrate neuropeptides, functioning both as a visceral and a skeletal neuromuscular transmitter, was chosen. The synthetic gene was introduced into bacteria and tobacco plants, where it was efficiently transcribed. We present our results as a possible approach for the expression, in a variety of organisms, of synthetic genes coding for a wide repertoire of insect neuropeptides.

[Classification systems for the clinical approach to pervasive developmental disorders]

This paper compares four systems for the classification of pervasive developmental disorders: DSM-III-R, ICD-10, the French classification of mental disorders in children and adolescents and Manzano and Palacio-Espasa's operational classification. Five children were examined according to a protocol which included clinical and instrumental examination, the BSE scale, a development scale and a psychodynamic observation recorded by video camera. A detailed discussion of the diagnosis of one of the cases is reported as an example, while a synthetic description is given of the other four. The comparison highlights the characteristics of the four systems considered. The differing theoretical premises which inspire them mean that it is important to use all four in the clinical investigation of each case: DSM-III-R and ICD-10 can be used for the initial screening, whilst the other two can be used to classify more specifically all the forms of infantile psychosis.

Some unknown episodes in the history of population dynamics concerning the logistic law: the lesson of the great epidemiologists

The author discusses the work of "the two great epidemiologists R. Ross and A. G. McKendrick. This talk is basically devoted to their 'lesson' about logistic theory and it is organised as follows: section 2 is devoted to McKendrick's [1911] contribution to the growth of microorganism populations, a paper which was not widely acclaimed, but which marks the first experimental laboratory verification of the logistic law. Section 3 is also devoted to McKendrick and to the way he repeatedly derived the logistic equation as a model for 'simple epidemics'. Finally, in section 4, we present Ross's 'A priori pathometry' theory that really emphasizes...the role played by the logistic law as the 'first principle' of the mathematical epidemiology."

[Logistic effects in the two-sex model with "harmonic mean" fertility function]

"In the present paper the effects of the presence of logistic terms in [a] two-sex random mating model with 'harmonic mean' fertility function are discussed. The behaviour of the model is studied by means of a phase plane analysis. It [is] possible to show the existence, under quite natural conditions, of one (and only one) meaningful equilibrium point that is globally stable. This equilibrium is the final result of an adjustment process [and includes an]...initial period during which it is possible to observe a preliminary balancing process of the sex composition...." (SUMMARY IN ENG)