Characterization of human invasive isolates of Listeria monocytogenes in Sweden 1986-2007

Since 1986, 68% of the Listeria monocytogenes isolates from human cases of invasive listeriosis in Sweden are available for retrospective studies. The aim of the present study was to characterize 601 human invasive isolates of L. monocytogenes in Sweden from 1986 to 2007 by using serotyping and pulsed-field gel electrophoresis. Since 1996, serovar 4b was permanently reduced to the second or third most common serovar in human cases in Sweden. During the latter period, 2000-2007, only 13% belonged to serovar 4b and 71% to 1/2a. The dendrogram, based on pulsovars, reveals two clusters with different serovars. Cluster 1 exhibits serovars 4b and 1/2b, whereas cluster 2 consists of serovar 1/2a. Serovar 1/2a seems to be more heterogeneous than serovar 4b.

Cloning, expression, purification, crystallization and preliminary X-ray analysis of the pilus-associated sortase C from Streptococcus pneumoniae

The pilus-associated sortase C from Streptococcus pneumoniae (SrtC or Srt-2) acts as a polymerase for the pilus subunit proteins RrgA and RrgB. Here, the crystallization and preliminary X-ray diffraction analysis of three crystal forms of SrtC are reported. One crystal form belongs to space group P2(1)2(1)2(1), with unit-cell parameters a = 48.9, b = 96.9, c = 98.9 A, alpha = beta = gamma = 90 degrees . The other two crystal forms belong to space group P222, with unit-cell parameters a = 48.8, b = 97.2, c = 99.2 A, alpha = beta = gamma = 90 degrees and a = 48.6, b = 96.5, c = 98.8 A, alpha = beta = gamma = 90 degrees , respectively. Preliminary analysis indicates the presence of two molecules in the asymmetric unit of the crystal for all three forms.

Sortase-mediated assembly and surface topology of adhesive pneumococcal pili

The rlrA genetic islet encodes an extracellular pilus in the Gram-positive pathogen Streptococcus pneumoniae. Of the three genes for structural subunits, rrgB encodes the major pilin, while rrgA and rrgC encode ancillary pilin subunits decorating the pilus shaft and tip. Deletion of all three pilus-associated sortase genes, srtB, srtC and srtD, completely prevents pilus biogenesis. Expression of srtB alone is sufficient to covalently associate RrgB subunits to one another as well as linking the RrgA adhesin and the RrgC subunit into the polymer. The active-site cysteine residue of SrtB (Cys 177) is crucial for incorporating RrgC, even when the two other sortase genes are expressed. SrtC is redundant to SrtB in permitting RrgB polymerization, and in linking RrgA to the RrgB filament, but SrtC is insufficient to incorporate RrgC. In contrast, expression of srtD alone fails to mediate RrgB polymerization, and a srtD mutant assembles heterotrimeric pilus indistinguishable from wild type. Topological studies demonstrate that pilus antigens are localized to symmetric foci at the cell surface in the presence of all three sortases. This symmetric focal presentation is abrogated in the absence of either srtB or srtD, while deletion of srtC had no effect. In addition, strains expressing srtB alone or srtC alone also displayed disrupted antigen localization, despite polymerizing subunits. Our data suggest that both SrtB and SrtC act as pilus subunit polymerases, with SrtB processing all three pilus subunit proteins, while SrtC only RrgB and RrgA. In contrast, SrtD does not act as a pilus subunit polymerase, but instead is required for wild-type focal presentation of the pilus at the cell surface.

Bacterial ligand of TLR2 signals Stat activation via induction of IRF1/2 and interferon-alpha production

Both type I interferons (IFNs) and interferon regulatory factors (IRFs) are well characterized in viral infections, whereas they are far less studied in bacterially activated toll-like receptor (TLR) pathways. Here, we studied the involvement of IRF1 and IRF2 in TLR2-mediated responses. In mouse macrophages, IRF2 was activated by lipoteichoic acid (LTA) of Staphylococcus aureus, resulting in up-regulation of IRF1 and rapid secretion of IFN-alpha. In addition, LTA-induced activation of Signal transducers and activators of transcription 1 (Stat1) and Stat3 via IRF2. The secretion of IFN-alpha was reduced in IRF2-silenced macrophages, resulting in a disappearance of tyrosine-phosphorylated Stat3 and a reduction of pro-inflammatory responses, despite induction of Mal adapter protein. These results provide a mechanistic insight into the pro-inflammatory responses against S. aureus LTA in mouse macrophages. IRFs can be intersecting factors of viral and bacterial responses in activated TLR signalling pathways.

Epidemiology of severe Streptococcus pyogenes disease in Europe

The past 2 decades have brought worrying increases in severe Streptococcus pyogenes diseases globally. To investigate and compare the epidemiological patterns of these diseases within Europe, data were collected through a European Union FP-5-funded program (Strep-EURO). Prospective population-based surveillance of severe S. pyogenes infection diagnosed during 2003 and 2004 was undertaken in 11 countries across Europe (Cyprus, the Czech Republic, Denmark, Finland, France, Germany, Greece, Italy, Romania, Sweden, and the United Kingdom) using a standardized case definition. A total of 5,522 cases were identified across the 11 countries during this period. Rates of reported infection varied, reaching 3/100,000 population in the northern European countries. Seasonal patterns of infection showed remarkable congruence between countries. The risk of infection was highest among the elderly, and rates were higher in males than in females in most countries. Skin lesions/wounds were the most common predisposing factor, reported in 25% of cases; 21% had no predisposing factors reported. Skin and soft tissue were the most common foci of infection, with 32% of patients having cellulitis and 8% necrotizing fasciitis. The overall 7-day case fatality rate was 19%; it was 44% among patients who developed streptococcal toxic shock syndrome. The findings from Strep-EURO confirm a high incidence of severe S. pyogenes disease in Europe. Furthermore, these results have identified targets for public health intervention, as well as raising awareness of severe S. pyogenes disease across Europe.

Streptococcus pneumoniae contains 3 rlrA pilus variants that are clonally related

BACKGROUND

Pilus components of Streptococcus pneumoniae encoded by rlrA were recently shown to elicit protection in an animal model of infection. Limited data are available on the prevalence of the rlrA operon in pneumococci; therefore, we investigated its distribution and its antigenic variation among disease-causing strains.

METHODS

The prevalence of rlrA and its association with serotype and genotype were evaluated in a global panel of 424 pneumococci isolates (including the 26 drug-resistant clones described by the Pneumococcal Molecular Epidemiology Network).

RESULTS

The rlrA islet was found in 130 isolates (30.6%) of the defined collection. Sequence alignment of 15 rlrA islets defined the presence of 3 clade types, with an overall homology of 88%-92%. The presence or absence of a pilus-encoding operon correlated with S. pneumoniae genotype (P < .001), as determined by multilocus sequence typing, and not with serotype. Further investigation identified a positive trend of rlrA occurrence among antimicrobial-resistant pneumococci.

CONCLUSIONS

On the basis of S. pneumoniae genotype, it is possible to predict the incidence of the rlrA pilus operon in a collection of pneumococcal isolates. This will facilitate the development of a protein vaccine.

Secreted enteric antimicrobial activity localises to the mucus surface layer

OBJECTIVES

The intestinal mucosa is constantly exposed to a dense and highly dynamic microbial flora and challenged by a variety of enteropathogenic bacteria. Antibacterial protection is provided in part by Paneth cell-derived antibacterial peptides such as the alpha-defensins. The mechanism of peptide-mediated antibacterial control and its functional importance for gut homeostasis has recently been appreciated in patients with Crohn's ileitis. In the present study, the spatial distribution of antimicrobial peptides was analysed within the small intestinal anatomical compartments such as the intestinal crypts, the overlaying mucus and the luminal content.

METHODS

Preparations from the different intestinal locations as well as whole mouse small intestine were extracted and separated by reversed-phase high-performance liquid chromatography. Antibacterial activity was determined in extracts, and the presence of antimicrobial peptides/proteins was confirmed by N-terminal sequencing, mass spectrometry analysis and immunodetection.

RESULTS

The secreted antibacterial activity was largely confined to the layer of mucus, whereas only minute amounts of activity were noted in the luminal content. The extractable activity originating from either crypt/mucus/lumen compartments respectively (given as a percentage) was for Listeria monocytogenes, 48 (4)/44 (4)/8 (8); Enterococcus faecalis, 44 (10)/49 (3)/7 (7); Bacterium megaterium, 56 (4)/42 (3)/2 (1); Streptococcus pyogenes, 48 (4)/46 (3)/6 (6); Escherichia coli, 46 (4)/47 (3)/7 (7); and Salmonella enterica sv. Typhimurium, 38 (3)/43 (7)/19 (10). A spectrum of antimicrobial peptides was identified in isolated mucus, which exhibited strong and contact-dependent antibacterial activity against both commensal and pathogenic bacteria.

CONCLUSION

These findings show that secreted antimicrobial peptides are retained by the surface-overlaying mucus and thereby provide a combined physical and antibacterial barrier to prevent bacterial attachment and invasion. This distribution facilitates high local peptide concentration on vulnerable mucosal surfaces, while still allowing the presence of an enteric microbiota.

ETosis: a novel cell death pathway

The formation of extracellular traps (ETs) by neutrophils and mast cells is an important mechanism in the innate immune response. These structures consist of a chromatin-DNA backbone with attached antimicrobial peptides and enzymes that trap and kill microbes. After stimulation of neutrophils and mast cells with phorbol esters, chemoattractant peptides, or chemokines, the generation of reactive oxygen species (ROS), such as hydrogen peroxide, by NAPDH [nicotinamide adenine dinucleotide phosphate (reduced form)] oxidase initiates a signaling cascade that leads to the disintegration of the nuclear and cellular membranes and the formation of ETs. This form of cell death is neither apoptotic nor necrotic, but whether it occurs because of the oxidation of phosphatases and kinases, as in other ROS-mediated signaling cascades, remains to be elucidated. These findings implicate "ETosis" as a novel cell death pathway in leukocytes.

Identification of heparin/heparan sulfate interacting protein as a major broad-spectrum antimicrobial protein in lung and small intestine

The lungs are continuously exposed to a broad array of microbes through inhalation, and microorganisms that escape clearance by the upper airway mucociliary motion will deposit in the alveolar compartment of the lower airways. The pulmonary epithelium in the alveolar compartment is covered by a thin aqueous layer that contains surfactant proteins but also microbicidal components. We have here identified the epithelial cell surface-expressed heparin/heparan sulfate interacting protein (HIP/RPL29) by high-performance liquid chromatography-fractionation, N-terminal sequencing, and mass spectrometry analysis as a major antimicrobial component in extracts of mouse lung tissue. HIP/RPL29 was also detected in extracts of mouse small intestinal tissue. HIP/RPL29 exhibited broad antibacterial activity, notably against Pseudomonas aeruginosa strains. Human recombinant HIP/RPL29 exhibited killing activity in the same order of magnitude. The HIP/RPL29 protein was demonstrated to be localized to the epithelial cells and cell surface of the lungs and intestines by immunohistochemistry. We suggest that HIP/RPL29 fulfills a function as an abundant antibacterial factor of the epithelial innate defense shield against invading bacteria in both the lungs and the small intestine.

Lysogenic transfer of group A Streptococcus superantigen gene among Streptococci

A group A Streptococcus (GAS) isolate, serotype M12, recovered from a patient with streptococcal toxic shock syndrome was analyzed for superantigen-carrying prophages, revealing phi149, which encodes superantigen SSA. Sequence analysis of the att-L proximal region of phi149 showed that the phage had a mosaic nature. Remarkably, we successfully obtained lysogenic conversion of GAS clinical isolates of various M serotypes (M1, M3, M5, M12, M19, M28, and M94), as well as of group C Streptococcus equisimilis (GCSE) clinical isolates, via transfer of a recombinant phage phi149::Km(r). Phage phi149::Km(r) from selected lysogenized GAS and GCSE strains could be transferred back to M12 GAS strains. Our data indicate that horizontal transfer of lysogenic phages among GAS can occur across the M-type barrier; these data also provide further support for the hypothesis that toxigenic conversion can occur via lysogeny between species. Streptococci might employ this mechanism specifically to allow more efficient adaptation to changing host challenges, potentially leading to fitter and more virulent clones.

Developmental switch of intestinal antimicrobial peptide expression

Paneth cell-derived enteric antimicrobial peptides provide protection from intestinal infection and maintenance of enteric homeostasis. Paneth cells, however, evolve only after the neonatal period, and the antimicrobial mechanisms that protect the newborn intestine are ill defined. Using quantitative reverse transcription-polymerase chain reaction, immunohistology, reverse-phase high-performance liquid chromatography, and mass spectrometry, we analyzed the antimicrobial repertoire in intestinal epithelial cells during postnatal development. Surprisingly, constitutive expression of the cathelin-related antimicrobial peptide (CRAMP) was observed, and the processed, antimicrobially active form was identified in neonatal epithelium. Peptide synthesis was limited to the first two weeks after birth and gradually disappeared with the onset of increased stem cell proliferation and epithelial cell migration along the crypt-villus axis. CRAMP conferred significant protection from intestinal bacterial growth of the newborn enteric pathogen Listeria monocytogenes. Thus, we describe the first example of a complete developmental switch in innate immune effector expression and anatomical distribution. Epithelial CRAMP expression might contribute to bacterial colonization and the establishment of gut homeostasis, and provide protection from enteric infection during the postnatal period.

Discovery of a novel class of highly conserved vaccine antigens using genomic scale antigenic fingerprinting of pneumococcus with human antibodies

Pneumococcus is one of the most important human pathogens that causes life-threatening invasive diseases, especially at the extremities of age. Capsular polysaccharides (CPSs) are known to induce protective antibodies; however, it is not feasible to develop CPS-based vaccines that cover all of the 90 disease-causing serotypes. We applied a genomic approach and described the antibody repertoire for pneumococcal proteins using display libraries expressing 15–150 amino acid fragments of the pathogen's proteome. Serum antibodies of exposed, but not infected, individuals and convalescing patients identified the ANTIGENome of pneumococcus consisting of ∼140 antigens, many of them surface exposed. Based on several in vitro assays, 18 novel candidates were preselected for animal studies, and 4 of them showed significant protection against lethal sepsis. Two lead vaccine candidates, protein required for cell wall separation of group B streptococcus (PcsB) and serine/threonine protein kinase (StkP), were found to be exceptionally conserved among clinical isolates (>99.5% identity) and cross-protective against four different serotypes in lethal sepsis and pneumonia models, and have important nonredundant functions in bacterial multiplication based on gene deletion studies. We describe for the first time opsonophagocytic killing activity for pneumococcal protein antigens. A vaccine containing PcsB and StkP is intended for the prevention of infections caused by all serotypes of pneumococcus in the elderly and in children.

RrgA is a pilus-associated adhesin in Streptococcus pneumoniae

Adherence to host cells is important in microbial colonization of a mucosal surface, and Streptococcus pneumoniae adherence was significantly enhanced by expression of an extracellular pilus composed of three subunits, RrgA, RrgB and RrgC. We sought to determine which subunit(s) confers adherence. Bacteria deficient in RrgA are significantly less adherent than wild-type organisms, while overexpression of RrgA enhances adherence. Recombinant monomeric RrgA binds to respiratory cells, as does RrgC with less affinity, and pre-incubation of epithelial cells with RrgA reduces adherence of wild-type piliated pneumococci. Non-adherent RrgA-negative, RrgB- and RrgC-positive organisms produce pili, suggesting that pilus-mediated adherence is due to expression of RrgA, rather than the pilus backbone itself. In contrast, RrgA-positive strains with disrupted rrgB and rrgC genes exhibit wild-type adherence despite failure to produce pili by Western blot or immunoelectron microscopy. The density of bacteria colonizing the upper respiratory tract of mice inoculated with piliated RrgA-negative pneumococci was significantly less compared with wild-type; in contrast, non-piliated pneumococci expressing non-polymeric RrgA had similar numbers of bacteria in the nasopharynx as piliated wild-type bacteria. These data suggest that RrgA is central in pilus-mediated adherence and disease, even in the absence of polymeric pilus production.

Clonal success of piliated penicillin nonsusceptible pneumococci

Antibiotic resistance in pneumococci is due to the spread of strains belonging to a limited number of clones. The Spain(9V)-3 clone of sequence type (ST)156 is one of the most successful clones with reduced susceptibility to penicillin [pneumococci nonsusceptible to penicillin (PNSP)]. In Sweden during 2000-2003, a dramatic increase in the number of PNSP isolates was observed. Molecular characterization of these isolates showed that a single clone of sequence type ST156 increased from 40% to 80% of all serotype 14, thus causing the serotype expansion. Additionally, during the same time period, we examined the clonal composition of two serotypes 9V and 19F: all 9V and 20% of 19F isolates belonged to the clonal cluster of ST156, and overall approximately 50% of all PNSP belonged to the ST156 clonal cluster. Moreover, microarray and PCR analysis showed that all ST156 isolates, irrespective of capsular type, carried the rlrA pilus islet. This islet was also found to be present in the penicillin-sensitive ST162 clone, which is believed to be the drug-susceptible ancestor of ST156. Competitive experiments between related ST156 serotype 19F strains confirmed that those containing the rlrA pilus islet were more successful in an animal model of carriage. We conclude that the pilus island is an important biological factor common to ST156 isolates and other successful PNSP clones. In Sweden, a country where the low antibiotic usage does not explain the spread of resistant strains, at least 70% of all PNSP isolates collected during year 2003 carried the pilus islet.

Role of the innate immune system in host defence against bacterial infections: focus on the Toll-like receptors

The innate immunity plays a critical role in host protection against pathogens and it relies amongst others on pattern recognition receptors such as the Toll-like receptors (TLRs) and the nucleotide-binding oligomerization domains proteins (NOD-like receptors, NLRs) to alert the immune system of the presence of invading bacteria. Since their recent discovery less than a decade ago, both TLRs and NLRs have been shown to be crucial in host protection against microbial infections but also in homeostasis of the colonizing microflora. They recognize specific microbial ligands and with the use of distinct adaptor molecules, they activate different signalling pathways that in turns trigger subsequent inflammatory and immune responses that allows a immediate response towards bacterial infections and the initiation of the long-lasting adaptive immunity. In this review, we will focus on the role of the TLRs against bacterial infections in humans in contrast to mice that have been used extensively in experimental models of infections and discuss their role in controlling normal flora or nonpathogenic bacteria. We also highlight how bacteria can evade recognition by TLRs.

Capsule and D-alanylated lipoteichoic acids protect Streptococcus pneumoniae against neutrophil extracellular traps

Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. Pneumococci can counteract the action of neutrophils with an antiphagocytic capsule and through electrochemical repulsion of antimicrobial peptides via addition of positive charge to the surface. Pneumococci are captured, but not killed in neutrophil extracellular traps (NETs). Here, we study the role of the polysaccharide capsule and lipoteichoic acid (LTA) modification on pneumococcal interaction with NETs. Expression of capsule (serotypes 1, 2, 4 and 9V) significantly reduced trapping by NETs, but was not required for resistance to NET-mediated killing. Pneumococci contain a dlt operon that mediates the incorporation of d-alanine residues into LTAs, thereby introducing positive charge. Genetic inactivation of dltA in non-encapsulated pneumococci rendered the organism sensitive to killing by antimicrobial components present in NETs. However, the encapsulated dltA mutant remained resistant to NET-mediated killing in vitro. Nevertheless, in a murine model of pneumococcal pneumonia, the encapsulated dltA-mutant strain was outcompeted by the wild-type upon invasion into the lungs and bloodstream. This suggests a non-redundant role for LTA alanylation in pneumococcal virulence at the early stage of invasive disease when capsule expression has been shown to be low.

International quality assurance study for characterization of Streptococcus pyogenes

Surveillance of group A streptococcal (GAS) infections was undertaken as a major component of the European Commission-funded project on severe GAS disease in Europe (strep-EURO). One aim of strep-EURO was to improve the quality of GAS characterization by standardization of methods. An external quality assurance study (EQA) was therefore carried out to evaluate current global performance. Eleven strep-EURO and seven other streptococcal reference centers received a panel of 20 coded GAS isolates for typing. Conventional phenotypic typing (based on cell surface T and M protein antigens and opacity factor [OF] production) and molecular methods (emm gene typing) were used either as single or combined approaches to GAS typing. T typing was performed by 16 centers; 12 centers found one or more of the 20 strains nontypeable (typeability, 89%), and 11 centers reported at least one incorrect result (concordance, 93%). The 10 centers that tested for OF production achieved 96% concordance. Limited availability of antisera resulted in poor typeability values from the four centers that performed phenotypic M typing (41%), three of which also performed anti-OF typing (typeability, 63%); however, concordance was high for both M (100%) and anti-OF (94%) typing. In contrast, the 15 centers that performed emm gene sequencing achieved excellent typeability (97%) and concordance (98%), although comparison of the performance between centers yielded typeability rates from 65 to 100% and concordance values from 83 to 100%. With the rapid expansion and use of molecular genotypic methods to characterize GAS, continuation of EQA is essential in order to achieve international standardization and comparison of type distributions.

Small molecule inhibitors of type III secretion inYersiniablock theChlamydia pneumoniaeinfection cycle

Intracellular parasitism by Chlamydiales is a complex process involving transmission of metabolically inactive particles that differentiate, replicate, and re-differentiate within the host cell. A type three secretion system (T3SS) has been implicated in this process. We have here identified small molecules of a chemical class of acylated hydrazones of salicylaldehydes that specifically blocks the T3SS of Chlamydia. These compounds also affect the developmental cycle showing that the T3SS has a pivotal role in the pathogenesis of Chlamydia. Our results suggest a previously unexplored avenue for development of novel anti-chlamydial drugs.

Neutrophil extracellular traps: casting the NET over pathogenesis

Neutrophil extracellular traps (NETs) are considered to be part of the human innate immunity because they trap and kill pathogens. NETs are formed by activated neutrophils and consist of a DNA backbone with embedded antimicrobial peptides and enzymes. They are involved in host defense during pneumococcal pneumonia, streptococcal necrotizing fasciitis, appendicitis and insemination. Recently, bacterial virulence factors that counteract NETs have been identified. These include the degradation of the NET-backbone by DNases enabling the liberation of bacteria from NETs, as well as capsule formation, which reduces bacterial trapping. Furthermore, pathogens can resist NET-mediated killing by adding positive charge to their cell surface.

The fallacies of hope: will we discover new antibiotics to combat pathogenic bacteria in time?

While newly developed technologies have revolutionized the classical approaches to combating infectious diseases, the difficulties associated with developing novel antimicrobials mean that these technologies have not yet been used to introduce new compounds into the market. The new technologies, including genomics and structural biology, open up exciting possibilities for the discovery of antibiotics. However, a substantial effort to pursue research, and moreover to incorporate the results into the production chain, is required in order to bring new antimicrobials to the final user. In the current scenario of emerging diseases and the rapid spread of antibiotic resistance, an active policy to support these requirements is vital. Otherwise, many valuable programmes may never be fully developed for lack of "interest" and funds (private and public). Will we react in time to avoid potential disaster?

Toll-like receptor 9 acts at an early stage in host defence against pneumococcal infection

Toll-like receptor 9 (TLR9) induces an inflammatory response by recognition of unmethylated CpG dinucleotides, mainly present in prokaryotic DNA. So far, TLR9-deficient mice have been shown to be more sensitive than wild-type mice to viral, but not to bacterial infections. Here, we show that mice deficient in TLR9 but not in TLR1, TLR2, TLR4 and TLR6 or IL-1R/IL-18R are more susceptible to a respiratory tract bacterial infection caused by Streptococcus pneumoniae. Intranasal challenge studies revealed that TLR9 plays a protective role in the lungs at an early stage of infection prior to the entry of circulating inflammatory cells. Alveolar as well as bone marrow-derived macrophages deficient in either TLR9 or the myeloid adaptor differentiation protein MyD88 were impaired in pneumococcal uptake and in pneumococcal killing. Our data suggest that in the airways, pneumococcal infection triggers a TLR9 and MyD88-dependent activation of phagocytic activity from resident macrophages leading to an early clearance of bacteria from the lower respiratory tract.

A small-molecule inhibitor of type III secretion inhibits different stages of the infectious cycle of Chlamydia trachomatis

The intracellular pathogen Chlamydia trachomatis possesses a type III secretion (TTS) system believed to deliver a series of effector proteins into the inclusion membrane (Inc-proteins) as well as into the host cytosol with perceived consequences for the pathogenicity of this common venereal pathogen. Recently, small molecules were shown to block the TTS system of Yersinia pseudotuberculosis. Here, we show that one of these compounds, INP0400, inhibits intracellular replication and infectivity of C. trachomatis at micromolar concentrations resulting in small inclusion bodies frequently containing only one or a few reticulate bodies (RBs). INP0400, at high concentration, given at the time of infection, partially blocked entry of elementary bodies into host cells. Early treatment inhibited the localization of the mammalian protein 14-3-3beta to the inclusions, indicative of absence of the early induced TTS effector IncG from the inclusion membrane. Treatment with INP0400 during chlamydial mid-cycle prevented secretion of the TTS effector IncA and homotypic vesicular fusions mediated by this protein. INP0400 given during the late phase resulted in the detachment of RBs from the inclusion membrane concomitant with an inhibition of RB to elementary body conversion causing a marked decrease in infectivity.

An endonuclease allows Streptococcus pneumoniae to escape from neutrophil extracellular traps

Streptococcus pneumoniae (pneumococcus) is the most common cause of community-acquired pneumonia, with high morbidity and mortality worldwide. A major feature of pneumococcal pneumonia is an abundant neutrophil infiltration . It was recently shown that activated neutrophils release neutrophil extracellular traps (NETs), which contain antimicrobial proteins bound to a DNA scaffold. NETs provide a high local concentration of antimicrobial components and bind, disarm, and kill microbes extracellularly. Here, we show that pneumococci are trapped but, unlike many other pathogens, not killed by NETs. NET trapping in the lungs, however, may allow the host to confine the infection, reducing the likelihood for the pathogen to spread into the bloodstream. DNases are expressed by many Gram-positive bacterial pathogens, but their role in virulence is not clear. Expression of a surface endonuclease encoded by endA is a common feature of many pneumococcal strains. We show that EndA allows pneumococci to degrade the DNA scaffold of NETs and escape. Furthermore, we demonstrate that escaping NETs promotes spreading of pneumococci from the upper airways to the lungs and from the lungs into the bloodstream during pneumonia.

Group A Streptococci from carriage and disease in Portugal: evolution of antimicrobial resistance and T antigenic types during 2000-2002

In this study, we analyzed the antimicrobial resistance properties and T antigenic types of 511 isolates collected in Lisbon district, Portugal, from throat swabs of healthy subjects (n=341), during 2000-2002 and from diverse infection sites (n=170) of outpatients and inpatients, during 1999-2002. Erythromycin resistance was higher in tonsillitis/pharyngitis (27.4%) and skin infection isolates (21.1%), than in carriage and invasive isolates (<or=10%). Differences in erythromycin resistance among children and adults were noticed only for carriage isolates (9.3% in children and 21.1% in adults). Most erythromycin-resistant isolates from carriage (82.4%) and tonsillitis/pharyngitis (71.9%) showed the M phenotype. All M phenotype isolates (n=53) carried mef(A), whereas all MLS(B) phenotype isolates (n=19) carried erm(B) and not erm(A). Resistance to tetracycline [mediated by tet(M) in most isolates] was <or=6% in tonsillitis/pharyngitis and carriage isolates, 36.8% in skin infection isolates, and 44.1% in invasive isolates. The M phenotype increased since 2000, linked to a decrease of tetracycline resistance, and was predominantly associated with T1 in 2000-2001 and T12 in 2002 among carriage isolates, and with T8/25/Imp19 through 2000-2002 among tonsillitis/pharyngitis isolates. The majority (53%) of the tetracycline-resistant invasive isolates were nontypable. All isolates were susceptible to penicillin and chloramphenicol. This study showed that tetracycline and macrolide resistance frequency and phenotypes differ among GAS from various origins and changed over time. Moreover, T typing suggested that most drug-resistant isolates causing oropharyngeal carriage are distinct from the majority of isolates causing noninvasive and invasive infection.