Lack of Effective Anti-Apoptotic Activities Restricts Growth of Parachlamydiaceae in Insect Cells

The fundamental role of programmed cell death in host defense is highlighted by the multitude of anti-apoptotic strategies evolved by various microbes, including the well-known obligate intracellular bacterial pathogens Chlamydia trachomatis and Chlamydia (Chlamydophila) pneumoniae. As inhibition of apoptosis is assumed to be essential for a successful infection of humans by these chlamydiae, we analyzed the anti-apoptotic capacity of close relatives that occur as symbionts of amoebae and might represent emerging pathogens. While Simkania negevensis was able to efficiently replicate within insect cells, which served as model for metazoan-derived host cells, the Parachlamydiaceae (Parachlamydia acanthamoebae and Protochlamydia amoebophila) displayed limited intracellular growth, yet these bacteria induced typical features of apoptotic cell death, including formation of apoptotic bodies, nuclear condensation, internucleosomal DNA fragmentation, and effector caspase activity. Induction of apoptosis was dependent on bacterial activity, but not bacterial de novo protein synthesis, and was detectable already at very early stages of infection. Experimental inhibition of host cell death greatly enhanced parachlamydial replication, suggesting that lack of potent anti-apoptotic activities in Parachlamydiaceae may represent an important factor compromising their ability to successfully infect non-protozoan hosts. These findings highlight the importance of the evolution of anti-apoptotic traits for the success of chlamydiae as pathogens of humans and animals

Mycoplasma pneumoniae infections, 11 countries in Europe and Israel, 2011 to 2016

Background: Mycoplasma pneumoniae is a leading cause of community-acquired pneumonia, with large epidemics previously described to occur every 4 to 7 years. Aim: To better understand the diagnostic methods used to detect M. pneumoniae; to better understand M. pneumoniae testing and surveillance in use; to identify epidemics; to determine detection number per age group, age demographics for positive detections, concurrence of epidemics and annual peaks across geographical areas; and to determine the effect of geographical location on the timing of epidemics. Methods: A questionnaire was sent in May 2016 to Mycoplasma experts with national or regional responsibility within the ESCMID Study Group for Mycoplasma and Chlamydia Infections in 17 countries across Europe and Israel, retrospectively requesting details on M. pneumoniae-positive samples from January 2011 to April 2016. The Moving Epidemic Method was used to determine epidemic periods and effect of country latitude across the countries for the five periods under investigation. Results: Representatives from 12 countries provided data on M. pneumoniae infections, accounting for 95,666 positive samples. Two laboratories initiated routine macrolide resistance testing since 2013. Between 2011 and 2016, three epidemics were identified: 2011/12, 2014/15 and 2015/16. The distribution of patient ages for M. pneumoniae-positive samples showed three patterns. During epidemic years, an association between country latitude and calendar week when epidemic periods began was noted. Conclusions: An association between epidemics and latitude was observed. Differences were noted in the age distribution of positive cases and detection methods used and practice. A lack of macrolide resistance monitoring was noted

Community-acquired pneumonia related to intracellular pathogens

Community-acquired pneumonia (CAP) is associated with high rates of morbidity and mortality worldwide; the annual incidence of CAP among adults in Europe has ranged from 1.5 to 1.7 per 1000 population. Intracellular bacteria are common causes of CAP. However, there is considerable variation in the reported incidence between countries and change over time. The intracellular pathogens that are well established as causes of pneumonia are Legionella pneumophila, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Chlamydophila psittaci, and Coxiella burnetii. Since it is known that antibiotic treatment for severe CAP is empiric and includes coverage of typical and atypical pathogens, microbiological diagnosis bears an important relationship to prognosis of pneumonia. Factors such as adequacy of initial antibiotic or early de-escalation of therapy are important variables associated with outcomes, especially in severe cases. Intracellular pathogens sometimes appear to cause more severe disease with respiratory failure and multisystem dysfunction associated with fatal outcomes. The clinical relevance of intracellular pathogens in severe CAP has not been specifically investigated. We review the prevalence, general characteristics, and outcomes of severe CAP cases caused by intracellular pathogens

Mécanismes génétiques de la résistance aux fluoroquinolones liée à la cible chez Mycoplasma hominis

*INRA. Centre de Recherches de Bordeaux. Laboratoire de Biologie Cellulaire et Moléculaire (FRA) Diffusion du document : INRA. Centre de Recherches de Bordeaux. Laboratoire de Biologie Cellulaire et Moléculaire (FRA) Diplôme : Dr. d'Universitéabsentabsen

Characterization of Mycoplasma hominis mutations involved in resistance to fluoroquinolones.

Fluoroquinolone-resistant mutants of Mycoplasma hominis were selected in vitro from the PG21 susceptible reference strain either by multistep selection on increasing concentrations of various fluoroquinolones or by one-step selection on agar medium with ofloxacin. The quinolone resistance-determining regions (QRDR) of the structural genes encoding the A and b subunits of DNA gyrase were amplified by PCR, and the nucleotide sequences of eight multistep-selected resistant strains were compared to those of susceptible strain PG21. Four high-level resistant mutants that were selected on norfloxacin or ofloxacin contained a C-to-T transition in the gyrA QRDR, leading to substitution of Ser-83 by Leu in the GyrA protein. Analysis of the sequence of the gyrB QRDR of the eight multistep-selected mutants did not reveal any difference compared to that of the gyrB QRDR of the reference strain M. hominis PG21. Similar analyses of eight one-step-selected mutants did not reveal any base change in the gyrA and gyrB QRDRs. These results suggest that in M. hominis, like in other bacterial species, a gyrA mutation at Ser-83 is associated with fluoroquinolone resistance

Cloning and nucleotide sequences of the Topoisomerase IV prC and prE genes of Mycoplasma hominis

International audienc

Résistance aux tétracyclines liée à la cible chez deux mycoplasmes humains (mycoplasma hominis et mycoplasma pneumoniae)

Chez les mycoplasmes humains, la résistance clinique acquise aux tétracyclines concerne uniquement les espèces du tractus urogénital, Ureaplasma spp. et Mycoplasma hominis. Cette résistance est associée à la présence du gène tet (M). Nous avons étudié l'autre mécanisme de résistance aux tétraclyclines, liée à la cible, les mutations de l' ARNr 16S chez M.hominis et M. pneumoniae. Les souches de mycoplasmes résistantes aux tétracyclines ont été obtenues par sélection en milieu liquide et en milieu solide en présence de concentrations subinhibitrices ou inhibitrices croissantes de doxycycline. Les gènes ARNr16S de ces souches ont été amplifiés et séquencés, puis comparés aux séquences des souches de référence M.hominis PG21 et M. pneumoniae FH. Pour M. hominis, 4 substitutions ont été identifiées dans le site primaire de fixation des tétracyclines au niveau des hélices H31 et H34 sur l'opéron rrnB. Les substituons A965T, G966T, et A967T (numérotation Escherichia coli)au niveau de l'hélice H31 et la substitution C1054T au niveau de l'hélice H31 et la substitution C1054T au niveau de l'hélice H34 sont associées à une augmentation significative des CMI des tétracyclines. Pour M. pneumoniae, les mutations de l'ARNr 16S de l'unique opéron concernent les nucléotides T968 et G1193 au niveau des hélices H31 et H34 respectivement. En résumé, nous avons décrit pour la première fois des souches de mycoplasmes humains résistantes aux tétracyclines par mutations de l'ARNr 16S au niveau du site de fixation des tétracyclines.BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF

Rôle immunomodulateur de Mycoplasma hominis sur les cellules dendritiques humaines

INTRODUCTION. Mycoplasma hominis peut être présent à l'état commensal mais aussi entraîner des infections génitales ou plus rarement extragénitales, et notamment articulaires. Le mécanisme par lequel M. hominis interagit avec le système immunitaire inné humain reste mal connu. L'objectif de cette étude était de préciser l'effet immunomodulateur de M. hominis pour déterminer l'orientation de la réponse immunitaire induite et la fraction bioactive de la bactérie en étudiant la souche de référence PG21 et plusieurs souches cliniques isolées de différentes pathologies. MATERIELS ET METHODES. Génération de cellules dendritiques à partir de monocytes humains, incubation avec M. hominis entier ou ses différentes fractions et identification des cytokines produites par ELISA. Identification du Toll-like récepteur (TLR) mis en jeu à l'aide d'anticorps anti-TLR. Extraction des différentes fractions de M. hominis par centrifugations différentielles et Triton X-114. Co-incubation des cellules dendritiques activées avec des lymphocytes T allogéniques. RESULTATS. M. hominis PG21 induit la production d'IL-23 par les cellules dendritiques humaines via TLR2. La fraction bioactive correspond aux lipoprotéines de membrane. La production de cytokines et le profil lipoprotéique varient suivant les souches cliniques. L'orientation de la réponse adaptative vers Th17 est en cours d'exploration. CONCLUSION. Crs données indiquent que l'IL-23 joue un rôle important dans la défense contre M. hominis. Ces résultats apportent un argument supplémentaire à l'étiologie infectieuse des poussées de maladies inflammatoires.BACKGROUND. The interactions of mycoplasmas with the human immune system have been studied for several species. However, little is known about the innate immune response to infections by Mycoplasma hominis. This human species is involved by gynæcological and neonate infections, but also in extragenital infections, like arthritis, more frequently in immunocompromised patients. The aim of this study was to identify te cytokine secretion profile of monocytes and dendritic cells (DCs) induced by M. hominis, the bioactive fraction of M. hominis and the pattern recognition receptor which interacts with it. Furthermore we would like to precise the T cell response skewing induced by the reference strain M. hominis PG21 and by the clinical strains isolated from different clinical pictures. METHODS. Microbiological methods culture of genital and extragenital mycoplasmal strains, cell fractionation of M. hominis (cytosol, membranes, and lipoproteins), and infection of human cells with the different mycoplasmal fractions. Immunological methods : Ficoll extraction of blood peripheral monocuclear cells, DC generation from monocytes isolated by magnetic separation, flow cytometry to phenotype the dendriic cells before and after mycoplasmal infection, ELISA measurement of cytokine production by infected cells, analysis of cytokine mRNA by RT-PCR, Toll-like receptor pathway identification by using anti-TLR antibodies, co-culture of T lymphocytes and M. hominis-infected CDs. RESULTS. The bioactive fraction of M. hominis was contained by membrane lipoproteins. It activated the human CDs and efficiently induced the exclusive produciohn of IL-23. This activation was the result of the TLR2 pathway signalling. The DCs activated by M. hominis were capable of involving a Th17 response from human T-lymphocytes. M. hominis sttrains isolated from different clinical situations induced different patterns of DCs activation and presented different lipoproteic profiles. CONCLUSION. These data indicate that IL-23 may participate in the protection against M. hominis. It might be a new argument in favour of the infectious hypothesis of inflammatory diseases.BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF