Chlamydia trachomatis induces disassembly of the primary cilium to promote the intracellular infection.

Chlamydia trachomatis is a clinically important bacterium that infects epithelial cells of the genitourinary and respiratory tracts and the eye. These differentiated cells are in a quiescent growth state and have a surface organelle called a primary cilium, but the standard Chlamydia cell culture infection model uses cycling cells that lack primary cilia. To investigate if these differences are relevant, we performed infections with host cells that have a primary cilium. We found that C. trachomatis caused progressive loss of the primary cilium that was prevented by disrupting Aurora A (AurA), HDAC6 or calmodulin, which are components of the cellular cilia disassembly pathway. Stabilization of the primary cilium by targeting this pathway caused a large reduction in infectious progeny although there were no changes in chlamydial inclusion growth, chlamydial replication or the ultrastructural appearance of dividing and infectious forms (RBs and EBs, respectively). Thus, the presence of a primary cilium interfered with the production of infectious EBs at a late step in the developmental cycle. C. trachomatis infection also induced quiescent cells to re-enter the cell cycle, as detected by EdU incorporation in S-phase, and Chlamydia-induced cilia disassembly was necessary for cell cycle re-entry. This study therefore describes a novel host-pathogen interaction in which the primary cilium limits a productive Chlamydia infection, and the bacterium counteracts this host cell defense by activating the cellular cilia disassembly pathway.

Eucalyptol protects lungs against bacterial invasion through attenuating ciliated cell damage and suppressing MUC5AC expression.

This study was conducted to investigate whether eucalyptol plays a role in influencing bacterial growth in cigarette smoke-exposed lungs. Rats were exposed to air (control) and cigarette smoke (smoking) in the presence and absence of eucalyptol (260 mg/day). Morphological analysis of lung structures and status of airway mucous production were observed under microscope. Pathological changes of ciliated columnar epithelium in airways were examined using transmission electron microscopy. MUC5AC protein and messenger RNA (mRNA) expression in bronchoalveolar lavage fluid (BALF) and lungs were determined. Application of eucalyptol reduced pulmonary bullae formation and airway mucus overproduction in the smoke-exposed lungs. Treatment with eucalyptol attenuated ciliated cell damage in cigarette smoke-exposed lungs. Bacterial colonies of lungs were obviously lower in the eucalyptol-treated rats than that in the smoking rats (p < 0.01). Treatment with eucalyptol reduced the counts of bacterial colonization residing in the challenged lungs (p < 0.01). Application of eucalyptol not only decreased MUC5AC protein expression in BALF and tobacco-exposed lungs but also suppressed its mRNA expression in the lungs (all p < 0.05). Intervention of eucalyptol benefits elimination of bacterial organisms from tobacco-exposed lungs through attenuating ciliated cell damage and suppressing MUC5AC expression in the lungs.

Surface proteins mhp390 (P68) contributes to cilium adherence and mediates inflammation and apoptosis in Mycoplasma hyopneumoniae.

Mycoplasma hyopneumoniae is the causative agent of porcine enzootic pneumonia (EP) and responsible for major economic losses in global swine industry. After colonization of the respiratory epithelium, M. hyopneumoniae elicits a general mucociliary clearance loss, prolonged inflammatory response, host immunosuppression and secondary infections. Until now, the pathogenesis of M. hyopneumoniae is not completely elucidated. This present study explores the pathogenicity of mhp390 (P68, a membrane-associated lipoprotein) by elucidating its multiple functions. Microtitrer plate adherence assay demonstrated that mhp390 is a new cilia adhesin that plays an important role in binding to swine tracheal cilia. Notably, mhp390 could induce significant apoptosis of lymphocytes and monocytes from peripheral blood mononuclear cells (PBMCs), as well as primary alveolar macrophages (PAMs), which might weaken the host immune response. In addition, mhp390 contributes to the production of proinflammatory cytokines, at least partially, via the release of IL-1ß and TNF-α. To the best of our knowledge, this is the first report of the multiple functions of M. hyopneumoniae mhp390, which may supplement known virulence genes and further develop our understanding of the pathogenicity of M. hyopneumoniae.

Bordetella pseudohinzii targets cilia and impairs tracheal cilia-driven transport in naturally acquired infection in mice.

Several species of the Gram-negative genus Bordetella are the cause of respiratory infections in mammals and birds, including whooping cough (pertussis) in humans. Very recently, a novel atypical species, Bordetella pseudohinzii, was isolated from laboratory mice. These mice presented no obvious clinical symptoms but elevated numbers of neutrophils in bronchoalveolar lavage fluid and inflammatory signs in histopathology. We noted that this species can occur at high prevalence in a mouse facility despite regular pathogen testing according to the FELASA-recommendations. Affected C57BL/6 J mice had, in addition to the reported pulmonary alterations, tracheal inflammation with reduced numbers of ciliated cells, slower ciliary beat frequency, and largely (>50%) compromised cilia-driven particle transport speed on the mucosal surface, a primary innate defence mechanism. In an in vitro-model, Bordetella pseudohinzii attached to respiratory kinocilia, impaired ciliary function within 4 h and caused epithelial damage within 24 h. Regular testing for this ciliotropic Bordetella species and excluding it from colonies that provide mice for lung research shall be recommended. On the other hand, controlled colonization and infection with Bordetella pseudohinzii may serve as an experimental model to investigate mechanisms of mucociliary clearance and microbial strategies to escape from this primary innate defence response.

The presence of bacterial microcolonies on the maxillary sinus ciliary epithelium in healthy young individuals.

OBJECTIVE: The aim of this cross-sectional in vitro study was to evaluate the mucosal surfaces of healthy maxillary sinuses, explore different forms of bacterial microorganism colonies present on the mucous membrane, and determine a mucosal surface area they occupy. METHODS: Samples of the maxillary sinus mucosa were collected from 30 healthy patients (M = 11; F = 19). The material was obtained during the Le Fort I osteotomy performed during corrective jaw surgery. The morphological and morphometric analysis of sinus mucosa and bacterial film that was grown on it was performed using scanning electron microscopy (SEM) as well as imaging software. RESULTS: Scanning electron microscopy analysis showed the presence of different bacterium and bacteria-like structures in all the analyzed samples. In most cases, the bacterial film was mostly composed of diplococci-like and streptococci-like structures on the mucosa of the paranasal sinus. In any case, the mucous layer did not cover the whole lining of the evaluated sample. Each colony consists of more than 20 single bacterial cells, which has grown in aggregates. CONCLUSIONS: Under the conditions of normal homeostasis of the body, the maxillary sinuses present diverse bacterial colonization. The bacteria are dispersed or concentrated in single microcolonies of the biofilm on the border of the mucous covering the ciliary epithelium. There is no uniform layer of the biofilm covering the mucosa of the maxillary sinuses. Because the biofilm is detected on healthy individuals sinus mucosa, the clinical question if it may become pathogenic is unclear and require an explanation.

Stepwise metamorphosis of the tubeworm Hydroides elegans is mediated by a bacterial inducer and MAPK signaling.

Diverse animal taxa metamorphose between larval and juvenile phases in response to bacteria. Although bacteria-induced metamorphosis is widespread among metazoans, little is known about the molecular changes that occur in the animal upon stimulation by bacteria. Larvae of the tubeworm Hydroides elegans metamorphose in response to surface-bound Pseudoalteromonas luteoviolacea bacteria, producing ordered arrays of phage tail-like metamorphosis-associated contractile structures (MACs). Sequencing the Hydroides genome and transcripts during five developmental stages revealed that MACs induce the regulation of groups of genes important for tissue remodeling, innate immunity, and mitogen-activated protein kinase (MAPK) signaling. Using two MAC mutations that block P. luteoviolacea from inducing settlement or metamorphosis and three MAPK inhibitors, we established a sequence of bacteria-induced metamorphic events: MACs induce larval settlement; then, particular properties of MACs encoded by a specific locus in P. luteoviolacea initiate cilia loss and activate metamorphosis-associated transcription; finally, signaling through p38 and c-Jun N-terminal kinase (JNK) MAPK pathways alters gene expression and leads to morphological changes upon initiation of metamorphosis. Our results reveal that the intricate interaction between Hydroides and P. luteoviolacea can be dissected using genomic, genetic, and pharmacological tools. Hydroides' dependency on bacteria for metamorphosis highlights the importance of external stimuli to orchestrate animal development. The conservation of Hydroides genome content with distantly related deuterostomes (urchins, sea squirts, and humans) suggests that mechanisms of bacteria-induced metamorphosis in Hydroides may have conserved features in diverse animals. As a major biofouling agent, insight into the triggers of Hydroides metamorphosis might lead to practical strategies for fouling control.

Cilia-associated bacteria in fatal Bordetella bronchiseptica pneumonia of dogs and cats.

Bordetella bronchiseptica frequently causes nonfatal tracheobronchitis, but its role in fatal pneumonia is less recognized. Our study evaluated histologic identification of cilia-associated bacteria as a method for diagnosis of B. bronchiseptica pneumonia. Cases of fatal bronchopneumonia were studied retrospectively, excluding neonates and cases of aspiration pneumonia, minor lung lesions, or autolysis. The study population comprised 36 canine and 31 feline cases of bronchopneumonia. B. bronchiseptica was identified in 8 of 36 canine and 14 of 31 feline cases based on immunohistochemistry (IHC) using serum from a rabbit hyperimmunized with pertactin, PCR testing (Fla2/Fla12), and/or bacterial culture data when available. Of these, IHC was positive in 4 canine and 7 feline cases, PCR was positive in 8 canine and 14 feline cases, and B. bronchiseptica was isolated in 2 of 5 canine and 3 of 9 feline cases tested. Examination of histologic sections stained with hematoxylin and eosin revealed bronchial cilia-associated bacteria in 4 of 36 canine and 5 of 31 feline cases; these were all positive by IHC and PCR. The presence of cilia-associated bacteria had been noted in the pathology report for only 2 of these 9 cases. Thus, the presence of cilia-associated bacteria seems frequently overlooked by pathologists, but is a diagnostically significant feature of B. bronchiseptica pneumonia. A specific diagnosis of B. bronchiseptica pneumonia is important because it suggests primary or opportunistic bacterial pneumonia rather than aspiration pneumonia, and because of the risk of animal-to-animal transmission of B. bronchiseptica, the availability of vaccines for disease prevention, and the potential zoonotic risk to immunocompromised pet owners.

Relationships between the varied ciliated respiratory epithelium abnormalities and severity of Mycoplasma pneumoniae pneumonia.

BACKGROUND: The pathogenesis of Mycoplasma pneumoniae infection involves cytoadherence of M. pneumoniae to the ciliated respiratory epithelium (CRE), followed by CRE injury caused by the M. pneumoniae. However, whether CRE abnormalities are related to the severity of M. pneumoniae pneumonia (MP) remains to be determined. METHODS: Thirty-eight patients with MP and 8 controls who underwent fiber-optic bronchoscopy with bronchial biopsy were included in this study. Patients with MP were divided into 2 groups: a mild disease group (12 patients) and a severe disease group (26 patients). The clinical features, laboratory findings, chest radiographic findings, and CRE abnormalities were characterized. RESULTS: Patients with severe pneumonia had a higher epithelial integrity score than those with mild pneumonia (5.1 ± 0.76 vs 3.8 ± 0.75; p < 0.01). Patients with severe CRE abnormalities had a longer duration of fever (p < 0.01), higher C-reactive protein (p < 0.01), and lower proportion of blood lymphocytes (p < 0.05) compared to those with mild abnormalities. Patients with a positive bacteria culture had a higher epithelial integrity score compared to those with a negative culture (6.0 ± 0.44 vs 4.8 ± 0.71; p < 0.01). CONCLUSIONS: CRE abnormalities are closely related to the severity of MP. These findings extend our current knowledge of MP.

Methylglyoxal-augmented manuka honey as a topical anti-Staphylococcus aureus biofilm agent: safety and efficacy in an in vivo model.

BACKGROUND: Bacterial biofilms are thought to contribute to recalcitrance in chronic rhinosinusitis (CRS) patients. Manuka honey (MH) and its active component methylglyoxal (MGO) have demonstrated antibiofilm activity in vitro. This study evaluated the safety and efficacy of these agents in an in vivo model. METHODS: To assess safety, ovine frontal sinuses were flushed twice daily for 14 days. In each sheep, 1 sinus was flushed with a panel of MGO concentrations ranging from 0.5 to 7.2 mg/mL alone and flushed with a panel of with 16.5% wt/vol MH enriched with MGO at the same range of concentrations (0.5-7.2 mg/mL; designated MH/MGO). Contralateral sinuses were flushed with saline control. Tissue morphology was assessed histologically and with scanning electron microscopy. Efficacy was tested by developing Staphylococcus aureus biofilms in sheep sinuses. Twice-daily irrigation for 5 days was commenced with either saline, MGO (0.5-3.6 mg/mL) alone, or MH/MGO (with 0.5-3.6 mg/mL MGO). Biofilm biomass was compared between the groups (n = 4) using LIVE/DEAD BacLight staining and confocal scanning laser microscopy. RESULTS: The results of the safety assessment, for normal sinuses treated with MGO alone or with MH/MGO (≤1.8 mg/mL) showed normal pseudostratified epithelium and cilia structure; however, higher concentrations caused cilia denudation and squamous metaplasia. As for efficacy, when compared to saline flush, treatment with MH/MGO at 0.9 mg/mL (0.608 ± 0.110 vs 0.316 ± 0.197 µm(3) /µm(2) , respectively; p = 0.015) and 1.8 mg/mL (0.676 ± 0.079 vs 0.114 ± 0.033 µm(3) /µm(2) , respectively; p = 0.001) significantly reduced biofilm biomass. CONCLUSION: Sinus irrigation with MH/MGO at MGO concentrations between 0.9 and 1.8 mg/mL is both safe to mucosa and efficacious against S. aureus biofilm. MH/MGO irrigation could represent a viable treatment option for recalcitrant CRS.

The first engagement of partners in the Euprymna scolopes-Vibrio fischeri symbiosis is a two-step process initiated by a few environmental symbiont cells.

We studied the Euprymna scolopes-Vibrio fischeri symbiosis to characterize, in vivo and in real time, the transition between the bacterial partner's free-living and symbiotic life styles. Previous studies using high inocula demonstrated that environmental V. fischeri cells aggregate during a 3 h period in host-shed mucus along the light organ's superficial ciliated epithelia. Under lower inoculum conditions, similar to the levels of symbiont cells in the environment, this interaction induces haemocyte trafficking into these tissues. Here, in experiments simulating natural conditions, microscopy revealed that at 3 h following first exposure, only ∼ 5 V. fischeri cells aggregated on the organ surface. These cells associated with host cilia and induced haemocyte trafficking. Symbiont viability was essential and mutants defective in symbiosis initiation and/or production of certain surface features, including the Mam7 protein, which is implicated in host cell attachment of V. cholerae, associated normally with host cilia. Studies with exopolysaccharide mutants, which are defective in aggregation, suggest a two-step process of V. fischeri cell engagement: association with host cilia followed by aggregation, i.e. host cell-symbiont interaction with subsequent symbiont-symbiont cell interaction. Taken together, these data provide a new model of early partner engagement, a complex model of host-symbiont interaction with exquisite sensitivity.

The effect of antimicrobial photodynamic therapy on human ciliated respiratory mucosa.

BACKGROUND: Chronic recurrent sinusitis (CRS) is one of the most common chronic conditions in the United States. There is a significant subpopulation of CRS patients who remain resistant to cure despite rigorous treatment regimens including surgery, allergy therapy, and prolonged antibiotic therapy. Antimicrobial photodynamic therapy (aPDT) is a noninvasive nonantibiotic broad spectrum antimicrobial treatment. Our previous in vitro studies demonstrated that aPDT reduced CRS polymicrobial biofilm and planktonic bacteria and fungi by > 99.9% after a single treatment. Prior to human treatment however, aPDT treatment must be demonstrated to not result in histologic damage to the sinus ciliated respiratory epithelium. The objective of this study was to demonstrate the safety of aPDT treatment on a living human ciliated respiratory mucosal model (EpiAirway). METHODS: A study of aPDT treatment of EpiAirway was performed. Treatment groups included a nontreatment control, laser light alone, photosensitizer alone, and therapeutic photosensitizer and light combination (aPDT). At completion of treatment, the EpiAirway tissue was fixed in 10% formalin, paraffin-embedded, sectioned, H&E stained and mounted. All samples were blinded and microscopically examined by a human pathologist to assess any effect of aPDT on the tissue, cilia, or mucosal glands. The results were correlated with the treatment parameters. RESULTS: The EpiAirway histologic study demonstrated no histologic alteration of the respiratory cilia or mucosal epithelium in any of the treatment groups. CONCLUSIONS: aPDT is a safe treatment for CRS resulting in no histologic alteration of human ciliated respiratory mucosa as is found in the human sinuses.

[Micromorphological observation of bacterial biofilms on ciliated epithelia of chronic rhinosinusitis].

OBJECTIVE: To observe the micromorphological characteristic of bacterial biofilm on mucosa of chronic rhinosinusitis (CRS). METHOD: Mucosa samples of middle turbinate were obtained from 4 patients of CRS during ESS. The size of each sample was about 4 mm x 4 mm. The samples were fixed in 4% paraformaldehyde for 24 hours, then fixed in 1% osmium tetroxide for 2 hours, graded dehydration with ethanol, dried with carbon dioxide and sputter coated with gold. The ultrastructure of these samples was observed by scanning electron microscope. RESULT: Bacterial biofilms were found on samples in all 4 patients. The biofilms were mainly formed on the surface of cilia. The bacterial flagella and cilia were intertwined. The biofilms could be found in a lot kinds of bacterial infections or mixed infections which were caused by multiple bacteria and fungi. CONCLUSION: Bacterial biofilm could be formed on ciliated epithelia.

The lytic transglycosylases of Neisseria gonorrhoeae.

Neisseria gonorrhoeae encodes five lytic transglycosylases (LTs) in the core genome, and most gonococcal strains also carry the gonococcal genetic island that encodes one or two additional LTs. These peptidoglycan (PG)-degrading enzymes are required for a number of processes that are either involved in the normal growth of the bacteria or affect the pathogenesis and gene transfer aspects of this species that make N. gonorrhoeae highly inflammatory and highly genetically variable. Systematic mutagenesis determined that two LTs are involved in producing the 1,6-anhydro PG monomers that cause the death of ciliated cells in Fallopian tubes. Here, we review the information available on these enzymes and discuss their roles in bacterial growth, cell separation, autolysis, type IV secretion, and pathogenesis.

Regulation of murine sinonasal cilia function by microbial secreted factors.

BACKGROUND: Chronic rhinosinusitis is a multifactorial disease resulting in impaired mucociliary clearance. Recent literature suggests that different bacterial species are associated with varied disease severity. We examined the immediate effect of microbial secreted factors on sinonasal ciliary function. METHODS: Murine primary sinonasal cultures were established in an air-liquid interface (ALI). Bacterial supernatants were isolated from H. influenza, S. pneumoniae, S. aureus, and P. aeruginosa cultures, as well as co-cultures of H. influenza/S. pneumoniae and S. aureus/P. aeruginosa. Controlling for pH and osmolarity, supernatants were administered at 50% concentration to the apical surface of the ALI culture. Basal ciliary beat frequency (CBF) was recorded for 20 minutes, at 5-minute intervals. Control groups were treated with culture broth. At minimum, experiments were performed in triplicate. Stimulated CBF was recorded after mechanical stimulation via short bursts of pressurized air (55 mmHg). RESULTS: All supernatants reduced basal CBF. S. pneumoniae and P. aeruginosa caused significant reduction in CBF at all time points, with the largest decrease of -46.3 ± 1.6% (p < 0.001) for S. pneumoniae and -27.1 ± 2.8% (p < 0.001) for P. aeruginosa. S. aureus caused the basal CBF to decline by -33.0 ± 2.8% (p < 0.001) at 5 minutes, which reversed by 20 minutes. Overall, H. influenza yielded the least change in CBF (-20.0 ± 2.8%, p < 0.002). Co-cultures (H. influenza/S. pneumoniae and S. aureus/P. aeruginosa) resulted in delayed CBF reduction compared with monocultures. P. aeruginosa also blunted stimulated CBF (p < 0.02). CONCLUSION: Results demonstrated acute decreases in murine sinonasal CBF after exposure to bacterial supernatants. Moreover, P. aeruginosa resulted in diminished ciliary stimulation capacity.

Sequence TTKF ↓ QE defines the site of proteolytic cleavage in Mhp683 protein, a novel glycosaminoglycan and cilium adhesin of Mycoplasma hyopneumoniae.

Mycoplasma hyopneumoniae colonizes the ciliated respiratory epithelium of swine, disrupting mucociliary function and inducing chronic inflammation. P97 and P102 family members are major surface proteins of M. hyopneumoniae and play key roles in colonizing cilia via interactions with glycosaminoglycans and mucin. The p102 paralog, mhp683, and homologs in strains from different geographic origins encode a 135-kDa pre-protein (P135) that is cleaved into three fragments identified here as P45(683), P48(683), and P50(683). A peptide sequence (TTKF↓QE) was identified surrounding both cleavage sites in Mhp683. N-terminal sequences of P48(683) and P50(683), determined by Edman degradation and mass spectrometry, confirmed cleavage after the phenylalanine residue. A similar proteolytic cleavage site was identified by mass spectrometry in another paralog of the P97/P102 family. Trypsin digestion and surface biotinylation studies showed that P45(683), P48(683), and P50(683) reside on the M. hyopneumoniae cell surface. Binding assays of recombinant proteins F1(683)-F5(683), spanning Mhp683, showed saturable and dose-dependent binding to biotinylated heparin that was inhibited by unlabeled heparin, fucoidan, and mucin. F1(683)-F5(683) also bound porcine epithelial cilia, and antisera to F2(683) and F5(683) significantly inhibited cilium binding by M. hyopneumoniae cells. These data suggest that P45(683), P48(683), and P50(683) each display cilium- and proteoglycan-binding sites. Mhp683 is the first characterized glycosaminoglycan-binding member of the P102 family.

Inherent differences in nasal and tracheal ciliary function in response to Pseudomonas aeruginosa challenge.

BACKGROUND: Sinonasal mucosal biofilms are recognized as contributors to the pathogenesis of chronic rhinosinusitis (CRS). Attachment of bacteria to the sinonasal surface is an initial step in biofilm formation. A critical defense against this occurrence is mucociliary clearance (MCC). To ascertain whether the ciliary component of MCC is uniform throughout the airway we compared ciliary beat frequency (CBF) in the murine nasal septum and trachea at baseline and after challenge with Pseudomonas aeruginosa, a common pathogen of CRS. METHODS: Murine septal and tracheal air-liquid interface cultures were evaluated for basal and stimulated CBF after exposure to control or conditioned media from Pseudomonas. Additionally, the attachment of Pseudomonas to nasal and tracheal cultures was assessed after pretreatment with control or conditioned media. RESULTS: Basal CBF is significantly slower in primary nasal airway cultures compared with tracheal airway cultures. Tracheal airway cultures show resistance to Pseudomonas secreted ciliotoxins not evident in nasal septal cultures. Furthermore, after challenge with viable Pseudomonas, significantly more bacteria attach to the nasal cultures compared with the tracheal cultures. CONCLUSION: Using primary murine nasal and tracheal airway cultures we show inherent differences in cilia function and increased susceptibility of the upper airway to attachment by Pseudomonas. Understanding the differences between upper and subglottic airway mucociliary clearance should lead to novel approaches in the management of upper airway infection.

Repeat regions R1 and R2 in the P97 paralogue Mhp271 of Mycoplasma hyopneumoniae bind heparin, fibronectin and porcine cilia.

Mycoplasma hyopneumoniae, the causative agent of porcine enzootic pneumonia, adheres to ciliated respiratory epithelia resulting in ciliostasis and epithelial cell death. The cilium adhesin P97 (Mhp183) contains two repeat regions, designated R1 and R2, that play key roles in adherence. Eight pentapeptide repeats in R1 are sufficient to bind porcine cilia; however, both R1 and R2 are needed to bind heparin. Mhp271, a paralogue of P97, is the only other M. hyopneumoniae protein to contain both R1 and R2 repeats. These repeats are arranged as a set of three pentapeptide repeats (designated R1A271), two decapeptide repeats (designated R2271), and a second set of six pentapeptide repeats (designated R1B271). To determine their function, recombinant proteins containing R1A271) (F1271) and R2271-R1B271 (F2271) were constructed and used in in vitro binding assays. F2271, but not F1271, bound heparin (K(D)=8.1 ± 0.4 nM), fibronectin (K(D)=174 ± 13 nM) and porcine cilia. Pre-incubation of F2271 with 100 µM heparin blocked cilium binding by ~69%. Cell surface shaving with trypsin combined with two-dimensional liquid chromatography coupled to tandem mass spectrometry analysis identified Mhp271 as surface-exposed. Our data suggest that both R1 and R2 in Mhp271 are involved in binding to host molecules.

The behaviour of both Listeria monocytogenes and rat ciliated ependymal cells is altered during their co-culture.

BACKGROUND: Ciliated ependymal cells line the cerebral ventricles and aqueducts separating the infected CSF from the brain parenchyma in meningitis. PRINCIPAL FINDINGS: Investigation of the interaction of Listeria monocytogenes with cultured rat brain ependymal cells showed that certain strains reduced the beat frequency of the cilia but all the strains studied significantly reduced the ciliary beat amplitude (the linear distance travelled by the tip of each cilium per beat cycle). CONCLUSION: The presence of the ependyma caused aggregation of some listeria strains and in some cases extracellular material also was seen in association with bacterial aggregates. These observations were dependent on the expression of genes required for invasion, intracellular survival and listerial cell to cell spread that are regulated by the transcriptional activator, positive regulatory factor A (PrfA).

Influenza virus infection decreases tracheal mucociliary velocity and clearance of Streptococcus pneumoniae.

Influenza virus infections increase susceptibility to secondary bacterial infections, such as pneumococcal pneumonia, resulting in increased morbidity and mortality. Influenza-induced tissue damage is hypothesized to increase susceptibility to Streptococcus pneumoniae infection by increasing adherence to the respiratory epithelium. Using a mouse model of influenza infection followed by S. pneumoniae infection, we found that an influenza infection does not increase the number of pneumococci initially present within the trachea, but does inhibit pneumococcal clearance by 2 hours after infection. To determine whether influenza damage increases pneumococcal adherence, we developed a novel murine tracheal explant system to determine influenza-induced tissue damage and subsequent pneumococcal adherence. Murine tracheas were kept viable ex vivo as shown by microscopic examination of ciliary beating and cellular morphology using continuous media flow for up to 8 days. Tracheas were infected with influenza virus for 0.5-5 days ex vivo, and influenza-induced tissue damage and the early stages of repair to the epithelium were assessed histologically. A prior influenza infection did not increase pneumococcal adherence, even when the basement membrane was maximally denuded or during the repopulation of the basement membrane with undifferentiated epithelial cells. We measured mucociliary clearance in vivo and found it was decreased in influenza-infected mice. Together, our results indicate that exposure of the tracheal basement membrane contributes minimally to pneumococcal adherence. Instead, an influenza infection results in decreased tracheal mucociliary velocity and initial clearance of pneumococci, leading to an increased pneumococcal burden as early as 2 hours after pneumococcal infection.