Modeling airway persistent infection of Moraxella catarrhalis and nontypeable Haemophilus influenzae by using human in vitro models.

Non-typeable Haemophilus influenzae (NTHi) and Moraxella catarrhalis (Mcat) are two common respiratory tract pathogens often associated with acute exacerbations in Chronic Obstructive Pulmonary Disease (COPD) as well as with otitis media (OM) in children. Although there is evidence that these pathogens can adopt persistence mechanisms such as biofilm formation, the precise means through which they contribute to disease severity and chronicity remains incompletely understood, posing challenges for their effective eradication. The identification of potential vaccine candidates frequently entails the characterization of the host-pathogen interplay in vitro even though this approach is limited by the fact that conventional models do not permit long term bacterial infections. In the present work, by using air-liquid-interface (ALI) human airway in vitro models, we aimed to recreate COPD-related persistent bacterial infections. In particular, we explored an alternative use of the ALI system consisting in the assembly of an inverted epithelium grown on the basal part of a transwell membrane with the aim to enable the functionality of natural defense mechanisms such as mucociliary clearance and cellular extrusion that are usually hampered during conventional ALI infection experiments. The inversion of the epithelium did not affect tissue differentiation and considerably delayed NTHi or Mcat infection progression, allowing one to monitor host-pathogen interactions for up to three weeks. Notably, the use of these models, coupled with confocal and transmission electron microscopy, revealed unique features associated with NTHi and Mcat infection, highlighting persistence strategies including the formation of intracellular bacterial communities (IBCs) and surface-associated biofilm-like structures. Overall, this study demonstrates the possibility to perform long term host-pathogen investigations in vitro with the aim to define persistence mechanisms adopted by respiratory pathogens and individuate potential new vaccine targets.

Genomic characterization of Moraxella bovis and Moraxella bovoculi Uruguayan strains isolated from calves with infectious bovine keratoconjunctivitis.

Infectious bovine keratoconjunctivitis (IBK) is an ocular disease that affects bovines and has significant economic and health effects worldwide. Gram negative bacteria Moraxella bovis and Moraxella bovoculi are its main etiological agents. Antimicrobial therapy against IBK is often difficult in beef and dairy herds and, although vaccines are commercially available, their efficacy is variable and dependent on local strains. The aim of this study was to analyze for the first time the genomes of Uruguayan clinical isolates of M. bovis and M. bovoculi. The genomes were de novo assembled and annotated; the genetic basis of fimbrial synthesis was analyzed and virulence factors were identified. A 94% coverage in the reference genomes of both species, and more than 80% similarity to the reference genomes were observed. The mechanism of fimbrial phase variation in M. bovis was detected, and the tfpQ orientation of these genes confirmed, in an inversion region of approximately 2.18kb. No phase variation was determined in the fimbrial gene of M. bovoculi. When virulence factors were compared between strains, it was observed that fimbrial genes have 36.2% sequence similarity. In contrast, the TonB-dependent lactoferrin/transferrin receptor exhibited the highest percentage of amino acid similarity (97.7%) between strains, followed by cytotoxins MbxA/MbvA and the ferric uptake regulator. The role of these virulence factors in the pathogenesis of IBK and their potential as vaccine components should be explored.

Targeted next-generation sequencing assay to detect 3 Moraxella spp. directly from bovine ocular swabs.

Infectious bovine keratoconjunctivitis (IBK) is associated with 2 species of Moraxella: M. bovis and M. bovoculi. A third novel Moraxella spp., designated tentatively as M. oculi, has been identified from the eyes of cattle with and without pinkeye. These 3 Moraxella spp. can be found in various combinations within the same clinical sample, making speciation of this genus directly from a sample impossible with Sanger sequencing. Assessing Moraxella diversity found in IBK- and non-IBK-affected cattle eyes, independent of culture, may provide additional information about IBK by avoiding the selectivity bias of culturing. We developed a targeted NGS panel to detect and speciate these 3 Moraxella spp. directly from bovine ocular swabs. Our targeted panel amplifies bacterial essential genes and the 16S-23S ribosomal RNA intergenic spacer region (ITS) of the 3 Moraxella spp. and speciates based on these sequences. Our panel was able to differentiate the 3 species directly from DNA extracted from 13 swabs (6 from healthy animals, 7 from animals with IBK), and every swab except one (clinically healthy eye) had the 3 Moraxella spp. Targeted NGS with sequencing of Moraxella spp. housekeeping genes appears to be a suitable method for speciation of Moraxella directly from ocular swabs.

Investigation of the pathogens contributing to naturally occurring outbreaks of infectious bovine keratoconjunctivitis (pinkeye) using Next Generation Sequencing.

Infectious bovine keratoconjunctivitis (IBK), commonly known as pinkeye, has a marked negative impact on the economy of the cattle industry. Moraxella species, including Mor. bovis and Mor. bovoculi, which have been associated with this disease, colonize clinically healthy eyes as well, suggesting that there are intrinsic changes that may occur to the ocular microbiota or the involvement of additional unrecognized organisms that contribute to IBK. To evaluate this, 104 ocular swabs collected from eyes with IBK or clinically healthy eyes from 16 different cattle herds were subjected to 16 S rRNA gene PCR and next generation sequencing (NGS) analysis. Organisms detected were similar across the herds and there was no difference in the total number of bacterial groups detected among IBK cases and controls. However, the percentages of the different organisms detected varied between the two groups, including Moraxella spp., with more Moraxella spp. in eyes with IBK than controls. Further, using culture and whole genome NGS, a new species of Moraxella (suggested name Mor. oculobovii) was detected from the eyes of cattle from two farms. This strain is non-hemolytic on blood agar, is missing the RTX operon, and is likely a non-pathogenic strain of the bovine ocular microbiome. Alteration of the ocular microbiota composition may have a predisposing role, enhancing bacterial infection and the occurrence of clinical IBK. Future studies are required to evaluate if these changes are permanent or if there is a shift in the microbiome following recovery from the infection and how antibiotics might affect the microbiome.

Antibiofilm action using water-soluble tetra-cationic porphyrin and antibacterial photodynamic therapy against Moraxella spp. from cattle.

Infectious bovine keratoconjunctivitis (IBK) is the most important eye disease in ruminants worldwide. Moraxella bovis and Moraxella bovoculi can form biofilm and are frequently isolated from affected animals. Antimicrobials are used worldwide to treat clinical cases of IBK, although they have limited success in clearing the infection. Therefore, photodynamic therapy using porphyrins as photosensitizing molecules is an alternative method to eliminate microorganisms, including biofilms. We evaluated the antibacterial activity of a zinc(II) metalloporphyrin (ZnTMeP) against M. bovis and M. bovoculi biofilms since this compound can efficiently inactivate planktonic Moraxella spp. This study was carried out with two reference strains of Moraxella spp. (M. bovis: ATCC® 10900 and M. bovoculli: ATCC® BAA1259). The antibacterial activity of 4.0 µM of the ZnTMeP porphyrin was evaluated on forming and consolidate biofilms with three 30-min cycles of white-light exposure for three days. The ZnTMeP porphyrin reduced M. bovis and M. bovoculi biofilm formation. In addition, ZnTMeP partially destroyed consolidated M. bovoculi biofilms in the second white-light irradiation cycle, although the porphyrin had no effect against the consolidated biofilm of M. bovis. Despite the biofilm still not being completely inactivated, our findings are promising and encourage further experiments using the phototherapy protocol.

Antimicrobial efficacy of in vitro and ex vivo photodynamic therapy using porphyrins against Moraxella spp. isolated from bovine keratoconjunctivitis.

Infectious bovine keratoconjunctivitis (IBK) is an ocular disease affecting bovine herds worldwide, and it causes significant economic loss. The etiologic agent of IBK is considered to be Moraxella bovis, but M. ovis and M. bovoculi are frequently recovered of animals presenting clinical signs of IBK. The therapeutic measures available for its control have limited efficacy. Antimicrobial photodynamic therapy (aPDT) using porphyrins as photosensitizing molecules is an alternative method that can be used to reduce microbial growth. We evaluated the antibacterial activity of aPDT using two water-soluble tetra-cationic porphyrins (H2TMeP and ZnTMeP) against 22 clinical isolates and standard strains of Moraxella spp. in vitro and in an ex vivo model. For the in vitro assay, 4.0 µM of porphyrin was incubated with approximately 1.0 × 104 CFU/mL of each Moraxella sp. isolate and exposed to artificial light for 0, 2.5, 5, and 7.5 min. Next, 50 µL of this solution was plated and incubated for 24 h until CFU measurement. For the ex vivo assay, corneas excised from the eyeballs of slaughtered cattle were irrigated with Moraxella spp. culture, followed by the addition of zinc(II) porphyrin ZnTMeP (4.0 µM). The corneal samples were irradiated for 0, 7.5, and 30 min, followed by swab collection, plating, and CFU count. The results demonstrated the in vitro inactivation of the strains and clinical isolates of Moraxella spp. after 2.5 min of irradiation using ZnTMeP, reaching complete inactivation until 7.5 min. In the ex vivo experiment, the use of ZnTMeP resulted in the most significant reduction in bacterial concentration after 30 min of irradiation. These results encourage future in vivo experiments to investigate the role of metalloporphyrin ZnTMeP in the inactivation of Moraxella spp. isolates causing IBK.

Moraxella-dominated pediatric nasopharyngeal microbiota associate with upper respiratory infection and sinusitis.

BACKGROUND: Distinct bacterial upper airway microbiota structures have been described in pediatric populations, and relate to risk of respiratory viral infection and, exacerbations of asthma. We hypothesized that distinct nasopharyngeal (NP) microbiota structures exist in pediatric populations, relate to environmental exposures and modify risk of acute sinusitis or upper respiratory infection (URI) in children. METHODS: Bacterial 16S rRNA profiles from nasopharyngeal swabs (n = 354) collected longitudinally over a one-year period from 58 children, aged four to seven years, were analyzed and correlated with environmental variables, URI, and sinusitis outcomes. RESULTS: Variance in nasopharyngeal microbiota composition significantly related to clinical outcomes, participant characteristics and environmental exposures including dominant bacterial genus, season, daycare attendance and tobacco exposure. Four distinct nasopharyngeal microbiota structures (Cluster I-IV) were evident and differed with respect to URI and sinusitis outcomes. These clusters were characteristically either dominated by Moraxella with sparse underlying taxa (Cluster I), comprised of a non-dominated, diverse microbiota (Cluster II), dominated by Alloiococcus/Corynebacterium (Cluster III), or by Haemophilus (Cluster IV). Cluster I was associated with increased risk of URI and sinusitis (RR = 1.18, p = 0.046; RR = 1.25, p = 0.009, respectively) in the population studied. CONCLUSION: In a pediatric population, URI and sinusitis associate with the presence of Moraxella-dominated NP microbiota.

Composition of nasal bacterial community and its seasonal variation in health care workers stationed in a clinical research laboratory.

The microorganisms at the workplace contribute towards a large portion of the biodiversity a person encounters in his or her life. Health care professionals are often at risk due to their frontline nature of work. Competition and cooperation between nasal bacterial communities of individuals working in a health care setting have been shown to mediate pathogenic microbes. Therefore, we investigated the nasal bacterial community of 47 healthy individuals working in a clinical research laboratory in Kuwait. The taxonomic profiling and core microbiome analysis identified three pre-dominant genera as Corynebacterium (15.0%), Staphylococcus (10.3%) and, Moraxella (10.0%). All the bacterial genera exhibited seasonal variations in summer, winter, autumn and spring. SparCC correlation network analysis revealed positive and negative correlations among the classified genera. A rich set of 16 genera (q < 0.05) were significantly differentially abundant (LEfSe) across the four seasons. The highest species counts, richness and evenness (P < 0.005) were recorded in autumn. Community structure profiling indicated that the entire bacterial population followed a seasonal distribution (R2-0.371; P < 0.001). Other demographic factors such as age, gender and, ethnicity contributed minimally towards community clustering in a closed indoor laboratory setting. Intra-personal diversity also witnessed rich species variety (maximum 6.8 folds). Seasonal changes in the indoor working place in conjunction with the outdoor atmosphere seems to be important for the variations in the nasal bacterial communities of professionals working in a health care setting.

Component Causes of Infectious Bovine Keratoconjunctivitis - The Role of Moraxella Species in the Epidemiology of Infectious Bovine Keratoconjunctivitis.

Infectious bovine keratoconjunctivitis (IBK) involves multiple factors and opportunistic pathogens, including members of the genus Moraxella, specifically M bovis. The causal role of M bovis is clear, where the presence of virulence factors that facilitate colonization (pili) and host cytotoxicity (RTX toxins) are well characterized, and IBK has been reproduced in many models. Experimental infection with M bovoculi has failed to reproduce IBK-typical lesions in cattle thus far. However, recent work using genomics and mass spectrometry have found genomic diversity and recombination within these species, making species differentiation complex and challenging the ability to assign IBK causality to these organisms.

Applying Concepts of Causal Inference to Infectious Bovine Keratoconjunctivitis.

Establishing causation, otherwise known as causal assessment, is a difficult task, made more difficult by the variety of causal assessment frameworks available to consider. In this article, Bradford Hill viewpoints are used to discuss the evidence base for Moraxella bovis and Moraxella bovoculi being component causes of infectious bovine keratoconjunctivitis. Each of the nine Bradford Hill viewpoints are introduced and explained: strength, consistency, specificity, temporality, biologic gradient, plausibility, coherence, experiment, and analogy. Examples of how the viewpoints have been applied for other causal relations are provided, and then the evidence base for M bovis and M bovoculi is discussed.

Phloretin, an Apple Polyphenol, Inhibits Pathogen-Induced Mucin Overproduction.

SCOPE: Bacterial infection induces mucus overproduction, contributing to acute exacerbations and lung function decline in chronic respiratory diseases. A diet enriched in apples may provide protection from pulmonary disease development and progression. This study examined whether phloretin, an apple polyphenol, inhibits mucus synthesis and secretion induced by the predominant bacteria associated with chronic respiratory diseases. METHODS AND RESULTS: The expression of mucus constituent mucin 5AC (MUC5AC) in FVB/NJ mice and NCI-H292 epithelial cells is analyzed. Nontypeable Haemophilus influenzae (NTHi)-infected mice developed increased MUC5AC mRNA, which a diet containing phloretin inhibited. In NCI-H292 cells, NTHi, Moraxella catarrhalis, Streptococcus pneumoniae, and Pseudomonas aeruginosa increased MUC5AC mRNA, which phloretin inhibited. Phloretin also diminished NTHi-induced MUC5AC protein secretion. NTHi-induced increased MUC5AC required toll-like receptor 4 (TLR4) and NADH oxidase 4 (NOX4) signaling and subsequent activation of the epidermal growth factor receptor (EGFR)/mitogen-activated protein kinase (MAPK) pathway. Phloretin inhibited NTHi-induced TLR4/NOX4 and EGFR/MAPK signaling, thereby preventing increased MUC5AC mRNA. EGFR activation can also result from increased EGFR ligand synthesis and subsequent ligand activation by matrix metalloproteinases (MMPs). In NCI-H292 cells, NTHi increased EGFR ligand and MMP1 and MMP13 mRNA, which phloretin inhibited. CONCLUSIONS: In summary, phloretin is a promising therapeutic candidate for preventing bacterial-induced mucus overproduction.

Lymphocyte predominant Hodgkin lymphoma, antigen-driven after all?

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) was suggested as an entity separate from other types of Hodgkin lymphoma 40 years ago and recognized in the WHO classification in 2001. Based on its relatively benign course with late distant relapses, relation with lymph node hyperplasia with progressively transformed germinal centers, presence of clonal immunoglobulin gene rearrangements with somatic hypermutations and ongoing mutations, and relation with a number of inherited defects affecting the immune system, it has been suspected that NLPHL might be antigen-driven. Recent evidence has shown that cases of IgD-positive NLPHL are associated with infection by Moraxella catarrhalis, a common bacterium in the upper respiratory tract and in lymph nodes. This review summarizes the evidence for NLPHL as a B-cell lymphoma involving follicular T-lymphocytes normally found in germinal centers, its molecular features and relation to inherited immune defects, and its relation and differential diagnosis from similar entities. Finally, it discusses the evidence that in many cases a watch and wait policy might be a viable initial management strategy. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Moraxella keratitis: epidemiology and outcomes.

We aimed to assess the prevalence, risk factors, and visual outcome of Moraxella keratitis. We retrospectively reviewed the medical charts of patients diagnosed with Moraxella spp. keratitis at the Quinze-Vingts National Ophthalmology Hospital, Paris, France, between January 2016 and December 2018. Definitive microbiological identification was performed on archival strains using matrix-assisted laser desorption ionization time of flight coupled to mass spectrometry. One hundred one culture-proven cases of Moraxella keratitis were identified. The most common isolates were Moraxella lacunata (50%) and Moraxella nonliquefasciens (38%). Systemic predisposing factors, principally diabetes mellitus (13%) were identified in 28% of patients, and 87% of patients had ocular surface conditions, including blepharitis (25%), prior ocular surgery (21%), glaucoma (17%), exposure keratopathy (16%), and trauma (16%). Severely affected inpatients were treated empirically with fortified antibiotics including vancomycin, piperacillin, and gentamicin. The presence of hypopyon and being over the age of 60 years were associated with a poorer final visual acuity (p < 0.05). Adjuvant treatment, mostly amniotic membrane transplantation, was required for 31 eyes. The prognostic factors significantly associated with the need for adjuvant treatment were a larger infiltrate and hypoesthesia. The clinical features including ulcer healing, treatment duration, and infiltrate size were not different between Moraxella species. Keratitis caused by Moraxella spp. are rare in France but may threaten sight. The early identification of patients with a poor ocular surface, particularly those with neurotrophic keratopathy and anesthetic cornea, is crucial to prevent delayed healing of ulcers and the need for adjuvant treatment.

Queratitis bacteriana por Moraxella nonliquefaciens / Bacterial keratitis due to Moraxella nonliquefaciens

La queratitis bacteriana por Moraxella spp. puede producir importantes complicaciones, siendo la producida por la Moraxella nonliquefaciens(M. nonliquefaciens) la de peor pronóstico. Solo existen tres publicaciones de queratitis por M. nonliquefaciens. Presentamos el caso clínico de un hombre de 79 años, con queratopatía bullosa, recientemente afectado con queratitis infecciosa grave. En la exploración se observa infiltrado estromal denso, profundo y central con hifema. Tras la identificación en cultivo de M. nonliquefaciens y dada la progresión se modifica el tratamiento empírico, según antibiograma, a ciprofloxacino y ceftazidima tópicos, asociando ciprofloxacino y amoxicilina clavulánico orales. Tras 27 días se aprecia resolución total de la lesión con leucoma residual central. La queratitis infecciosa por M. nonliquefaciens es rara y se debe sospechar en pacientes mayores con factores locales predisponentes como daño corneal o cirugía ocular previa. Es importante un tratamiento precoz guiado por antibiograma y un seguimiento cercano para evitar complicaciones y mal cumplimiento

Moraxella keratitis can lead to important complications. Moraxella nonliquefaciens(M. nonliquefaciens) has the worst prognosis. Only three cases of corneal infections due to M. nonliquefaciens have been published. The case is presented of a 79-year-old man with bullous keratopathy, recently affected with severe infectious keratitis. Dense, deep, and central stromal infiltrates and hyphaema were detected. After the identification of M. nonliquefaciens in the culture, and given the progression of the condition, the initial empirical treatment was modified to topical ciprofloxacin and ceftazidime in accordance with the antibiogram, combining oral ciprofloxacin and amoxicillin-clavulanate. After 27 days, there was total resolution of the lesion, with central residual leucoma. Keratitis caused by M. nonliquefaciens is rare and must be suspected in elderly patients with local predisposing factors, such as corneal damage or previous eye surgery. Early antibiogram-guided treatment and close monitoring are important to avoid complications and poor compliance

Rapid differentiation of Moraxella bovoculi genotypes 1 and 2 using MALDI-TOF mass spectrometry profiles.

Moraxella bovoculi is the most frequently isolated bacteria from the eyes of cattle with Infectious Bovine Keratoconjunctivitis (IBK), also known as bovine pinkeye. Two distinct genotypes of M. bovoculi, genotype 1 and genotype 2, were characterized after whole genome sequencing showed a large degree of single nucleotide polymorphism (SNP) diversity within the species. To date, both genotypes have been isolated from the eyes of cattle without clinical signs of IBK while only genotype 1 strains have been isolated from the eyes of cattle with clinical signs of IBK. We used 38 known genotype 1 strains and 26 known genotype 2 strains to assess the ability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to accurately genotype M. bovoculi strains using mass spectrum biomarkers. Mass spectrum data was analyzed with ClinProTools 3.0 software and six models were developed that classify strain genotypes with accuracies ranging from 90.6% - 100%. Finally, using four of the most genotype-specific peaks that also exhibited high peak intensities from the six automated models, we developed a customized model (UNL assisted model) that had recognition capability, validation, and classification accuracies of 100% for genotype classification. Our results indicate that MALDI-TOF MS biomarkers can be used to accurately discriminate genotypes of M. bovoculi without the need for additional methods.

Bacterial keratitis due to Moraxella nonliquefaciens. / Queratitis bacteriana por Moraxella nonliquefaciens.

Moraxella keratitis can lead to important complications. Moraxella nonliquefaciens(M. nonliquefaciens) has the worst prognosis. Only three cases of corneal infections due to M. nonliquefaciens have been published. The case is presented of a 79-year-old man with bullous keratopathy, recently affected with severe infectious keratitis. Dense, deep, and central stromal infiltrates and hyphaema were detected. After the identification of M. nonliquefaciens in the culture, and given the progression of the condition, the initial empirical treatment was modified to topical ciprofloxacin and ceftazidime in accordance with the antibiogram, combining oral ciprofloxacin and amoxicillin-clavulanate. After 27 days, there was total resolution of the lesion, with central residual leucoma. Keratitis caused by M. nonliquefaciens is rare and must be suspected in elderly patients with local predisposing factors, such as corneal damage or previous eye surgery. Early antibiogram-guided treatment and close monitoring are important to avoid complications and poor compliance.

Co-carriage of Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis among three different age categories of children in Hungary.

BACKGROUND: The nasopharynx can from time to time accommodate otherwise pathogenic bacteria. This phenomenon is called asymptomatic carriage. However, in case of decreased immunity, viral infection or any other enhancing factors, severe disease can develop. Our aim in this study was to survey the nasal carriage rates of four important respiratory pathogens in three different age groups of children attending nurseries, day-care centres and primary schools. This is the first study from Hungary about the asymptomatic carriage of H. influenzae and M. catarrhalis. METHODS: Altogether 580 asymptomatic children were screened in three Hungarian cities. Samples were collected from both nostrils with cotton swabs. The identification was based on both colony morphology and species-specific PCRs. Serotyping was performed for S. pneumoniae, H. influenzae and M. catarrhalis. Antibiotic susceptibility was determined with agar dilution, according to the EUCAST guidelines. Clonality was examined by PFGE. RESULTS AND CONCLUSIONS: Whereas the carriage rates of S. pneumoniae, H. influenzae and M. catarrhalis clearly decreased with age, that of S. aureus showed an opposite tendency. Multiple carriage was least prevalent if S. aureus was one of the participants. The negative association between this bacterium and the others was statistically significant. For pneumococcus, the overall carriage rate was lower compared to earlier years, and PCV13 serotypes were present in only 6.2% of the children. The majority of H. influenzae isolates was non-typeable and no type b was detected; serotype A was dominant among M. catarrhalis. All four bacteria were more sensitive to antibiotics compared to clinical isolates. No MRSAs were detected, but we found three mupirocin resistant strains. The positive effect of Hib- and PCV-vaccination is undoubted. Continued surveillance of these pathogens is required.

Genotypic differences in CC224, CC363, CC449 and CC446 of Moraxella catarrhalis isolates based on whole genome SNP, MLST and PFGE typing.

Understanding the evolutionary path of M. catarrhalis from macrolide-susceptible to macrolide-resistant organism, is important for hindering macrolide resistance from propagation. Multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE) and whole genome SNP typing (WGST), as useful and practical typing tools, have both advantages and disadvantages. We studied the utility of these 3 typing methods, including the level of agreement, consistency and drawbacks, in characterizing M. catarrhalis clones and clonal complexes. We focused on four clonal complexes [CC224, CC363, CC449 (CCN10) and CC446 (CCN08)] and found that PFGE and WGST had a high level of agreement and a proper consistency of the same clone or very closely related clones, while MLST is less discriminatory for different clones. Furthermore, we also established an evolutionary distance cut-off value for "The same clone". Moreover, we detected macrolide-resistant M. catarrhalis in CC224, which had previously been considered as a macrolide-susceptible clonal complex. A higher number of isolates belonged to ST215 compared to ST446, implying that ST215 is more likely to be the primary founder. Our study also demonstrated that all the four clonal complexes belong to the M. catarrhalis lineage 1, which is considered to be related to increased virulence potential and serum resistance. We also observed that copB II was highly related to CC449 and LOS type B was mainly confined in CC224. In conclusion, these findings provide further insight into the evolutionary characteristics of M. catarrhalis.

The Moraxella catarrhalis phase-variable DNA methyltransferase ModM3 is an epigenetic regulator that affects bacterial survival in an in vivo model of otitis media.

BACKGROUND: Moraxella catarrhalis is a leading cause of otitis media (OM) and chronic obstructive pulmonary disease (COPD). M. catarrhalis contains a Type III DNA adenine methyltransferase (ModM) that is phase-variably expressed (i.e., its expression is subject to random, reversible ON/OFF switching). ModM has six target recognition domain alleles (modM1-6), and we have previously shown that modM2 is the predominant allele, while modM3 is associated with OM. Phase-variable DNA methyltransferases mediate epigenetic regulation and modulate pathogenesis in several bacteria. ModM2 of M. catarrhalis regulates the expression of a phasevarion containing genes important for colonization and infection. Here we describe the phase-variable expression of modM3, the ModM3 methylation site and the suite of genes regulated within the ModM3 phasevarion. RESULTS: Phase-variable expression of modM3, mediated by variation in length of a 5'-(CAAC)n-3' tetranucleotide repeat tract in the open reading frame was demonstrated in M. catarrhalis strain CCRI-195ME with GeneScan fragment length analysis and western immunoblot. We determined that ModM3 is an active N6-adenine methyltransferase that methylates the sequence 5'-ACm6ATC-3'. Methylation was detected at all 4446 5'-ACATC-3' sites in the genome when ModM3 is expressed. RNASeq analysis identified 31 genes that are differentially expressed between modM3 ON and OFF variants, including five genes that are involved in the response to oxidative and nitrosative stress, with potential roles in biofilm formation and survival in anaerobic environments. An in vivo chinchilla (Chinchilla lanigera) model of otitis media demonstrated that transbullar challenge with the modM3 OFF variant resulted in an increased middle ear bacterial load compared to a modM3 ON variant. In addition, co-infection experiments with NTHi and M. catarrhalis modM3 ON or modM3 OFF variants revealed that phase variation of modM3 altered survival of NTHi in the middle ear during early and late stage infection. CONCLUSIONS: Phase variation of ModM3 epigenetically regulates the expression of a phasevarion containing multiple genes that are potentially important in the progression of otitis media.