Hays, J.P.

Differential Virulence Gene Expression of Group A Streptococcus Serotype M3 in Response to Co-Culture with Moraxella catarrhalis (Article)

2013-04-23T00:00:00Z

Streptococcus pyogenes (group A Streptococcus, GAS) and Moraxella catarrhalis are important colonizers and (opportunistic) pathogens of the human respiratory tract. However, current knowledge regarding colonization and pathogenic potential of these two pathogens is based on work involving single bacterial species, even though the interplay between respiratory bacterial species is increasingly important in niche occupation and the development of disease. Therefore, to further define and understand polymicrobial species interactions, we investigated whether gene expression (and hence virulence potential) of GAS would be affected upon co-culture with M. catarrhalis. For co-culture experiments, GAS and M. catarrhalis were cultured in Todd-Hewitt broth supplemented with 0.2% yeast extract (THY) at 37°C with 5% CO2aeration. Each strain was grown in triplicate so that triplicate experiments could be performed. Bacterial RNA was isolated, cDNA synthesized, and microarray transcriptome expression analysis performed. We observed significantly increased (≥4-fold) expression for genes playing a role in GAS virulence such as hyaluronan synthase (hasA), streptococcal mitogenic exotoxin Z (smeZ) and IgG endopeptidase (ideS). In contrast, significantly decreased (≥4-fold) expression was observed in genes involved in energy metabolism and in 12 conserved GAS two-component regulatory systems. This study provides the first evidence that M. catarrhalis increases GAS virulence gene expression during co-culture, and again shows the importance of polymicrobial infections in directing bacterial virulence.

Highly specific protease-based approach for detection of porphyromonas gingivalis in diagnosis of periodontitis (Article)

2012-01-01T00:00:00Z

Porphyromonas gingivalis is associated with the development of periodontitis. Here we describe the development of a highly specific protease-based diagnostic method for the detection of P. gingivalis in gingival crevicular fluid. Screening of a proteolytic peptide substrate library, including fluorogenic dipeptides that contain D-amino acids, led to the discovery of five P. gingivalis-specific substrates. Due to the presence of lysine and arginine residues in these substrates, it was hypothesized that the cleavage was mediated by the gingipains, a group of P. gingivalis-specific proteases. This hypothesis was confirmed by the observation that P. gingivalis gingipain knockout strains demonstrated clearly impaired substrate cleavage efficacy. Further, proteolytic activity on the substrates was increased by the addition of the gingipain stimulators dithiothreitol and L-cysteine and decreased by the inhibitors leupeptin and N-ethylmaleimide. Screening of saliva and gingival crevicular fluid of periodontitis patients and healthy controls showed the potential of the substrates to diagnose the presence of P. gingivalis proteases. By using paper points, a sensitivity of approximately 105CFU/ml was achieved. P. gingivalis-reactive substrates fully composed of L-amino acids and Bz-L-Arg-NHPhNO2showed a relatively low specificity (44 to 85%). However, the five P. gingivalis-specific substrates that each contained a single D-amino acid showed high specificity (96 to 100%). This observation underlines the importance of the presence of D-amino acids in substrates used for the detection of bacterial proteases. We envisage that these substrates may improve the specificity of the current enzyme-based diagnosis of periodontitis associated with P. gingivalis. Copyright

Temporal development of the humoral immune response to surface antigens of Moraxella catarrhalis in young infants (Article)

2011-08-05T00:00:00Z

The primary Moraxella catarrhalis-specific humoral immune response, and its association with nasopharyngeal colonization, was studied in a cohort of infants from birth to 2 years of age.Results indicated that the levels of antigen-specific IgG, IgA and IgM showed extensive inter-individual variability over time, with IgM and IgA levels to all 9 recombinant domains, from 7 different OMPs, being relatively low throughout the study period. In contrast, the level of antigen-specific IgG was significantly higher for the recombinant domains Hag385-863, MID764-913, MID962-1200, UspA1557-704and UspA2165-318in cord blood compared to 6 months of age (P≤0.001). This was a most likely a consequence of maternal transmission of antigen-specific IgG to newborn babies, possibly indicating a future role for these 3 surface antigens in the development of an effective humoral immune response to M. catarrhalis. Finally, at 2 years of age, the levels of antigen-specific IgG still remained far below that obtained from cord blood samples, indicating that the immune response to M. catarrhalis has not matured at 2 years of age.We provide evidence that a humoral antibody response to OMPs UspA1, UspA2 and Hag/MID may play a role in the immune response to community acquired M. catarrhalis colonization events.

Antimicrobial resistance trends in blood culture positive Salmonella Typhi isolates from Pondicherry, India, 2005-2009 (Article)

2011-07-01T00:00:00Z

Clin Microbiol Infect Typhoid fever is caused by Salmonella enterica serovar Typhi, a major public health concern in developing countries. Recently, there has been an upsurge in the occurrence of bacterial isolates that are resistant to ciprofloxacin, and the emergence of broad spectrum β-lactamases in typhoidal salmonellae constitutes a new challenge for the clinician. A total of 337 blood culture isolates of S. Typhi, isolated from Pondicherry, India, between January 2005 and December 2009, were investigated using phenotypic, molecular and serological methods. Of the 337 isolates, 74 (22%) were found to be multidrug resistant (MDR) and 264 (78%) nalidixic acid resistant (NAR). Isolates with reduced susceptibility to ciprofloxacin possessed single mutations in the gyrA gene. A high rate of resistance (8%) was found to ciprofloxacin. All isolates with a ciprofloxacin MIC≥4mg/L possessed both double mutations in the QRDR of the gyrA gene and a single mutation in the parC gene. Active efflux pump mechanisms were also found to be involved in ciprofloxacin resistance. Finally, a large number of PFGE patterns (non-clonal genotypes) were observed among the S. Typhi isolates. In conclusion, a high rate of ciprofloxacin resistance was observed in comparison to other endemic areas in blood culture isolates of S. Typhi from Pondicherry, India, with steadily increasing NAR but decreasing MDR isolations over the study period. This is most likely to be due to an increased use of ciprofloxacin as a first-line drug of choice over more traditional antimicrobial agents for the treatment of typhoid fever. © 2011 The Authors. Clinical Microbiology and Infection

Comparative analysis and supragenome modeling of twelve Moraxella catarrhalis clinical isolates (Article)

2011-01-26T00:00:00Z

Background: M. catarrhalis is a gram-negative, gamma-proteobacterium and an opportunistic human pathogen associated with otitis media (OM) and exacerbations of chronic obstructive pulmonary disease (COPD). With direct and indirect costs for treating these conditions annually exceeding $33 billion in the United States alone, and nearly ubiquitous resistance to beta-lactam antibiotics among M. catarrhalis clinical isolates, a greater understanding of this pathogen's genome and its variability among isolates is needed.Results: The genomic sequences of ten geographically and phenotypically diverse clinical isolates of M. catarrhalis were determined and analyzed together with two publicly available genomes. These twelve genomes were subjected to detailed comparative and predictive analyses aimed at characterizing the supragenome and understanding the metabolic and pathogenic potential of this species. A total of 2383 gene clusters were identified, of which 1755 are core with the remaining 628 clusters unevenly distributed among the twelve isolates. These findings are consistent with the distributed genome hypothesis (DGH), which posits that the species genome possesses a far greater number of genes than any single isolate. Multiple and pair-wise whole genome alignments highlight limited chromosomal re-arrangement.Conclusions: M. catarrhalis gene content and chromosomal organization data, although supportive of the DGH, show modest overall genic diversity. These findings are in stark contrast with the reported heterogeneity of the species as a whole, as wells as to other bacterial pathogens mediating OM and COPD, providing important insight into M. catarrhalis pathogenesis that will aid in the development of novel therapeutic regimens.

Colonization of healthy children by Moraxella catarrhalis is characterized by genotype heterogeneity, virulence gene diversity and co-colonization with Haemophilus influenzae (Article)

2011-01-01T00:00:00Z

The colonization dynamics of Moraxella catarrhalis were studied in a population comprising 1079 healthy children living in Rotterdam, The Netherlands (the Generation R Focus cohort). A total of 2751 nasal swabs were obtained during four clinic visits timed to take place at 1.5, 6, 14 and 24 months of age, yielding a total of 709 M. catarrhalis and 621 Haemophilus influenzae isolates. Between January 2004 and December 2006, approximate but regular 6-monthly cycles of colonization were observed, with peak colonization incidences occurring in the autumn/winter for M. catarrhalis, and winter/spring for H. influenzae. Co-colonization was significantly more likely than single-species colonization with either M. catarrhalis or H. influenzae, with genotypic analysis revealing no clonality for co-colonizing or single colonizers of either bacterial species. This finding is especially relevant considering the recent discovery of the importance of H. influenzae-M. catarrhalis quorum sensing in biofilm formation and host clearance. Bacterial genotype heterogeneity was maintained over the 3-year period of the study, even within this relatively localized geographical region, and there was no association of genotypes with either season or year of isolation. Furthermore, chronological and genotypic diversity in three immunologically important M. catarrhalis virulence genes (uspA1, uspA2 and hag/mid) was also observed. This study indicates that genotypic variation is a key factor contributing to the success of M. catarrhalis colonization of healthy children in the first years of life. Furthermore, variation in immunologically relevant virulence genes within colonizing populations, and even within genotypically identical M. catarrhalis isolates, may be a result of immune evasion by this pathogen. Finally, the factors facilitating M. catarrhalis and H. influenzae co-colonization need to be further investigated.

Molecular characterization of antimicrobial resistance in non-typhoidal salmonellae associated with systemic manifestations from India (Article)

2010-12-01T00:00:00Z

Extended-spectrum cephalosporins and fluoroquinolones are essential antimicrobials for treating invasive salmonellosis, although emerging resistance to these antimicrobials is of growing concern, especially in India. Therefore, a study was conducted to characterize the antimicrobial susceptibility phenotypes, types of extended-spectrum β-lactamase (ESBL) gene plasmids and serological relationships of 21 non-typhoidal Salmonella isolates from patients who attended three different hospitals in India from 2006 to 2008. The isolates were cultured from stool, blood and cerebrospinal fluid samples obtained from patients presenting with diarrhoea and accompanying systemic manifestations such as fever, vomiting and meningism. Non-typhoidal Salmonella isolates were investigated using serotyping and antimicrobial susceptibility testing. PCR screening was also performed to detect the β-lactamase, qnr and aac(6′)-Ib-cr genes and class 1 integrons. Sequencing for quinolone resistance mutations and plasmid replicon typing were also performed. An antimicrobial resistance microarray was used for preliminary screening and identification of blaTEM and blaSHV genes, and phenotypic testing for the presence of efflux pumps was also performed. Ten out of 21 isolates (48 %) possessed the extended-spectrum cephalosporin resistance phenotype, with PCR amplification and sequencing revealing that isolates possessed TEM-1, SHV-12, DHA-1, OXA-1-like and CTX-M-15 ESBL genes. FII s plasmid replicons were detected in seven isolates (33 %). The involvement of efflux pumps was detected in four isolates (19 %) resistant to ciprofloxacin. It was concluded that SHV-12-carrying Salmonella serotype Agona may play an important role in ESBL-mediated resistance in non-typhoidal salmonellae in India. The very high percentage (48 %) of ESBL-producing non-typhoidal salmonellae isolated from these patients represents a real and immediate challenge to the effective antimicrobial therapy of Salmonella infections associated with systemic manifestations. Continued surveillance for the presence of ESBL-producing (non-typhoidal) salmonellae in India is essential.

Determinants of Moraxella catarrhalis colonization in healthy Dutch children during the first 14 months of life (Article)

2010-07-01T00:00:00Z

Moraxella catarrhalis is an established bacterial pathogen, previously thought to be an innocent commensal of the respiratory tract of children and adults. The objective of this study was to identify significant risk factors associated with M. catarrhalis colonization in the first year of life in healthy Dutch children. This study investigated a target cohort group of 1079 children forming part of the Generation R Study, a population-based prospective cohort study following children from fetal life until young adulthood, conducted in Rotterdam, The Netherlands. Nasopharyngeal swabs for M. catarrhalis culture were obtained at 1.5, 6 and 14 months of age, with all three swabs being available for analyses from 443 children. Data on risk factors possibly associated with M. catarrhalis colonization were obtained by questionnaire at 2, 6 and 12 months. M. catarrhalis colonization increased from 11.8% at age 1.5 months to 29.9% and 29.7% at 6 and 14 months, respectively. Two significantly important colonization risk factors were found: the presence of siblings and day-care attendance, which both increased the risk of being positive for M. catarrhalis colonization on two or more occasions within the first year of life. Colonization with M. catarrhalis was not associated with gender, educational level of the mother, maternal smoking, breast-feeding, or antibiotic use. Apparently, crowding is an important risk factor for early and frequent colonization with M. catarrhalis in the first year of life.

Genome analysis of Moraxella catarrhalis strain RH4, a human respiratory tract pathogen (Article)

2010-07-01T00:00:00Z

Moraxella catarrhalis is an emerging human-restricted respiratory tract pathogen that is a common cause of childhood otitis media and exacerbations of chronic obstructive pulmonary disease in adults. Here, we report the first completely assembled and annotated genome sequence of an isolate of M. catarrhalis, strain RH4, which originally was isolated from blood of an infected patient. The RH4 genome consists of 1,863,286 nucleotides that form 1,886 protein-encoding genes. Comparison of the RH4 genome to the ATCC 43617 contigs demonstrated that the gene content of both strains is highly conserved. In silico phylogenetic analyses based on both 16S rRNA and multilocus sequence typing revealed that RH4 belongs to the seroresistant lineage. We were able to identify almost the entire repertoire of known M. catarrhalis virulence factors and mapped the members of the biosynthetic pathways for lipooligosaccharide, peptidoglycan, and type IV pili. Reconstruction of the central metabolic pathways suggested that RH4 relies on fatty acid and acetate metabolism, as the genes encoding the enzymes required for the glyoxylate pathway, the tricarboxylic acid cycle, the gluconeogenic pathway, the nonoxidative branch of the pentose phosphate pathway, the beta-oxidation pathway of fatty acids, and acetate metabolism were present. Moreover, pathways important for survival under challenging in vivo conditions, such as the iron-acquisition pathways, nitrogen metabolism, and oxidative stress responses, were identified. Finally, we showed by microarray expression profiling that ∼88% of the predicted coding sequences are transcribed under in vitro conditions. Overall, these results provide a foundation for future research into the mechanisms of M. catarrhalis pathogenesis and vaccine development.

High prevalence of ST-78 infection-associated vancomycin-resistant Enterococcus faecium from hospitals in Asunción, Paraguay (Article)

2010-06-01T00:00:00Z

Forty infection-associated VanA-type vancomycin-resistant Enterococcus faecium (VRE) strains obtained from five collaborating hospitals in Asunción, Paraguay were investigated. Genotyping using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing revealed the presence of 17 cluster types and four STs, with 93% (37/40) of isolates comprising ST type 78. Other ST types included ST-132, ST-210 and one new ST type (ST-438). All but one isolate (ST-438) were associated with clonal complex 17 (CC17), and 97% of the total isolates carried the esp gene. Three Tn. 1546 variants were found, including a new lineage containing an IS. Efa5 insertion in an existing IS1251 element.

bro β-Lactamase and antibiotic resistances in a global cross-sectional study of Moraxella catarrhalis from children and adults (Article)

2009-11-04T00:00:00Z

Objectives: To compare and contrast the geographic and demographic distribution of bro β-lactamase and antibiotic MIC50/90for 1440 global Moraxella catarrhalis isolates obtained from children and adults between 2001 and 2002. Methods: One thousand four hundred and forty M. catarrhalis isolates originating from seven world regions were investigated. The isolates were recovered from 411 children <5 years of age and 1029 adults >20 years of age. PCR-restriction fragment length polymorphism (RFLP) was performed to determine bro prevalence and to distinguish between bro types. MIC values of 12 different antibiotics were determined using the CLSI (formerly NCCLS) broth microdilution method. Results: Of the 1440 isolates, 1313 (91%) possessed the bro-1 gene and 64 (4%) possessed the bro-2 gene. Additionally, the prevalence of bro positivity between the child and adult age groups was significantly different (P<0.0001), though bro-1 and bro-2 prevalences within age groups were not significantly different. Consistently higher β-lactam MICs were observed for M. catarrhalis isolates originating in the Far East. Significant correlations in MICs were observed for several antibiotic combinations, including all five β-lactams with each other, and among the two quinolones. Conclusions: The worldwide prevalence of bro gene carriage in clinical isolates of M. catarrhalis is now approaching 95%, with children significantly more likely to harbour bro-positive isolates than adults. Further, statistically significant differences in the distribution of β-lactam MICs were observed between different world regions, particularly with respect to the Far East.

The evaluation of putative endogenous control housekeeping genes for real-time polymerase chain reaction expression studies in Moraxella catarrhalis (Article)

2009-11-01T00:00:00Z

Comparisons of endogenous control genes in real-time polymerase chain reaction gene expression studies involving Moraxella catarrhalis are rare. This study shows that a combination of the iron sequestering gene copB and 16S rRNA genes would be useful for lineage 1 (16S rRNA type 1) isolates, but not lineage 2 (16S rRNA types 2 and 3) isolates.

Dominance of CTX-M-2 and CTX-M-56 among extended-spectrum β-lactamases produced by Klebsiella pneumoniae and escherichia coli isolated in hospitals in paraguay (Article)

2009-10-23T00:00:00Z

Molecular aspects of Moraxella catarrhalis pathogenesis (Article)

2009-09-01T00:00:00Z

Moraxella catarrhalis: A mini review (Article)

2009-08-14T00:00:00Z

Moraxella catarrhalis is a human-specific bacterium previously discounted as a simple commensal organism with only limited pathogenic potential. This view has changed considerably and we now know that M. catarrhalis is associated with a range of disease states affecting both children and adults. In particular, M. catarrhalis tends to be associated with upper respiratory tract infections, including otitis media and sinusitis in children and lower respiratory tract infections in adults with pre-existing pulmonary disease, e.g., exacerbations of chronic obstructive pulmonary disease. Colonization with this bacterium is especially common in infants and young children, the age group most affected by M. catarrhalis-mediated disease. Research is just beginning to unravel the complex interaction between this pathogen and the human host and is providing insights into its diverse genetic population structure and numerous virulence traits. These latter markers include multiple potential cellular adhesion molecules that are currently being researched as potential vaccine candidates. This mini-review is intended to provide the reader with a short introduction to M. catarrhalis as a pathogen and includes recent advances in the understanding of mechanisms associated with bacterial virulence.

Analysis of VanA vancomycin-resistant Enterococcus faecium isolates from Saudi Arabian hospitals reveals the presence of clonal cluster 17 and two new Tn 1546 lineage types (Article)

2008-08-01T00:00:00Z

Objectives; The aim of this study was to characterize 34 vancomycin-resistant VanA Enterococcus faecium isolates obtained from two hospitals in Saudi Arabia and to assess Tn 1546 variation within these isolates. Methods: PFGE and multilocus sequence typing (MLST) genotypes, antibiotic susceptibility patterns, the presence of enterococcal surface protein (esp) and hyaluronidase (hyl) genes and conjugation frequencies were determined. In addition, Tn 1546 elements were characterized. Results: PFGE and MLST analysis revealed the presence of 31 and 6 different genotypes, respectively. Further, three new ST types were discovered. Ninety-seven percent (33/34) of the isolates were associated with clonal complex 17 (CC17), with all isolates but one being resistant to ampicillin and all isolates being susceptible to linezolid. The esp and hyl genes were found in 44% (15/34) and 53% (18/34) of the isolates, respectively. Tn 1546 analysis revealed that the isolates belonged to five different groups, including two new lineages. The IS-element insertions described did not abolish the transfer of VanA resistance. Conclusions: VanA vancomycin-resistant E. faecium isolates obtained from Saudi Arabian hospitals include CC17 MLST types, a clonal cluster associated with E. faecium nosocomial infection worldwide. Novel E. faecium MLST types are circulating in Saudi Arabia, as well as novel Tn 1546 types. It seems likely that CC17 E. faecium isolates may be distributed throughout the Middle East as well as Europe, America, Africa and Australia.

Age-related genotypic and phenotypic differences in Moraxella catarrhalis isolates from children and adults presenting with respiratory disease in 2001-2002 (Article)

2008-04-01T00:00:00Z

Moraxella catarrhalis is generally associated with upper respiratory tract infections in children and lower respiratory tract infections in adults. However, little is known regarding the population biology of isolates infecting these two age groups. To address this, a population-screening strategy was employed to investigate 195 worldwide M. catarrhalis isolates cultured from children (<5 years of age) and adults (>20 years of age) presenting with respiratory disease in the years 2001-2002. Parameters compared included: genotype analysis; autoagglutination/biofilm-forming ability; serum resistance; uspA1, uspA2, uspA2H, hag and mcaP incidonce; cop/B/LOS/ompCD/16S rRNA types; and UspA1/Hag expression. A significant difference in biofilm formation (P=0.002), but not in autoagglutination or serum resistance, was observed, as well as significant differences in the incidence of uspA2- and uspA2H-positive isolates, and the distribution of lipooligosaccharide (LOS) types (P<0.0001 and P=0.01, respectively). Further, a significant decrease in the incidence of Hag expression (for isolates possessing the hag gene) was observed in adult isolates (P=0.001). Both uspA2H and LOS type B were associated with 16S rRNA type 1 isolates only, and two surtogate markers (copB and ompCD PCR RFLP types) for the two major M. catarrhalis 16S rRNA genetic lineages were identified. In conclusion, there are significant differences in phenotype and gene incidence between M. catarrhalis isolates from children and adults presenting with respiratory disease, possibly as a result of immune evasion in the adult age group. Our results should also be useful in the choice of effective vaccine candidates against M. catarrhalis.

High-throughput amplification fragment length polymorphism (htAFLP) analysis identifies genetic lineage markers but not complement phenotype-specific markers in Moraxella catarrhalis (Article)

2007-01-01T00:00:00Z

Comparative high-throughput amplified fragment length polymorphism (htAFLP) analysis was performed on a set of 25 complement-resistant and 23 complement-sensitive isolates of Moraxella catarrhalis in order to determine whether there were complement phenotype-specific markers within this species. The htAFLP analysis used 21 primer-pair combinations, generating 41364 individual fragments and 2273 fragment length polymorphisms, with an average of 862 polymorphisms per isolate. Analysis of polymorphism data clearly indicated the presence of two phylogenetic lineages and 40 (2%) lineage-specific polymorphisms. However, despite the presence of 361 (16%) statistically significant complement phenotype-associated polymorphisms, no single marker was 100% complement phenotype-specific. Furthermore, no complement phenotype-specific marker was found within different phylogenetic lineages. These findings agree with previous results indicating that the complement resistance phenotype within M. catarrhalis is probably defined by multiple genes, although not all of these genes may be present within all M. catarrhalis isolates.

Studies into the Genetic Diversity and Complement Resistance Phenotype of Moraxella catarrhalis (Doctoral Thesis)

2006-02-08T00:00:00Z

The aim of this thesis was to help define the contribution of Moraxella catarrhalis genetic diversity on the ability of the bacterium to colonise and cause infection in the human host, as well as to investigate novel genes/mechanisms associated with isolates exhibiting the complement resistance phenotype. In this respect, we show that M. catarrhalis is a genetically diverse organism in hospitalised children, with type-switching not leading to an increase in disease burden. Further, vaccination with a Streptococcus pneumoniae vaccine (an organism that shares the same biological niche as M. catarrhalis) does not affect M. catarrhalis diversity. Finally, genetically diverse isolates were found within otitis media-prone children, as well as a low frequency of intra-genomic variation in two complement resistance associated genes. With respect to genes/mechanisms associated with the complement phenotype, a novel major outer membrane protein of M. catarrhalis (OMP J) associated (but not conferring) complement resistance was identified and characterised. This protein existed in two major forms, was immunogenic, but was found not to be a suitable vaccine candidate. In a further study, both complement resistant and complement sensitive isolates of M. catarrhalis were found to be only weak activators of the mannose-binding lectin (MBL) pathway of complement activation (a useful survival strategy). Finally, a novel plasmid of M. catarrhalis is described named pEMCJH03 (and only the second plasmid to be identified within this species). This plasmid may be useful as a cloning and expression vector for putative M. catarrhalis virulence genes (including the testing of complement resistance-associated genes).

Identification and characterization of a novel outer membrane protein (OMPJ) of Moraxella catarrhalis that exists in two major forms. (Article)

2005-12-01T00:00:00Z

Moraxella catarrhalis is a common commensal of the human respiratory tract that has been associated with a number of disease states, including acute otitis media in children and exacerbations of chronic obstructive pulmonary disease in adults. During studies to investigate the outer membrane proteins of this bacterium, two novel major proteins, of approximately 19 kDa and 16 kDa (named OMP J1 and OMP J2, respectively), were identified. Further analysis indicated that these two proteins possessed almost identical gene sequences, apart from two insertion/deletion events in predicted external loops present within the putative barrel-like structure of the proteins. The development of a PCR screening strategy found a 100% (96/96) incidence for the genes encoding the OMP J1 and OMP J2 proteins within a set of geographically diverse M. catarrhalis isolates, as well as a significant association of OMP J1/OMP J2 with both the genetic lineage and the complement resistance phenotype (Fisher's exact test; P < 0.01). Experiments using two DeltaompJ2 mutants (one complement resistant and the other complement sensitive) indicated that both were less easily cleared from the lungs of mice than were their isogenic wild-type counterparts, with a significant difference in bacterial clearance being observed for the complement-resistant isolate but not for its isogenic DeltaompJ2 mutant (unpaired Student's t test; P < 0.001 and P = 0.32). In this publication, we characterize a novel outer membrane protein of Moraxella catarrhalis which exists in two variant forms associated with particular genetic lineages, and both forms are suggested to contribute to bacterial clearance from the lungs.

Changes in genetic types and population dynamics of Moraxella catarrhalis in hospitalized children are not associated with an exacerbation of existing disease (Article)

2003-01-01T00:00:00Z

Pulsed-field gel electrophoresis typing was performed on a retrospective set of 129 Moraxella catarrhalis isolates obtained over a 20 month period from 70 children admitted to, or presenting at, the Erasmus University Medical Center, Rotterdam, The Netherlands. The mean age of the children (at the end of the study) was 2.5 years, with a range of 6 months to 15 years. Fifty-one different M. catarrhalis types were isolated from the hospitalized children, with 31 % (22/70) being infected with two particularly prevalent M. catarrhalis types. These two prevalent types also exhibited different protein profiles. The majority (72%; 16/22) of the children infected with these two predominant types had spent at least 1 week on two paediatric intensive care wards. No exacerbation of existing disease or new disease was observed in children who experienced M. catarrhalis type changes.