Epidemiological typing of Moraxella catarrhalis by using DNA probes

A comparison of molecular typing methods for Moraxella catarrhalis

AIMS

Three molecular typing techniques were examined to determine which method was the most discriminatory in order to perform epidemiological typing of Moraxella catarrhalis.

METHODS AND RESULTS

Twenty-five Mor. catarrhalis isolates obtained from nasopharyngeal aspirates collected from Aboriginal and non-Aboriginal children were subjected to random amplified polymorphic DNA (RAPD) analysis, automated ribotyping and pulsed field gel electrophoresis (PFGE). RAPD analysis determined two Mor. catarrhalis types, automated ribotyping with PstI determined four Mor. catarrhalis ribogroups and PFGE analysis with NotI determined 21 pulse field groups within the 25 isolates examined.

CONCLUSIONS

Analysis of discrimination index and typeability demonstrated that PFGE is the most discriminatory method for typing Mor. catarrhalis.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study confirms that PFGE is the most appropriate molecular tool for the epidemiological study of Mor. catarrhalis.

Total genome polymorphism and low frequency of intra-genomic variation in the uspA1 and uspA2 genes of Moraxella catarrhalis in otitis prone and non-prone children up to 2 years of age. Consequences for vaccine design?

Intra-genomic variation in the uspA1 and uspA2 genes of Moraxella catarrhalis was studied using pulsed field gel electrophoresis (PFGE) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. From a set of 91 M. catarrhalis isolates, 19 pairs of PFGE identical isolates were found. Five pairs originated from otitis non-prone children, 11 pairs from otitis prone children and for 3 pairs, one of the pair originated from an otitis prone and the other from an otitis non-prone child. No particular M. catarrhalis isolate was associated with either the otitis prone or non-prone children. One of these 19 pairs of isolates was found to exhibit both uspA1 and uspA2 intra-genomic variation, whilst another pair exhibited uspA2 intra-genomic variation only. Sequence data obtained from these variants showed that PCR-RFLP pattern differences reflected actual changes in predicted amino acid composition and that minor amino acid changes in a 23 base pair "NINNIY" repeat region (a conserved UspA1 and UspA2 binding site for the neutralising antibody mAb17C7) occurred. Variation in the uspA2 5' non-coding "AGAT" repeat region was also observed. These results may have implications for future M. catarrhalis vaccines comprising UspA1 or UspA2 components.

Moraxella catarrhalis: from emerging to established pathogen

Moraxella catarrhalis (formerly known as Branhamella catarrhalis) has emerged as a significant bacterial pathogen of humans over the past two decades. During this period, microbiological and molecular diagnostic techniques have been developed and improved for M. catarrhalis, allowing the adequate determination and taxonomic positioning of this pathogen. Over the same period, studies have revealed its involvement in respiratory (e.g., sinusitis, otitis media, bronchitis, and pneumonia) and ocular infections in children and in laryngitis, bronchitis, and pneumonia in adults. The development of (molecular) epidemiological tools has enabled the national and international distribution of M. catarrhalis strains to be established, and has allowed the monitoring of nosocomial infections and the dynamics of carriage. Indeed, such monitoring has revealed an increasing number of B-lactamase-positive M. catarrhalis isolates (now well above 90%), underscoring the pathogenic potential of this organism. Although a number of putative M. catarrhalis virulence factors have been identified and described in detail, their relationship to actual bacterial adhesion, invasion, complement resistance, etc. (and ultimately their role in infection and immunity), has been established in a only few cases. In the past 10 years, various animal models for the study of M. catarrhalis pathogenicity have been described, although not all of these models are equally suitable for the study of human infection. Techniques involving the molecular manipulation of M. catarrhalis genes and antigens are also advancing our knowledge of the host response to and pathogenesis of this bacterial species in humans, as well as providing insights into possible vaccine candidates. This review aims to outline our current knowledge of M. catarrhalis, an organism that has evolved from an emerging to a well-established human pathogen.

Bacterial infection in chronic obstructive pulmonary disease in 2000: a state-of-the-art review

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States. The precise role of bacterial infection in the course and pathogenesis of COPD has been a source of controversy for decades. Chronic bacterial colonization of the lower airways contributes to airway inflammation; more research is needed to test the hypothesis that this bacterial colonization accelerates the progressive decline in lung function seen in COPD (the vicious circle hypothesis). The course of COPD is characterized by intermittent exacerbations of the disease. Studies of samples obtained by bronchoscopy with the protected specimen brush, analysis of the human immune response with appropriate immunoassays, and antibiotic trials reveal that approximately half of exacerbations are caused by bacteria. Nontypeable Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae are the most common causes of exacerbations, while Chlamydia pneumoniae causes a small proportion. The role of Haemophilus parainfluenzae and gram-negative bacilli remains to be established. Recent progress in studies of the molecular mechanisms of pathogenesis of infection in the human respiratory tract and in vaccine development guided by such studies promises to lead to novel ways to treat and prevent bacterial infections in COPD.

Moraxella catarrhalis: a review of an important human mucosal pathogen

Moraxella catarrhalis has again been recognized as a significant pathogen. The past decade has witnessed an increased amount of research and understanding of the pathogenesis of the organism. This review will summarize the research pertaining to the epidemiology and components of pathogenesis in M. catarrhalis.

Complement-resistant Moraxella catarrhalis forms a genetically distinct lineage within the species

Moraxella catarrhalis is a bacterial species that has been implicated in 15-20% of all cases of otitis media in the USA and the complement-resistant variant of M. catarrhalis has been considered particularly pathogenic. A collection of geographically diverse, complement-sensitive (n=28) and -resistant strains (n=47) of M. catarrhalis was assembled in order to analyse the bacterial population structure. All strains were identified as M. catarrhalis by conventional microbiological and biochemical methods. Amplification of the small subunit (ssu) ribosomal RNA gene followed by restriction fragment length polymorphism (RFLP) analysis did not reveal consistent differences between serum-susceptible and -resistant M. catarrhalis isolates. Interestingly, upon automated ribotyping using the Qualicon RiboPrinter(R) microbial characterisation system, the complement-sensitive and -resistant strains segregated into two groups. This suggested the existence of two clearly distinguishable lineages within the species M. catarrhalis. This observation was corroborated by pulsed field gel electrophoresis (PFGE) of DNA macro-restriction fragments, a non-ribosomal PCR RFLP procedure and random amplification of polymorphic DNA (RAPD) analysis. All procedures grouped the two variants similarly. Redefinition of the taxonomic status of complement-resistant M. catarrhalis or even the definition of a new species may be opportune.

Comparison of randomly amplified polymorphic DNA analysis and pulsed-field gel electrophoresis for typing of Moraxella catarrhalis strains

Randomly amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE) for the analysis of 13 Moraxella catarrhalis isolates, 11 successive strains isolated from sputa of five children and 2 isolates obtained the same day from twins, were compared. RAPD and PFGE both yielded nine types from the 13 isolates, showing a chronic colonization with one strain in three patients and a successive colonization with different strains in two patients. The promising results obtained with RAPD should be confirmed with a larger number of strains, but RAPD seems as suitable as PFGE for the typing of M. catarrhalis.

Genetic diversity among strains of Moraxella catarrhalis: analysis using multiple DNA probes and a single-locus PCR-restriction fragment length polymorphism method

Moraxella (Branhamella) catarrhalis, a causative agent of otitis media, sinusitis, and exacerbation of bronchitis, has acquired widespread ability to produce beta-lactamase and can be nosocomially transmitted. The typing methods used in epidemiological analyses of M. catarrhalis are not optimal for genetic analyses. Two methods, a multiple-locus Southern blot (SB) method and a single-locus PCR-restriction fragment length polymorphism (RFLP) method, were developed and used to assess genetic diversity and potential clinical and geographic relationships in M. catarrhalis. Nine randomly cloned M. catarrhalis DNA fragments were used as probes of SBs containing DNA from 54 geographically and clinically diverse strains. For comparison, a PCR-RFLP method was developed as a quick, inexpensive, and discriminating alternative. A highly variable 3.7-kb genomic region (M46) was cloned and sequenced, and 3.5 kb of the cloned DNA was targeted for PCR amplification. DNAs from the 54 strains were subjected to PCR-RFLP. SB analysis distinguished all strains that had no apparent epidemiological linkage (40 of 54), and PCR-RFLP distinguished fewer strains (21 of 54). Epidemiologically linked strains appeared genetically identical by both methods. PCR-RFLP was compared to pulsed-field gel electrophoresis (PFGE) for 8 of the 54 strains and 23 additional strains. PCR-RFLP distinguished fewer strains than PFGE typing (16 of 31 versus 20 of 31 strains), but PCR-RFLP was more useful for inferring interstrain relatedness. Separate cluster analyses of multilocus SB and single locus PCR-RFLP data showed high genetic diversity within and across geographic locations and clinical presentations. The resultant dendrograms were not entirely concordant, but both methods often gave similar strain clusters at the terminal branches. High genetic diversity, nonconcordance of cluster analyses from different genetic loci, and shared genotypes among epidemiologically linked strains support a hypothesis of high recombination relative to spread of clones. Single-locus PCR-RFLP may be suitable for short-term epidemiological studies, but the SB data demonstrate that greater strain discrimination may be obtained by sampling variation at multiple genomic sites.

Branhamella catarrhalis: epidemiology, surface antigenic structure, and immune response

Over the past decade, Branhamella catarrhalis has emerged as an important human pathogen. The bacterium is a common cause of otitis media in children and of lower respiratory tract infections in adults with chronic obstructive pulmonary disease. B. catarrhalis is exclusively a human pathogen. It colonizes the respiratory tract of a small proportion of adults and a larger proportion of children. Studies involving restriction enzyme analysis of genomic DNA show that colonization is a dynamic process, with the human host eliminating and acquiring new strains frequently. The surface of B. catarrhalis contains outer membrane proteins, lipooligosaccharide, and pili. The genes which encode several outer membrane proteins have been cloned, and some of these proteins are being studied as potential vaccine antigens. Analysis of the immune response has been limited by the lack of an adequate animal model of B. catarrhalis infection. New information regarding outer membrane structure should guide studies of the human immune response to B. catarrhalis. Immunoassays which specifically detect antibodies to determinants exposed on the bacterial surface will elucidate the most relevant immune response. The recognition of B. catarrhalis as an important human pathogen has stimulated research on the epidemiology and surface structures of the bacterium. Future studies to understand the mechanisms of infection and to elucidate the human immune response to infection hold promise of developing new methods to treat and prevent infections caused by B. catarrhalis.

Moraxella (Branhamella) catarrhalis: restriction enzyme analysis typing with HinfI, HaeIII and PstI

Restriction enzyme analysis typing with HinfI, HaeIII and PstI was performed on Moraxella (Branhamella) catarrhalis strains consecutively collected from children suspected of respiratory tract infection and the type strain. Use of HinfI gave the most distinct patterns. Great polymorphism was seen among strains.

Epidemiological typing of Moraxella catarrhalis by pulsed field gel electrophoresis

Pulsed field gel electrophoresis (pfge) was used to compare 59 strains of Moraxella catarrhalis to evaluate pfge for the epidemiological typing of this organism. pfge-generated patterns were compared with those obtained by small fragment restriction enzyme analysis (rea) and species-specific probe hybridization. The strains used in the study were isolated from various geographic locations and included proven epidemiologically related strains. pfge yielded more unique patterns than dna-dna hybridization - 30 versus 18, respectively - but fewer than rea, which generated 45 unique patterns. Strains that demonstrated the same rea pattern or dna-dna hybridization pattern did not always demonstrate the same pfge pattern. For example, in 23 epidemiologically unrelated strains that shared six rea patterns, pfge differentiated the isolates into 12 patterns. Conversely, strains that demonstrated the same pfge pattern did not always demonstrate the same rea pattern or hybridization pattern. For example, in 42 strains that shared 13 pfge patterns, rea differentiated the isolates into 31 patterns and dna-dna hybridization differentiated them into 16 patterns. However, compared with rea, pfge yielded less complex patterns that were more easily comparable, and compared with dna-dna hybridization, pfge was technically easier.

Restriction fragment length polymorphism (RFLP) of genomic DNA of Moraxella (Branhamella) catarrhalis isolates in a hospital

Epidemiological typing, based on restriction fragment length polymorphism (RFLP) by pulsed-field gel electrophoresis (PFGE), was attempted for the 38 clinical isolates of Moraxella catarrhalis obtained at Shinshu University Hospital during the years 1987 and 1993. Digestion with SmaI or NotI generated well separable, 12 to 5 genomic DNA fragments ranging from 1,000 kb to 30 kb and the strains could be classified into 14 or 13 types, respectively. The electrophoretic profile differed with the strain in most of them and was hence useful to distinguish the each strain. Investigation for their RFLP have, however, suggested that majority of them, including the type strain ATCC25238, may have derived from a common ancestor.