A prospective study of isolation of Moraxella catarrhalis in a hospital during the winter months

Molecular epidemiology study of a nosocomial Moraxella catarrhalis outbreak in a neurological rehabilitation unit

BACKGROUND

Moraxella catarrhalis is a common agent causing upper and lower respiratory tract infections, particularly of ventilated patients. The bacteria are transmitted between humans by direct and indirect contacts. However, reports of nosocomial outbreaks by this pathogen are scarce.

AIM

To analyse M. catarrhalis strains isolated during an outbreak in a medical rehabilitation centre to reveal their clonal relationship and to elucidate potential transmission routes.

METHODS

Extensive environmental and medical staff sampling was performed. Phenotypic and genotypic analyses of 15 isolates were executed, including repetitive element palindromic polymerase chain reaction (repPCR) and whole-genome sequencing. Furthermore, an intensified hygiene regimen was installed.

FINDINGS

The clonal nature of nine patient isolates and a simultaneous presence of separate entities including a strain isolated from a physician during staff screening was confirmed. Although neither asymptomatic carriers among the staff persons nor outbreak strain-contaminated fomites were identified for a specific intervention, the outbreak ceased due to maximum general and specific hygiene precautions. Retrospective analysis showed the increasing prevalence of M. catarrhalis strains over a period of two years before the incidence. Since then and after returning to the regular hygiene regimen, only one patient with a phenotypically diverse M. catarrhalis isolate has been documented.

CONCLUSION

The first M. catarrhalis outbreak involving nine patients of a neurological and trauma rehabilitation centre was reported. Potential transmission pathways were discussed. Comprehensive outbreak analyses insinuated the extension of routine laboratory storage time for defined species.

The other siblings: respiratory infections caused by Moraxella catarrhalis and Haemophilus influenzae

Respiratory infections remain substantial causes of morbidity and mortality globally. In this paper, two substantial players in bacterial-associated respiratory disease are assessed as to their respective roles in children and adults and in the developed and developing world. Moraxella catarrhalis, although initially thought to be a nonpathogen, continues to emerge as a cause of upper respiratory disease in children and pneumonia in adults. No vaccine is currently available to prevent M. catarrhalis infection. Haemophilus influenzae type b, originally thought to be the cause of influenza, has now been limited epidemiologically in the developed world due to an effective immunization but it continues to be a major player in the developing world. Nonencapsulated strains of H. influenzae still remain as significant causes of respiratory infections in the developing world especially in exacerbation of chronic obstructive lung disease. Finally, and in brief, the spectrum of Brazilian purpuric fever due to a specific biotype of H. influenzae is discussed.

Molecular epidemiological study of Moraxella catarrhalis isolated from nosocomial respiratory infection patients in a community hospital in Japan

BACKGROUND

Moraxella catarrhalis, occasionally, plays the essential role in nosocomial respiratory infection (NRI). Few studies have reported the route by which this organism spreads in a nosocomial infection outbreak. We identified characteristics of the strains isolated from NRI and attempted to reveal the potential nosocomial transmission routes.

METHODS

A follow-up study has been performed in a Japanese community hospital between July 2002 and January 2003. M. catarrhalis clinical isolates were identified and beta-lactamase production test as well as the minimal inhibitory concentrations (MICs) have been examined. Pulsed-field gel electrophoresis (PFGE) and the multi locus sequence typing method (MLST) have been introduced as the effective "fingerprinting" methods.

RESULTS

A total of 29 strains were isolated from 17 participants; 7 independent DNA fragment patterns were detected by PFGE. Pattern B (defined in this study) was dominant, and was detected both in strains from a health care worker (HCW) and inpatients. In the 9 selected strains analyzed by MLST, 7 unique MLST types were identified, which showed the congruence with the results of PFGE results.

CONCLUSION

Epidemiological analysis proved the transmission route from patient to patient, and suggested that more studies should be focused on identifying the possible transmission route between HCWs and inpatients.

Nosocomial transmission clusters and risk factors inMoraxella catarrhalis

We report an objective examination of nosocomial transmission events derived from long-term (10-year) data from a single medical centre. Cluster analysis, based on the temporal proximity of genetically identical isolates of the respiratory pathogenMoraxella catarrhalis, identified 40 transmission events involving 33 of the 52 genotypes represented by multiple isolates. There was no evidence of highly transmissible or outbreak-prone genotypes. Although most clusters were small (mean size 3·6 isolates) and of short duration (median duration 25 days), clustering accounted for 38·7% of all isolates. Significant risk factors for clustering were multi-bed wards, and winter and spring season, but bacterial antibiotic resistance, manifested as the ability to produce a β-lactamase was not a risk factor. The use of cluster analysis to identify transmission events and its application to long-term data demonstrate an approach to pathogen transmission that should find wide application beyond hospital populations.

Possible relationship of PFGE patterns of Moraxella catarrhalis between hospital- and community-acquired respiratory infections in a community hospital

We describe a prospective study of molecular analysis of Moraxella catarrhalis isolated from a community hospital. Our study was designed to investigate the possible relationship of pulsed-field gel electrophoresis (PFGE) patterns of M. catarrhalis between hospital- and community-acquired respiratory infections. A nosocomial outbreak of M. catarrhalis was observed between September 2000 and September 2001. During the study period, 40 strains of M. catarrhalis were isolated from a total of 32 patients with respiratory infections (26 strains from 18 inpatients, and 14 strains from 14 outpatients). We compared the PFGE patterns in 40 strains of M. catarrhalis isolated from the respiratory tract of the study patients. The genomic types of M. catarrhalis were classified into three PFGE patterns (A, B, and C). Interestingly, the nosocomial outbreak of M. catarrhalis included two patterns (A and B). Of the three patterns, two patterns (A and B) were found in both inpatients and outpatients. More interestingly, two subtypes of pattern B (B1 and B4) were simultaneously found in both inpatients and outpatients. Our results indicated that PFGE with SmaI chromosomal digestion is a suitable technique to establish the inter-strain genetic relatedness of M. catarrhalis, and suggested that the outbreak of M. catarrhalis occasionally included miscellaneous PFGE patterns. The results also showed that PFGE patterns of M. catarrhalis isolates were similar between hospital- and community-acquired respiratory infections. Analysis of the subtypes suggested that there might be some association between hospital- and community-acquired respiratory infections caused by M. catarrhalis.

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

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.

Gram-negative Diplococcal Respiratory Infections

Human respiratory tract infections caused by gram- negative diplococci continue to remain significant issues in health care. Although not addressed as frequently as the classical diplococcal pneumonia, the gram-positive Streptococcus pneumoniae (the pneumococcus), infections due to Neisseria meningitidis (the meningococcus), and Moraxella catarrhalis (formerly called both Neisseria catarrhalis and Branhamella catarrhalis) are addressed here including their microbiology, respiratory tract manifestations, antimicrobial treatment, and potential prevention with immunization.

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.

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.

Moraxella catarrhalis: clinical significance, antimicrobial susceptibility and BRO beta-lactamases

Moraxella catarrhalis is an important pathogen of humans. It is a common cause of respiratory infections, particularly otitis media in children and lower respiratory tract infections in the elderly. Colonisation of the upper respiratory tract appears to be associated with infection in many cases, although this association is not well understood. Nosocomial transmission is being increasingly documented and the emergence of this organism as a cause of bacteremia is of concern. The widespread production of a beta-lactamase enzyme renders Moraxella catarrhalis resistant to the penicillins. Cephalosporins and beta-lactamase inhibitor combinations are effective for treatment of beta-lactamase producers, and the organism remains nearly universally susceptible to the macrolides, fluoroquinolones, tetracyclines and the combination of trimethoprim and sulfamethoxazole. Two major beta-lactamase forms, BRO-1 and BRO-2, have been described on the basis of their isoelectric focusing patterns. The BRO-1 enzyme is found in the majority of beta-lactamase-producing isolates and confers a higher level of resistance to strains than BRO-2. The BRO enzymes are membrane associated and their production appears to be mediated by chromosomal determinants which are transmissible by an unknown mechanism. The origin of these novel proteins is unknown.

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.