Genotypic and Phenotypic Characteristics of Moraxella catarrhalis from Patients and Healthy Asymptomatic Participants among Preschool Children

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Abstract

(1) Background: M. catarrhalis can ascend into the middle ear, where it is a prevalent causative agent of otitis media in children, or enter the lower respiratory tract, where it is associated with community-acquired pneumonia (CAP). In this study, we aimed to provide an overview of the prevalence of M. catarrhalis in preschool children. (2) Methods: M. catarrhalis strains were isolated from samples. All isolates were characterized in terms of serotypes (STs), virulence genes, multilocus sequence type, and antibiotic susceptibility. (3) Results: The percentages of strains expressing lipooligosaccharides (LOSs), serotype A, B, C, or unknown were 67.61%, 15.71%, 4.28%, and 12.38%, respectively. Among the strains, 185 (88.10%) carried ompB2, 207 (98.57%) carried ompE, and 151 (71.90%) carried ompCD. The most frequently identified STs were ST449 (n = 13), ST64 (n = 11), and ST215 (n = 10). The resistance rates to the antibiotics cefuroxime, azithromycin, and erythromycin were 43.33%, 28.10%, and 39.05%, respectively. (4) Conclusions: High prevalence of some-specific ST types and high rates of antibiotic resistance indicate the necessity for an increased vigilance of resistant strains, a rational use of antibiotics in preschool children, and most importantly, the surveillance of healthy asymptomatic participants preschool children with M. catarrhalis. Our findings provide a platform for the development of novel M. catarrhalis vaccines.

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Moraxella catarrhalis, a human respiratory tract pathogen.

Timothy F Murphy, G Parameswaran (2009)

Moraxella catarrhalis is an exclusively human pathogen and is a common cause of otitis media in infants and children, causing 15%-20% of acute otitis media episodes. M. catarrhalis causes an estimated 2-4 million exacerbations of chronic obstructive pulmonary disease in adults annually in the United States. M. catarrhalis resembles commensal Neisseria species in culture and, thus, may be overlooked in samples from the human respiratory tract. The prevalence of colonization of the upper respiratory tract is high in infants and children but decreases substantially in adulthood. Most strains produce beta-lactamase and are thus resistant to ampicillin but susceptible to several classes of oral antimicrobial agents. Recent work has elucidated mechanisms of pathogenesis and focused on vaccine development to prevent otitis media in children and respiratory tract infections caused by M. catarrhalis in adults with chronic obstructive pulmonary disease.

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Nasopharyngeal carriage of Streptococcus pneumoniae and other bacteria in the 7th year after implementation of the pneumococcal conjugate vaccine in the Netherlands.

Astrid Bosch, Marlies van Houten, Jacob Bruin … (2016)

After introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in the infant national immunization program (NIP) in the Netherlands in 2006, Streptococcus pneumoniae strains of the non-vaccine serotype 19A emerged and became the dominant serotype in carriage in children and their parents. Similar patterns were observed in other European countries and the United States. Increases in carriage rates of Staphylococcus aureus and non-typeable (NT) Haemophilus influenzae were also observed. After switching of PCV7 to 10-valent vaccine (PCV10) in 2011, a new carriage surveillance study was performed in the winter of 2012/2013. Nasopharyngeal carriage of S. pneumoniae, H. influenzae, S. aureus, and Moraxella catarrhalis was determined by conventional culture in 330 PCV10-vaccinated 11-month-old children, 330 PCV7-vaccinated 24-month-old children, and their parents. Carriage prevalence was compared with similar carriage studies conducted in 2005, 2009, and 2010/2011. Although serotype 19A remained the most frequently carried pneumococcal serotype in children, prevalence of 19A significantly declined in PCV7-vaccinated 24-month-old children (14% to 8%, p=0.01), but less in PCV10-vaccinated 11-month-old children (12% to 9%, p=0.31). Carriage of H. influenzae remained stable at an elevated level (65% in 11-month-olds and 69% in 24-month-olds), while the carriage of S. aureus returned to pre-PCV7 levels in 11-month-old children (14% in 2010/2011 to 7% in 2012/2013), but not in 24-month-olds (remained at 7%). Our results might indicate a new balance between replacing non-vaccine pneumococcal serotypes and other potential pathogenic bacteria in nasopharyngeal carriage. Carriage studies are valuable tools in assessing vaccine effects on pathogens circulating in the population, for evaluation of PCV impact, and in predicting changes in respiratory and invasive disease.

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Molecular aspects of Moraxella catarrhalis pathogenesis.

C. Hays, Sandra de Kort, H. Bootsma … (2009)

In recent years, Moraxella catarrhalis has established its position as an important human mucosal pathogen, no longer being regarded as just a commensal bacterium. Further, current research in the field has led to a better understanding of the molecular mechanisms involved in M. catarrhalis pathogenesis, including mechanisms associated with cellular adherence, target cell invasion, modulation of the host's immune response, and metabolism. Additionally, in order to be successful in the host, M. catarrhalis has to be able to interact and compete with the commensal flora and overcome stressful environmental conditions, such as nutrient limitation. In this review, we provide a timely overview of the current understanding of the molecular mechanisms associated with M. catarrhalis virulence and pathogenesis.