Production of BRO beta-lactamases and resistance to complement in European Moraxella catarrhalis isolates

The burden of antibiotic resistance of the main microorganisms causing infections in humans - review of the literature

One of the biggest threats to human well-being and public health is antibiotic resistance. If allowed to spread unchecked, it might become a major health risk and trigger another pandemic. This proves the need to develop antibiotic resistance-related global health solutions that take into consideration microdata from various global locations. Establishing positive social norms, guiding individual and group behavioral habits that support global human health, and ultimately raising public awareness of the need for such action could all have a positive impact. Antibiotic resistance is not just a growing clinical concern but also complicates therapy, making adherence to current guidelines for managing antibiotic resistance extremely difficult. Numerous genetic components have been connected to the development of resistance; some of these components have intricate paths of transfer between microorganisms. Beyond this, the subject of antibiotic resistance is becoming increasingly significant in medical microbiology as new mechanisms underpinning its development are identified. In addition to genetic factors, behaviors such as misdiagnosis, exposure to broad-spectrum antibiotics, and delayed diagnosis contribute to the development of resistance. However, advancements in bioinformatics and DNA sequencing technology have completely transformed the diagnostic sector, enabling real-time identification of the components and causes of antibiotic resistance. This information is crucial for developing effective control and prevention strategies to counter the threat.

Moraxella Bacteremia in Cancer Patients

Moraxella is a gram-negative bacterium part of the Moraxellaceae family. It is a pathogen that is commonly found in the upper respiratory tract of humans. It is a rare cause of community-acquired pneumonia and can be found in immunocompromised individuals, especially those with impaired humoral immunity such as hypogammaglobulinemia and those with lung diseases.

We present three cases of Moraxella infections at the Moffitt Cancer Center between the years 2011 and 2017. We performed a literature review of Moraxella bacteremia in cancer patients and included three patients, two with a history of multiple myeloma and one undergoing radiation therapy for non-small cell lung carcinoma. None of the patients died as a result of the infection. Moraxella infections can result in a range of severity with increasing resistance to antibiotic therapy.

Characterization of antibiotic resistance and host-microbiome interactions in the human upper respiratory tract during influenza infection

BACKGROUND

The abundance and diversity of antibiotic resistance genes (ARGs) in the human respiratory microbiome remain poorly characterized. In the context of influenza virus infection, interactions between the virus, the host, and resident bacteria with pathogenic potential are known to complicate and worsen disease, resulting in coinfection and increased morbidity and mortality of infected individuals. When pathogenic bacteria acquire antibiotic resistance, they are more difficult to treat and of global health concern. Characterization of ARG expression in the upper respiratory tract could help better understand the role antibiotic resistance plays in the pathogenesis of influenza-associated bacterial secondary infection.

RESULTS

Thirty-seven individuals participating in the Household Influenza Transmission Study (HITS) in Managua, Nicaragua, were selected for this study. We performed metatranscriptomics and 16S rRNA gene sequencing analyses on nasal and throat swab samples, and host transcriptome profiling on blood samples. Individuals clustered into two groups based on their microbial gene expression profiles, with several microbial pathways enriched with genes differentially expressed between groups. We also analyzed antibiotic resistance gene expression and determined that approximately 25% of the sequence reads that corresponded to antibiotic resistance genes mapped to Streptococcus pneumoniae and Staphylococcus aureus. Following construction of an integrated network of ARG expression with host gene co-expression, we identified several host key regulators involved in the host response to influenza virus and bacterial infections, and host gene pathways associated with specific antibiotic resistance genes.

CONCLUSIONS

This study indicates the host response to influenza infection could indirectly affect antibiotic resistance gene expression in the respiratory tract by impacting the microbial community structure and overall microbial gene expression. Interactions between the host systemic responses to influenza infection and antibiotic resistance gene expression highlight the importance of viral-bacterial co-infection in acute respiratory infections like influenza. Video abstract.

Molecular Characterization of Fluoroquinolone-Resistant Moraxella catarrhalis Variants Generated In Vitro by Stepwise Selection

Moraxella catarrhalis causes respiratory infections. In this study, fluoroquinolone-resistant strains were selected in vitro to evaluate the mechanism of fluoroquinolone resistance. Strains with reduced fluoroquinolone susceptibility were obtained by stepwise selection in levofloxacin, and fluoroquinolone targets gyr and par were sequenced. Six novel mutations in GyrA (D84Y, T594dup, and A722dup), GyrB (E479K and D439N), and ParE (Q395R) involved in M. catarrhalis resistance to fluoroquinolones were revealed.

Virulence determinants of Moraxella catarrhalis: distribution and considerations for vaccine development

Moraxella catarrhalis is a human-restricted opportunistic bacterial pathogen of the respiratory mucosa. It frequently colonizes the nasopharynx asymptomatically, but is also an important causative agent of otitis media (OM) in children, and plays a significant role in acute exacerbations of chronic obstructive pulmonary disease (COPD) in adults. As the current treatment options for M. catarrhalis infection in OM and exacerbations of COPD are often ineffective, the development of an efficacious vaccine is warranted. However, no vaccine candidates for M. catarrhalis have progressed to clinical trials, and information regarding the distribution of M. catarrhalis virulence factors and vaccine candidates is inconsistent in the literature. It is largely unknown if virulence is associated with particular strains or subpopulations of M. catarrhalis, or if differences in clinical manifestation can be attributed to the heterogeneous expression of specific M. catarrhalis virulence factors in the circulating population. Further investigation of the distribution of M. catarrhalis virulence factors in the context of carriage and disease is required so that vaccine development may be targeted at relevant antigens that are conserved among disease-causing strains. The challenge of determining which of the proposed M. catarrhalis virulence factors are relevant to human disease is amplified by the lack of a standardized M. catarrhalis typing system to facilitate direct comparisons of worldwide isolates. Here we summarize and evaluate proposed relationships between M. catarrhalis subpopulations and specific virulence factors in the context of colonization and disease, as well as the current methods used to infer these associations.

[Acute otitis media in the children: etiology and the problems of antibacterial therapy]

The objective of the present review was to summarize the currently available literature data on etiology of acute otitis media in the children, the role of biofilms in the development of this pathology, and sensitivity of its principal causative factors to various antibiotic medications. The secondary objective was to elaborate the practical guidelines for the prevention of acute otitis media in the children.

Prevalence and resistance pattern of Moraxella catarrhalis in community-acquired lower respiratory tract infections

Introduction

Moraxella catarrhalis previously considered as commensal of upper respiratory tract has gained importance as a pathogen responsible for respiratory tract infections. Its beta-lactamase-producing ability draws even more attention toward its varying patterns of resistance.

Methods

This was an observational study conducted to evaluate the prevalence and resistance pattern of M. catarrhalis. Patients aged 20–80 years admitted in the Department of Chest Medicine of Liaquat National Hospital from March 2012 to December 2012 were included in the study. Respiratory samples of sputum, tracheal secretions, and bronchoalveolar lavage were included, and their cultures were followed.

Results

Out of 110 respiratory samples, 22 showed positive cultures for M. catarrhalis in which 14 were males and eight were females. Ten samples out of 22 showed resistance to clarithromycin, and 13 samples out of 22 displayed resistance to erythromycin, whereas 13 showed resistance to levofloxacin. Hence, 45% of the cultures showed resistance to macrolides so far and 59% showed resistance to quinolones.

Conclusion

Our study shows that in our environment, M. catarrhalis may be resistant to macrolides and quinolones; hence, these should not be recommended as an alternative treatment in community-acquired lower respiratory tract infections caused by M. catarrhalis. However, a study of larger sample size should be conducted to determine if the recommendations are required to be changed.

Use of the Chinchilla model to evaluate the vaccinogenic potential of the Moraxella catarrhalis filamentous hemagglutinin-like proteins MhaB1 and MhaB2

Moraxella catarrhalis causes significant health problems, including 15–20% of otitis media cases in children and ∼10% of respiratory infections in adults with chronic obstructive pulmonary disease. The lack of an efficacious vaccine, the rapid emergence of antibiotic resistance in clinical isolates, and high carriage rates reported in children are cause for concern. In addition, the effectiveness of conjugate vaccines at reducing the incidence of otitis media caused by Streptococcus pneumoniae and nontypeable Haemophilus influenzae suggest that M. catarrhalis infections may become even more prevalent. Hence, M. catarrhalis is an important and emerging cause of infectious disease for which the development of a vaccine is highly desirable. Studying the pathogenesis of M. catarrhalis and the testing of vaccine candidates have both been hindered by the lack of an animal model that mimics human colonization and infection. To address this, we intranasally infected chinchilla with M. catarrhalis to investigate colonization and examine the efficacy of a protein-based vaccine. The data reveal that infected chinchillas produce antibodies against antigens known to be major targets of the immune response in humans, thus establishing immune parallels between chinchillas and humans during M. catarrhalis infection. Our data also demonstrate that a mutant lacking expression of the adherence proteins MhaB1 and MhaB2 is impaired in its ability to colonize the chinchilla nasopharynx, and that immunization with a polypeptide shared by MhaB1 and MhaB2 elicits antibodies interfering with colonization. These findings underscore the importance of adherence proteins in colonization and emphasize the relevance of the chinchilla model to study M. catarrhalis–host interactions.

Moraxella catarrhalis uses a twin-arginine translocation system to secrete the β-lactamase BRO-2

Background

Moraxella catarrhalis is a human-specific gram-negative bacterium readily isolated from the respiratory tract of healthy individuals. The organism also causes significant health problems, including 15-20% of otitis media cases in children and ~10% of respiratory infections in adults with chronic obstructive pulmonary disease. The lack of an efficacious vaccine, the rapid emergence of antibiotic resistance in clinical isolates, and high carriage rates reported in children are cause for concern. Virtually all Moraxella catarrhalis isolates are resistant to β-lactam antibiotics, which are generally the first antibiotics prescribed to treat otitis media in children. The enzymes responsible for this resistance, BRO-1 and BRO-2, are lipoproteins and the mechanism by which they are secreted to the periplasm of M. catarrhalis cells has not been described.

Results

Comparative genomic analyses identified M. catarrhalis gene products resembling the TatA, TatB, and TatC proteins of the well-characterized Twin Arginine Translocation (TAT) secretory apparatus. Mutations in the M. catarrhalis tatA, tatB and tatC genes revealed that the proteins are necessary for optimal growth and resistance to β-lactams. Site-directed mutagenesis was used to replace highly-conserved twin arginine residues in the predicted signal sequence of M. catarrhalis strain O35E BRO-2, which abolished resistance to the β-lactam antibiotic carbanecillin.

Conclusions

Moraxella catarrhalis possesses a TAT secretory apparatus, which plays a key role in growth of the organism and is necessary for secretion of BRO-2 into the periplasm where the enzyme can protect the peptidoglycan cell wall from the antimicrobial activity of β-lactam antibiotics.

Hag mediates adherence of Moraxella catarrhalis to ciliated human airway cells

Moraxella catarrhalis is a human pathogen causing otitis media in infants and respiratory infections in adults, particularly patients with chronic obstructive pulmonary disease. The surface protein Hag (also designated MID) has previously been shown to be a key adherence factor for several epithelial cell lines relevant to pathogenesis by M. catarrhalis, including NCIH292 lung cells, middle ear cells, and A549 type II pneumocytes. In this study, we demonstrate that Hag mediates adherence to air-liquid interface cultures of normal human bronchial epithelium (NHBE) exhibiting mucociliary activity. Immunofluorescent staining and laser scanning confocal microscopy experiments demonstrated that the M. catarrhalis wild-type isolates O35E, O12E, TTA37, V1171, and McGHS1 bind principally to ciliated NHBE cells and that their corresponding hag mutant strains no longer associate with cilia. The hag gene product of M. catarrhalis isolate O35E was expressed in the heterologous genetic background of a nonadherent Haemophilus influenzae strain, and quantitative assays revealed that the adherence of these recombinant bacteria to NHBE cultures was increased 27-fold. These experiments conclusively demonstrate that the hag gene product is responsible for the previously unidentified tropism of M. catarrhalis for ciliated NHBE cells.

Current progress of adhesins as vaccine candidates for Moraxella catarrhalis

Moraxella catarrhalis is an emerging pathogen and all isolates are now considered beta-lactamase producing. Potential further use of vaccines against Streptococcus pneumoniae and nontypeable Haemophilus influenzae means that M. catarrhalis might be thrust further into the limelight. However, a vaccine has not yet been designed. In this review, the progress of M. catarrhalis adhesins as vaccine candidates is discussed with a focus on various candidate antigens that spanned those discovered more than 10 years ago, for example, the ubiquitous surface proteins to newer antigens, such as the Moraxella IgD-binding hemagglutinin.

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

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 incidence; copB/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 surrogate 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.

Evaluation of susceptibility patterns and BRO beta-lactamase types among clinical isolates of Moraxella catarrhalis

The aims of this study were to detect BRO beta-lactamase types and to evaluate any correlation with the susceptibility patterns of 90 clinical isolates of Moraxella catarrhalis. The overall prevalences of the bro-1 and bro-2 genes were 78% and 12%, respectively. Penicillin G MICs for BRO-1+ isolates were significantly higher than those for BRO-2+ isolates. All the isolates were susceptible to amoxycillin-clavulanate, levofloxacin and cefixime. Resistance to clarithromycin, tetracycline and trimethoprim-sulphamethoxazole was 1.1%, 2.2% and 1.1%, respectively. One-step, length-based PCR was an efficient method to screen for BRO beta-lactamase genes.

Bactericidal Monoclonal Antibody Against Moraxella catarrhalis Lipooligosaccharide Cross-Reacts with Haemophilus Spp

Monoclonal antibodies (MAbs) against lipooligosaccharide (LOS) determinants after immunization of BALB/c mice with heat inactivated Moraxella catarrhalis serotype A were generated. MAb 219A9 was specific for a common epitope of A, B, and C M. catarrhalis serotypes in ELISA and immunofluorescent test (IFT). In both tests it also cross-reacted with whole bacteria and LPS antigens isolated from non-typeable H. influenzae and H. parainfluenzae strains. IgM antibody clone 219A9 possessed a strong bactericidal effect against the three serotypes in the presence of complement. Our results demonstrate that antibodies directed to a single LOS epitope common for A, B, and C serotype could be highly protective. This suggests that the common determinants are very promising in the development of LOS-based vaccine against M. catarrhalis. The cross-reactions of MAb 219A9 with Haemophilus spp. also show that immunization could result in immune response to epitopes conserved in other important respiratory pathogens.

The UspA2 protein of Moraxella catarrhalis is directly involved in the expression of serum resistance

Many strains of Moraxella catarrhalis are resistant to the bactericidal activity of normal human serum. Previous studies have shown that mutations involving the insertion of an antibiotic resistance cartridge into the M. catarrhalis uspA2 gene resulted in the conversion of a serum-resistant strain to a serum-sensitive phenotype. In the present study, the deletion of the entire uspA2 gene from the serum-resistant M. catarrhalis strain O35E resulted in a serum-sensitive phenotype and did not affect either the rate of growth or the lipooligosaccharide expression profile of this mutant. Inactivation of the classical complement pathway in normal human serum with Mg2+ and EGTA resulted in the survival of this uspA2 mutant. In contrast, blocking of the alternative complement pathway did not protect this uspA2 mutant from complement-mediated killing. To determine whether the UspA2 protein is directly involved in serum resistance, transformation and allelic exchange were used to replace the uspA2 gene in the serum-resistant strain O35E with the uspA2 gene from the serum-sensitive M. catarrhalis strain MC317. The resultant O35E transformant exhibited a serum-sensitive phenotype. Similarly, when the uspA2 gene from the serum-resistant strain O35E was used to replace the uspA2 gene in the serum-sensitive strain MC317, the MC317 transformant acquired serum resistance. The use of hybrid O35E-MC317 uspA2 genes showed that the N-terminal half of the O35E protein contained a 102-amino-acid region that was involved in the expression of serum resistance. In addition, when the uspA2 genes from strains O35E and MC317 were cloned and expressed in Haemophilus influenzae DB117, only the O35E UspA2 protein caused a significant increase in the serum resistance of the H. influenzae recombinant strain. These results prove that the UspA2 protein is directly involved in the expression of serum resistance by certain M. catarrhalis strains.

Evaluation of restriction endonuclease analysis of BRO beta-lactamases in clinical and carrier isolates of Moraxella catarrhalis

A rapid increase in the prevalance of beta-lactamase producing M. catarrhalis isolates has highlighted its pathogenic potential. In this study, we aimed to detect the BRO beta-lactamases of our clinical (n = 32) and carrier (n =32) strains of Moraxella catarrhalis and compare the relationship of the enzyme type in assesment of MIC results of the antibiotics tested. BRO beta-lactamases were differentiated by restriction endonuclease analysis. Antibiotic susceptibility was performed by the agar dilution method recommended by NCCLS (M7A5). The clinical isolates produced 96.9%, whereas the carrier strains produced 90.6% beta-lactamase positivity by the restriction enzyme analysis. BRO-1 was isolated as 90.6% (n =29) while the BRO-2 and non-beta-lactamase producers (NBLP) were isolated as 6.3% (n =2) and 3.1% (n =1) respectively among clinical isolates. The rate of BRO-1 in the carrier strains was 75.0% (n =24), BRO-2 was 15.6% (n =5) and NBLP was 9.4%, (n =3). The beta-lactamase production with nitrocefin test was 96.9% (31/32) in clinical isolates and 90.6% (29/32) in carrier strains. M. catarrhalis needs a continous monitoring of antibiotic susceptibility; in this era restriction endonuclease analysis could be useful to screen BRO beta-lactamase genes.

Presumed endocarditis caused by BRO beta-lactamase-producing Moraxella lacunata in an infant with Fallot's tetrad

A case of presumed endocarditis caused by Moraxella lacunata in a 15-month-old male infant with Fallot's tetrad is described. This infection may have occurred as the result of transmission of this organism between the father and his son. This is the first report of BRO beta-lactamase-producing M. lacunata causing presumed endocarditis.