Genome Analysis of Moraxella catarrhalis Strain RH4, a Human Respiratory Tract Pathogen

Abstract

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 ϳ88% 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.Moraxella catarrhalis is an emerging human-restricted unencapsulated Gram-negative mucosal pathogen. Long considered to be a commensal of the upper respiratory tract, this bacterium has now firmly been established to be an etiological cause of otitis media (OM) and exacerbations of chronic obstructive pulmonary disease (COPD). It is the third most common cause of childhood OM after Haemophilus influenzae and Streptococcus pneumoniae (37, 64), and it is responsible for up to 20% of the cases (64, 65). Further, M. catarrhalis is the second most common cause of exacerbations of COPD after H. influenzae; it is responsible for 10 to 15% of the exacerbations and annually causes 2 to 4 million episodes in the United States (47, 60). Antibiotics are widely used for treatment of OM, but the high prevalence of this disease and the increasing incidence of antibiotic-resistant strains mean that multivalent vaccines, preferably vaccines with protective antigens for all three causative bacterial agents, must be developed (46).M. catarrhalis is able to colonize the mucosal surfaces of the middle ear in OM patients and the lower respiratory tract in COPD patients (31,60). Successful colonization of the human host is a complex process which requires the expression ...

Molecular mechanism of macrolide–lincosamide resistance in Moraxella catarrhalis

“…Bacterial genomic DNA was extracted by using a Tissue Genomic DNA Extraction mini kit (Favorgen Biotech). Since M. catarrhalis has four copies of the 23S rRNA gene (de Vries et al, 2010) according to the genome sequence, a specific primer for each of the alleles of this gene was constructed using the Primer3 software (http:// frodo.wi.mit.edu/). PCR amplification of all four alleles was performed using primer Mc23S-F paired with the 23S rRNA allele-specific primers (Table 1).…”

“…However, since M. catarrhalis has four copies of the 23S rRNA operon (de Vries et al, 2010), the role of mutations in each of the 23S rRNA alleles in macrolide-resistant M. catarrhalis has been unclear.…”

Natural insertion of the bro-1 β-lactamase gene into the gatCAB operon affects Moraxella catarrhalis aspartyl-tRNAAsn amidotransferase activity

“…(c) Alignment of the C-terminal sequences of GatAs from these strains and 12 new genome sequences from geographically and phenotypically diverse clinical isolates of M. catarrhalis. There are three identical GatA(479-492) BRO-2 sequences, eight identical GatA(479-492) BRO-1 sequences and two identical GatA(479-491) wt sequences (de Vries et al, 2010;Davie et al, 2011). Amino acids in lower-case type are not conserved in the three sequences.…”

Immune Evasion ofMoraxella catarrhalisInvolves Ubiquitous Surface Protein A-Dependent C3d Binding

“…In contrast, no significant binding of C3met was observed with the UspA1/A2H-deficient double mutant (RH4 DuspA1/A2H) even at the highest C3met concentration (750 mg/ml) used. The UspA2H of M. catarrhalis RH4 was formerly known as UspA2, but the C3met binding capacity of UspA2 and UspA2H is similar (26,28,62). The experiments shown in Fig.…”

“…The UspA1-deficient mutant was cultured in BHI supplemented with 1.5 mg/ml chloramphenicol (Sigma-Aldrich, St. Louis, MO), and the UspA2H-deficient mutant was incubated with 7 mg/ml zeocin (Invitrogen, Carlsbad, CA). The UspA2H of M. catarrhalis RH4 was formerly known as UspA2 (26,28,62). Both chloramphenicol and zeocin were used for growth of the UspA1/A2H double mutants.…”