AMB Volume 42, Issue 2, 2026 Pages 231-236 https://doi.org/10.59393/amb26420207
Distribution of Virulence Factors among Bulgarian Moraxella catarrhalis Isolates
Boyanov V.S., Alexandrova A.S., Gergova R.T.
Moraxella catarrhalis (M. catarrhalis) is one of the most common bacterial pathogens associated with respiratory infections in children as well as exacerbation of chronic lung diseases in adults. This pathogen expresses proteins on its surface that determine the interactions with the host and thereby the pathogenesis of the infection. In the current study, we isolated 98 M. catarrhalis strains during routine diagnostics from nasal and nasopharyngeal swabs, ear and sinus punctures, and sputum samples. The patients included in the study were divided into two categories based on their diagnoses: upper respiratory tract infections (65.3%, age range 1-15) and lower respiratory tract infections (34.7%, age range 45-81). We detected six important virulence factors through conventional PCR, with the following frequencies: mcaP (100.0%), ompB2 (98.0%), ompCD (87.8%), ompE (93.9%), uspA1 (94.9%), and uspA2 (81.6%). Three of these factors (uspA1, uspA2, and mcaP) were tested for the first time among Bulgarian patients. The results related to OMP proteins were compared with previous research conducted in Bulgaria (1997-2007), which indicated an increased frequency of omp genes across all studied groups, as well as statistical significance in the distribution of ompB2. These findings suggested an increased virulence in strains of M. catarrhalis. Furthermore, the factors that were examined were recognized as potential vaccine candidates, highlighting the importance of monitoring their prevalence.
Keywords: Moraxella catarrhalis, respiratory infections, virulence factors, vaccine
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