Antimicrobial susceptibility of Moraxella catarrhalis in Russia: results of the PEGAS 2010–2021 multicenter study

Objective. To study the antimicrobial susceptibility profile of Moraxella catarrhalis isolates from different regions of Russia in 2010–2021. Materials and Methods. The study included 352 isolates of M. catarrhalis isolated in 11 cities of Russia (Volgograd, Irkutsk, Kazan, Kirov, Moscow, Murmansk, Perm, Seversk, Togliatti, Tomsk, and Ulan-Ude) in 2010–2021. Identification was done by MALDI-TOF mass spectrometry. Antimicrobial susceptibility testing was determined by broth microdilution method in accordance with the ISO 20776-1:2020. Interpretation of results was done in accordance with EUCAST guidelines (v.14.0). Results. Most of the isolates were isolated from respiratory specimens: 225 (63.9%) from sputum, 49 (13.9%) from nasal swabs, 41 (11.6%) from sinus aspirates, 17 (4.8%) from bronchoalveolar lavage, 8 (2.3%) from middle ear fluid, 6 (1.7%) from pharyngeal swabs, and 5 (1.4%) from conjunctival secretions. All tested isolates were susceptible to beta-lactams for which interpretive criteria have been established (amoxicillin-clavulanate, cefixime, ceftriaxone, cefuroxime). The susceptibility to clarithromycin and azithromycin was 99.7% and 100%, respectively. Ciprofloxacin, levofloxacin and moxifloxacin were active against 98.9%, 99.2% and 99.7% of isolates tested, respectively. Susceptibility to tetracycline was 99.7% and to trimethoprim-sulfamethoxazole was 99.4% (92% of isolates susceptible, 7.4% – susceptible at increased exposure). Conclusions. In the Russian Federation there is a favorable situation regarding the susceptibility of M. catarrhalis to antimicrobials. Amoxicillin-clavulanic acid, cefixime, ceftriaxone, azithromycin, clarithromycin, ciprofloxacin, levofloxacin, moxifloxacin and tetracycline retain high in vitro activity