DIFFICULTIES IN IDENTIFICATION OF СOMAMONAS KERSTERSII STRAINS ISOLATED FROM INTESTINAL MICROBIOTA OF RESIDENTS OF REPUBLIC OF GUINEA AND RUSSIAN FEDERATION
Authors: Voitenkova E. V. , Matveeva Z. N. , Makarova M. A. , Egorova S. A. , Zabrovskaia A. V. , Suzhaeva L. V. , Zueva E. V. , Kaftyreva L. A. 
Published: September 2018

The Сomamonas genus, described in 1985, included one species — Сomamonas terrigena. At present, the Сomamonas genus includes 21 species. The ability of Comamonas to survive in environmental objects (samples of water, soil and plants), including hospital environment and medical equipment, allows them to be considered as opportunistic microorganisms. The purpose of the research was to study the biological properties and antimicrobial susceptibility of Сomamonas kerstersii strains isolated from fecal samples of healthy people living in Saint Petersburg (Russian Federation) and the Republic of Guinea. The study was carried out in the laboratory of enteric infections of the St. Petersburg Pasteur Institute. 1532 fecal samples were obtained from residents of St. Petersburg and 46 samples from residents of the Republic of Guinea. The generic and species identification of the isolated microorganisms was carried out using routine biochemical tests, the NEFERM test24 commercial test system (MIKROLATEST, Erba Rus, Russia) and Vitek 2 Compact (BioMerieux). The difficult for identification microorganisms were studied by MALDI-TOF mass spectrometry, on a “Microflex LRF” mass-spectrometer. Antimicrobial susceptibility was determined by the gradient method with MICEvaluator™ (OXOID, UK) on Müller– Hinton agar (Russia). In the intestine microbiota of 1532 St. Petersburg residents among the opportunistic microorganisms two strains of С. kerstersii were isolated (0.13%). In a survey of 46 residents of the Republic of Guinea in 8 cases (17.4%) С. kerstersii were isolated. The identification of C. kerstersii strains using various methods and biochemical tests has shown different results: routine biochemical tests allowed the strains to be assigned to the group of non-fermenting gram-negative bacteria; NEFERM test24 kit identified all strains as С. testosteroni; VITEC 2 referred all strains to С. testosteroni; using mass spectrometry with a coincidence ratio of 2.19–2.33, all strains were identified as С. kerstersii. It should be taken into account that the С. kerstersii bacteria cannot be identified by the tests of NEFERM test24 kit and the GN VITEC 2 card, since only the С. testosteroni is represented in the databases of both methods. The taxonomic base of mass spectrometry includes reference spectra of five species of Сomamonas from 21 known ones, including С. kerstersii. Strains isolated from the inhabitants of the Republic of Guinea were unsusceptible to at least one tested antibiotic: ciprofloxacin (4 strains), tetracycline (5 strains) and trimethoprim/sulfamethoxazole (5 strains), almost all strains being simultaneously unsusceptible to several antibio tics: ciprofloxacin and trimethoprim/sulfamethoxazole (2 strains), tetracycline and trimethoprim/sulfamethoxazole (2 strains), ciprofloxacin and tetracycline (1 strain). One strain was unsusceptible to ciprofloxacin, tetracycline, and trimethoprim/sulfamethoxazole.