ИСТИНА

Background: In cancer patients anaerobic infections are most often caused by gram-negative rods Bacteroides spp., Prevotella spp., Fusobacterium spp., Porhyromonas spp., as well as gram-negative cocci Veillonella spp. They are isolated in association with aerobic microflora, as well as in anaerobic monoculture. Gram-negative anaerobes can cause infections of any location. The aim of the study was to identify gram-negative anaerobic microorganisms and to determine their antimicrobial susceptibility. Materials/methods: biomaterials (wound discharge, aspirates, bile, blood etc) from 86 cancer patients with infectious complications in 2017 were analyzed. Identification was carried out using MALDI-ToF MS (Bruker, Germany) and antimicrobial susceptibility to penicillin, amoxicillin/clavulanate, imipenem, metronidazole was determined using E-test strips (MIC Evaluator, Oxoid, England). Results: 107 gram-negative anaerobic microorganisms were isolated from 86 biomaterials. Associations of 2 or 3 anaerobic pathogens were revealed in 17 cases. Bacteroides spp. (49/107, 45.8%) was the most often isolated gram-negative anaerobic rod, followed by Prevotella spp. (32/107, 29.9%), Fusobacterium spp. (12/107, 11.2%), Porphyromonas spp. (2/107, 1.9%) and gram-negative cocci Veillonella spp. (12/107, 11.2%). All isolates of Prevotella spp. and Fusobacterium spp. were resistant to penicillin (MICs from 16 to 32 mcg/ml) and susceptible to amoxicillin/clavulanate, imipenem and metronidazole. Intrinsically penicillin-resistant strains of Bacteroides spp. showed differential resistance to antibiotics tested. 12% of strains were resistant to metronidazole, 11% - to amoxicillin/clavulanate and 8% -to imipenem (p>0.05). 100% of Veillonella spp. were resistant to penicillin. 60% of Veillonella spp. were susceptible to metronidazole, 33% - to amoxicillin/clavulanate and 100% to imipenem (p>0.05). Conclusions: Identification of resistant strains of anaerobes dictates the urgent need to determine and monitor their resistance to antibiotics and will help to contribute to rational approach to antimicrobial treatment.