The antibiotic sensitivity of Corynebacterium diphtheriaе gravis tox+ in composition of mixed biofilms.

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The purpose of study is to determine sensibility of strains of C. diphtheriae gravis tox+ in the composition of mixed biofilms to antibacterial medications. The object of study was strains of Corynebacterium diphtheriae gravis tox+ № 665, Corynebacterium pseudodiphtheriticum (poly-resistant), Corynebacterium pseudodiphtheriticum (antibiotic-resistant). Two mixed biofilms (120- and 720-hours) of strain of Corynebacterium diphtheriae gravis tox+ № 665 with strains of Corynebacterium pseudodiphtheriticum (poly-resistant), Corynebacterium pseudodiphtheriticum (antibiotic-resistant) were formed. The sensibility of typical and biofilm cultures of Corynebacteria to antibiotic medications was established using technique of serial dilution in fluid growth medium on the basis of MPC (mg/l). The typical culture of museum strain C. diphtheriae gravis tox+ № 665, modeling mixed biofilms had a sensitivity to all used antibacterial medications. The analysis of antibiotic resistance of strain of C. diphtheriae gravis tox+ № 665 in content of biofilm with strain С. pseudodiphtheriticum, poly-resistant to four antibacterial medications (cefazolin, kanamycin, azithromycin, ciprofloxacin, IPC from 1.25±0,00 to >5±0,00 mkg/ml) set reduction (p≤0,05) sensitivity 120-hour biofilm cultures of this strain to cefazolin, azithromycin, ciprofloxacin (MIC of 0, 234 and up to ±0,11>5±0,00 ug / ml) established decreasing (p≤0,05) of sensitivity of 120-hours biofilm culture of this strain to cefazolin, azithromycin, ciprofloxacin (MIC from 0, 234±0,11 to >5±0,00 mkg/ml) and 720-hours culture - to all mentioned medications (MIC from 0,312±0,00 to >5±0,00 mkg/ml). The comparison of antibiotics resistance of biofilm cultures of strain C. diphtheriae gravis tox+ № 665 established that indices of MIC of most of antibacterial medications and especially to those that poly-resistant and forming biofilm strain С. рseudodiphtheriticum was resistant, were higher as related to biofilm cultures of diphtheritic bacteria separated from biofilm with antibiotic resistant strain С. рseudodiphtheriticum. The trend was established related to decreasing of antibiotic sensitivity of Corynebacteria at cultivation in content of mixed biofilms with representatives of opportunistic Corynebacteria having polyresistance to antibacterial medications.