Vìsnik Dnìpropetrovsʹkogo Unìversitetu: Serìâ Bìologìâ, Medicina (Apr 2014)
Ceftriaxone and tetracycline effect on biofilm-formation strains of Staphylococcus epidermidis
Abstract
122 strains of staphylococci were identified. Among the examined 122 clinical strains of staphylococci, 67 strains belonged to coagulase-positive, and 55 strains to the coagulase-negative ones. According to the study of physiological and biochemical properties, it was found that 37 strains (30.3%) belonged to S. epidermidis species. One of the biological properties of many bacteria is the ability to film formation and these strains attract special attention, since it is known that the film antibiotic resistance is higher than in planktonic cultures. It was determined that 20 strains of those under study were film-forming, 17 strains – non-biofilm forming ones. The film was formed during three days, and settled to the bottom of the plate holes. The clinical (Cl) strain of S. epidermidis was sensitive to ceftriaxone and tetracicline. The control (C) strains of S. epidermidis were sensitive to ceftriaxone, tetracycline and sizomicine. The study of biofilm growth for 2, 3 and 4 days of incubation was carried out. The maximum rate of biofilm S. epidermidis C was observed during 2–3 days; there is the most intense increase of cells number from 5.2 × 108 CFU/ml, for S. epidermidis Cl to 5.6 × 108 CFU/ml. The effect of ceftriaxone and tetracycline on biofilm formation by 2 investigation strains of S. epidermidis was found. We determined differences in minimal inhibitory concentrations (MIC) for planktonic cultures and biofilm of strains under study. It was established that MIC antibiotics inhibited the growth of planktonic cultures on average 2 times lower compared to the MIC which inhibited the biofilm formation. MIC for planktonic culture of S. epidermidis Cl defined for ceftriaxone was equal to 10 mg/ml, and for tetracycline – 1 mg/ml. MIC of ceftriaxone for the control strain was equal to 12 mg/ml, MIC of tetracycline – 0.7 mg/ml. MIC values for dynamics biofilm formation of S. epidermidis Cl strain on the plater were as follows: to ceftriaxone – 20 mg/ml and for tetracycline – 2 mg/ml, MIC of ceftriaxone for S. epidermidis C strain – 24 mg/ml, MIC of tetracycline – 1.5 mg/ml. The effect of ceftriaxone and tetracycline was defined to the larger extent, than MIC for biofilm-forming on the plate (10, 50 and 100 times). More effective action of tetracycline was shown for 1- and 2-daily biofilm cultures of S. epidermidis clinical strain. Adding tetracycline concentration of 20 mg/ml in the culture medium of the 1-day biofilm of S. epidermidis Cl strain reduced the cell number of biofilm formation 590 times, increasing concentrations of tetracycline to 100 mg/ml and added to the 1-day biofilm of the clinical strain reduced the number of bacterial cell 4400 times compared with control.
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