The ability of bacteria to form biofilms was one of the pathogenetic factors of the chronic infection process formation that plays an important role in the clinical medicine. Among the bacteria exposed to the film formation that often cause infections, the staphylococci and the representatives of the Enterobacteriaceae family dominate. An important symbiont and member of various ecosystems of the human body is lactobacillus. Their antagonistic effect appears in the growth inhabitation of pathogenic and opportunistic pathogenic microorganisms. The purpose of this study is to examine the changes in the morphological structures of clinical strains of the film forming staphylococci at the biofilms forming in the mixed culture with the clinical and probiotic strains of lactobacilli.

Materials and methods. For the experiment the film forming clinical strains of S. aureus (n = 5) were selected, which are isolated from the skin of patients with acne vulgaris. On the upper respiratory tracts of healthy patients was allocated the clinical strain of L. fermentum (n = 4).

To isolate the Lactobacilli the standard environment of MRS-agar (de Man, Rogosa, Sharpe, India) were used. As benchmarks was used the living culture L. plantarum 8P-A3 of the probiotic medication "Lactobacterin", the culture S. epidermidis ATCC 12228, which does not form a film, and the film-forming S. aureus ATCC 25923.

The staphylococci biofilms were formed on the bottom of plastic cups (Ø 50 mm) using nutrient broth, the lactobacilli biofilm – MRS-broth. The staphylococci cups were incubated in an incubator for 24 hours and lactobacilli – 48 h at 37 °C. Similarly the mixed cultures of staphylococci and lactobacilli were formed in MRS-broth for 48 hours at 37 °C. Samples preparation for the transmission electron microscopy (TEM) was performed using classical techniques.

Results and discussion. According to the research of electrograms in control samples of the 24-hour monocultures of the film-forming and plankton staphylococci and the 48-hour lactobacilli the natural population growth was observed at the cellular level. Comparing the electrograms of the 48-hour staphylococci monocultures and mixed with lactobacilli the effect of the cell wall destabilization was observed, which was becoming in cocci the irregular form, significant thickening of the cell wall, cytoplasmic membrane detachment of the cell wall and full destruction of the peptidoglycan layer. Due to the high electron density of cytoplasm in the Nucleoid area the clearly evident characteristic of fibrillar and threadlike structure of DNA is not expressed, on some electrograms the mesosome-type formations are weakly contrasted. All the above mentioned destructive changes detected in ultrathin sections of film-forming cells and plankton staphylococci influenced both probiotic and clinical lactobacilli.

Similar results were obtained by other researchers by the action to the gram-positive and gram-negative silver bacteria and under the influence of cold stress. Comparing our results with those of other researchers, it can be suggested that such cell wall reaction may be common for bacterial cells under various stress factors.

Conclusions. At the population level the ratio of morphological types of cells S. aureus has changed with number increasing of aging and lysed cells.

The obtained results can be used to improve the integrated schemes of the complex antimicrobial therapy of inflammatory processes with the use of biopharmaceuticals that include the lactobacilli, also in form of a local application.

Added: 16.11.2016

Keywords: biofilm, Lactobacillus, Staphylococcus, transmission electron microscopy

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