Modulation of drug resistance and biofilm formation of Staphylococcus aureus isolated from the oral cavity of Tunisian children

Abstract Objectives: This study aims to investigate the antimicrobial and the anti-biofilm activities of Lactobacillus plantarum extract (LPE) against a panel of oral Staphylococcus aureus (n = 9) and S. aureus ATCC 25923. The in vitro ability of LPE to modulate bacterial resistance to tetracycline, benzalchonium chloride, and chlorhexidine were tested also. Methods: The minimum inhibitory concentrations (MICs) and the minimal bactericidal concentrations of Lactobacillus plantarum extract, tetracycline, benzalchonium chloride and clohrhexidine were determined in absence and in presence of a sub-MIC doses of LPE (1/2 MIC). In addition, the LPE potential to inhibit biofilm formation was assessed by microtiter plate and atomic force microscopy assays. Statistical analysis was performed on SPSS v. 17.0 software using Friedman test and Wilcoxon signed ranks test. These tests were used to assess inter-group difference (p < 0.05). Results: Our results revealed that LPE exhibited a significant antimicrobial and anti-biofilm activities against the tested strains. A synergistic effect of LPEs and drug susceptibility was observed with a 2–8-fold reduction. Conclusion: LPE may be considered to have resistance-modifying activity. A more detailed investigation is necessary to determine the active compound responsible for therapeutic and disinfectant modulation.

Adherence assays and Slime production of Vibrio alginolyticus and Vibrio parahaemolyticus / Ensaios de adesão e produção de muco por Vibrio alginolyticus e Vibrio parahaemolyticus

In this study we investigated the phenotypic slime production of Vibrio alginolyticus and Vibrioparahaemolyticus strains, food-borne pathogens, using a Congo red agar plate assay. Furthermore, westudied their ability to adhere to abiotic surfaces and Vero cells line. Our results showed that only V.alginolyticus ATCC 17749 was a slime-producer developing almost black colonies on Congo red agar plate.Adherence to glace tube showed that all V. alginolyticus strains were more adherent than V. parahaemolyticus.Only V. alginolyticus ATCC 17749 was found to be able to form biofilm on polystyrene microplate wells (OD570= 0.532). Adherence to Vero cells showed that all tested strains were non adherent after 30 min, however after60 min all the studied strains become adherent. The percentage of adherence ranged from1.23% to 4.66%.

Neste estudo, investigou-se a produção de muco por cepas de Vibrio alginolyticus e Vibrio parahaemolyticus através do teste em placa de ágar com vermelho congo. Estudou-se também a capacidade de adesão à superfícies abióticas e células Vero. Os resultados indicaram que somente V. alginolyticus ATCC 17749 produziu muco, formando colônias quase negras nas placas de ágar com vermelho congo. O teste de adesão a tubos de vidro indicou que as cepas de V. alginolyticus foram maisaderentes do que as de V. parahaemolyticus. Somente V. alginolyticus ATCC 17749 foi capaz de formar biofilme nos poços das microplacas de poliestireno (OD570=0,532). Testes de adesão a células Vero mostraram que nenhuma das cepas apresentou adesão em 30 min, mas todas aderiram após 60 min. Aporcentagem de adesão variou de 1,23% a 4,66%.