دراسة تأثير البروبيوتك الفموي لجنس Streptococcus salivarius على البكتريا المرضية المكونة للغشاء الحيوي المعزولة من الفم

Study of the effect of oral probiotics of the genus Streptococcus salivariuson on pathogenic biofilm-forming bacteria isolated from the mouth

Abstract
This study was conducted to evaluate the inhibitory effect of probiotics extracted from Streptococcus salivarius bacteria on the growth of pathogenic bacteria and their biofilms isolated from the oral cavity and surrounding teeth of patients visiting the health center in Al-Abbas district/center, the health center in Al-Hur district, the health center in Aoun district, and the specialized dental clinic in Al-Iskan Street in Karbala Governorate, Iraq. A total of 83 oral swabs were collected from both genders, with ages ranging from 6 to 63 years, from December 10, 2022 to February 12, 2023.
This study included three axes, at first the isolation and identification of S. salivarius. The bacteria were cultured on Mitis-salivarius agar and HiCrom strep B selective agar. Based on the bacterial culture characteristics and after diagnosis with the Vitek-2 device, 19 isolates of S. salivarius were obtained and molecularly identified using PCR technique by detecting the gtfk gene. Secondly the isolation and identification of pathogenic bacteria from patients visiting the same centers. Based on the morphological characteristics of the bacterial cultures and the diagnosis with the Vitek-2 device, four types of pathogenic bacteria were obtained, as follows: Staphylococcus aureus, Staphylococcus epidermidis, Klebsiella pneumoniae, and Enterobacter cloacae. The ability of the pathogenic isolates to form biofilms was also tested using two methods: The Congo red agar method and the microtiter plate method. The results showed that all isolates formed biofilms. At last the study of the inhibitory effect of the probiotic extract on the growth of pathogenic bacteria at the following dilutions: 75, 150, 300, and 600 microliters/ml. The results showed that the pathogenic bacteria were sensitive to the extract. The concentration of 600 microliters/ml showed the highest inhibitory diameter in all species, as follows: (7 mm) K. pneumoniae, (10 mm) E. cloacae, (11 mm) S. aureus, and (10 mm) S. epidermidis. The concentration of 75 microliters showed the lowest inhibitory diameter, as follows: (0 mm) K. pneumoniae, (0 mm) E. cloacae, (2 mm) S. aureus, and (0 mm) S. epidermidis.
The anti-biofilm efficacy of the probiotic was also studied using a series of half-dilutions from (2 – 1048) micrograms/ml and determining the minimum inhibitory concentration (MIC). The results showed a significant decrease in the adsorption values of the biofilms. The largest decrease rates were at the concentrations (1048, 524, 262) micrograms/ml, and the lowest decrease rates were at the concentrations (8, 16) micrograms/ml. The probiotic showed no effect on the biofilms at a concentration of (2) micrograms/ml. The MIC value was (4) micrograms/ml, at which no visible bacterial growth was observed.
Based on the results of this study, we conclude that the probiotic extract isolated from S. salivarius bacteria has high efficacy against the growth of pathogenic bacteria isolated from the oral cavity and surrounding teeth and forming biofilms.