Evaluation of the Impact of some Plant Extracts against Streptococcus Spp. Isolated from Dental Decay Infection

Anas Abdullah Hamad1, *, Maryam S. Alhumaidi2, Azadeh Manayi3
1 University of Fallujah, College of Veterinary Medicine, Branch of Microbiology, Iraq, AL Anbar, Fallujah
2 Department of Biology, College of Science, University of Hafr Al Batin, Hafr Al Batin 31991, P.O. Box 1803, Kingdom of Saudi Arabia
3 Medicinal Plants Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran

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© 2023 Hamad et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondencwe to this author at the University of Fallujah, College of Veterinary Medicine, Branch of Microbiology, Iraq, AL Anbar, Fallujah Postal Address: P.O.Box: 31002 Al Anbar, Fallujah; E-mail:



This study aimed to isolate and identify the Streptococcus spp. bacteria from patients with dental caries infection. Furthermore, the antibacterial activity of new plant extracts on isolated Streptococcus spp. was also evaluated.


A total of 150 samples were obtained at random from people of various ages and genders who were suffering from dental caries infection. Four different culture media were used for isolation: nutrient agar, MacConkey agar, blood agar, and Streptococcus selection agar. The identification of bacterial isolates was distinguished by macroscopic examination and the VITEK 2 system.


Only 120 cases (80%) showed positive culture, and these were distributed as follows: Streptococcus sanguinis had the highest rate and accounted for 38.33%, and Streptococcus pseudoporcinus represented only 29.16%. A 20% decline was reported for Streptococcus salivarius, with the lowest proportion being 12.5% for Staphylococcus warneri. The MIC for 16 tested plant extracts ranged from 0.97 to 125 µg/mL, whereas the MBC values ranged from 3.9 to 500 µg/mL. Imipenem was a positive control, with MIC values ranging from 3.9 µg/mL to 15.6 µg/mL; the MBCs varied from 31.2 to 125 µg/mL against all isolated species.


Among the isolated bacterial species from tooth decay, Streptococcus sanguinis had the highest rate of isolated bacteria and accounted for 38.33%, while Staphylococcus warneri had the lowest percentage at 12.5%. Sargassum, Proskia, and Cicer arietinum were three distinct extracts that demonstrated superior antibacterial activity against all of the tested bacterial species. Their MIC values ranged from 0.97 µg/mL to 15.6 µg/mL, and the MBC values were between 3.9 µg/mL and 31.2 µg/mL.

Keywords: New plant, Extracts, Dental caries, Streptococcus spp., Antibacterial activity, Dental decay infection.