90 saliva samples will be isolated from patient who possess different ages and caries activity, attending outpatient clinic of October University of Modern Sciences and Arts. Then the determination of the best selective media for mutans streptococcus isolated from saliva and authenticate the MS via PCR technique.

Inclusion Criteria:

• healthy participant

Exclusion Criteria:

• participant received antimicrobial therapy in previous month.
• participant who taking xylitol chewing gum or undergo fluoride therapy.

patients attending out patient clinic of October University for Modern Sciences and Arts.