Increased resistance to penicillin of oral viridans streptococci in dental students.

Salivary samples were taken annually in October from 48 dental students as they progressed from pre-clinical studies to final year. The MICs of penicillin for the viridans streptococci were determined. Over the three years these organisms became progressively more resistant but not to a level of clinical significance. The findings were confirmed by a cross-sectional study of 57 pre-clinical and 37 final year students. The increase in resistance might have been related to age, but a further study of 20 postgraduate chemistry students of the same age as the final year dental students showed that the former had a population of streptococci similar to that found in the pre-clinical students. Whether the increase in resistance is a result of the dental students working in the clinic or having penicillin more frequently prescribed for them personally is a matter for speculation.