Maximum Inhibitory Dilution of Mouthwashes Containing Chlorhexidine and Polyhexamethylene Biguanide against Salivary Staphylococcus Aureus

OBJECTIVE The aim of the present study was to determine the in vitro maximum inhibitory dilution (MID) of two chlorhexidinebased oral mouthwashes (CHX): Noplak, Periogard, and one polyhexamethylene biguanide-based mouthwash (PHMB): Sanifill Premium against 28 field Staphylococcus aureus strains using the agar dilution method. MATERIALS AND METHODS For each product, decimal dilutions ranging from 1/10 to 1/655,360 were prepared in distilled water and added to Mueller Hinton Agar culture medium. After homogenization, the culture medium was poured onto Petri dishes. Strains were inoculated using a Steers multipoint inoculator and dishes were incubated at 37 degrees C for 24 hours. For reading, MID was considered as the maximum dilution of the mouthwash still capable of inhibiting microbial growth. RESULTS Sanifill Premium inhibited the growth of all strains at 1/40 dilution and of 1 strain at 1/80 dilution. Noplak inhibited the growth of 23 strains at 1/640 dilution and of all 28 strains at 1/320 dilution. Periogard showed inhibited growth of 7 strains at 1/640 dilution and of all 28 strains at 1/320 dilution. Data were submitted to Kruskal-Wallis statistical test, showing significant differences between the mouthwashes evaluated (p<0.05). No significant difference was found between Noplak and Periogard (p>0.05). Sanifill Premium was the least effective (p<0.05). CONCLUSION It was concluded that CHX-based mouthwashes present better antimicrobial activity against S. Aureus than the PHMB-based mouthwash.