RESUMO
OBJECTIVE: To compare the sporicidal activity of benzalkonium chloride (BKC) with that of glutaraldehyde. MATERIAL AND METHODS: A comparative study was conducted at the microbiology laboratory of Facultad de Odontología, Universidad Nacional Autónoma de México. Bacillus subtilis ATCC 9372 spores were exposed to these germicides (1 spore x mL) on a 0.22 mm filter. After completing the contact time the spores were washed and the filters were incubated on nutrient agar for 72 h at 37 degrees C. RESULTS: BKC did not eliminate B. subtilis spores at the concentration used, not even after increasing contact time to 15 h (900-fold the recommended time). Two percent glutaraldehyde destroyed spores only after 10 h of contact. Urea and sodium chloride showed no sporicidal activity. CONCLUSIONS: The results confirm that BKC lacks sporicidal activity and confirm that this quaternary ammonium compound is not able to "sterilize" or "disinfect" medical and dental instruments.
