Tn. Phan et al., Selective sensitization of bacteria to peroxide damage associated with fluoride inhibition of catalase and pseudocatalase, ORAL MICROB, 16(1), 2001, pp. 28-33
Fluoride and sulfide are known inhibitors of heme catalases in acid environ
ments. Staphylococcus aureus H cells were found to be sensitized by fluorid
e or sulfide to H2O2 killing at acid pH values in the range of 3.5 to 4.0,
and catalase activity was reduced concomitantly. In contrast, fluoride had
little effect on H2O2 killing of Streptococcus mutans GS-5, which has fluor
ide-insensitive peroxidase activity, but still is more sensitive to H2O2 th
an is S. aureus in the absence of fluoride. Fluoride but not sulfide was in
hibitory also for the Mn-containing, nonheme pseudocatalase of Lactobacillu
s plantarum ATCC 14431 over a wide pH range, and this inhibitory effect was
reflected in enhanced H2O2 killing in the presence of fluoride. In additio
n, we found that catalase-positive S. aureus or Neisseria sicca could prote
ct catalase-negative S. mutans against killing by H2O2 in mixed suspensions
, but protection was compromised by fluoride or sulfide under acid conditio
ns. Thus, catalase-positive organisms could protect a catalase-negative org
anism against peroxide damage, but inhibition of catalase reduced protectio
n. These findings are pertinent to the widespread use of fluoride and perox
ide in oral health care products.