Introduction: Various strategies have been researched to enhance the susceptibility of biofilms, given their tolerance to antibiotics. This study evaluated the effect of the antimicrobial peptide nisin in association with antibiotics used in regenerative endodontics, exploring different treatment times and biofilm growth conditions.
Methods: A mixture of ten bacterial species was cultivated on dentin specimens anaerobically for 21 days. Biofilms were treated with 1 mL of high-purity nisin Z (nisin ZP, 200 μg/mL) and a triple antibiotic mixture (TAP: ciprofloxacin + metronidazole + minocycline, 5mg/ mL), alone or in combination. The effectiveness of antimicrobial agents was assessed after one and seven days. During the 7-day period, biofilms were treated under two conditions: a single dose in a nutrient-depleted setting (i.e., no replenishment of growth medium) and multiple doses in a nutrient-rich environment (i.e., renewal of medium and antimicrobial agents every 48 h). After treatments, biofilm cells were dispersed, and total colony-forming units were counted.
Results: After 1d-treatment, nisin ZP + TAP resulted in 2-log cell reduction compared to TAP alone (P < .05). After 7 d-treatment with a single dose, nisin ZP + TAP and TAP reduced bacteria to non-culturable levels (P < .05), whereas repeated antimicrobial doses did not eliminate bacteria in a nutrient-rich environment. No bacterial reduction was observed with nisin ZP alone in any treatment time.
Conclusions: The additional use of nisin improved the TAP activity only after a short exposure time. Longer exposure to TAP or nisin + TAP in a nutrient-deprived environment effectively eliminated biofilms.
Keywords: antimicrobial peptide; endodontic biofilm; nisin; regenerative endodontics; triple antibiotic paste.
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