Antimicrobial efficacy of the alkaloid harmaline alone and in combination with chlorhexidine digluconate against clinical isolates of Staphylococcus aureus grown in planktonic and biofilm cultures

Abstract

Aims: To investigate the antimicrobial efficacy of an alkaloid, harmaline alone and in combination with chlorhexidine digluconate (CHG) against clinical isolates of Staphylococcus aureus (S. aureus) grown in planktonic and biofilm cultures. Methods: Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined for each micro‐organism grown in suspension and in biofilm using microbroth dilution method. Chequerboard assays were used to determine synergistic, indifferent or antagonistic interactions between harmaline and CHG, and the some of results were verified by confocal laser scanning microscopy. Results: Harmaline and CHG showed effective antimicrobial activity against suspensions and biofilm cultures of S. aureus, respectively. As determined by fractional inhibitory concentration index (FICI), synergistic antimicrobial effects between harmaline and CHG were observed in nine and 11 of the 13 S. aureus strains when in suspension and in biofilm, respectively. FICI values were from 0·375 to 1·25 when in suspension and from 0·25 to 1·25 when in biofilm. Conclusions: Synergistic activity of harmaline and CHG against clinical isolates of S. aureus (in suspension and in biofilm) was observed in vitro. Significance and Impact of the Study: This study might provide alternative methods to overcome the problem of drug‐resistance of S. aureus both in suspension and in biofilm.

In Vitro Antiseptic Susceptibilities for Staphylococcus Pseudintermedius Isolated from Canine Superficial Pyoderma in Japan

“…29 Staphylococcus aureus within a biofilm reportedly decreases the efficacy of chlorhexidine as a disinfectant. 30 A recent report suggests that S. pseudintermedius has the potential to form a biofilm. 31 Another explanation could be related to the fact that organic matter decreases the efficacy of disinfectants, including chlorhexidine.…”

Modulatory activity and chemical profile of a hydroalcoholic extract of Crateva tapia L.

“…Xing et al (2012) evaluated the activity of the alkaloid harmaline against clinically isolated strains of S. aureus in combination with the antibiotic chlorhexidine. Their study found that harmaline is a relatively weak substance when confronted with strains tested in cells in suspension as well as in biofilms.…”

The synergy of berberine chloride and totarol against Staphylococcus aureus grown in planktonic and biofilm cultures

“…Following incubation of the set plates at 37 uC for 24 h, the minimum biofilm inhibition concentrations (MBICs) were determined as the lowest concentration to show growth below or equal to that of the control. The minimum biofilm bactericidal concentrations (MBBCs) were identified as the lowest concentration demonstrating no bacterial growth (Hendry et al, 2009;Xing et al, 2012).…”