The Investigation of Effect of Carvacrol on Biofilm positive Salmonella spp and Listeria monocytogenes isolates

İlknur  Dağ*,  BükayYenice Gürsu, Gökhan Dikmen,

¹ Eskişehir Osmangazi University; Central Research Laboratory Application and Research Center (ARUM)  26480, Odunpazarı, Eskişehir-Turkey

idag280@gmail.com

Salmonella spp. and Listeria monocytogenes are important pathogenic bacteria, which are transmitted by food. It is known that both microorganisms may produce biofilm on biotic or abiotic surfaces. An adherence of pathogenic microorganisms to food contact surfaces and biofilm formation is dangerous with respect to food security. Because biofilms provide several advantages to their members including such as protection from antibiotics, disinfectans and chemicals.

Recently, alternative strategies or more effective agents exhibiting activity against biofilm-producing microorganisms are of great interest. Researchs focused on effects on plant materials and essential oils. It is reported that the Carvacrol [2-methyl-5-(1-methylethyl)phenol] exhibited strong antimicrobial activity and it is one of the phenolic components of thyme. The aims of this study were (i) to investigate the biofilm existing of Salmonella ve L. monocytogenesis obtained from variety food samples, (ii) to extend the research to evalute the antimicrobial activity of carvacrol on planctonic cells of biofilm positive Salmonella spp ve L. monocytogenesis strains by microbiological and electronmicroscopic methods.

Among the 603 food samples taken for analysis, a total of 6 samples were confirmed positive L. monocytogenes; 8 samples were confirmed positive for Salmonella spp. Isolates were identified by standard microbiological procedures. Biofilm detection was evaluated by microtiter plate assay and tube method. In addition, biofilm production and developments were also investigated on granit surfaces by Scanning electron microscope. All tested Salmonella spp and L. monocytogenes isolates produced biofilm. The minimum inhibitory concentration (MIC) of carvacrol was determined using the broth microdilution method according to M7-A8 of the Clinical Laboratory Standards Institute. Carvacrol was introduced into Mueller Hinton Broth at a concentration of 0.0015, 0.003%, 0.006%, 0.013%, 0.025%, 0.05%, 0.1%, 0.2%, 0.4% and 0.8% (vol/vol) to determine the minimum inhibitory concentration (MIC) and the maximal tolerated concentration (MTC) for each isolates evaluated. Ampicillin was used as a standard drug against E. coli ATCC 25922. MIC results showed a MIC ⩽ 0.025% (vol/vol) for all isolates tested. For Scanning and Transmission electron microscopic studies, isolates were also exposured to the carvacrol at concentrations of  2xMIC, MIC and ½ MIC and results were compared with the control. According to our results, carvacrol showed a high antibacterial potential with very low MIC values on planktonic cells of Salmonella spp and L. monocytogenes. Electronmicroscopically, no growth was observed for the MIC value and a  concentrations higher; cellular damage was also determined at sub MIC concentrations.

Key words: Carvacrol, Salmonella spp, Listeria monocytogenesis, electron microscope

Acknowledgment

This work was supported by a grant from Eskisehir Osmangazi University (Project number  2015-910).

Figures:

Figure 1. (a) TEM micrograph of L. monocytogenes control cells, (b) Carvacrol exposured L. monocytogenes cells.

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