Inactivation of Listeria monocytogenes and Escherichia coli O157:H7 Biofilms by Micelle-Encapsulated Eugenol and Carvacrol

Abstract

Carvacrol and eugenol were encapsulated in micellar nonionic surfactant solutions to increase active component concentrations in the aqueous phase and used to treat two strains of Listeria monocytogenes (Scott A and 101) and two strains of Escherichia coli O157:H7 (4388 and 43895) grown as biofilms in a Centers for Disease Control and Prevention reactor. L. monocytogenes biofilms were grown in two different growth media, 1:20 TSB and Modified Welshimer's broth (MWB), while E. coli O157:H7 was grown in M9. In general, L. monocytogenes strains were more resistant to both micelle-encapsulated antimicrobials than E. coli O157:H7 strains. The two antimicrobials were equally effective against both strains of E. coli O157:H7, decreasing viable counts by 3.5 to 4.8 log CFU/cm(2) within 20 min. For both bacteria, most of the bactericidal activity took place in the first 10 min of antimicrobial exposure. Biofilm morphology and viability were assessed by the BacLight RedoxSensor CTC Vitality kit and confocal scanning laser microscopy, revealing an increasing number of dead cells when biofilms were treated with sufficiently high concentrations of carvacrol- or eugenol-loaded micelles. This study demonstrates the effectiveness of the application of surfactant-encapsulated essential oil components on two pathogen biofilm formers such as E. coli O157:H7 and L. monocytogenes grown on stainless steel coupons.

Impacts of Sample Preparation Methods on Solubility and Antilisterial Characteristics of Essential Oil Components in Milk

“…In order to improve the distribution of EOs/EOCs in food matrices and reduce interference by food components, various delivery systems, such as emulsions (9,10) and biopolymer capsules (6,(11)(12)(13), have been studied to enhance the antimicrobial activity and reduce the usage level. Commonly, the efficacy of delivery systems is compared to the same concentrations of free (unencapsulated) EOs/EOCs.…”

Effect of Carvacrol on <i>Salmonella</i> Saintpaul Biofilms on Stainless Steel Surface

“…The concentration of 78 µg ml -1 produced a greater reduction in the number of bacterial cells that adhered to the microplate. The authors used SEM and found that the amount of biofilm was reduced in the presence of 39 µg ml -1 carvacrol and was almost absent at 78 µg ml Interesting findings were also reported by PerezConesa et al [7] who assessed the effects of encapsulated carvacrol on the inactivation of L. monocytogenes and E. coli O157:H7 biofilms on stainless steel. The morphological evaluation of biofilm revealed an increasing number of dead cells when the biofilms were treated with sufficiently high concentrations of carvacrol and a reduction of bacterial counts.…”

Antibiotics in Aquaculture – Use, Abuse and Alternatives

“…To enhance shelf life and avoid the degradation of EO in supplemented feed, the encapsulation of EOs could be a plausible means of delivering active EOs into the fish gut, as this would reduce interactions with the food matrix and possibly reduce any toxic effects. This approach has recently been evaluated, and the application of this method to aquaculture is highly promising Piva et al, 2007;Pérez-Conesa et al, 2011;van Vuuren et al, 2010;Donsi et al, 2011).…”