Antimicrobial Effect of an Essential Oil Blend on Surface-attached Salmonella on Polyvinyl Chloride

Introduction: The majority of drinking water lines for broilers are made of polyvinyl chloride (PVC) and surface attachment of Salmonella on the inner surface of water lines can be the initial stage of biofilm development. These biofilms can be the source of Salmonella infection in water lines and are known to resist many antimicrobial compounds. Essential oils (EO) have antimicrobial properties and can be mixed with water at low concentrations to deactivate Salmonella attached to PVC surfaces.

Purpose:  The objective of this study was to determine the effect of an essential oil blend on Salmonella attached to PVC coupon (1.8 by 2 cm tetragonal piece) surfaces compared to chlorine and untreated control.

Methods: Sterilized PVC Type 1 coupons (n = 30) were incubated in 2.2 × 10⁷ CFU/ml of Salmonella strain cocktail (Enteritidis, Heidelberg, and Typhimurium) in TSB for 96h at 37°C at 100 rpm to develop Salmonella attachment. Coupons (n = 10/group) with attached Salmonella were treated with EO (0.05%), sodium hypochlorite (5 ppm), or deionized water, and incubated at 25°C for 24h at 100 rpm. After rinsing with PBS, coupon surfaces were swabbed using a sterile sponge premoistened with 8 ml of D/E neutralizing broth, then stomached in 50 ml of D/E neutralizing broth for 1 min at 260 rpm, and enumerated on XLT-4 plates and enriched for Salmonella (when direct plating was negative).

Results:  There were no Salmonella colonies detected via direct plating and enrichment on PVC coupons treated with EO or sodium hypochlorite. The average log CFU/cm² (± standard error) of the control was 2.6 ± 0.34, which was significantly higher than treated groups.

Significance: The EO mixture and chlorine with water may be used to deactivate Salmonella attached to PVC surfaces.