Influence of growth conditions on biofilm formation of Listeria monocytogenes

Abstract

Listeria monocytogenes is ubiquitous in nature and a major concern for the food industry, since it is the causal agent of the serious foodborne illness listeriosis. This organism can be introduced through many routes to food-processing environments and may become established on food-processing equipment. Subsequently, food products may become contaminated during processing. In addition, the bacterium can grow at refrigeration temperatures. Biofilms are regarded as important with respect to the survival and growth of microorganisms in the food industry. Microorganisms growing in biofilms are protected against cleaning and disinfection and are difficult to eradicate. L. monocytogenes may grow in biofilms that protect them against environmental stress and can be isolated from surfaces after cleaning and disinfection. In this study, a total of eight L. monocytogenes strains isolated from the meat industry and one reference strain L. monocytogenes ATCC 19111 were studied for their capability to form a biofilm. The biofilm forming behavior of nine L. monocytogenes strains was determined in two different media, Tryptone soya yeast extract broth (TSYEB) or Brain-heart infusion broth (BHI), at temperatures 7 ºC, 25 ºC, 37 ºC, 42 ºC for 5 days. The method used to assess biofilm formation was crystal violet staining. All strains were able to form biofilm, but the growth condition affected the levels formed. The lowest biofilm formation was observed at 7 ºC. Further, the most effective medium in promoting biofilm production by the L. monocytogenes isolates from meat was BHI medium while for reference strain L. monocytogenes ATCC 19111 it was TSYEB. Incubation temperature was the most significant factor influencing the biofilm production levels, and also the type of used nutritive medium was important factor.

Growth, viability and architecture of biofilms of Listeria monocytogenes formed on abiotic surfaces

“…On the other hand, Zeraik and Nitschke 14 demonstrated that L. monocytogenes produced more biofilm in nutrient rich medium. In the present study, BHI broth was used because it has been reported as an effective medium to promote biofilm formation by L. monocytogenes isolates from different origins, at various surfaces 2, 15. It was observed 10 6 –10 8 CFU of L. monocytogenes /cm 2 were present in biofilms formed on stainless steel and glass coupons, despite incubation times evaluated.…”

Influence of incubation conditions on the formation of model biofilms byListeria monocytogenesandSalmonellaTyphimurium on abiotic surfaces

“…; Tomičić et al . ), all performed in microtiter plates and at temperatures ranging between 7 and 42°C, nutrient‐rich medium was reported to favour increased L. monocytogenes biofilm formation. However, in a few of these studies (e.g.…”

Assessment of drug susceptibility and biofilm formation ability by clinical strains of Listeria monocytogenes

“…Due to its ability to produce biofilm, L. monocytogenes is more resistant to antibiotics, host immune system [7,8], biocides, or stress [13,14]. L. monocytogenes can produce biofilms on various surfaces used in medicine or industry, such as polystyrene, glass, and stainless steel [15,16].…”