Can Campylobacter jejuni form biofilm on uncoated plastic polymers?

Biofilm formation is one the major strategies developed by bacteria to survive under extreme conditions. In the food industry, foodborne pathogens are able to adhere to and colonize diverse surfaces, such as plastic, stainless steel and glass, leading to biofilm formation, which endangers the effectivity of the cleaning and disinfection procedures. Among them, Campylobacter jejuni poses a significant food safety risk for causing most of the foodborne bacterial infectious gastroenteritis cases reported worldwide. However, their survival strategies are poorly understood. Previous studies have focused on evaluating the effect of (plasma‐)treated plastic surfaces with improved hydrophilicity on the ability of C. jejuni to form biofilm (Ortega-Sanz et al., 2024). However, little is known about the impact of pristine (micro)plastics with strong hydrophobic properties in the survival of the pathogen. In this study, we analysed the ability of 5 C. jejuni strains to form biofilm on flat-bottomed, non-treated 96-well microtiter plates made of polypropylene (PP) and polystyrene (PS) for 96 h at 22 °C and 37 °C under aerobiosis following the crystal violet staining method. Based on the formula of Stepanović et al. (2007), that classifies the isolates as non-, weak, moderate or strong biofilm formers, only 3 isolates (including the two isolates from human origin) were able to form biofilm on PP at both temperatures, although weakly, showing optical density values at 590 nm ranging between 0.098 and 0.103 (Figure 1). However, their ability to form biofilm showed no significant difference compared to the negative control (0.092 ± 0.002) (p > 0.05). The findings indicate that C. jejuni is not really capable of forming biofilm on the hydrophobic plastic materials tested, highlighting the relevance of the surface coating on the attachment and colonization of the pathogen.