Biofilm Formation by Listeria monocytogenes Utilizes a Primary Colonizing Microorganism in Flowing Systems

Abstract

Listeria monocytogenes serotype 3a and Pseudomonas fragi ATCC 4973 were examined for attachment capability and biofilm development on glass coverslips under flowing systems. Tryptic soy broth supplemented with yeast extract was the growth medium. A continuous flow slide chamber was developed for in situ observations using phase-contrast microscopy. Glass coverslips were examined by epifluorescent and scanning electron microscopy for biofilm formation. The ultrastructure of attached test organisms was examined for the presence of exopolymers using transmission electron microscopy. In pure cultures, attachment of L. monocytogenes to glass coverslips was sparse, while P. fragi accumulated on glass coverslips as a confluent layer of cells. When L. monocytogenes was grown in mixed culture with P. fragi, an exopolymer-producing microorganism, attachment and microcolony formation by L. monocytogenes was enhanced. Results suggest that under flowing conditions the presence of an exopolymer-producing microorganism may be more important than hydrophobicity, surface charge, or flagellar movement in attachment of L. monocytogenes to inert surfaces.

Differential efficacy of a chlorine dioxide-containing sanitizer against single species and binary biofilms of a dairy-associated Bacillus cereus and a Pseudomonas fluorescens isolate

“…enhance the attachment of Gram-positive bacteria, such as L. monocytogenes, to stainless steel surfaces (Sasahara and Zottola 1993). Similarly, in this study, counts of attached B. cereus DL5 cells increased by ca 0á5±1 log cfu cm ±2 when co-cultured with Ps.¯uorescens M2.…”

“…It has been hypothesized that the EPS produced by Pseudomonas spp. may contribute to this phenomenon (Sasahara and Zottola 1993). In this study, apparent EPS was visible in scanning electron micrographs of binary bio®lms of B. cereus DL5 and Ps.¯uorescens M2.…”

“…In addition, the colonization of a surface by one bacterium can reportedly enhance the attachment of others to the same surface (Sasahara and Zottola 1993;Jones and Bradshaw 1997;Mùller et al 1998).…”

“…However, it has recently been reported that two bacteria present in an in vitro binary bio®lm may enhance each other's survival of sanitizer treatments compared with the corresponding single species bio®lms (Leriche and Carpentier 1995). Studies involving in vitro binary bio®lms have focused mainly on the interactions between two Gram-negative bacteria (Banks and Bryers 1991;Stewart et al 1994;Huang et al 1995;Leriche and Carpentier 1995;Cowan et al 2000), with the exception of binary species bio®lms of Pseudomonas and Listeria monocytogenes (Sasahara and Zottola 1993;Fatemi and Frank 1999). In this study, the growth and response to repeat treatments with chlorine dioxide of two bacteria of dairy origin (B. cereus DL5 and Ps.¯uorescens M2) was evaluated in vitro in single and binary bio®lms using a laboratory-scale¯ow chamber.…”

Microbial contamination after sanitation of food contact surfaces in dairy and meat processing plants

“…Some bacteria (such as in genera klebsiella, Pseudomonas and Staphylococcus) produce exopolymers that can fix additional microorganisms. Firmly attached to the surface, these can survive in the form of mixed biofilms (Sasahara & Zottola 1993). Both pathogenic and food spoilage microorganisms have been isolated from such bacterial communities.…”