title: Assessment of the in vitro inhibitory activity of specific probiotic bacteria against different Escherichia coli strains.
abstract: BACKGROUND
  Lactobacilli and bifidobacteria are often associated with health-promoting effects. These live microorganisms, defined as probiotics, are commonly consumed as part of fermented foods, such as yoghurt and fermented milks, or as dietary supplements. Escherichia coli is a gram-negative, rod-shaped bacterium commonly found in the lower intestine of warm-blooded organisms. As a part of the normal gut microbiota, this microorganism colonizes the gastrointestinal tract of animals and humans within a few hours after birth. All E. coli strains can produce a wide variety of biogenic amines responsible for potentially harmful systemic intoxications. Enterohemorrhagic E. coli serotype O157:H7 is a pathotype of diarrhoeagenic strains with a large virulence plasmid pO157 able to produce 1 or more Shiga toxins.
  
  
  METHODS
  The overall aim of this study was to determine the inhibitory effects of different strains of probiotics on E. coli serotypes, including E. coli O157:H7 (CQ9485). In particular, the antagonistic activity of 4 Bifidobacterium strains (Probiotical SpA, Italy) and 16 lactic acid bacteria, more specifically 14 Lactobacillus spp. and 2 Streptococcus spp., was assessed against selected E. coli biotypes (ATCC 8739, ATCC 10536, ATCC 35218, and ATCC 25922). The diarrhoeagenic serotype O157:H7 was also tested.
  
  
  RESULTS
  The experimental data collected demonstrated an in vitro significant inhibitory effect of 6 Lactobacillus strains, namely L. rhamnosus LR04, L. rhamnosus LR06, L. plantarum LP01, L. plantarum LP02, L. pentosus LPS01, and L. delbrueckii subsp. delbrueckii LDD01, and 2 Bifidobacterium strains, B. breve BR03 and B. breve B632. The inhibiting extent was slightly different among these strains, with L. delbrueckii subsp. delbrueckii LDD01 showing the highest activity on E. coli O157:H7.
  
  
  CONCLUSIONS
  Most of the probiotics studied are able to antagonize the growth of the 5 strains of E. coli tested, including the O157:H7 biotype, well known for their characteristic to produce a wide variety of biogenic amines considered responsible for dangerous systemic intoxications.
authors.affiliation: Biolab Research Srl, Novarese, Italy. l.mogna@mofinalce.it
authors.forename: Luca
authors.initials: L
authors.lastname: Mogna
authors.forename: Mario
authors.initials: M
authors.lastname: Del Piano
authors.forename: Francesca
authors.initials: F
authors.lastname: Deidda
authors.forename: Stefania
authors.initials: S
authors.lastname: Nicola
authors.forename: Liliana
authors.initials: L
authors.lastname: Soattini
authors.forename: Rosaria
authors.initials: R
authors.lastname: Debiaggi
authors.forename: Filomena
authors.initials: F
authors.lastname: Sforza
authors.forename: Gianpaolo
authors.initials: G
authors.lastname: Strozzi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Mogna
mesh_terms: D000818:Animals; D000898:Antibiosis; D001644:Bifidobacterium / Q000254:growth & development*; D015169:Colony Count, Microbial; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects / Q000254:growth & development*; D019453:Escherichia coli O157 / Q000187:drug effects / Q000254:growth & development*; D006801:Humans; D007422:Intestines / Q000382:microbiology*; D007778:Lactobacillus / Q000145:classification / Q000254:growth & development*; D019936:Probiotics / Q000494:pharmacology*; D012703:Serotyping