Knowledge Based Bio-Economy


Confronting the clinical relevance of biocide induced antibiotic resistance (FOOD QUALITY AND SAFETY)

Project acronym: BIOHYPO

Title of project: Confronting the clinical relevance of biocide induced antibiotic resistance

Research area: Food Quality and Safety

Contract No: 227258

EU contribution: €2 999 705

Start date: June 2009

Duration: 42 months

Status: finalised

Biocides have been in use for hundreds of years as antiseptics and for disinfection and preservation. Despite this widespread and growing use, most bacterial and fungal species remain susceptible to biocides. The dramatic increase and spread of resistance to antibiotics, linked to reports of co- and cross-resistance between antibiotics and biocides, has raised speculation on the potential hazard of biocide use.

BIOHYPO investigated whether biocide use in the food chain would result in a clinically relevant increase of antibiotic resistance in human pathogens and tested four individual hypotheses. These are:

  • That the use of biocides produces an increase in antibiotic resistance in microorganisms.
  • That antibiotic resistance due to biocides is of clinical relevance.
  • That intervention strategies can limit the impact of biocide use on antibiotic resistance and permit their safe use.
  • That biocide use generates a reduction in susceptibility to biocides.

The core of BIOHYPO involved phenotypic screening of human pathogens (organisms that cause disease such as bacteria) that are responsible for food-borne infections. This phenotypic screening has shown, in selected cases, evidence of phenotypes with reduced susceptibility to biocides. BIOHYPO has screened over 4 000 strains of multiple species, including staphylococcus aureus (1 600 strains), salmonella enteritidis (900 strains), escherichia coli (500 strains), and the yeast candida albicans (600); and, in addition, species of interest to the dairy sector including streptococci, lactococci and lactobacilli.

This large effort on susceptibility testing for biocides allows us, for the first time, to define epidemiological cut-off values (ECOFFs) and clear identification of the ‘normal’ susceptibility profile for many bacterial species to biocides. The ECOFF values are being published and the graphs are available on the project website .

Only in a few cases were bacterial populations with a clearly decreased susceptibility profile found. No evidence for resistance to biocides could be found in food-grade bacteria and no evidence of reduced susceptibility was detected in any species towards sodium hypochlorite (bleach).

In summary, the BIOHYPO investigation into the susceptibility profiles for the biocides sodium hypochlorite, triclosan, benzalkonium chloride and chlorhexidine, indicates no risk of antibiotic resistance in food-grade bacteria or evidence of antibiotic resistance selection in enterobacteria.

In staphylococci, sodium hypochlorite and triclosan do not currently present any hazard for antibiotic resistance; while cationic biocides may represent – at least in staphylococci – a hazard, by potentially exerting a selective pressure on plasmid carrying MDR clones. Based on the data of the phenotypic and molecular analysis, the consortium came to the conclusion that biocide use throughout the food chain appears to be far from representing a direct risk for promoting clinically-relevant antibiotic resistance in pathogens.

Website of project:

Coordinator: Dr. Marco Rinaldo Oggioni,



  • QBR, Quotient Bioresearch Limited, UK,
  • ISS, Istituto Superiore di Sanità, Italy,
  • INESC-ID, Instituto de Engenharia de Sistemas e Computadores, Investigação e Desenvolvimento em Lisboa, Portugal,
  • METU Department of Environmental Engineering, Middle East Technical University, Turkey,
  • LYSOFORM,  Dr. Rosemann GmbH, Germany,
  • BIOLAB, Biolab Española, S.L.; Parc Científic de Barcelona, Spain,
  • CSIC, Departamento de Biotecnologia Microbiana, Centro Nacional de Biotecnologia, Spain,
  • GU, Department of Microbiology, Gazi University Faculty of Medicine, Turkey,
  • UMI Dip. Scienze e Tecnologie Alimentari e Microbiologiche (Di.S.T.A.M.), Università di Milano, Italy,
  • UNIBE Institute for Infectious Diseases, University of Bern, Switzerland,
  • UNIFI, Dip. di Biotecnologie Agrarie, Università degli Studi di Firenze, Italy,
  • AAT, Advanced Analytical Technologies S.r.l., Italy,