Food Safety/Bacteriology

The Genus Enterococcus: a challenge for the food industry.

Brief Report

Enterococci are members of the lactic acid bacteria (LAB) group. The species of this genus are Gram positive cocci, facultative anaerobe organisms which and tolerant to a wide range of conditions: temperature (10 - 45°C), pH (4.5 - 10.0) and high sodium chloride concentrations [1, 2]. The use of LAB and/or their metabolites for food preservation is generally accepted by consumers as something “natural” and “health promoting”.

Most species of this genus are commensal bacteria of the gastrointestinal tracts of humans and other mammals, so these bacteria are generally considered as low pathogenic, however the isolation of species of Enterococcus that produce important nosocomial infections and acquired antibiotic resistance patterns have been increasing in recent years. Scientific data regarding the emergence of vancomycin-resistant enterococci revealed that antibiotic resistant species show an increased ability to colonize and/or cause disease in hospitalized patients worldwide [3, 4].

The hypothesis is that the species of enterococci with antimicrobial resistant and virulence factors [5, 6, 7] that colonize animal foods might enter into the human food chain and be a potential public health risk in inmunocompromised patients [8].

Another use of these organisms is as potential probiotics. As the bibliography expresses (FAO-WHO) [9], “…probiotics are additives containing live microbes that beneficially affect a host by improving the properties of the host intestinal microflora”. Enterococcus strains are used as probiotics but do not have virulence factors and antimicrobial resistance genes. Most bacteria are used as probiotics, however Enterococcus spp. have the ability to exchange resistance determinants intra-species and inter-species and become more virulent.

For these reasons and to differentiate secure species from pathogenic species, food microbiology has initiated investigations about the presence and characterization of these bacteria in animal foods and dairy products such as sausages, meat, cheese and milk.

In conclusion, the dualistic aspects of enterococci still represent a great challenge to the food industry and constitute a vast field for scientific research.

References

1. Foulquié Moreno MR, Sarantinopoulos P, Tsakalidou E, De Vuyst L. The role and application of enterococci in food and health. International Journal Food Microbiology. 2006;106:1-24.

2. Hardie JM, Whiley RA. Classification and overview of the genera Streptococcus and Enterococcus. Journal Applied Microbiology.1997;83:1S-11S.

3. Torres-Viera C, Dembry LM. Approaches to vancomycin-resistant enterococci. Current Opinion in Infectious Diseases. 2004;17:541-547.

4. de Bruin MA, Riley LW. Does vancomycin prescribing intervention affect vancomycin-resistant enterococcus infection and colonization in hospitals? A systematic review. BMC Infectious Diseases. 2007;7:24.

5. Eaton TJ, Gasson MJ. Molecular screening of Enterococcus virulence determinants and potential for genetic exchange between food and medical isolates. Applied Environmental Microbiology. 2001;67:1628-1635.

6. Robredo B, Singh KV, Baquero F, Murray BE, Torres C. Vancomycin resistant enterococci isolated from animals and food. International Journal Food Microbiology. 2000;54:197-204.

7. Gelsomino R, Vancanneyt M, Cogan TM, Condon S, Swings J. Source of enterococci in a farmhouse raw-milk cheese. Applied Environmental Microbiology. 2002;68:3560-3565.

8. Huys G, D'Haene K, Collard JM, Swings J. Prevalence and Molecular Characterization of Tetracycline Resistance in Enterococcus isolates from Food. Appl Environ Microbiol. 2004; 70(3): 1555-1562.

9. FAO-WHO 2001. Food and agriculture organization of the United Nations, World Health Organization. Report of a joint FAO-WHO expert consultation on evaluation of health and nutritional properties of probiotics in food including powder milk with live lactic acid bacteria. Córdoba, 2001. Available in: ftp://ftp.fao.org/docrep/fao/009/a0512e/a0512e00.pdf