Rational evaluation of antimicrobial properties of lactobacilli isolates against some pathogenic microorganisms: a new method comparing the susceptibility of indicator microorganisms

Authors

1 Department of Food Hygiene and Quality Control, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran; Department of Molecular Genetics, National Institute of Genetic Engineering and Biotechnology, Tehran, Iran

2 Department of Food Hygiene and Quality Control, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran

3 Department of Medicinal Chemistry, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran

4 Department of Biotechnology, Faculty of New Technologies and Energy Engineering, Shahid Beheshti University- GC, Tehran, Iran

5 Department of Molecular Genetics, National Institute of Genetic Engineering and Biotechnology, Tehran, Iran

Abstract

BACKGROUND: Lactobacilli are known as a valuable source
of antimicrobial compounds and have a high potential of use in
food biopreservation against food related microorganisms.
OBJECTIVES: Antimicrobial potency of 63 dairy lactobacilli
isolates against four highly important food-related microorganisms
were evaluated. In addition, a new way in data organization was
introduced, which led to a more informative and rational
comparison of indicator microorganisms' susceptibilities to a set
of compounds. Correlation of pH and antimicrobial properties
was investigated. METHODS: Microbroth dilution assay was
used to evaluate indicator microorganisms' susceptibility to
lactobacilli CFCS (cell free culture supernatant). Results were
organized by both the conventional way - demonstrating the
minimum inhibitory and lethal concentrations of CFCS - and a
new suggested method, representing comparative effectiveness
of each CFCS specimen against indicator microorganisms of
comparison interest. RESULTS: Susceptibilities of tested strains
were in the following order: Escherichia coliO157:H7 > Listeria
monocytogenes > Aspergillus parasiticus> Candida parapsilosis.
Despite the high susceptibility of L. monocytogenes, it showed
the highest resistance to death among the tested microorganisms.
Eefficiency of Lactobacilli CFCS in killing the tested strains
showed the following susceptibility order: E. coli O157:H7 > A.
parasiticus> C. parapsilosis> L. monocytogenes. Antimicrobial
property was in correlation with the pH value of CFCS. PH had
a pronounced impact on susceptibilities of C. parapsilosisand E.
coli in pH values of concentrated CFCS lower than 4 and 4.5,
respectively. CONCLUSIONS: Potency of lactobacilli isolates in
growth inhibition of the indicator microorganisms was found
promising, and the suggested data organization method provided
additional information, leading to more precise comparison of
indicator microorganisms.

Keywords

Iranian Journal of Veterinary Medicine
Volume 7, Issue 4 - Serial Number 4
January 2014
Pages 243-252

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