Rational evaluation of antimicrobial properties of lactobacilliisolates against some pathogenic microorganisms: a new methodcomparing the susceptibility of indicator microorganisms

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 microorganismswere 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 strainswere in the following order: Escherichia coliO157:H7 > Listeria monocytogenes > Aspergillus parasiticus> Candida parapsilosis. Despite the high susceptibility of L. monocytogenes, it showedthe highest resistance to death among the tested microorganisms.Eefficiency of Lactobacilli CFCS in killing the tested strainsshowed the following susceptibility order: E. coli O157:H7 > A.parasiticus> C. parapsilosis> L. monocytogenes. Antimicrobialproperty was in correlation with the pH value of CFCS. PH hada 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 ingrowth inhibition of the indicator microorganisms was foundpromising, and the suggested data organization method providedadditional information, leading to more precise comparison ofindicator microorganisms

کلیدواژه ها:

Aspergillus parasiticus ، Candidaparapsilosis ، data organizationmethod ، Escherichia coli O157:H7 ، Listeria monocytogenes