Antimicrobial susceptibility of lactic acid bacteria isolated from Sombor cheese

Abstract

Extensive literature data pointed out that some lactic acid bacteria (LABs), the predominant microbiota in fermented dairy products, may serve as reservoirs of antibiotic resistance genes potentially transferable to human pathogens. Hence, there is a growing interest in the possible role of LAB as vectors of antibiotic resistance determinants. This paper reports the susceptibility patterns of a number of LAB species (belonging to the genera Lactococcus, Lactobacillus, and Enterococcus) isolated from different batches of autochthonous Sombor cheese, traditionally made without the addition of starter cultures, and currently proposed as a candidate for PDO/PGI designation. The experimental work was performed to select strains that do not contain antibiotic resistance genes among those with desirable technological characteristics such as rapid acidification, proteolysis, ability to metabolise citrate and form aromogenic compounds. In addition, the results of these screening procedures could also indicate the types and degrees of antimicrobial resistance already present among the LAB community of Sombor cheese, which according to their geographically restricted areas of production, specific manufacturing process and characteristic aroma and appearance, represent a distinct ecological niche.

Opsežni literaturni podaci ukazuju da pojedine bakterije mlečne kiseline, čineći dominantnu mikrofloru u fermentisanim proizvodima od mleka, mogu poslužiti kao rezervoar gena rezistencije na antibiotike, potencijalno prenosivih na patogene mikroorganizme. Stoga postoji rastući interes o mogućoj ulozi bakterija mlečne kiseline kao vektora determinanti rezistencije. Ovaj rad izveštava o profilima antibiotske osetljivosti vrsta bakterija mlečne kiseline (rodovi Lactococcus, Lactobacillus i Enterococcus) izolovanih iz različitih linija proizvodnje autohtonog Somborskog sira, tradicionalno proizvedenog bez dodatka starter kulture, a predloženog za dobijanje oznake geografskog porekla. Eksperimentalni rad je izveden u cilju selekcije sojeva koji ne sadrže gene rezistencije na antibiotike, ali su ujedno nosioci poželjnih tehnoloških karakteristika kao što su brza acidifikacija, proteoliza, sposobnost metabolisanja citrata i formiranje aromogenih komponenti. Ujedno, rezultati ovih 'screening' procedura mogu ukazati na tip i stepen antimikrobne rezistencije prisutne među zajednicom bakterija mlečne kiseline Somborskog sira, koji prema geografski određenom području proizvodnje, specifičnom procesu proizvodnje i karakterističnoj aromi i izgledu predstavlja zasebnu ekološku nišu.