title: Antimicrobial activity and antibiotic susceptibility ofLactobacillusandBifidobacteriumspp. intended for use as starter and probiotic cultures.
abstract: Antimicrobial activity and antibiotic susceptibility were tested for 23Lactobacillusand threeBifidobacteriumstrains isolated from different ecological niches. Agar-well diffusion method was used to test the antagonistic effect (againstStaphylococcus aureus,Escherichia coli,Bacillus cereusandCandida albicans) of acid and neutralized (pH 5.5) lyophilized concentrated supernatants (cell-free supernatant; CFS) and whey (cell-free whey fractions; CFW) from de Man-Rogosa-Sharpe/trypticase-phytone-yeast broth and skim milk. Acid CFS and CFW showed high acidification rate-dependent bacterial inhibition; five strains were active againstC. albicans.Neutralized CFS/CFW assays showed six strains active againstS. aureus(L. acidophilusL-1,L. brevis1,L. fermentum1,B. animalissubsp. lactisL-3),E. coli(L. bulgaricus6) orB. cereus(L. plantarum24-4В). Inhibition of two pathogens with neutralized CFS (L. bulgaricus6,L. helveticus3,L. plantarum24-2L,L. fermentum1)/CFW (L. plantarum24-5D,L. plantarum24-4В) was detected. Some strains maintained activity after pH neutralization, indicating presence of active substances. The antibiotics minimum inhibitory concentrations (MICs) were determined by the Epsilometer test method. All strains were susceptible to ampicillin, gentamicin, erythromycin and tetracycline. Four lactobacilli were resistant to one antibiotic (L. rhamnosusLio 1 to streptomycin) or two antibiotics (L. acidophilusL-1 andL. brevis1 to kanamycin and clindamycin;L. caseiL-4 to clindamycin and chloramphenicol). Vancomycin MICs > 256 μg/mL indicated intrinsic resistance for all heterofermentative lactobacilli. The antimicrobially active strains do not cause concerns about antibiotic resistance transfer and could be used as natural biopreservatives in food and therapeutic formulations.
authors.affiliation: Lactina Ltd. , Bankya , Bulgaria.
authors.forename: Ralitsa
authors.initials: R
authors.lastname: Georgieva
authors.affiliation: Department of Biology, Medical Genetics and Microbiology, Faculty of Medicine, Sofia University "St. Kliment Ohridski" , Sofia , Bulgaria.
authors.forename: Lyubomira
authors.initials: L
authors.lastname: Yocheva
authors.affiliation: Department of Biology, Medical Genetics and Microbiology, Faculty of Medicine, Sofia University "St. Kliment Ohridski" , Sofia , Bulgaria.
authors.forename: Lilia
authors.initials: L
authors.lastname: Tserovska
authors.affiliation: Department of Biology, Medical Genetics and Microbiology, Faculty of Medicine, Sofia University "St. Kliment Ohridski" , Sofia , Bulgaria.
authors.forename: Galina
authors.initials: G
authors.lastname: Zhelezova
authors.affiliation: Lactina Ltd. , Bankya , Bulgaria.
authors.forename: Nina
authors.initials: N
authors.lastname: Stefanova
authors.affiliation: Lactina Ltd. , Bankya , Bulgaria.
authors.forename: Akseniya
authors.initials: A
authors.lastname: Atanasova
authors.affiliation: Lactina Ltd. , Bankya , Bulgaria.
authors.forename: Antonia
authors.initials: A
authors.lastname: Danguleva
authors.affiliation: Lactina Ltd. , Bankya , Bulgaria.
authors.forename: Gergana
authors.initials: G
authors.lastname: Ivanova
authors.affiliation: Lactina Ltd. , Bankya , Bulgaria.
authors.forename: Nikolay
authors.initials: N
authors.lastname: Karapetkov
authors.affiliation: Lactina Ltd. , Bankya , Bulgaria.
authors.forename: Nevenka
authors.initials: N
authors.lastname: Rumyan
authors.affiliation: Lactina Ltd. , Bankya , Bulgaria.
authors.forename: Elena
authors.initials: E
authors.lastname: Karaivanova
keywords: MIC; antagonistic effect; lactic acid bacteria