Development and use of a selective medium for isolation of Leuconostoc spp. from vegetables and dairy products

Institut Agronomique et Veterinaire Hassan II, Departement de Microbiologie Alimentaire et de Biotechnologie, Rabat-Instituts, Morocco.
Applied and Environmental Microbiology (Impact Factor: 3.67). 03/1993; 59(2):607-9.
Source: PubMed


A selective medium (LUSM medium) for the isolation of Leuconostoc spp. was developed. This medium contained 1.0% glucose, 1.0% Bacto Peptone (Difco), 0.5% yeast extract (BBL), 0.5% meat extract (Difco), 0.25% gelatin (Difco), 0.5% calcium lactate, 0.05% sorbic acid, 75 ppm of sodium azide (Sigma), 0.25% sodium acetate, 0.1% (vol/vol) Tween 80, 15% tomato juice, 30 micrograms of vancomycin (Sigma) per ml, 0.20 microgram of tetracycline (Serva) per ml, 0.5 mg of cysteine hydrochloride per ml, and 1.5% agar (Difco). LUSM medium was used successfully for isolation and enumeration of Leuconostoc spp. in dairy products and vegetables. Of 116 colony isolates obtained from fresh raw milk, curdled milk, or various vegetables, 115 were identified as members of the genus Leuconostoc. A total of 89 of these isolates were identified to species; 13.5% of the isolates were Leuconostoc cremoris, 7.9% were Leuconostoc mesenteroides subsp. mesenteroides, 11.2% were Leuconostoc mesenteroides subsp. dextranicum, 16.9% were Leuconostoc mesenteroides subsp. paramesenteroides, 10.1% were leuconostoc lactis, and 40.4% were Leuconostoc oenos. When we compared the counts obtained for two Leuconostoc strains, Leuconostoc dextranicum 181 and L. cremoris JLL8, on MRS agar and LUSM medium, we found no significant difference between the values obtained on the two media.

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    • "Four diverse media and cultural conditions were applied . de Man, Rogosa, and Sharpe (MRS) agar (De Man et al., 1960), Elliker agar (Elliker et al., 1956), KF Streptococcus agar (Devriese et al., 1983), and Leuconostoc selective medium (LUSM; Benkerroum et al., 1993) were used to culture lactobacilli at 37°C, lactococci at 30°C, enterococci at 37°C, and leuconostocs at 25°C, respectively. Ten grams of each sample was added to 90 mL of sterile physiological saline and homogenized for 10 min. "
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