Suitability of Different PCR-DGGE Primer Sets for the Monitoring of Lactic Acid Bacteria in Wine

Lactic acid bacteria (LAB) play a dual role in winemaking as they are the main effectors of malolactic fermentation, but some members can also cause wine spoilage. PCR-DGGE has proved to be a quick tool to study the LAB community and their fluctuation in wine. For detecting wine-associated LAB by PCR-DGGE, the primer sets WLAB1/WLAB2GC, WBAC1/WBAC2GC, Lac1/Lac1o/Lac2GC, 341fGC/518r and rpoB1/rpoB1o/rpoB2GC were tested and evaluated in this study. The primer systems were assessed by the separation of LAB reference strains on DGGE gels and by attributing the resulting amplicons to defined species. Subsequently, the detection of LAB in wine samples and enrichments thereof was compared. While the primer systems WBAC1/WBAC2GC and 341fGC/518r were not appropriate, the Lac1/Lac1o/Lac2GC primer set performed well. However, multiple bands complicated the evaluation. The rpoB1/rpoB1o/rpoB2GC set seemed to be promising for the detection of LAB in wine, although further improvements in terms of the detection limit need to be done. Due to the pronounced sensitivity and the sufficient discrimination of LAB at species level, the WLAB1/WLAB2GC primer system was found to be most suitable for studying the occurrence of LAB in wine

Resistance determinant erm(X) is borne by transposon Tn5432 in Bifidobacterium thermophilum and Bifidobacterium animals subsp. lactis

The erm(X) gene from erythromycin- and clindamycin-resistant Bifidobacterium strains was characterised by polymerase chain reaction and sequence analysis, including flanking regions. Results suggest that the resistance determinant was part of transposon Tn5432 that has been described in several opportunistic pathogens such as Corynebacterium striatum and Propionibacterium acnes

Resistance determinant erm(X) is borne by transposon Tn5432 in Bifidobacterium thermophilum and Bifidobacterium animals subsp. lactis

The erm(X) gene from erythromycin- and clindamycin-resistant Bifidobacterium strains was characterised by polymerase chain reaction and sequence analysis, including flanking regions. Results suggest that the resistance determinant was part of transposon Tn5432 that has been described in several opportunistic pathogens such as Corynebacterium striatum and Propionibacterium acnes

Antibiotic susceptibility of members of the Lactobacillus acidophilus group using broth microdilution and molecular identification of their resistance determinants

The range of antibiotic susceptibility to 13 antibiotics in 101 strains of the Lactobacillus acidophilus group was examined using the lactic acid bacteria susceptibility test medium (LSM) and broth microdilution. Additionally, microarray analysis and PCR were applied to identify resistance genes responsible for the displayed resistant phenotypes in a selection of strains. In general, narrow as well as broad unimodal and bimodal MIC distributions were observed for the Lactobacillus acidophilus group and the tested antimicrobial agents. Atypically resistant strains could be determined by visual inspection of the obtained MIC ranges for ampicillin, chloramphenicol, clindamycin, erythromycin, quinupristin/dalfopristin, streptomycin and tetracycline. For most of these atypically resistant strains underlying resistance determinants were found. To our knowledge erm(A) was detected in lactobacilli for the first time within this study. Data derived from this study can be used as a basis for reviewing present microbiological breakpoints for categorization of susceptible and resistant strains within the Lactobacillus acidophilus group to assess the safety of microorganisms intended for use in food and feed application

Bacterial diversity of naturally fermented game meat sausages: Sources of new starter cultures.

Bacterial communities associated with the ripening process in artisanal wild boar and deer meat sausages were investigated by molecular barcoding using the 16S rRNA gene as a marker. A core microbiota shared by 83.54% of the samples indicated remarkable level of Lactobacillus sake/and Lactobacillus curvatus, accounting for 20.55% in initial and 70.48% in final products as well as spoilage-associated bacteria including Stenotrophomonas, Bacillus, Pseudomonas, Carnobacterium and Brochothrbc, with an average abundance 44.15% at the beginning and 13.98% at the end of the production. Of selected LAB isolates (n = 555), 43.83% were not suitable for food application due to the antibiotic resistance or the presence of the tric gene. Most of the strains designated as safe were able to grow at 25 degrees C even in the presence of 3.0 and 6.0% of NaCl or pH 4.5, but exposure to the same stressors resulted in growth reduction at 12 degrees C. Acidification and antimicrobial activity were found in 65.62% and 37.50% of strains, respectively. Most of the strains showed lipolytic and proteolytic activity, but only 9.37% were able to degrade sarcoplasmic proteins. These results give important information for the development of new starter formulation for the production of high quality game meat sausages

Susceptibility of human and probiotic Bifidobacterium spp. to selected antibiotics as determined by the Etest method

This study reports the antibiotic susceptibility of 203 strains representing human or probiotic associated Bifidobacterium species as determined by the Etest method. Strains showing minimum inhibitory concentration (MIC) for tetracycline >= 16 mu g mL(-1) were detected in all studied Bifidobacterium species/groups (prevalence 4-18%). Mostly the high MICs could be associated with a tet gene, although the correspondence between the phenotypic susceptibility and detection of let determinants was not complete. In addition to tet(W), tet(O), which has not been previously described in bifidobacteria, was detected. Occasional erythromycin (2%) and/or clindamycin (5%) resistant strains were found, while the strains were uniformly susceptible to ampicillin and vancomycin. Bifidobacterium strains displayed,generally high MICs for streptomycin and gentamicin suggesting intrinsic resistance. The Etest on lactic acid bacteria susceptibility test medium supplemented with cysteine proved to be an applicable technique for antimicrobial susceptibility testing of bifidobacteria, and is especially useful when susceptibility data of individual strains is needed. (c) 2007 Elsevier Ltd. All rights reserved