RESUMO
The aim of this study was to evaluate the susceptibility of 197 isolates of Lactobacillus paracasei, isolated from Italian fermented products coming from different geographical areas, to tetracycline and erythromycin, two antimicrobials widely used in clinical and animal therapy. Isolation media were supplemented with antibiotics according to the microbiological breakpoints (BPs) defined by European Food Safety Authority (EFSA). Isolates were identified at the species level and were typed by rep-PCR using the (GTG)(5) primer. A total of 121 genotypically different strains were detected and their phenotypic antimicrobial resistance to tetracycline and erythromycin was determined as the minimum inhibitory concentration (MIC) using the broth microdilution method. The presence of the genes ermB, ermC and tetL, tetM, tetS, tetW, in the phenotypically resistant isolates was investigated by PCR. Tetracycline induction of tetM expression on representative resistant strains, grown in medium either lacking or containing the antibiotic, was also analyzed by RT-PCR. Among the 121 tested strains, 77.7% were susceptible to tetracycline (MIC
Assuntos
Antibacterianos/farmacologia , Farmacorresistência Bacteriana/genética , Contaminação de Alimentos/análise , Transferência Genética Horizontal , Lactobacillus/efeitos dos fármacos , Contagem de Colônia Microbiana , Qualidade de Produtos para o Consumidor , DNA Bacteriano/análise , Relação Dose-Resposta a Droga , Eritromicina/farmacologia , Fermentação , Microbiologia de Alimentos , Humanos , Itália , Lactobacillus/genética , Testes de Sensibilidade Microbiana , Tetraciclina/farmacologiaRESUMO
Microbial succession during Parmigiano-Reggiano cheesemaking was monitored by length heterogeneity PCR (LH-PCR), considering the intact and lysed cells at different stages of cheese production and ripening. When starter species underwent autolysis, species coming from milk were able to grow. For the first time, the LH-PCR technique was applied to study a fermented food.
Assuntos
Bactérias/classificação , Bactérias/crescimento & desenvolvimento , Biodiversidade , Queijo/microbiologia , Bactérias/genética , Bactérias/isolamento & purificação , Bacteriólise , Análise por Conglomerados , Impressões Digitais de DNA , DNA Bacteriano/genética , Genótipo , Reação em Cadeia da Polimerase/métodos , Técnica de Amplificação ao Acaso de DNA PolimórficoRESUMO
A sensitive PCR method amplifying an internal fragment of the major tail protein gene was developed to detect Lactobacillus delbrueckii subsp. lactis lytic bacteriophages in undefined, thermophilic whey starters used in Italy for production of Grana and Provolone cheeses. PCR was applied to several lytic Lb. delbrueckii subsp. lactis bacteriophages, which were highly diverse according to restriction analysis and phage host range. PCR detected the presence of phages in two out of 11 cultures, when applied to whey starters for Grana Padano cheese sampled from different cheese plants. The presence of actively growing phages in infected cultures was confirmed by traditional test. The PCR method proved to be useful to screen for the presence of Lb. delbrueckii subsp. lactis phages in thermophilic whey starters.