3/13/2016 yersinia enterocolitica yersinia enterocolitica classification susceptibility and tolerance 18 flagellar H-antigens have been Grows at temperatures below 40c identified ·Doubling times Complete O and H serotyping is seldom -300C is about 34 min done -220C is about 1h Other schemes for serotyping -70C is about 5 h bacteriophage typing -10C is about 40 h -multienzyme electrophoresis Withstands freezing for extended periods -RFLP restriction fragment length of time polymorphisms Persists longer in cooked foods than raw plasmid DNA foods yersinia enterocolitica Yersinia enterocolitica susceptibility and tolerance susceptibility and tolerance Number of bacteria may increase a million fold on cooked pork within 24h at ·Susceptible to heat 250C or within 10 days at 70C Killed by pasteurization at 71.80C for 18 Can grow in refrigerated vacuum-packed min foods Killed by exposure to hot water 800C for Grows over a pH range of 4-10 with an 10-20min optimum pH of 7.6 Killed by ionizing radiation and sodium Acid tolerance is enhanced with by nitrite and nitrate production of urease which hydrolyzed urea to release ammonia Tolerates 5%sodium chloride3/13/2016 4 Yersinia enterocolitica classification • 18 flagellar H-antigens have been identified • Complete O and H serotyping is seldom done • Other schemes for serotyping - bacteriophage typing - multienzyme electrophoresis - RFLP restriction fragment length polymorphisms - plasmid DNA Yersinia enterocolitica susceptibility and tolerance • Grows at temperatures below 4 O C • D gm oublin g ti mes - 30 OC is about 34 min - 22 OC is about 1 h - 7 OC is about 5 h - 1 OC is about 40 h • Withstands freezing for extended periods of time • Persists longer in cooked foods than raw foods Yersinia enterocolitica susceptibility and tolerance • Number of bacteria may increase a million fold on cooked pork within 24h at 25 OC or within 10 days at 7 O C • Can grow in refrigerated vacuum-packed foods • Grows over a pH range of 4-10 with an opti H f 7 6 timum pH of 7.6 • Acid tolerance is enhanced with by production of urease which hydrolyzed urea to release ammonia Yersinia enterocolitica susceptibility and tolerance • Susceptible to heat • Killed by pasteurization at 71.8 OC for 18 min • Killed by exposure to hot water 80 OC for 10-20 min • Killed by ionizing radiation and sodium nitrite and nitrate • Tolerates 5% sodium chloride