The effect of resuscitation and the incubation-temperature on recovery of uninjured, heat injured and freeze injured enterococci.
Five strains of enterococci were inoculated on the Slanetz and Bartley enterococcus agar (EA), and incubated at 37 degrees C and 44 degrees C following: no injury, heat-injury and freeze-injury. The experiments were repeated introducing a 2 h resuscitation step in Tryptic Soy Agar (TSA) at 37 degrees C and subsequent overlay with EA (TSA/EA) followed by incubation at both 37 degrees C and 44 degrees C. The TSA/EA method gave a significantly better recovery (1% confidence level) than the EA method at both 37 degrees C and 44 degrees C. The effect of incubation-temperature was only significant for two strains of Enterococcus durans, as one strain showed no growth at 44 degrees C and the other strain was recovered significantly (5% confidence level) better at 37 degrees C that at 44 degrees C when employing the EA method. Interpretation of the results using TSA/EA method was easier than that of the EA. Different lactic streptococci and lactobacilli commonly employed in the dairy industry did not develop false positive colonies in TSA/EA incubated at 37 degrees C.
Ewald
S
S
Department of Food Hygiene, Norwegian College of Veterinary Medicine, Oslo.
Eie
T
T
D003470:Culture Media; D016983:Enterococcus / Q000254:growth & development* / Q000302:isolation & purification; D013293:Enterococcus faecalis / Q000254:growth & development* / Q000302:isolation & purification; D016984:Enterococcus faecium / Q000254:growth & development* / Q000302:isolation & purification; D005516:Food Microbiology; D005615:Freezing; D006358:Hot Temperature; D014871:Water Microbiology
D003470:Culture Media