Autolysis of Listeria monocytogenes strains isolated from food and clinical specimens

Abstract

Autolysis of Listeria monocytogenes strains isolated from clinical and food specimens were tested under starvation conditions. Late exponential phase harvested bacterial cells were transferred in potassium phosphate buffer (100 mM, pH 7) and incubated at 37 degrees C to induce lysis. At the end of the 48 h incubation period a heterogeneous autolysis profile was observed among the tested strains. All the clinical strains exhibited high autolysis i.e. above 75%. Meanwhile, the extent of food isolates was not as high as the clinical ones but demonstrated a great variability - ranging between 22 to 88%. An increase in the amount of intracellular markers upon lysis was also measured in the higher autolytic clinicat strain - UVF172, compared to low autolytic food strain - UVF114. The results obtained from the study provided evidence that autolysis in L. monocytogenes is strain dependent and revealed that tested clinical isolates had a higher level of autolysis than food isolates.