Molecular typing of Listeria monocytogenes isolated from clinical and food samples

Listeria monocytogenes is an emergent foodborne pathogen acquired by the ingestion of contaminated food. This bacterium causes a disease called listeriosis, whose mortality rate world wide is around 20% to 30%, reaching up to 80% in cases of neonatal infections. The random amplified polymorphic DNA technique allows different isolates to be distinguished and characterized at the molecular level, which can provide useful information about the diversity of this pathogen in Colombia. To molecularly characterize different L. monocytogenes isolates from food and clinical samples using this technique to determine possible relationships among these two origins. Thirty eight L. monocytogenes isolates were analyzed; 22 from human clinical samples and 16 from food processing plants and food using two 10bp primers (HLW74, Arbitrary). The data were analyzed using Quantity One and SYN-TAX software. A high percentage of polymorphism was detected with both primers (HLWL-74, 81.81%; Arbitrary, 85.71%). Two major lineages were found, which were divided into four major clusters (A, B C and D) and great genetic diversity was observed. Most of the clinical isolates were grouped within the same cluster, and were more distantly related to the food isolates. The results of this study demonstrate a high degree of genetic diversity of DNA polymorphisms among the L. monocytogenes isolates circulating in Colombia, which could reflect phenotypic and pathogenic differences in these isolates.