[Molecular methods in the epidemiology of gram-negative bacterial infections]

Abstract

Identification and typing of bacterial isolates from patients and environment are necessary in order to detect the sources of infections. In recent years different molecular typing methods have been carried out and proved more reliable than methods based on phenotypical characters. We have applied two methods of genotyping, i. e. ribotyping and rrnARDRA (Amplified Ribosomal DNA Restriction Analysis) methods, to the study of different bacterial species. Ribotyping was the first universal method for molecular typing of bacteria. We have succeded both in typing various species of enterobacteria (Salmonella Wien, S. Enteritidis, Shigella sonnei, Proteus spp., Morganella morganii, Providencia spp.) by using different restriction endonucleases and in demonstrating the epidemiological importance of the ribotypes identified in each species. Genotyping by rrnARDRA is an identification method based on the analysis of the electrophoretic patterns obtained after restriction endonucleases digestion of the rrn operon sequences amplified by polymerase chain reaction. This is a universal method, because both the same primers and the same endonucleases are utilized for the identification of Gram-positive as well as Gram-negative bacteria. The identification of a bacterial isolate is performed by comparing its profile (number of bands and molecular weight of the fragments) with those from a data-base of profiles of the various species.