Ribotyping for use in studying molecular epidemiology of Serratia marcescens: comparison with biotyping

Ribotyping carried out with a nonradioactive probe (acetylaminofluorene ribosomal RNA kit I from Eurogentec, Seraing, Belgium) was performed for the characterization of 139 hospital strains of Serratia marcescens. These strains, which belonged to 11 biotypes and 1 nontypeable group, were isolated in seven hospitals in Belgium between 1986 and 1992. EcoRI and HindIII were used to obtain cleavage patterns. Analysis of the results produced 27 different patterns with EcoRI and 23 patterns with HindIII. Typeability reached 100%. Combination of the patterns obtained with each enzyme produced 38 distinct ribotypes. Percent similarity values, calculated by using the Dice coefficient and unweighted-pair group average linkage clustering, showed four main clusters and nine subclusters of ribopatterns at a similarity rate of approximately 80% or less. These groups did not coincide with those delimited by biotyping, although a rather good correlation was observed. The simultaneous use of the two methods has potential value in epidemiological studies.