Comparison of three molecular methods used for subtyping of Legionella pneumophila strains isolated during an epidemic of Legionellosis in Rome

Abstract

In the summer of 2003 a community-acquired outbreak of Legionella pneumophila occurred in Rome, Italy. Three molecular typing methods, pulse-field gel electrophoresis, amplified fragment length polymorphism analysis, and sequence-based typing (SBT), were used to establish the clonal correlation among the isolates of the epidemic cluster. By comparison of the methods, SBT was the most rapid and the easiest to perform and provided unambiguous results.

FIG. 1.

PFGE analysis of genomic DNA from a clinical isolate (sample in lane 1) and environmental isolates (samples in lanes 2 to 10) from the epidemic. The samples in lanes 11 and 12 were unrelated environmental and clinical strains, respectively, and the sample in lane 13 was the L. pneumophila ATCC 33152 type strain. Lanes M, molecular weight marker (S. cerevisiae).

FIG. 2.

AFLP analysis. (A) AFLP performed according to the version 1.2 standard EWGLI AFLP protocol; (B) AFLP performed with Taq polymerase from a commercial PCR kit. The genomic patterns of the clinical isolate (sample in lane 1) and environmental isolates (samples in lanes 2 to 10) from the epidemic are shown. The samples in lanes 11 and 12 are unrelated environmental and clinical strains, respectively. The sample in lane 13 is the L. pneumophila ATCC 33152 type strain. Lanes M, MBI Fermentas ladder mix.