PULSED-FIELD GEL-ELECTROPHORESIS FOR MOLECULAR EPIDEMIOLOGY OF PENICILLIN-RESISTANT STREPTOCOCCUS-PNEUMONIAE STRAINS

The emergence of strains of Streptococcus pneumoniae resistant to peni cillin and other antibiotics has become a major concern for anti-micro bial therapy of pneumococcal infections. The spread of that resistance over the world increases the need for their epidemiological surveilla nce : specific epidemiological markers are required. In this study, pu lsed field gel electrophoresis of genomic DNA was carried out on sixte en resistant isolates of S. pneumoniae from different parts of the wor ld and fifteen resistant isolates from Toulouse. The restriction endon ucleases ApaI and SmaI were used to digest intact chromosomes and the fragments were resolved by field inversion gel electrophoresis (FIGE). Each digest produced 10 to 19 fragments for comparison between strain s. The polymorphism obtained with FIGE was greater than that obtained with serotyping which appeared to be not a good criterion for genetic relatedness. Three common clones could be recognized among the penicil lin-resistant isolates. Two clones were found in Spain and in Toulouse and were associated with serotypes 6B and 9V, respectively. The third clone was isolated in South Africa and in Spain and contained serotyp e 23F isolates and one serotype 19F strain. The FIGE profiles observed in this study also demonstrated that serogroup 23 multiresistant stra ins isolated in Toulouse are genetically closely related and might hav e originated from the same Spanish 23F clone. These results underline the importance of the geographic spread of resistant clones in the inc rease in the incidence of penicillin-resistant pneumococci. They indic ate that pulsed field gel electrophoresis should be an effective tool for the typing of resistant S. pneumoniae strains capable of tracing t heir origin.