Stability of clonally related DNA fingerprints and cell-wall peptide patterns in geographic isolates of multiresistant epidemic clones of Streptococcus pneumoniae

Abstract

Objective: To determine the stability of multidrug-resistant epidemic clones of Streptococcus pneumonia. Methods: Polymerase chain reaction (PCR) was used to amplify the penicillin-binding protein (PBP) genes 1A, 2X, and 2B, followed by fingerprinting after restriction digestion of the amplified molecules. Cell walls were isolated, digested by the autolytic amidase of pneumococcus, and the family of stem peptides was separated by high-pressure liquid chromatography. Results: Twenty-eight isolates of multidrug-resistant capsular type 6B S. pneumoniae recovered in Iceland between 1990 and 1992 and ten isolates of the multidrug-resistant capsular type 23F S. pneumoniae recovered in the United States, Portugal, Croatia, and South Korea between 1989 and 1996 were compared for restriction fragmentation length polymorphism (RFLP) of their PBP genes 1A, 2X, and 2B, using the PCR for amplification. Five isolates each of the multidrug-resistant capsular type 6B pneumococci from Iceland and the capsular type 23F isolates from Cleveland, Ohio, were also compared for their muropeptide profiles, using a high-performance liquid chromatography (HPLC) system to separate the family of stem peptides generated by enzymatic hydrolysis. The isolates representing the two major and internationally spread epidemic clones have retained the clone-specific RFLP fingerprints of their PBP genes and also reproduced distinct cell-wall stem peptide patterns characteristic of the two pneumococcal clones. Conclusions: The data further document the considerable stability of clonal types of the multiresistant epidemic clones of S. pneumoniae over time and over a wide range of geographic isolation sites.