Pneumococcal pspA sequence types of prevalent multiresistant pneumococcal strains in the United States and of internationally disseminated clones

In a recent genotypic survey of beta-lactam-resistant pneumococci recovered in different areas of United States during 1997, eight clonal types that e ach represented 3 to 40 isolates accounted for 134 of 144 isolates (G. Gher ardi, C. Whitney, R. Facklam, and B. Beall, J. Infect. Dis. 181:216-229, 20 00), We determined the degree of pspA gene diversity among these 134 isolat es and for 11 previously characterized internationally disseminated multire sistant strains. Thirty-four different pspA restriction profiles were deter mined for an amplicon encompassing the variable portion of the structural g ene that encodes the surface-exposed domain of PspA and a variable-length p roline-rich putative cell wall-associated domain, These restriction profile s closely correlated with those of 33 different pspA sequence types of an a pproximately WO-residue region corresponding to residues 182 to 410 of the strain Rx1 PspA. These residues encompass a 100-residue clade-defining regi on known to contain cross-protective epitopes for which 17 sequence types w ere found. Distinct, conserved pspA sequence types were found for the major ity of strains within seven of the eight U.S. clonal types assessed, while one pulsed-field gel electrophoresis type was represented by isolates of th ree distinct PspA clades, Sequence typing of pspA provides an added level o f specificity in the subtyping of isolates and is a necessary first step in determining the components needed in a PspA vaccine which could elicit eff ective cross protective coverage.