Invasive Streptococcus pneumoniae isolates from Argentinean children: serotypes, families of Pneumococcal Surface Protein A (PspA), and genetic diversity.

REGUEIRA M; PACE J; BONOFIGLIO L; CALLEJO R; RUVINSKY R; DI FABIO JL; MOLLERACH M; HOLLINGSHEAD S; BRILES D

Alaska

Simposio; 3rd International Symposium on Pneumococci and Pneumococcal Diseases (ISPPD); 2002

Control of pneumococcal diseases is being complicated by the prevalence of penicillin-resistant and multidrug-resistant pneumococcal strains. The 23-valent polysaccharide vaccine has a limited efficacy. Newer vaccines, in which smaller number of polysaccharides are chemically conjugated to carrier proteins elicit improved immune responses against capsular types included in the formulation. In a different approach PspA is one of the candidates to develope a better pneumococcal vaccine. A surveillance program for S. pneumoniae isolated from invasive disease occurring in children has been developed in different geographic areas of Argentina. From 1993 to 2000, 1293 invasive isolates recovered in 31 hospitals from 19 argentinian cities were studied to determine capsular type and antimicrobial susceptibility. The present study provides epidemiological information about serotypes, PspA family distribution and genetic diversity of S. pneumoniae isolates and expand our knowledge of coverage for the recently introduced 7-valent conjugated vaccine and for potential PspA based vaccines. The most frequent serotypes were 14, 5, 1, 6A/B, 7F, 9V and 19A,. According this distribution the recently introduced 7-valent conjugated vaccine would cover only 53,4% of invasive pathologies caused by S. pneumoniae in Argentina. The overall percentage would increase to 77,6% and 82,9% with the 9- and 11-valent conjugated vaccines respectively. We selected 148 isolates considering the prevalence of serotypes. PspA family was characterized by PCR: 54.7% were family 1 PspA, 41.9 % were family 2 and 3.3 % showed positive reaction for both families. BOX-PCR typing of 63 isolates belonging to capsular types 1, 5, 7F, 9V and 14 produced 38 distinct fingerprints which could be consolidated into 10 BOX-PCR types at the 85% homology level. Three different BOX-PCR types were detected for penicillin resistant serotype 14 and isolates of type 5 and 7F respectively. By contrast, isolates of serotype 9V, 1 and penicillin sensible serotype 14 presented higher diversity. Ongoing surveillance programs for invasive pneumococcal disease can be used to monitor the appropriateness of existing vaccine formulations and to decide the regional introduction of new vaccines that are currently under development.