Serotypes and genotypes of invasive pneumococci in the central part of Slovenia

Abstract

To investigate epidemiology of invasive pneumococcal disease (IPD) in the central part of Slovenia in a population with no routine pneumococcal vaccination, we carried out serotyping of isolates by sequential multiplex polymerase chain reaction (PCR) and genotyping by repetitive sequence-based PCR (rep-PCR) and some by multilocus sequence typing. IPD was confirmed in 134 (26.5 %) of 510 acutely ill patients, either by a positive blood culture or real-time PCR (rt-PCR). In 94 patients, isolates were available for typing (24 from blood and 70 from nasopharynx). They belonged to 12 different serotypes; the most prevalent were 14 (27.6 % isolates), 9V, 3 (12.7 % each), 7F (9.5 %), 19A, and 1 (7.4 % each) followed by 4, 6A/B, 19F, 23F, 18C, and 33F. Genotyping yielded 34 rep-PCR genotypes and 13 subtypes; six were found in serotype 14, one in 9V, four each in 3, 19A, and 6A/B, three each in 7F and 1, and two each in 4, 19F, 23F, and 18C. Serotype 9V was the most homogenous and 14 and 19A were heterogenous and had two divergent clonal groups each. The most common genotypes belonged to virulent widespread clones, like ST162, ST9, ST15, ST156, ST191, and ST1377; however, sporadic clones were also observed.