Denmark14-230 clone as an increasing cause of pneumococcal infection in Portugal within a background of diverse serotype 19A lineages

Abstract

Pneumococci of serotype 19A are increasingly found to be the cause of infection in various geographic regions. We have characterized the serotype 19A isolates (n = 288) found among pneumococci responsible for infections (n = 1,925) and pneumococci recovered from asymptomatic carriers (n = 1,973) in Portugal between 2001 and 2006. We show that despite the existence of serotype 19A clones that have a greater potential to cause invasive disease or an enhanced colonization capacity, the lineage that is increasing as a cause of infection in Portugal is a multiresistant clone that is competent at both. The expanding Denmark(14)-230 clone found in Portugal is disseminated in other Mediterranean countries, where it is also increasingly responsible for invasive infections in both children and adults. The lineages driving the rise of serotype 19A infections in Asia and the United States (sequence type 320 [ST320] and ST199) are either absent or account for only a small proportion of isolates in Portugal. These data highlight the importance of locally circulating clones with the ability to compete in the nasopharyngeal niche in the emergence of the serotype 19A lineages which are an increasing cause of infection in various geographic regions.

FIG. 1.

Macrorestriction dendrograms and ST information for serotype 19A isolates. Dice coefficient values (percentages) are indicated in the scale above the dendrogram. Whenever two or more isolates had a macrorestriction pattern with a Dice coefficient of ≥80%, a triangle proportional to the number of isolates is indicated in the dendrogram. The number in boldface type beside each triangle indicates the PFGE cluster number, and the number in parentheses indicates the number of isolates grouped in that cluster. All STs determined for isolates of each PFGE cluster are indicated, and the number in parentheses indicates the number of isolates exhibiting that ST. The distribution of the isolates found in each PFGE cluster (n ≥ 4) over the years of the study is presented. The superscript letters identify STs identifying clones spread internationally, as follows: a, Spain^23F-ST81; b, Netherlands^15B-ST199; c, Greece²¹-ST193; d, Denmark¹⁴-ST230; e, Spain^9V-ST156. Nonsusceptibility to various antimicrobial agents is indicated by superscripts, as follows: R, resistant; I, intermediate; CL, chloramphenicol; CM, clindamycin; EM, erythromycin; PV, penicillin; SXT, co-trimoxazole; TC, tetracycline. The number of isolates sharing the same antimicrobial resistance profile is indicated in parentheses.