Abstract
BackgroundMeningococcal disease is infrequently found in Taiwan, a country with 23 million people. Between 1996 and 2002, 17 to 81 clinical cases of the disease were reported annually. Reported cases dramatically increased in 2001–2002. Our record shows that only serogroup B and W135 meningococci have been isolated from patients with meningococcal disease until 2000. However, serogroup A, C and Y meningococci were detected for the first time in 2001 and continued to cause disease through 2002. Most of serogroup Y meningococcus infections localized in Central Taiwan in 2001, indicating that a small-scale outbreak of meningococcal disease had occurred. The occurrence of a meningococcal disease outbreak and the emergence of new meningococcal strains are of public health concern.MethodsNeisseria meningitidis isolates from patients with meningococcal disease from 1996 to 2002 were collected and characterized by serogrouping, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). The genetic relatedness and clonal relationship between the isolates were analyzed by using the PFGE patterns and the allelic profiles of the sequence types (STs).ResultsSerogroups A, B, C, W135, Y, and non-serogroupable Neisseria meningitidis were, respectively, responsible for 2%, 50%, 2%, 35%, 9%, and 2% of 158 culture-confirmed cases of meningococcal disease in 1996–2002. Among 100 N. meningitidis isolates available for PFGE and MLST analyses, 51 different PFGE patterns and 30 STs were identified with discriminatory indices of 0.95 and 0.87, respectively. Of the 30 STs, 21 were newly identified and of which 19 were found in serogroup B isolates. A total of 40 PFGE patterns were identified in 52 serogroup B isolates with the patterns distributed over several distinct clusters. In contrast, the isolates within each of the serogroups A, C, W135, and Y shared high levels of PFGE pattern similarity. Analysis of the allelic profile of the 30 STs suggested the serogroup B isolates be assigned into 5 clonally related groups/ clonal complexes and 7 unique clones. The ST-41/44 complex/Lineage 3, and the ST-3439 and ST-3200 groups represented 79% of the serogroup B meningococci. In contrast, isolates within serogroups A, serogroup W135 (and C), and serogroup Y, respectively, simply belonged to ST-7, ST-11, and ST-23 clones.ConclusionOur data suggested that serogroup B isolates were derived from several distinct lineages, most of which could either be indigenous or were introduced into Taiwan a long time ago. The serogroup A, W135 (and C), and Y isolates, respectively, belonged to the ST-7, ST-11, and ST-23, and the represented clones that are currently the major circulating clones in the world and are introduced into Taiwan more recently. The emergence of serogroup A, C and Y strains contributed partly to the increase in cases of meningococcal disease in 2001–2002.
Highlights
Meningococcal disease is infrequently found in Taiwan, a country with 23 million people
Serogroup Y meningococcus caused more cases of meningococcal disease than serogroup A and C combined. Most of these cases were in Central Taiwan, suggesting that a small-scale outbreak of serogroup Y meningococcal disease apparently occurred at that time
The cases caused by the emerging serogroup A, C and Y strains as well as the increased cases caused by serogroup W135 were attributed to the dramatic increase in cases of meningococcal disease in 2001
Summary
Meningococcal disease is infrequently found in Taiwan, a country with 23 million people. Most of serogroup Y meningococcus infections localized in Central Taiwan in 2001, indicating that a small-scale outbreak of meningococcal disease had occurred. Neisseria meningitidis is one of the major causative agents of bacterial meningitis and septicemia in children and young adults, with an estimated 500,000 cases and 50,000 deaths per year worldwide [1]. This organism is subdivided into 13 major serogroups based on the chemical and serological properties of the capsular polysaccharide [2]. Serogroup W135 meningococcus was responsible for the Hajj-associated meningococcal disease outbreak in 2000 and subsequent epidemics in Africa [35]. The incidence of serogroup Y meningococcal disease has increased since the 1990s in North America [6,7,8]
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