Serotypes, surface proteins, and clinical syndromes of invasive Group B streptococcal infections in northern Taiwan, 1998-2009

Abstract

Background: The incidence of invasive Group B streptococcal (GBS) infections is increasing in the elderly and immunocompromised adults in many countries worldwide. There are, however, few reports regarding the current status of the infection in northern Taiwan. This study investigated retrospectively the molecular epidemiology and clinical syndromes of the invasive GBS diseases in a tertiary care hospital in northern Taiwan over the past decade.

Methods: One hundred twenty episodes of invasive GBS disease were recorded at Cathay General Hospital, a tertiary care, teaching hospital in northern Taiwan, from January 1998 to June 2009. Clinical information was acquired from medical records. Capsular serotypes and alpha family of surface proteins were genotyped with multiplex and specific polymerase chain reaction.

Results: Of all episodes, 58.3% was found in the elderly (age ≥ 65), 36.1% in nonpregnant women and young adults (age 18-64), and 5.9% in the neonates (0-90 days). Case-fatality rate was 6.7%. Eighty-three (69%) of the invasive isolates were available for genotyping. In sharp contrast to the studies in southern Taiwan (1991-2004), Type Ib (26.5%) was the most frequent invasive isolate, followed by V (22.9%), III (18.1%), VI (12%), Ia (10.8%), II (6%), VIII (2.4%), and nontypable strain (1.2%). In particular, Serotype VI, which had been rarely implicated in invasive infection, emerged as a significant pathogen. A significant trend of increase in incidence was observed for the infection (p<0.0001), with concurrent increase of cases in the elderly and of Serotype Ib and VI. There was significant association with young adults of Type II and III and chronic skin conditions and older adults with Type Ia and V and chronic cardiovascular diseases. Type V was closely associated with skin and soft tissue infection. Recurrent episodes (10%) occurred most often in patients with concomitant malignancy, with an average of 314 days for recurrence.

Conclusions: The incidence of GBS invasive infection among nonpregnant women and adults is rising in northern Taiwan, particularly in the elderly caused by Serotype Ib and VI. Population-based surveillance program should be implanted for assessment of the disease burden to the susceptible adult population.