Identification of viridans streptococcal species causing bacterial meningitis in adults in Taiwan

In order to determine the species responsible for viridans-group streptococcal meningitis in adults in Taiwan, seven cases of culture-proven meningitis due to these organisms were studied. The cases were all identified at the Chang Gung Memorial Hospital-Kaohsiung over a period of 3 years, and they accounted for 9% (7/78) of all cases of culture-proven bacterial meningitis occurring in adults during this period. Of the seven viridans streptococci isolates recovered, Streptococcus constellatus accounted for four, Streptococcus anginosus for two, and Streptococcus oralis for one. Thus, it appears that streptococci of the milleri group are the most common species causing bacterial meningitis in adults in Taiwan. The tendency for these organisms to cause invasive central nervous system infections in adults should not be overlooked when these species are recovered from cerebrospinal fluid specimens. tracts, and they are often considered to be contaminants when isolated from blood cultures [1]. Viridans streptococci are playing an increasing role in infections among immunocompromised patients [2], although they are not a common pathogen in cases of adult bacterial meningitis [3]. In the relevant English-language literature, there is a relative paucity of large studies pertaining to viridans streptococcal meningitis in adults [4, 5, 6]. This fact, coupled with the acknowledged difficulty of making an accurate bacterial species identification using a commercial system, suggests that viridans streptococci isolated from the cerebrospinal fluid (CSF) of adult patients with bacterial meningitis is rarely identified to the species or group level [4, 5, 6]. In this study, we identified the species of seven viridans streptococcal isolates cultured from the CSF of seven adult patients suffering from bacterial meningitis. We then compared our results with the species-identification results of several large studies of adult patients with bacterial meningitis reported previously in the relevant English-language literature.