Streptococcus pneumoniae: pathogen or protector?

Identifying divergent streptococcal strains using pherotype: implications for pathogen emergence and epidemiology

Since the late 1980s, new and existing species of oral streptococci have been identified by complex and protracted DNA-based methods that are unsuitable for high-throughput testing in clinical laboratories. Developments of simpler DNA-based tests for routine diagnosis have been thwarted by the similarities of their genomes and their high recombination rates. Thus, phenotypic tests to differentiate oral streptococci, such as hemolysis and optochin sensitivity, remain in use. However, these tests are variable and can lead to misidentification, particularly in closely related species such as Streptococcus pneumoniae and the recently identified Streptococcus pseudopneumoniae. This report highlights recent DNA-based developments in differentiating oral streptococci. Reference will be made to the methods 'sequetyping' for identifying and serotyping the pneumococcus, and 'pherotyping' for distinguishing them from pseudopneumococcus strains. These tests are yet to be evaluated in the clinical setting; nevertheless, the identification of the pseudopneumococcus by pherotyping will enable its epidemiology and pathogenesis to be studied.

[West Nile fever/encephalitis]

West Nile virus (WNV), a member of the family Flaviviridae (genus Flavivirus), is a mosquito-borne virus first isolated in 1937 in the West Nile district of Uganda. The disease in humans is characterized by a dengue-like illness with fever, and a more severe form is characterized by central nervous system involvement, including encephalitis, meningitis, and myelitis. WN encephalitis was first reported in the Western Hemisphere in the summer of 1999, there was an outbreak in New York City. Epidemic WNV strains in North America are severely pathogenic, however, attenuated WNV strains were found in Texas and Mexico in 2003. The principal vectors of WNV transmission in North America are Culex. pipiens, Cx. Quinquefasciatus, Cx. restuans, Cx salinarius and Cx talsalis. The number of WN fever case has exceeded 27,000 since 1999 in the United States and 4,600 since 2002 in Canada. The first imported case of West Nile fever in Japan was confirmed in September, 2005. The patient had returned to Japan from the United States and developed symptoms the next day. There is currently no WN vaccine for use in humans. An inactivated WNV vaccine for use in horses has been available since 2001. A DNA vaccine, a chimeric live attenuated vaccine, and a recombinant vaccine have also been licensed for use in horses.