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Tick-borne encephalitis (TBE), caused by tick-borne encephalitis virus (TBEV) is one of the serious neurological infections seen especially in the Asian and North European countries. The principal vectors of TBEV are hard ticks belonging to Ixodes genus. The major vector of European TBEV subtype is I.ricinus and the major vector of Far-Eastern and Siberian subtypes is I.persulcatus. I.ricinus exists in many climatic regions of Turkey, especially in the coastal areas. The aim of this study was to investigate the TBEV seroprevalence among the residents of rural areas in Sinop (a province located at the coast of Central Black-Sea region of Turkey). A total of 273 blood samples have been collected from the subjects (age range: 11-83 years) inhabiting in 12 villages of the central district of Sinop, during the months of May and June in 2006 and 2007. The presence of TBEV IgG antibodies in serum samples were searched by a commercial indirect fluorescent antibody kit (Euroimmun, Deutschland). TBEV IgG positivity was detected in 2.9% (8/273) of the subjects at a screening titer (1/10) and 7 (2.6%) of them also yielded positive results at further dilutions (1/100). The rates of TBEV seropositivity were not found statistically significant (p > 0.05), with respect to gender (141 of the subjects were male), age (142 of the subjects were between 21-50 years old), occupation (17 foresters, 57 were shepherds, 199 were farmers/stockbreeders) and history of tick bite (169 of the subjects had been bitten by ticks). Presence of IgG antibodies against Borrelia burgdorferi, another agent which is transmitted by the same vector, were also investigated in TBEV seropositive 8 subjects by a commercial ELISA kit (Zeus Scientific, The Netherlands). Four of these subjects yielded B.burgdorferi IgG positivity, so the TBEV - B.burgdorferi coinfection rate was estimated as 1.5% (4/273). However, since the results obtained by the tests used in this study (TBEV IgG IFA and B.burgdorferi IgG ELISA) have not been confirmed by additional confirmational tests, these subjects were referred as "probable cases". In recent years the detection rates of vector-borne viral infections is in an increment trend in Turkey due to the developments in diagnostic tests and awareness for emerging infections. In conclusion since Sinop, which is placed in the northernmost point of Turkey, is located close to TBEV endemic areas, the presence of TBEV in Sinop and the Black Sea region should always be considered.

Viridans group streptococci (VGS) are gram-positive microorganisms that can form alpha-hemolytic colonies on sheep blood agar. They reside as normal flora in oral cavity, respiratory, gastrointestinal, urogenital tract and on skin. They can cause bacteremia, endocarditis, meningitis and septicemia following dental procedures. The diagnosis of VGS are difficult since the taxonomic classification and species na-mes may change due in time. Viridans group streptococci are classified into 5 groups (Sanguinis, Mitis, Mutans, Salivarius, Anginosus) according to biochemical reactions and 16S rRNA sequencing. Since Streptococcus pneumoniae is a member of the Mitis group, the other important species in this group deserves investigation. Genetic exchange between Streptococcus mitis, Streptococcus oralis and S.pneumoniae by transformation and lysis mechanisms occur continously as they share the same anatomical region. These mechanisms play role in exchanging capsular and antibiotic resistance genes between these species. The cultivation of VGS usually starts with the inoculation of various patient specimens into sheep blood agar and the detection of alpha-hemolytic colonies. Observation of gram-positive cocci microscopically, the detection of optochin-resistant and bile insoluble colonies with few exceptions are the further important steps in laboratory diagnosis. VGS are then identified at species level by using biochemical reactions, automated diagnostic systems and molecular methods. The last step in the laboratory diagnosis of VGS is antibiotic susceptibility testing which is of outmost importance as penicillin and erythromycin resistance are on rise. In this review article, classification of VGS, similarities between S.pneumoniae and Mitis group streptococci and the laboratory diagnosis of VGS have been discussed.