Diphtheria Epidemic
Diphtheria Epidemic
We used 199 Corynebacterium diphtheriae isolated in 1995 to 1997 in Russia to evaluate the ability of random amplified polymorphic DNA (RAPD) to identify the unique clonal group that emerged there in 1990. Our data show that RAPD can reliably, reproducibly, and rapidly screen a large number of strains to identify the epidemic clonal group.
Molecular subtyping, primarily by multilocus enzyme electrophoresis (MEE) and ribotyping, has identified substantial genetic diversity within the Corynebacterium diphtheriae species, leading to the identification of a unique clonal group that emerged in Russia in 1990 at the beginning of the current diphtheria epidemic. Strains of this clonal group belong to a distinct electrophoretic type complex (ET8 complex) and are of ribotypes G1 and G4. Identification of this clonal group has permitted precise monitoring of the epidemic's growth and rapid detection of imported cases in neighboring and other European countries.
Use of traditional subtyping methods in monitoring the expansion of the epidemic clone has helped differentiate epidemic, endemic, and imported cases and has allowed timely preventive measures. Even as the epidemic declines (from more than 50,000 cases in 1995 to 1,436 cases in 1998), identifying organisms belonging to this epidemic clone in cases of suspected importation into locations where diphtheria is rarely encountered continues to provide valuable information. Since both ribotyping and MEE are time-consuming, taking 3-4 working days to produce results, rapid methods that could distinguish the predominant clone would improve epidemic surveillance and prevention measures.
Random amplified polymorphic DNA (RAPD) is a simple and rapid molecular subtyping method. Recently, Nakao et al. optimized and standardized this assay for C. diphtheriae and showed that the discrimination level obtained by RAPD correlated well with that of ribotyping; each of 20-plus ribotyping patterns was associated with one or more distinct RAPD patterns. We compared these two techniques on a large number of C. diphtheriae Russian isolates from 1995 to 1997, focusing on the ability of RAPD to identify the isolates of the epidemic G1/4 clonal group.
We used 199 Corynebacterium diphtheriae isolated in 1995 to 1997 in Russia to evaluate the ability of random amplified polymorphic DNA (RAPD) to identify the unique clonal group that emerged there in 1990. Our data show that RAPD can reliably, reproducibly, and rapidly screen a large number of strains to identify the epidemic clonal group.
Molecular subtyping, primarily by multilocus enzyme electrophoresis (MEE) and ribotyping, has identified substantial genetic diversity within the Corynebacterium diphtheriae species, leading to the identification of a unique clonal group that emerged in Russia in 1990 at the beginning of the current diphtheria epidemic. Strains of this clonal group belong to a distinct electrophoretic type complex (ET8 complex) and are of ribotypes G1 and G4. Identification of this clonal group has permitted precise monitoring of the epidemic's growth and rapid detection of imported cases in neighboring and other European countries.
Use of traditional subtyping methods in monitoring the expansion of the epidemic clone has helped differentiate epidemic, endemic, and imported cases and has allowed timely preventive measures. Even as the epidemic declines (from more than 50,000 cases in 1995 to 1,436 cases in 1998), identifying organisms belonging to this epidemic clone in cases of suspected importation into locations where diphtheria is rarely encountered continues to provide valuable information. Since both ribotyping and MEE are time-consuming, taking 3-4 working days to produce results, rapid methods that could distinguish the predominant clone would improve epidemic surveillance and prevention measures.
Random amplified polymorphic DNA (RAPD) is a simple and rapid molecular subtyping method. Recently, Nakao et al. optimized and standardized this assay for C. diphtheriae and showed that the discrimination level obtained by RAPD correlated well with that of ribotyping; each of 20-plus ribotyping patterns was associated with one or more distinct RAPD patterns. We compared these two techniques on a large number of C. diphtheriae Russian isolates from 1995 to 1997, focusing on the ability of RAPD to identify the isolates of the epidemic G1/4 clonal group.
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