Comparison of traditional and molecular methods for typing nontoxigenic strains of Corynebacterium diphtheriae

Genotypic and phenotypic characteristics of Corynebacterium diphtheriae strains isolated from patients in belarus during an epidemic period

One hundred two Corynebacterium diphtheriae strains (93 of the gravis biotype and nine of the mitis biotype) isolated from clinical cases during the Belarus diphtheria epidemic were characterized by biotyping, toxigenicity testing by the Elek test and an indirect hemagglutination assay, phage typing, and ribotyping. The gravis biotype strains were characterized as high and medium toxin producers, and strains of biotype mitis were characterized as low and medium toxin producers. Most strains (82 of 102) were distributed among five phage types. Seventy-two strains (64 of the gravis biotype and 8 of the mitis biotype) belonged to phage type VI ls5,34add. Hybridization of genomic DNA digested with BstEII and PvuII revealed five ribotype patterns, namely, D1, D4, D6, D7, and D13. The majority of gravis biotype strains belonged to ribotypes D1 (49 of 93) and D4 (33 of 93) and included one clonal group of C. diphtheriae. This clone predominated in all regions in Belarus. There was a statistical association between ribotypes and phage types but not between ribotypes and levels of toxin production.

Characterization of United Kingdom isolates of Corynebacterium pseudotuberculosis using pulsed-field gel electrophoresis

Caseous lymphadenitis is a chronic suppurative disease caused by Corynebacterium pseudotuberculosis and is responsible for serious economic losses to the sheep and goat industry. Caseous lymphadenitis was first reported for goats in the United Kingdom in 1990 and for sheep in 1991. Recent evidence suggests that the prevalence of the disease within the national flock is increasing. Fifty isolates of C. pseudotuberculosis from the United Kingdom comprising sheep and horse isolates, the original goat outbreak strain, and the type strain were characterized by biotyping, antimicrobial susceptibility, production of phospholipase D, and genotyping by pulsed-field gel electrophoresis using SfiI and SmaI. All of the isolates were confirmed as C. pseudotuberculosis, and all produced phospholipase D but none reduced nitrate. Restriction with SfiI generated 16 to 18 bands between 48.5 and 290 kb and differentiated six pulsotypes. We conclude that 80% of the strains tested were epidemiologically related to the outbreak strain and that the equine profile was distinct both phenotypically and genotypically.

Single primer polymerase chain reaction fingerprinting for Pasteurella multocida isolates from laboratory rabbits

OBJECTIVE

To evaluate a rapid polymerase chain reaction (PCR) fingerprinting technique for discriminating among Pasteurella multocida isolates from laboratory rabbits.

SAMPLE POPULATION

33 P multocida isolates from rabbits with clinical pasteurellosis.

PROCEDURE

PCR assays were conducted with 2 minisatellites (core sequence and modified core sequence of phage M13) and 2 microsatellites ([GTG]5 and [GACA]4). Each bacterium was assigned to a PCR type for each of the primers used. Boiled bacterial extracts and purified genomic DNA were compared by use of PCR assays for phage M13 and (GACA)4. Plasmids were isolated from each bacterium, and their influence on PCR fingerprint was determined, using boiled extracts as a DNA source.

RESULTS

M13 core sequence and M13 modified core sequence yielded 5 and 8 PCR types, respectively. The microsatellites (GTG)5 and (GACA)4 yielded 4 and 9 PCR fingerprint types, respectively. Fingerprint patterns obtained by use of isolated DNA differed from those obtained by use of boiled extracts, although discrimination among P multocida isolates was similar. The presence or absence of plasmids did not affect PCR fingerprints.

CONCLUSION

Single primer PCR fingerprinting with minisatellite and microsatellite primers is an efficient and reproducible method for the discrimination of P multocida isolates from rabbits and can be performed directly, using boiled bacterial extracts as a source of template, although more bands were obtained from pure genomic DNA.

[Diphtheria and infections caused by Corynebacterium diphtheriae in 1997]

INTRODUCTION

Diphtheria is a reemerging disease. Two epidemics recently occurred in Algeria and Independent States Community, not so far from Europe. Imported cases were diagnosed in contiguous European countries. This review focuses on the data obtained from these epidemics, with particular emphasis on new clinical forms of Corynebacterium diphtheriae infections. CURRENTS KNOWLEDGE AND KEY POINTS: Sore throat with membranes is no longer the only clinical feature of diphtheria. However, patients' management is identical, with combination of antibiotics, injection of specific antisera, and immunization of patients' close contacts and relatives. French and American sero-epidemiological studies showed that antibody levels does not provide protection, particularly in the elderly. Adult populations would therefore be at risk every 10 years. Recent advances in molecular biology led to the development of gene amplification with polymerase chain reaction, that may be used for the detection of the toxin gene. They also promoted epidemiological surveys of circulating strains via ribotyping. Although this technic evidenced predominant strains in the various countries, genotypes encountered during an epidemics may differ. Besides diphtheria which has apparently been eradicated in France, systemic infections with non-toxigenic strains of C diphtheriae, such as endocarditis, septicemia and arthritis, are evenly diagnosed.

FUTURE PROSPECTS AND PROJECTS

A French national reference center for C diphtheriae has been recently created. This center collects most of the strains isolated in France, clinical data and assesses the toxigenicity of bacteria, allowing strict epidemiological survey.