Evaluation of the efficiency of a new dried nutrient medium for isolating Corynebacterium diphtheriae

Tellurite blood media prepared on a new dried base with amino peptide have been found to have advantages, when used for the bacteriological diagnosis of C. diphtheriae infection, over Buchin's selective quinosol medium with respect to the rate and time of the isolation of C. diphtheriae; besides, these new media have been found to possess pronounced differentiating properties with respect to the concomitant microflora.     

A new dried nutrient medium for the isolation of Corynebacterium diphtheriae (its development and experimental study)

A new dried diagnostic medium for the isolation of C. diphtheriae has been developed on the basis of aminopeptide. This new aminopeptide-based medium compares favorably with Buchin's medium in its growth and inhibitory properties.     

Adhesion of Corynebacterium diphtheriae

The conditions for the direct hemagglutination test performed to determine the degree of adhesion of C. diphtheriae were defined. For this test sheep red blood cells, trypsin-treated ex tempore, were used. Only newly isolated cultures, subcultured for not more than 2-5 times and stored for not more than 2-7 days or freeze-dried, were employed. The culture to be tested was grown in nutrient agar with 10% of normal horse serum. The test was made in microtitrator round-bottom wells. The mixture of different dilutions of the culture was incubated for 2 hours at 37 degrees C, then left overnight at 4 degrees C. All 147 newly isolated or freeze-dried C. diphtheriae strains under test had different degrees of adhesion. Their adhesive activity was unrelated to their biovar. Toxigenic strains were significantly more active in hemagglutination (53.5 +/- 3.0%) than nontoxigenic ones (23.5 +/- 3.9%). The strains isolated from the nose, irrespective of their biological properties, were more active than those isolated from the pharynx.     

Pathogenic properties of Corynebacterium diphtheriae

The main pathogenic properties of 73 C. diphtheriae strains (their adhesive, invasive and cytotoxic activity) were characterized in the cultures of cells HEp-2 and Vero. The quantitative determination of the toxigenicity of 381 strains in the indirect hemagglutination test was made, and the strains were distributed by the degree of their toxigenicity. The characteristics of C. diphtheriae obtained with the use of in vitro experimental models, coincided with the severity of clinical manifestations of the diphtheria in humans, which made it possible to regard the models used in this study as adequate. On the basis of the chosen criteria the characterized strains could be subdivided into highly, moderately and low virulent and the degree of their potential epidemic danger could be determined.     

Properties of Corynebacterium diphtheriae cultivated in the medium prepared from inedible raw materials

A nutrient medium for the cultivation of C. diphtheriae toxigenic strain was developed on the basis of raw materials unsuitable for use as foodstuffs and its main physico-chemical and cultivation properties were studied. The morphological, cultural, biochemical and toxigenic properties of C. diphtheriae cultivated in the experimental medium with horse serum were evaluated. As revealed in this study, C. diphtheriae retained their properties after prolonged cultivation and storage in the newly developed medium, both liquid and with agar added. The medium has a number of advantages: it is economical, raw materials for its production are readily available, the medium is free of ballast substances.     

Improved culture of Corynebacterium diphtheriae for obtaining toxin-anatoxin

The work deals with the optimization of the cultivation of C. diphtheriae with a view to obtaining diphtheria toxin--toxoid on the basis of the study of the kinetics of microbial growth and toxin formation. The combined cultivation process consisting of 3 cycles has been experimentally developed and realized under industrial conditions. The use of this cultivation method has made it possible to obtain more balanced cultures and to standardize the biological properties of the biomass and toxin thus obtained. The characteristic features of the toxoid preparations obtained on the basis of this method are a high degree of purification, good immunogenic properties and constant fractional composition; their degree of homogeneity approximates the molecular homogeneous state.     

Sensitivity of Corynebacterium diphtheriae isolated in Saint-Petersburg to antibacterial drugs]

One hundred and thirty strains of Corynebacterium diphtheriae isolated in St. Petersburg (42 toxigenic and 88 nontoxigenic) were tested with the method of serial dilutions in solid media for their susceptibility to 20 antibacterial drugs. The MICs of the drugs for the isolates ranged from < or = 0.015 to > or = 32.0 micrograms/ml. 13 per cent of the isolates was resistant at least to one antibacterial drug. The isolates resistant to erythromycin (11.5 per cent), lincomycin (11.5 per cent) and trimethoprim (8.5 per cent) were most frequent. 3 isolates (2.3 per cent) had multiple resistance to 8 drugs: benzylpenicillin, ampicillin, oxacillin, chloramphenicol, erythromycin, lincomycin, trimethoprim, and nitroxolin. No significant differences in the susceptibility of the toxigenic and nontoxigenic strains of C. diphtheriae were detected. Gentamicin, rifampicin, tetracycline, doxycycline and pefloxacin were the most active antibiotics.