Ninety-one Shigella flexneri and 29 Shigella sonnei strains isolated during 1994 from sporadic cases of shigellosis and healthy carriers were analyzed for plasmid profile in order to compare the discriminating ability of this method with that of serotyping and phage typing. Our study revealed 10 plasmid profiles (PP) among S. sonnei strains. A total of 26 out of 29 (89%) S. sonnei isolates could be placed into two phage types (type 1 and 20) comprising four PP for phage type 1 and seven PP for type 20, respectively. Twenty-three different PP were identified among S. flexneri strains. Each serotype was associated with a specific predominant plasmid profile, except serotype 2a. This serotype, the most frequently isolated in Romania, was still rather homogeneous: 33 out of 39 isolates belonged to phage type 125, 27 of which could be placed into two related PP (F10 and F17). Comparison of plasmid patterns of epidemiologically independent S. flexneri serotype 2a isolates with those exhibited by 45 serotype 2a isolates associated to six independent outbreaks revealed the same homogeneity. Thirty-eight strains, representing 4 of 6 outbreaks, had F10 and F17 plasmid patterns. The discrimination indices (D) for plasmid profile analysis alone (D = 0.890) and for the combination of serotyping and phage typing (D = 0.841) indicate that both typing systems have a nearly similar ability of discriminating among S. flexneri strains. By combining the results of the three typing methods, a total of 42 types are distinguished and the D value is 0.942. Our data suggest that plasmid profile analysis can complement phenotyping methods resulting in a degree of discrimination that cannot be achieved by either system alone.

Bacterial Typing Techniques↗

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Molecular subtyping of group A streptococcal strains based on virulence regulon polymorphism.

A total of 64 Streptococcus pyogenes isolates included in a previous study (Shundi et al., 2000) were further analyzed by Vir typing. Vir typing is based on restriction fragment length polymorphism (RFLP) analysis of a 4- to 8-kb pathogenicity island (vir regulon) encoding emm and other virulence genes. As all our isolates contained a single vir regulon, the stoichiometric yield of restriction fragments avoided ambiguities in interpretation of results. By using both HaeIII and HinfI restriction endonucleases to generate RFLP profiles, the 64 GAS isolates were distributed among 22 Hae- and 26 Hinf-Vir types respectively.

Bacterial Proteins↗

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Correlation between two DNA-based typing methods applied to Streptococcus pneumoniae strains: BOX-PCR assay as an alternative to ribotyping.

Seventy-nine Streptococcus pneumoniae isolates were characterized by ribotyping and BOX-PCR typing. The isolates comprised 14 most frequently identified serogroups and serotypes, 54 ribotypes (defined as each different combination of two DNA restriction fragment length polymorphism patterns obtained with HindIII and PvuII, respectively) and 51 BoxA-PCR patterns. There was close but not absolute correlation between molecular techniques. However, the discrimination indice of ribotyping--calculated on the basis of combination of the data obtained with both enzymes--equals that of BOX-PCR typing: D = 0.985 and the deduced genetic clustering of the pneumococcal strains was comparable.

Bacterial Typing Techniques↗

PubMedDate not supplied

[Sensitivity to antibiotics and chemotherapeutic agents in some strains of Salmonella typhi isolated in Romania during the period 1974-1976].

Investigations were carried out on 781 S. typhi strains isolated from patients and carriers. Testing of the sensitivity to chemotherapeutical agents by diffusiometry and the incorporation technique led to the detection of four resistant strains: 1 strain isolated by coproculture from a carrier since 1958, resistant to A, K, N, Ca and Cf and 3 strains isolated by coproculture, biliculture and uroculture from a carrier since 1974, resistant to A and Ca. The R factors of these strains were transferred in their totality. The resistant strains did not manifest any particular pathogenicity for the laboratory animal, and their immunogenic potential was below that of the current typhoid vaccine. None of the 781S typhi were resistant to Cmx, C, G, T, Co and Po. Consequently, in Romania Chloramphenicol may be used in continuation in the treatment of typhoid fever, and Cotrimoxazol, Gentamycin, Tetracyclin and Ampicillin are and remain reserve substitutes. The possible unexpected appearance of resistant S. typhi strains demand, however, further control of the sensitivity to chemotherapeutics of all the isolated strains.

Anti-Bacterial Agents↗

PubMedDate not supplied