Invasion of HeLa cells byEdwardsiella tarda

TwelveEdwardsiella tarda strains investigated proved to be strongly invasive for HeLa cells. All strains were negative in the Serény test and did not produce either enterotoxins LT and ST or cytotoxin detectable by the Y1, the infant mouse, and the Vero tests respectively. All strains were hemolytic on blood agar plates.     

Dynamics of proteins in a culture broth growing beta-hemolytic streptococci group C

The dynamic study of the protein spectrum of culture fluid during the growth of beta-hemolytic streptococcal strain H46A has been carried out by the methods of electrophoresis and isoelectrofocusing in polyacrylamide gel. Changes in the protein spectrum have phasic character and, on the whole, reflect the state of the microbial population, the presence of fractions corresponding to streptokinase and streptolysins being detected at all phases of growth. The electrophoretic mobility of streptokinase perceptibly changes at the end of the logarithmic phase; as shown by electrofocusing, at all stages of the population growth the heterogeneity of streptokinase is observed.     

Activation of natural killer cells in vitro by a product of beta-hemolytic streptococci

Streptokinase-streptodornase (SK-SD), a product of Group A and Group C β-hemolytic streptococci, activates natural killer (NK) cells in vitro. This effect appears to occur without the induction of interferon. It is not present in every individual but is reproducible. There appears to be no correlation between NK activation and assays for cellular immunity such as in vivo delayed skin reactions and/or in vitro cell proliferation.     

Occurrence and drug-resistance of beta-hemolytic streptococci

The aim of this study was the analysis of drug-resistance and frequency appearance of beta-hemolytic streptococci strains which were isolated in 2003-2005 in the University Hospital at the L. Rydygier Collegium Medicum in Bydgoszcz University of Nicolaus Copernicus in Toruń. Among investigeted beta-hemolytic streptococci the most frequency isolated species was S. agalactiae. All isolates examined in our study were susceptible to penicillin, the higest rate of resistance was found for tetracycline. The rates of resistence to macrolide-lincosamide-streptogramin B (phenotyp MLS(B)) were as follows: S. agalactiae (18.7%), S. pyogenes (10.1%), group G streptococci (10.6%) and group C streptococci (8.0%). In our study we presented also a special case patient from which in investigeted period S. agalactiae was isolated twenty eight times. For ten chromosomal DNA isolated from this patient three different PFGE profiles were obtained.     

Sensitivity of beta-hemolytic streptococci to antibiotics]

Susceptibility of 64 beta-hemolytic streptococcal strains isolated from the patients with sore throat was studied by the method of serial dilutions in fluid nutrient medium (Konikov broth). Heterogenecity with respect to the sensitivity was investigated in 34 strains among separate populations of the microbes (10 to 15 in every strain). The MIC of benzylpenicillin, oxacillin and erythromycin ranged within 0.007--0.24 U/ml, 0.02--0.36 gamma/ml and 0.005--0.1 gamma/ml respectively. The MIC of benzylpenicillin with respect to separate populations most sensitive to it was 0.007--0.015 U/ml, while that with respect to the lease sensitive populations ranged from 0.015 to 0.24 U/ml. The respective values for oxacillin were 0.02--0.12 and 0.18--0.36 gamma/ml and those for erythromycin were 0.005--0.025 and 0.05--0.1 gamma/ml. Therefore, the beta-hemolytic streptococci isolated from the patients with sore throat were characterized by a rather high sensitivity to the antibiotics which was important precondition for their efficiency in treatment of the patients with the above disease.     

Antibiotic sensitivity of beta-hemolytic Streptococcus group A on a new nutrient medium for the cultivation of streptococci

Sensitivity of 167 strains of beta-hemolytic streptococci of group A was studied with the method of serial dilutions on a solid agar medium for cultivation of streptococci. The medium was developed at the I. I. Mechnikov Research Institute of Vaccines and Sera. It does not require addition of blood or serum. The strains were found to be highly sensitive to penicillin, cephalothin and erythromycin. The number of the strains resistant to tetracycline, streptomycin, gentamycin, levomycetin (chloramphenicol) and ristomycin amounted to 51, 36, 23, 1.8 and 1.8 per cent, respectively. One of the strains (0.6 per cent) was resistant to lincomycin. Strains with multiple resistance were isolated. The necessity of regular control of distribution of antibiotic resistance among staphylococci is indicated.     

Conjugative transfer of multiple-antibiotic resistance markers in beta-hemolytic group A, B, F, and G streptococci in the absence of extrachromosomal deoxyribonucleic acid

Nine clinical isolates of group A, B, F, and G streptococci resistant to tetracycline, macrolides, lincosamides, and streptogramin B (MLS resistance) and to chloramphenicol were investigated for the conjugative transfer of the antibiotic-resistance markers into streptococcal recipients (groups B and D). The wild donors transferred the resistance markers en bloc, at a low frequency (10^?6 to 10^?8) and only into one of the two recipients tested. In addition, one of the strains transferred only the MLS resistance at a high frequency (10^?3). All attempts to detect extrachromosomal DNA in wild donors or in transconjugants were unsuccessful, except in one transconjugant. This plasmid DNA, designated pIP659, had a molecular weight of 17.5 × 10⁶ and a restriction fingerprint similar to other plasmids determining MLS resistance.     

Solubilization of IgG-binding proteins from group A and G streptococci

The release of IgG-binding proteins from the cell surface of streptococcal strains AR-1 and G148 with various proteolytic enzymes, acid, alkali or SDS was investigated. The IgG-binding proteins were purified by affinity chromatography using IgG-Sepharose Fast Flow. After SDS-polyacrylamide gel electrophoresis and immuno-electroblotting the major proteins identified varied in relative molecular mass from 15,000 to 65,000 depending on the solubilizing agent used. The results showed that solubilization with trypsin gave the highest yield of IgG-binding proteins, that strain G148 yielded about twice the amount of protein as strain AR-1, and that elastase released an IgG-binding protein of high relative molecular mass of 65,000.     

Protein G expressed by human group C and G streptococci: cloning of gene and binding properties

PCR generated fragments of the protein G gene from three GCS and GGS strains belonging to different G types had been cloned. The resulting PCR products were cloned intoE. coli using expression vector pQE31. The clones, producing IgG-binding peptides were selected. Recombinant plasmids carried different inserts and encoded proteins of different size and with different binding properties. Presented at theInternational Conference on Recent Problems in Microbiology and Immunology, Košice (Slovakia), 13–15 October 1999.     

Conjugative R plasmids in group C and G streptococci.

Two streptococcal isolates of groups C and G harbored conjugative R plasmids with molecular weights of 17 X 10(6) (pIP646) and 20 X 10(6) (pIP920). These plasmids carried genetic markers for resistance to macrolides and related drugs, as well as to chloramphenicol (pIP920), and have very similar HindIII restriction enzyme patterns.     

Platelet aggregation by group B streptococci

Forty-six strains of group B streptococci (GBS), including various serotypes and non-serotypable strains, were tested for their ability to induce platelet aggregation in human platelet-rich plasma; four strains, all belonging to type III, showed a positive reaction. The characteristics of the reaction were investigated in these four positive strains. Aggregation was dependent on the ratio of bacteria to platelets, being maximal at a ratio of 4.3. Platelet aggregation was inhibited by EDTA (100% inhibition at 3.1 mM), indomethacin (100% inhibition at 10 mM), acetylsalicylic acid (93-100% inhibition at 5.0 mM) and quinacrine (100% inhibition at 0.25 mM). Thus the reaction was cation-dependent and required cyclooxygenase activity. Assays for cytosolic lactate dehydrogenase did not indicate platelet lysis. GBS induced the release of [3H]serotonin, which was maximal (68-78%) at 10 min after the reaction was started. Experiments with gel-filtered platelets suggested that GBS-induced platelet aggregation required both fibrinogen and heat-resistant (56 degrees C, 30 min) serum factors. Type-specific antisera prevented the platelet aggregation activity of heat-killed bacteria, but not of live bacteria. Trypsin digestion of the bacterial cells caused an almost complete loss of the platelet aggregation activity.     

An epizootic of necrotic dermatitis in laboratory mice caused by Lancefield group G streptococci.

During a 7-mo period, mice from a group of 383 being used in a toxicology experiment developed severe progressive necrotic dermatitis, and some animals developed paralysis. The overall mortality rate for the group was 134/383 (35%). Seventeen mice were necropsied for bacteriologic and histopathologic examination. A streptococcus identified as Lancefield group G was isolated from the skin lesions of 15 of the mice, from 8 of 9 throats cultured, from 4 of 8 spleens, and occasionally from other sites. It was thought that the infections were initiated and perpetuated by bites from mice carrying the streptococcus in their mouth and throats. Microscopic examination of affected skin revealed necrotic dermatitis characterized by epithelial ulceration with suppuration. The skin lesions were reproduced in 6 of 15 mice inoculated with the isolated streptococcus.     

A rapid method of grouping beta-hemolytic streptococci using extemporaneous coagglutination

Extemporaneous coagglutination procedure for the serological grouping of beta-hemolytic streptococci is reported. Streptococcal group antigens were extracted with nitrous acid. 250 strains of groups A, B, C, F and G streptococci were tested with this method. An agreement of 100% was found between this method and the Lancefield capillary precipitation procedure. Extemporaneous coagglutination method was found to be rapid, reliable, easy and economical and could be adopted in any routine diagnostic laboratory.     

Adhesion of group B streptococci to vaginal epithelial cells

The work presents the results of studies on the optimum and standard conditions for the in vitro determination of the adhesiveness of group B streptococci with epithelial cell suspensions. Vaginal epithelium has proved to be the most convenient and adequate system for studying the adhesiveness of group B streptococci. The optimum infective dose of these bacteria has been found to range from 50 to 200 cocci per cell. The characteristics of the adhesion of group B streptococci to vaginal epithelium are highly reproducible and exhibit low dependence on the time of the incubation of the bacteria with epithelial cells; fluctuations in the adhesiveness of the cultures in the definite range of pH shifts are seemingly determined by the serotype of the strains.