Properties of poliovirus strains isolated over the period 1969-1978 from the main municipal sewerage system of the city of Prague

Biological properties (rct marker and antigenic relatedness) were compared in vaccine prototype strains and in 62 poliovirus strains isolated during a period 1969-1978 from the main municipal sewerage system of the City of Prague. None of the strains isolated from the municipal sewerage showed biologic properties that would fully differ from those observed in vaccine-derived strains. The strains detected very late postvaccination (after about a year) showed a lesser extent of changes than strains isolated earlier after vaccination. The most frequent changes were recorded in type 2 strains, less frequent in type 3 strains and the least frequency of changes was found in type 1 strains. To facilitate comparisons of these changes in dependence on time of postvaccination virus excretion a supporting evaluation criterion has been developed to help express the dynamics of changes in the isolated poliovirus strains. The recorded degree of the dynamics of changes was highest in type 2 strains, lower in type 3 strains and lowest in type 1 strains. The dynamics of changes detected in strains of various types was not always constant in the course of years: in a given year (or in a period of several years) changes occurred always in strains of the same serologic type, whereas strains of the other two types changed only insignificantly during the respective period.     

Bacteriocinogenic properties of Staphylococci isolated from the oral cavity

Two hundred ninety two staphylococcal strains were isolated out of 130 saliva samples taken from children and adults, among which 116 were coagulase-positive and 176 coagulase negative. Bacteriocinogenic activity against Staphylococcus aureus strain Oxford 209P was found in 13 (4.5%) of the strains only. On the other hand, when a set of 15 sensitive staphylococcal strains selected by cross checking was used for the study 260 (89.0%) strains were found to be bacteriocinogenic. It was found that a higher percentage of coagulase-positive staphylococcal strains is sensitive to staphylococcins than of coagulase-negative strains. However, mean zone of inhibition is smaller in the case of former than of the latter strains. It was shown, that in the case of active strains a positive correlation exists between a percentage of coagulase-positive and negative strains inhibited by them and also between a percentage of all inhibited strains and a mean diameter if the growth inhibition zone. Simultaneous occurrence in saliva of two or more staphylococcal strains was found in 106 persons examined. In 93.4% of those cases coexisting strains did not show antagonistic properties: in remaining 6.6% despite of the number of simultaneously existing strains in oral cavity only one strain showed antagonistic properties against the remaining strains.     

Investigation of specific substitutions in virulence genes characterizing phenotypic groups of low-virulence field strains of Listeria monocytogenes

Several models have shown that virulence varies from one strain of Listeria monocytogenes to another, but little is known about the cause of low virulence. Twenty-six field L. monocytogenes strains were shown to be of low virulence in a plaque-forming assay and in a subcutaneous inoculation test in mice. Using the results of cell infection assays and phospholipase activities, the low-virulence strains were assigned to one of four groups by cluster analysis and then virulence-related genes were sequenced. Group I included 11 strains that did not enter cells and had no phospholipase activity. These strains exhibited a mutated PrfA; eight strains had a single amino acid substitution, PrfAK220T, and the other three had a truncated PrfA, PrfADelta174-237. These genetic modifications could explain the low virulence of group I strains, since mutated PrfA proteins were inactive. Group II and III strains entered cells but did not form plaques. Group II strains had low phosphatidylcholine phospholipase C activity, whereas group III strains had low phosphatidylinositol phospholipase C activity. Several substitutions were observed for five out of six group III strains in the plcA gene and for one out of three group II strains in the plcB gene. Group IV strains poorly colonized spleens of mice and were practically indistinguishable from fully virulent strains on the basis of the above-mentioned in vitro criteria. These results demonstrate a relationship between the phenotypic classification and the genotypic modifications for at least group I and III strains and suggest a common evolution of these strains within a group.     

DNA uptake in competent Streptococcus pneumoniae requires ATP and is regulated by cytoplasmic pH

We analyzed the ability of 120 encapsulated strains of B. fragilis to agglutinate guinea pig and human red blood cells. Sixteen strains showed a strong hemagglutination (HA) ability, 21 strains a moderate HA ability, 7 strains a weak HA ability and 74 strains did not agglutinate the tested red blood cells. Six strains tested from each HA group were able to adhere to cheek epithelial cells and to a cultured human intestinal cell line. Hemagglutinating strains were the most adhesive. By electron microscopy, pilus-like structures were found in three of the encapsulated adhesive strains. Treatment of the bacterial cells with pronase E reduced both HA ability and adherence of piliated encapsulated, and of piliated non-encapsulated strains. Glucosidase treatment of cells reduced HA activity and adherence of piliated encapsulated and of non-piliated encapsulated strains. Finally, it was found that hemagglutinating strains are more frequently isolated from clinical specimens (55%) than from feces of healthy donors (20%).     

Variations in Strains of Streptomyces griseus Isolated from a Degenerating Streptomycin-Producing Culture

Streptomycin-resistant strains were isolated from a degenerated streptomycin-producing culture of Streptomyces griseus. From 250 resistant strains, 3 low, 2 intermediate, and 2 high potency strains were selected; these were compared in their morphological, cultural, physiological, and streptomycin-producing properties. Though no definite correlation between streptomycin production and the other properties could be obtained, the following correlations were considered as distinct differences among the low, intermediate, and high potency strains. (i) When streptomycin-producing ability degenerates, more submerged spore formation or fragmentation of mycelium into shorter filaments appears to occur. (ii) On agar medium, low and intermediate potency strains often show finely wrinkled growth; high potency strains do not show such characteristics. (iii) High potency strains excrete a distinct yellow soluble pigment on synthetic agar medium and on glucose-yeast extract agar, but low and intermediate potency strains show little or no ability to form this soluble pigment. (iv) In low and intermediate potency strains, inositol and arginine did not stimulate streptomycin production as they did in high potency strains. Streptamine showed some stimulating effect in the high potency strains and, in contrast, a depressive effect in intermediate potency strains, though streptidine showed a distinctly stimulating effect in all groups of strains employed.     

Starch gel electrophoresis: an effective method for separation of pathogenic and nonpathogenic Naegleria strains

Isoenzyme electrophoresis of 7 different enzyme systems was used to compare 24 strains of Naegleria fowleri and 6 strains of N. gruberi. The 30 strains could be grouped into 4 distinct categories based upon zymogram patterns. No interstrain band variation in all enzyme systems was demonstrated in pathogenic strains of N. fowleri. Three nonpathogenic high temperature-tolerant strains of Naegleria had similar zymograms. Four of the 5 remaining nonpathogenic Naegleria strains had no interstrain band variation. Based upon zymograms, the 22 pathogenic strains constitute a homogenous species. Similarly the high temperature-tolerant nonpathogenic strains formed a cohesive group. The remaining nonpathogenic strains could be separated into 2 groups.     

Production and characterization of neutralizing monoclonal antibodies against poliovirus type 1, 2, and 3

Neutralizing monoclonal antibodies were produced against a reference vaccine or a reference wild strain of poliovirus type 1, 2, and 3. After 26 fusions, 55 monoclonal antibodies were obtained with serotype 1 as the immunizing antigen, 180 with serotype 2, and 115 with serotype 3. The neutralizing activity of these monoclonal antibodies was tested first with the two reference strains and then if reactive, against a panel of 10 well-characterized strains of each serotype, 5 vaccinelike (VL) and 5 nonvaccinelike (NVL). All monoclonal antibodies were type specific without reactivity with any of the heterologous strains. There was a wide range of reactivity within the strains of each serotype. Several monoclonal antibodies to serotype 1 reacted with all type 1 strains, while several neutralized strongly all VL strains and weakly one or more of the NVL strains. Most of the 180 monoclonal antibodies to serotype 2 neutralized to various degrees all strains of this serotype and about half reacted very strongly with all homologous strains whether VL or NVL. None could differentiate all VL and NVL homologous strains. Of the 115 monoclonal antibodies to serotype 3, several monoclonal antibodies neutralize to various levels all homologous strains and some can differentiate VL and NVL strains.     

Characterisation of persistent and sporadic Listeria monocytogenes strains by pulsed-field gel electrophoresis (PFGE) and amplified fragment length polymorphism (AFLP)

This study was set up to evaluate the genetic similarity or dissimilarity of persistent and sporadic Listeria monocytogenes strains existing in eleven food processing facilities, including fish, dairy, meat and poultry processing plants. In each plant persistent and sporadic strains were selected on the basis of PFGE typing results. A total of 17 strains representing persistent strains and 38 sporadic strains originating from eleven food processing plants were included in the study. PFGE macrorestriction patterns of persistent and sporadic strains from different processing plants were compared and the strains were further studied by amplified fragment length polymorphism (AFLP), being a characterisation method giving more whole genome based information. The 17 persistent and 38 sporadic strains showed 14 and 35 pulsotypes, 14 and 28 AFLP types, respectively. The combination of PFGE and AFLP typing results yielded a total of 48 genotypes. Thirteen of 15 genotypes presented by persistent strains were only associated with persistent strains and similarly 94% (33/35) of genotypes showed by sporadic strains were recovered among sporadic strains only. Our results showed that L. monocytogenes strains causing persistent contamination differ from sporadic strains. In AFLP analysis persistent strains did not, however, form any specific clusters and neither was there any difference between the known two genomic groups. These results indicate that even though persistent strains differ from sporadic strains there seems not to be any specific evolutional lineage of persistent strains.     

Coaggregation between Prevotella nigrescens and Prevotella intermedia with Actinomyces naeslundii strains

Abstract Using a visual coaggregation assay, 43% (6 of 14) of Prevotella nigrescens and 50% (4 of 8) of Prevotella intermedia strains coaggregated with Actinomyces naeslundii strains which represented the six Actinomyces coaggregation groups (A to F). For both species, coaggregation occurred most frequently with A. naeslundii strains from coaggregation groups C, D and E. No coaggregation was observed with Actinomyces israelii , Actinomyces odontolyticus or six oral Streptococcus species. Coaggregation was not inhibited by lactose, saliva or serum. Pretreatment of Prevotella strains with heat, SDS and proteinase K abolished coaggregation when the treated cells were added to untreated Actinomyces strains. The same pretreatment of the Actinomyces strains had no effect on their ability to coaggregate with untreated Prevotella strains. Pretreatment of all coaggregating P. nigrescens strains with trypsin abolished coaggregation, whereas the coaggregation ability of the P. intermedia and Actinomyces strains was resistant to trypsin pretreatment. Pretreatment of the strains of both Prevotella species and the Actinomyces with periodate abolished coaggregation in all cases. These results suggest that the Prevotella strains each possess a protein coaggregation adhesin, which for the P. intermedia strains is resistant to trypsin, that interacts with a non-protein receptor on the A. naeslundii strains.     

Pulsed-field gel electrophoresis analysis of Vibrio vulnificus strains isolated from Taiwan and the United States

Vibrio vulnificus is a marine bacterium that causes human wound infections and septicemia with a high mortality rate. V. vulnificus strains from different clinical and environmental sources or geographic regions have been successfully characterized by ribotyping and several other methods. Pulsed-field gel electrophoresis (PFGE) is a highly discriminative method, but previous studies suggested that it was not suitable for examining the correlation of V. vulnificus strains from different origins. We employed PFGE to determine its efficacy for characterizing V. vulnificus strains from different geographic regions, characterizing a total of 153 strains from clinical and environmental origins from the United States and Taiwan after SfiI or NotI digestion. V. vulnificus strains showed a high intraspecific diversity by PFGE after SfiI or NotI digestion, and about 12% of the strains could not be typed by the use of either of these enzymes. For PFGE with SfiI digestion, most of the clinical and environmental strains from the United States were grouped into cluster A, while the strains from Taiwan were grouped into other clusters. Clinical strains from the United States showed a higher level of genetic homogeneity than clinical strains from Taiwan, and environmental strains from both regions showed a similarly high level of heterogeneity. PFGE with NotI digestion was useful for studying the correlation of clinical strains from the United States and Taiwan, but it was not suitable for analyzing environmental strains. The results showed that PFGE with SfiI digestion may be used to characterize V. vulnificus strains from distant geographic regions, with NotI being a recommended alternative enzyme.     

Characterization of Agrobacterium tumefaciens strains isolated from grapevine tumors in China

Thirteen strains of Agrobacterium tumefaciens isolated from grapevine tumors in northern China were surveyed. These strains varied in their host range properties, although all were tumorigenic on grapevines. Twelve of these strains belonged to Agrobacterium sp. biotype 3, and 11 strains resulted in the synthesis of the opine octopine in tumor tissue. Interestingly, one strain resulted in accumulation of arginine, a previously unrecognized opine, in tumor tissue. Although DNA in most of these strains showed homology to the previously characterized transferred DNA and vir loci, some virulent strains showed little or no homology to these loci. Thus, some of these strains represent widely divergent examples of Agrobacterium sp. The DNA in most strains exhibited little or no homology to a wide-host-range virA locus but did show strong homology to a limited-host-range virA locus. This finding further supports the idea that Agrobacterium strains associated with grapevines may have a specific virA locus.     

Ribotyping and plasmid profiling of Vibrio anguillarum serovar O2 and Vibrio ordalii

One hundred and twenty-nine strains of Vibrio anguillarum serovar O2 and 14 strains of Vibrio ordalii were ribotyped and examined for plasmid contents. A total of 35 different ribotypes were detected. The V. anguillarum serovar O2 strains were divided into 32 different ribotypes. The V. ordalii strains showed three different ribotypes, clearly distinct from those of the V. anguillarum strains.
Ribotypes were separated into seven clusters, of which one comprised the V. ordalii strains. Clustering of the strains indicated a genetic difference between North European and South European V. anguillarum O2 strains. Sero-subgroups O2a and O2b shared ribotypes; however, three of the clusters did not include O2a strains.
All V. ordalii strains had a plasmid of 32 kb. This plasmid was not detected in any of the V. anguillarum strains. Seventeen different plasmid profiles with 17 different sized plasmids were detected among the V. anguillarum strains. Most of the plasmids were small (< 6 kb) and found in several strains. Except for one South European strain, plasmids were detected only in the North European strains of V. anguillarum O2.     

Strain-typing of Lentinula edodes in China with inter simple sequence repeat markers

To validate strain typing by inter simple sequence repeat (ISSR) analysis in Lentinula edodes cultivars, 17 Chinese L. edodes strains including 15 cultivated strains cultivated on a large scale and two wild strains were analyzed with the ISSR technique. With the use of two ISSR primers, a total of 32 DNA products were detected, of which, 31 DNA products (96.9% of the detected products) were polymorphic between two or more strains. The profiles of those two primers could be employed to differentiate all of the tested strains. A cluster analysis based on ISSR data revealed that the 17 strains could be classified into two distinct groups. One group consisted of eight strains in which the cultivated strains were H (high-temperature)-type or B (broad-temperature)-type, and the other group comprised cultivated strains that were of the L (low-temperature)-type or M (medium-temperature)-type. In contrast to the two wild strains, the genetic diversity of 15 cultivated strains was very rich based on a similarity coefficient analysis.     

Conversion of Salmonella enteritidis phage type 4 to phage type 7 involves loss of lipopolysaccharide with concomitant loss of virulence

Three strains of Salmonella enteritidis phage type 4 (PT4) and 33 strains of S. enteritidis phage type 7 (PT7) were examined for the ability to produce lipopolysaccharide (LPS) and for plasmid carriage. The LPS of all strains of PT4 gave a typical 'ladder' pattern by SDS-PAGE and silver staining, and on serotyping these strains were shown to express the O-antigens 9, 12. In contrast, strains of PT7 did not express long-chain LPS and were autoagglutinable. All strains of PT4 and the majority of strains of PT7 carried a single plasmid of 38 MDa, indistinguishable when characterised by restriction endonuclease fragmentation analysis. Epidemiological and experimental observations have demonstrated a relationship between strains of S. enteritidis PT4 and PT7, and our results, using mice, show that the loss of ability of strains of PT4 to snythesise LPS is responsible for the conversion of highly virulent strains of PT4 to avirulent strains of PT7. From epidemiological data of human infections in England and Wales, we suggest that strains of S. enteritidis PT7 may be less virulent for humans.     

Differences in the initial events of infection of Botrytis cinerea strains isolated from tomato and grape

Various stages of the infection process among B. cinerea strains isolated from tomatoes or grapes, belonging to different genetic groups, were compared. It was found that strains of B. cinerea isolated from either grapes or tomatoes showed differences in adhesion patterns and in the percentage of germination on tomato cutin. In strains isolated from tomato the first stage of adhesion occurred faster than in strains isolated from grape. At the same time strains isolated from tomato showed a higher percentage of germination on tomato cutin than the other strains after 9 h of incubation. The production and isoenzymatic patterns of polygalacturonases, pectin methyl esterases, pectin lyases, p-nitrophenylbutyrate esterases and laccases by B. cinerea in solid-state fermentation also were analyzed. Correlation between the production of these enzymes and the origin of the strains was not found. On the other hand all strains produced different isoenzymes and a common pattern between the strains was not observed. The ability of B. cinerea strains to colonize tomato leaves also differs between the isolated strains obtained from grapes and tomato. Strains isolated from tomato were more virulent on tomato leaves than strains isolated from grapes.     

Characterization of Agrobacterium tumefaciens strains isolated from grapevine tumors in China.

Thirteen strains of Agrobacterium tumefaciens isolated from grapevine tumors in northern China were surveyed. These strains varied in their host range properties, although all were tumorigenic on grapevines. Twelve of these strains belonged to Agrobacterium sp. biotype 3, and 11 strains resulted in the synthesis of the opine octopine in tumor tissue. Interestingly, one strain resulted in accumulation of arginine, a previously unrecognized opine, in tumor tissue. Although DNA in most of these strains showed homology to the previously characterized transferred DNA and vir loci, some virulent strains showed little or no homology to these loci. Thus, some of these strains represent widely divergent examples of Agrobacterium sp. The DNA in most strains exhibited little or no homology to a wide-host-range virA locus but did show strong homology to a limited-host-range virA locus. This finding further supports the idea that Agrobacterium strains associated with grapevines may have a specific virA locus.     

Transduction of fimbriation demonstrating common ancestry in FIRN strains of Salmonella typhimurium.

The production of fimbriate (Fim+) recombinants was observed in transductional crosses between different pairs of wild-type strains of different biotypes of Salmonella typhimurium. Fim+ recombinants were readily produced in transductions from Fim+ donor strains to Fim- recipient strains and, less frequently, between some pairs of Fim- strains, for example, between almost any strain of the firn biogroup (Fim- Inl- Rha- Bxyl-) and many strains of the non-FIRN Fim- biogroup. None of numerous crosses between different pairs of FIRN strains gave Fim+ recombinants, suggesting that the fim mutation was present at the same intragenic site in all FIRN strains. FIRN strains are thought to have descended from a single ancestral FIRN bacterium which originated by a series of mutations from a strain of the common biotype 1a (Fim+ Inl+ Rha+ Bxyl+). Two FIRN-like (Fim- Inl+ Rha- Bxyl-) strains that did not yield Fim+ recombinants in crosses with FIRN strains were probably wild-type Inl+ mutants from FIRN strains.     

Emergence of uropathogenic extended-spectrum beta lactamases-producing Escherichia coli strains in the community

The aim of this study was to determine the virulence characteristics and resistance pattern of the extended-spectrum/lactamases (ESBLs)-producing Escherichia coli strains isolated from urine of outpatients in the Zagreb region during a five-month period, and to compare them with the non ESBLs-producing E. coli strains isolated in the same period. Out of 2451 E. coli strains isolated from urine of nonhospitalized patients with significant bacteriuria, a total of 39 ESBLs-producing strains (1.59%) were detected by a double-disk diffusion technique and by the broth-dilution minimal inhibitory concentration reduction method. The 45 non ESBLs-producing strains were randomly chosen, and phenotype of the two groups of strains was characterized and compared. Serogroup O4, hemolysin production, expression of P- and type 1 fimbriae as well as resistance to gentamicin and amikacin were significantly more prevalent characteristics among the ESBLs-producing strains than among non ESBLs-producing strains (p < 0.01), while higher prevalence of trimethoprim-sulfamethoxazole resistance among ESBLs-producing strains was not statistically significant (p > 0.05). Chromosomal DNA analysis by pulsed-field gel electrophoresis exhibited a great genomic similarity among ESBLs-producing strains and revealed that those highly virulent and resistant E. coli strains isolated from urine of outpatients in the Zagreb region had a clonal propagation.     

G9型人A组轮状病毒LL52696与LL52727株的主要基因及其编码蛋白特征的分析

人A组轮状病毒(Human rotavirus,HRV)是引起世界范围婴幼儿重症腹泻的最主要病原,也是导致发展中国家婴幼儿死亡的主要病因之一[1-3],世界卫生组织统计每年大约引起611 000婴儿和儿童死亡,特别是发展中国家[4].HRV感染广泛,且改善营养状况和卫生条件对HRV发病危险影响不大,因此在发达国家和发展中国家HRV感染率接近.HRV引起的腹泻至今无特效药,发展疫苗对控制HRV感染的作用就显得特别突出.     

Study of antimicrobial activity amongLactobacillus helveticus strains using three different assays

The antimicrobial activity of 18Lactobacillus helveticus strains as well as one control strain, the bacteriocin producingLactobacillus helveticus 481, was tested with three different inhibition assays. FourLactobacillus helveticus strains had antimicrobial activity against seven otherLactobacillus helveticus strains and twoLactobacillus delbrueckil strains while the remaining sevenLactobacillus helveticus strains were indifferent. Inhibition was also observed againstLactococcus andLeuconostoc species, due to production of organic acids or hydrogen peroxide. The strains with the highest antimicrobial activity produced a heat sensitive proteinacious bacteriocin with a narrow species activity spectrum against only thermophilicLactobacillus strains.