Identification of Streptococci to Species Level by Sequencing the Gene Encoding the Manganese-Dependent Superoxide Dismutase

We have used a PCR assay based on the use of degenerate primers in order to characterize an internal fragment (sodA_int) representing approximately 85% of the genes encoding the manganese-dependent superoxide dismutase in various streptococcal type strains (S. acidominimus, S. agalactiae, S. alactolyticus, S. anginosus, S. bovis, S. constellatus, S. canis, S. cricetus, S. downei, S. dysgalactiae, S. equi subsp. equi, S. equi subsp. zooepidemicus, S. equinus, S. gordonii, S. iniae, S. intermedius, S. mitis, S. mutans, S. oralis, S. parasanguis, S. pneumoniae, S. porcinus, S. pyogenes, S. salivarius, S. sanguis, S. sobrinus, S. suis, S. thermophilus, and S. vestibularis). Phylogenetic analysis of these sodA_int fragments yields an evolutionary tree having a topology similar to that of the tree constructed with the 16S rRNA sequences. We have shown that clinical isolates could be identified by determining the positions of their sodA_int fragments on the phylogenetic tree of the sodA_int fragments of the type species. We propose this method for the characterization of strains that cannot be assigned to a species on the basis of their conventional phenotypic reactions.     

Gene Loss and Movement in the Maize Genome

Maize (Zea mays L. ssp. mays), one of the most important agricultural crops in the world, originated by hybridization of two closely related progenitors. To investigate the fate of its genes after tetraploidization, we analyzed the sequence of five duplicated regions from different chromosomal locations. We also compared corresponding regions from sorghum and rice, two important crops that have largely collinear maps with maize. The split of sorghum and maize progenitors was recently estimated to be 11.9 Mya, whereas rice diverged from the common ancestor of maize and sorghum ~50 Mya. A data set of roughly 4 Mb yielded 206 predicted genes from the three species, excluding any transposon-related genes, but including eight gene remnants. On average, 14% of the genes within the aligned regions are noncollinear between any two species. However, scoring each maize region separately, the set of noncollinear genes between all four regions jumps to 68%. This is largely because at least 50% of the duplicated genes from the two progenitors of maize have been lost over a very short period of time, possibly as short as 5 million years. Using the nearly completed rice sequence, we found noncollinear genes in other chromosomal positions, frequently in more than one. This demonstrates that many genes in these species have moved to new chromosomal locations in the last 50 million years or less, most as single gene events that did not dramatically alter gene structure.     

Streptococci isolated from the bloodstream and gingival crevice of man

One hundred and twenty six strains of streptococci isolated from the bloodstreams of 123 hospital in-patients--55 with endocarditis--and 255 strains isolated from the gingival crevices of 66 volunteers were characterised. Species isolated were Streptococcus mitior, S. sanguis, undifferentiated viridans streptococci, S. salivarius, S. milleri, S. mutans, S. bovis and S. faecalis. There was no significant difference between the distribution of species in blood and in the gingival crevice. S. mitior and S. sanguis were found less frequently in blood than their presence in the gingival crevice would have suggested, whereas S. milleri was found more frequently. This may indicate that S. milleri is more invasive or that it enters the bloodstream from sources other than the gingival crevice.     

In Vitro Attachment of Streptococci to the Tooth Surface

The ability of Streptococcus strains to adhere to the tooth surface in vitro was investigated. Polished enamel slabs, with and without acquired pellicles, were incubated with buffer suspensions of oral streptococci, and attached bacteria were counted under a microscope using incident light. Low numbers of bacteria adhered to uncoated enamel; the presence of an acquired pellicle significantly enhanced the attachment of all strains tested. The adherence of Streptococcus sanguis was significantly greater than that of Streptococcus salivarius, and both of these strains adhered in greater numbers than did Streptococcus mutans. When bacteria were suspended in whole saliva, the adherence of S. salivarius and S. mutans was inhibited, whereas the adherence of S. sanguis was enhanced in some experiments and inhibited in others. The adherence of S. sanguis and S. salivarius was consistently inhibited by parotid fluid; this inhibitory effect persisted after thorough washing and resonication of the bacterial cells. Incubation in oral fluids was associated with the attachment of bacterial clumps to the pellicle, and parallel investigation revealed agglutination of S. sanguis and S. salivarius by whole saliva and, in particular, parotid fluid. The results are discussed in terms of surface microecology, and are related to the development of dental plaque.     

Streptococci from primary isolation plates grouped by reverse passive haemagglutination.

Reverse passive haemagglutination, a novel microtitre based assay, was compared with the Streptex (Wellcome UK) latex slide agglutination kit for streptococcal grouping in a diagnostic microbiology laboratory. Three hundred and fifty two extracts from 349 consecutive primary isolation plates were assayed by both methods. Reverse passive haemagglutination gave identical grouping results for 98.0% of the 345 streptococci identified by Streptex, and the kappa coefficient of agreement between the methods for all 352 extracts tested was 0.973. Cross reactions with Listeria spp seen with Streptex were not found by reverse passive haemagglutination. In the reverse passive haemagglutination method 11 streptococci could be grouped on each 96-well plate and most reactions were stable for at least 30 minutes. Reverse passive haemagglutination is more rapid to perform than latex slide agglutination when many organisms are to be grouped, and the patterns of haemagglutination are easily recognised. If the method was taken into routine use in a diagnostic laboratory, the persistence of reverse passive haemagglutination reactions would enable grouping results to be checked for quality control purposes.     

Predominance of two M-types among erythromycin-resistant group A Streptococci from Greek children

In order to investigate the potential relationship between erythromycin resistance and specific M-serotypes among clinical isolates of Streptococcus pyogenes from children in Greece, we randomly selected a total of 49 erythromycin-resistant (EryR) and 21 erythromycin-susceptible (EryS) isolates from the 1158 S. pyogenes isolates from the two main children's hospitals of Athens during the period October 1997 to October 1998. The isolates were further characterized by M-serotyping, examined for their susceptibility to penicillin, vancomycin and clindamycin, and categorized into resistance phenotypes. A total of 248 (21%) S. pyogenes isolates in the two main children's hospitals of Athens during the study period were resistant to erythromycin. All 49 EryR and 21 EryS isolates were susceptible to penicillin and vancomycin. With respect to erythromycin and clindamycin resistance, phenotypes M and IR MLS_B dominated, with 30 and 17 isolates, respectively, two isolates belonged to the CR MLS_B phenotype. Among the erythromycin resistant isolates, two M serotypes were dominant: M22 (30%) and M84 (41%). More specifically, M22 and M84 were most prevalent in resistance phenotypes IR MLS_B (65%) and M (63%), respectively. In the susceptible group, no isolate belonged to these two M-serotypes, nor was a predominant serotype found. In contrast to susceptible isolates, two distinct M-serotypes were highly represented among EryR S. pyogenes isolates and predominantly associated with two distinct phenotypes.     

Vaccination with FimA from Streptococcus parasanguis Protects Rats from Endocarditis Caused by Other Viridans Streptococci

The FimA protein of Streptococcus parasanguis is a virulence factor in the rat model of endocarditis, and immunization with FimA protects rats against homologous bacterial challenge. Because FimA-like proteins are widespread among the oral streptococci, the leading cause of native valve endocarditis, we evaluated the ability of this vaccinogen to protect rats when challenged by other streptococcal species. Here we report that FimA vaccination produced antibodies that cross-reacted with and protected against challenge by the oral streptococci S. mitis, S. mutans, and S. salivarius. FimA thus has promise as a vaccinogen to control infective endocarditis caused by oral streptococci.     

Characteristics of Emerging Human-Pathogenic Escherichia coli O26:H11 Strains Isolated in France between 2010 and 2013 and Carrying the stx2d Gene Only

Strains of Escherichia coli O26:H11 that were positive for stx₂ alone (n = 23), which were not epidemiologically related or part of an outbreak, were isolated from pediatric patients in France between 2010 and 2013. We were interested in comparing these strains with the new highly virulent stx_2a-positive E. coli O26 clone sequence type 29 (ST29) that has emerged recently in Europe, and we tested them by multilocus sequence typing (MLST), stx₂ subtyping, clustered regularly interspaced short palindromic repeat (CRISPR) sequencing, and plasmid (ehxA, katP, espP, and etpD) and chromosomal (Z2098, espK, and espV) virulence gene profiling. We showed that 16 of the 23 strains appeared to correspond to this new clone, but the characteristics of 12 strains differed significantly from the previously described characteristics, with negative results for both plasmid and chromosomal genetic markers. These 12 strains exhibited a ST29 genotype and related CRISPR arrays (CRISPR2a alleles 67 or 71), suggesting that they evolved in a common environment. This finding was corroborated by the presence of stx_2d in 7 of the 12 ST29 strains. This is the first time that E. coli O26:H11 carrying stx_2d has been isolated from humans. This is additional evidence of the continuing evolution of virulent Shiga toxin-producing E. coli (STEC) O26 strains. A new O26:H11 CRISPR PCR assay, SP_O26_E, has been developed for detection of these 12 particular ST29 strains of E. coli O26:H11. This test is useful to better characterize the stx₂-positive O26:H11 clinical isolates, which are associated with severe clinical outcomes such as bloody diarrhea and hemolytic uremic syndrome.     

The diagnosis of a group of Streptococci. 1 - Comparative study of various techniques for the extraction of the polyoside antigen from Streptococci]

The present importance of streptococcal pathology implicates the identification of the streptococcal groups. The authors have carried out a comparative study of the various methods of extraction of the group specific antigen. They demonstrated the advantages and disadvantages of each method and consider the pronase extraction method to be the simplest, the most rapid and the most specific.     

应用emm基因序列分析对104株A群链球菌分型

目的　通过emm基因序列分析对A群链球菌 (GAS)进行分型 ,探讨T型与emm型的对应关系。方法　用引物以PCR法扩增GASM蛋白的N末端并进行测序 ,确定GAS的emm型 ,并与T分型对照比较。结果　 (1) 10 4株菌株中 ,emm1所占比例最大 ,为 2 9.8% ,然后依次是emm18(9.6 % ) ,emm12 (7.7% ) ,和emm6 9(5 .8% )等。 (2 )T1、T12和T14 4 9与emm基因对应关系好 ,T116株全部对应emm1型 (10 0 % ) ,T12对应emm12 ,符合率 83.3% ,T14 4 92株均对应emm4 9型 ;其它菌型对应关系差 ;同一T型可对应数个emm基因型 ,同一emm基因型可对应不同的T型。 (3)发现 1株新的emm型菌株 ,序列已递交GenBank ,注册号为AY3472 5 9。结论　emm基因分型方法具有准确、快速、分辨力高的优点 ;我国部分地区A群链球菌emm基因分型主导型为emm1、18、12、6 9、110等菌型。     

Directional and nondirectional spectral reflection from the human fovea

A model of the directional and nondirectional reflection spectrum of the human fovea is developed, incorporating reflectors, absorbers, and a wavelength-dependent optical Stiles-Crawford effect (OSCE). Data from 102 healthy subjects between 18 and 75 years obtained with the fundus reflection analyzer (FRA), an imaging spectrograph that measures the directional reflection profile of the human fovea in the pupil plane from 400 to 950 nm, were analyzed. Subgroups of young (<40 years) and old (>50 years) observers were defined. Mean results of the young group defined a template for directionality versus wavelength. For the whole group, mean reflection at 550 nm from the cones was 2.12%, from the retinal pigment epithelium 0.56%, and from the choroid 7.92%. Lens density, cone disc reflection, and blood layer thickness showed significant trends versus age. The model for the first time simultaneously describes the spectra of the directional and nondirectional reflection of the human fovea. Rayleigh scatter losses of the media and in preretinal layers were assumed zero in the nondirectional pathway. Mean density of the macular pigment of a subgroup (53 subjects, 19 to 75 years) correlated significantly with independent data from reflectance and autoflourescence images obtained by scanning laser ophthalmoscope (SLO) and data from flicker photometry.