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PubMed1998

Sequence polymorphism in the beta-tubulin gene reveals heterogeneous and variable population structures in Cryptosporidium parvum.

Restriction fragment length polymorphism (RFLP) analysis of isolates of Cryptosporidium parvum has revealed two subgroups, termed H and C. The limited resolution of the RFLP method precludes an in-depth study of the genetic structure of C. parvum populations. Published C. parvum restriction polymorphisms lie within protein-coding regions known to be more homogeneous than noncoding sequences. To better assess the degrees of heterogeneity between and within C. parvum isolates, sequence polymorphism in the beta-tubulin intron, the only C. parvum intron described to date, was investigated. In contrast to the two genotypes distinguished by multilocus RFLP, several alleles were detected by sequence and RFLP analysis of the beta-tubulin intron and adjacent exon 2. Isolates carrying different beta-tubulin alleles were found. Significantly, one of the beta-tubulin alleles present in two geographically unrelated isolates combined features of C- and H-type isolates, suggesting that it might have arisen from a recombination event. A comparison of multiple samples of a calf-propagated laboratory isolate showed that the ratio of different beta-tubulin alleles fluctuated during serial passage.

Animals↗

PubMed1992

Evidence consistent with horizontal transfer of the gene (emm12) encoding serotype M12 protein between group A and group G pathogenic streptococci.

Human isolates of Lancefield group G streptococci harbor sequences homologous with the structural gene (emm) encoding M protein, a major virulence factor in Streptococcus pyogenes (a group A Streptococcus species). We used DNA-DNA hybridization, restriction endonuclease chromosomal profiling, and multilocus enzyme electrophoresis to examine genetic relationships between group A and group G streptococcal strains expressing homologous serologic type 12 M (M12) protein. All M12 group A strains studied had very similar restriction endonuclease genomic profiles and multilocus enzyme genotypes. In contrast, the restriction enzyme genomic profile and multilocus enzyme genotype of the M12 group G strain CS140 were strikingly different from those characterizing the M12 group A organisms. DNA-DNA hybridization studies revealed, on average, 57% genomic similarity between the M12 group A and group G strains. Taken together, our data demonstrate that a gene encoding M12 protein occurs in two highly divergent chromosomal backgrounds, a result suggesting that an episode of horizontal gene transfer and recombination has occurred between two streptococcal lineages.

Antigens, Bacterial↗

PubMed1998

A microsatellite-based multilocus phylogeny of the Drosophila melanogaster species complex.

Uncovering the genealogy of closely related species remains a major challenge for phylogenetic reconstruction. It is unlikely that the phylogeny of a single gene will represent the phylogeny of a species as a whole [1], but DNA sequence data across a large number of loci can be combined in order to obtain a consensus tree [2]. Long sequences are needed, however, to minimize the effect of (infrequent) base substitutions, and sufficient individuals must be sequenced per species to account for intraspecific polymorphisms, an overwhelming task using current DNA sequencing technology. By contrast, microsatellites are easy to type [3], allowing the analysis of many loci in multiple individuals. Despite their successful use in mapping [4,5], behavioural ecology [6] and population genetics [7], their usefulness for the phylogenetic reconstruction of closely related taxa has never been demonstrated, even though microsatellites are often conserved across species [8-10]. One drawback to microsatellite use is their high mutation rate (10(-4)-10(-2)), combined with an incomplete understanding of their mutation patterns. Many microsatellites are available for Drosophila melanogaster, and they are distributed throughout the genome [11]. Most can be amplified in the D. melanogaster species complex [12,13] and have low mutation rates [14, 15]. We show that microsatellite-specific distance measurements [16] correlate with other multilocus distances, such as those obtained from DNA-DNA hybridization data. Thus microsatellites may provide an ideal tool for building multilocus phylogenies. Our phylogenetic reconstruction of the D. melanogaster complex provides strong evidence that D. sechellia arose first, followed by a split between D. simulans and D. mauritiana.

Animals↗

PubMed1995

Vir typing: a long-PCR typing method for group A streptococci.

We have developed a new procedure (Vir typing) for typing Streptococcus pyogenes, by amplifying the entire 5- to 7-kb variable vir regulon by long PCR. The amplified DNA is then cleaved with HaeIII and visualized by ethidium bromide fluorescence after agarose gel electrophoresis. A simple procedure for preparing DNA of sufficiently high quality from 96 samples was employed simultaneously. This DNA was also used to develop a random amplified polymorphic DNA (RAPD) procedure. The discriminatory power of the two DNA-based procedures was compared with previous methods, M typing, and multilocus enzyme electrophoresis. Both procedures were highly discriminatory, but the stoichiometric yield of restriction fragments in Vir typing allows unambiguous interpretation of results.

Bacterial Proteins↗

PubMed1998

Rhizobium mongolense sp. nov. is one of three rhizobial genotypes identified which nodulate and form nitrogen-fixing symbioses with Medicago ruthenica [(L.) Ledebour].

Medicago ruthenica [(L.) Ledebour] is native to inner Mongolia where rhizosphere samples were collected for the isolation of 106 rhizobial cultures. Besides nodulating the original trap host, the isolates formed nitrogen-fixing symbioses with Phaseolus vulgaris. Only half of the isolates nodulated alfalfa (Medicago sativa), but these did not form nitrogen-fixing symbioses. Rhizobium tropici also formed nitrogen-fixing symbioses with Medicago ruthenica. A total of 56 distinctive multilocus electrophoretic types (ETs) were identified among 94 of the 106 isolates which were analysed for variation in electrophoretic mobility of 12 enzyme loci. One isolate (USDA 1920) possessed a unique ET, while the ETs of the other isolates formed two weakly divergent subgroups approximately equal in size. It was concluded from small subunit rRNA gene sequences of eight isolates of Medicago ruthenica that they belonged to the genus Rhizobium and not to the genus Sinorhizobium which is more commonly associated with Medicago. Genomic similarity, determined from DNA hybridization analysis, between USDA 1920 and the strain representing the remaining isolates (USDA 1844) was lower than 20%. Based upon these observations it was concluded that at least three genomic species of rhizobia form nitrogen-fixing symbioses with Medicago ruthenica. One of these genomic species is R. tropici, another is represented by the single isolate USDA 1920 and the name Rhizobium mongolense is proposed for the third genomic species represented by USDA 1844.

Alleles↗

PubMed2025

Double Genetic Diagnosis Involving MECP2 and EPHB4 in a Child with Neurodevelopmental Delay and Vascular Anomalies: A Case Report.

BACKGROUND: Double genetic diagnoses are increasingly identified with the advent of genome-wide sequencing techniques. While MECP2 mutations are associated with Rett syndrome and EPHB4 mutations with vascular malformation syndromes, their co-occurrence has not been previously described. CASE PRESENTATION: We describe an 8-year-and-2-month-old girl presenting with global developmental delay, autism spectrum disorder, and stereotypic behaviors, along with multiple well-demarcated cutaneous vascular lesions. Although she had no clinical seizures, electroencephalogram revealed epileptiform discharges. Physical examination showed dysmorphic features and vascular anomalies, including telangiectatic pink-to-red macular vascular lesions. Whole exome sequencing (WES) identified two de novo heterozygous pathogenic variants: a missense mutation in MECP2 (c.433C>T; p.Arg145Cys), a gene classically implicated in Rett syndrome, and a nonsense mutation in EPHB4 (c.1093C>T; p.Arg365Ter), which has been previously associated with capillary malformation-arteriovenous malformation syndrome type 2. The neurodevelopmental findings, while consistent with the broader spectrum of MECP2-related disorders, along with coexisting vascular anomalies, were best accounted for by a dual genetic diagnosis involving both MECP2 and EPHB4. CONCLUSION: This case underscores the diagnostic value of considering dual genetic diagnoses in patients with complex phenotypes and highlights the role of WES in uncovering multilocus variation, thereby expanding the known phenotypic spectrum associated with MECP2 and EPHB4 mutations.

Double genetic diagnosis↗

PubMed1999

Molecular typing of Borrelia burgdorferi sensu lato: taxonomic, epidemiological, and clinical implications.

Borrelia burgdorferi sensu lato, the spirochete that causes human Lyme borreliosis (LB), is a genetically and phenotypically divergent species. In the past several years, various molecular approaches have been developed and used to determine the phenotypic and genetic heterogeneity within the LB-related spirochetes and their potential association with distinct clinical syndromes. These methods include serotyping, multilocus enzyme electrophoresis, DNA-DNA reassociation analysis, rRNA gene restriction analysis (ribotyping), pulsed-field gel electrophoresis, plasmid fingerprinting, randomly amplified polymorphic DNA fingerprinting analysis, species-specific PCR and PCR-based restriction fragment length polymorphism (RFLP) analysis, and sequence analysis of 16S rRNA and other conserved genes. On the basis of DNA-DNA reassociation analysis, 10 different Borrelia species have been described within the B. burgdorferi sensu lato complex: B. burgdorferi sensu stricto, Borrelia garinii, Borrelia afzelii, Borrelia japonica, Borrelia andersonii, Borrelia valaisiana, Borrelia lusitaniae, Borrelia tanukii, Borrelia turdi, and Borrelia bissettii sp. nov. To date, only B. burgdorferi sensu stricto, B. garinii, and B. afzelii are well known to be responsible for causing human disease. Different Borrelia species have been associated with distinct clinical manifestations of LB. In addition, Borrelia species are differentially distributed worldwide and may be maintained through different transmission cycles in nature. In this paper, the molecular methods used for typing of B. burgdorferi sensu lato are reviewed. The current taxonomic status of B. burgdorferi sensu lato and its epidemiological and clinical implications, especiallly correlation between the variable clinical presentations and the infecting Borrelia species, are discussed in detail.

Bacterial Typing Techniques↗

PubMed1988

X-ray-induced specific locus mutations in the ad-3 region of two-component heterokaryons of Neurospora crassa. I. Modification of the heterozygous effects of multilocus deletions covering the ad-3A or ad-3B loci.

The basis for the reduced growth rates of heterokaryons between strains carrying nonallelic combinations of gene/point mutations (ad-3R) and multilocus deletion mutations (ad-3IR) has been investigated by a simple genetic test. The growth rates of forced 2-component heterokaryons (dikaryons) between multilocus deletion mutations were compared with forced 3-component heterokaryons (trikaryons) containing an ad-3AR ad-3BR double mutant as their third component. Since the third component has no genetic damage at other loci immediately adjacent to the ad-3A or ad-3B locus, the growth rate on minimal medium depends on the functional activity of the unaltered (and presumed "wild-type") ad-3A and ad-3B loci in the first two components. In many cases, the requirements of the original dikaryons have been satisfied by the addition of unaltered genes (in the third component), and these trikaryons grow at wild-type rate on minimal medium. Those trikaryons growing at less than wild-type rate were shown to be adenine-requiring, and wild-type growth rate was obtained with the addition of low levels of adenine to the medium. Such tests in the present experiments have shown that ad-3IR mutations result not only in inactivation of the ad-3 loci by multilocus deletion but also, in many cases, in partial gene inactivation by an unknown mechanisms at other loci in the immediately adjacent regions. The heterozygous effects observed in our present experiments with multilocus deletions in Neurospora can be explained either by a spreading-type position effect of the type found by others in Drosophila, mice, Oenothera and Aspergillus or by undetected genetic damage ("cryptic mutations") in the immediately adjacent genetic regions. An attempt will be made to distinguish between these two alternative hypotheses with techniques for DNA cloning and sequencing in future experiments.

Adenine↗

PubMed1995

Genetic diversity and relationships among Streptococcus pyogenes strains expressing serotype M1 protein: recent intercontinental spread of a subclone causing episodes of invasive disease.

Chromosomal diversity and relationships among 126 Streptococcus pyogenes strains expressing M1 protein from 13 countries on five continents were analyzed by multilocus enzyme electrophoresis and restriction fragment profiling by pulsed-field gel electrophoresis. All isolates were studied for the presence of the gene encoding streptococcal pyrogenic exotoxin A by PCR. Strain subsets were also examined by automated DNA sequencing for allelic polymorphism in genes encoding M protein (emm), streptococcal pyrogenic exotoxin A (speA), streptokinase (ska), pyrogenic exotoxin B (interleukin-1 beta convertase) (speB), and C5a peptidase (scp). Seven distinct emm1 alleles that encode M proteins differing at one or more amino acids in the N-terminal variable region were identified. Although substantial levels of genetic diversity exist among M1-expressing organisms, most invasive disease episodes are caused by two subclones marked by distinctive multilocus enzyme electrophoretic profiles and pulsed-field gel electrophoresis restriction fragment length polymorphism (RFLP) types. One of these subclones (ET 1/RFLP pattern 1a) has the speA gene and was recovered worldwide. Identity of speA, emm1, speB, and ska alleles in virtually all isolates of ET 1/RFLP type 1a means that these organisms share a common ancestor and that global dispersion of this M1-expressing subclone has occurred very recently. The occurrence of the same emm and ska alleles in strains that are well differentiated in overall chromosomal character demonstrates that horizontal transfer and recombination play a fundamental role in diversifying natural populations of S. pyogenes.

Amino Acid Sequence↗

PubMed2001

High genetic diversity in arbuscular mycorrhizal fungi: evidence for recombination events.

The genetic diversity of spores of two indigenous species of Glomus isolated from three soils of a long-term field experiment amended by different quantities of sewage sludges has been evaluated. Three populations of spores of Glomus claroideum (W2537) and three populations of spores of Glomus DAOM 225952 (W2538) were analysed using a microsatellite primer and aliquots of genomic DNA were obtained from single spores (Inter Simple Sequence Repeat (ISSR) fingerprints). 39 polymorphic bands were found for G. claroideum, and 43 in Glomus DAOM 225952. The intraspecific diversity was high, ranging from 22 to 33 different electrophoretic types for G. claroideum, and 15-27 for Glomus DAOM 225952 depending on the population. Resampling experiments showed that the number of polymorphic bands was sufficient to score all multilocus profiles in the populations and to describe the clonality structure within populations. On average, one multilocus profile was represented by about four spores whatever the population and the species. Partitioning of the within-species phenotypic variance showed that more than 92% of the variation was found within populations, while the among-population variance component accounted for less than 8%, even though it was statistically different from 0. This result is confirmed by the fact that only few multilocus profiles were shared by two populations of G. claroideum, and none by populations of Glomus DAOM 225952. In addition to the high level of diversity observed within populations, linkage disequilibria analyses and association indices calculated across loci indicates that reproduction cannot be solely clonal. Recombination or recombination-like events are likely to occur in these arbuscular mycorrhizal fungi. An 'epidemic' population structure was found for both fungal species in the soil that had received high amounts of sewage sludge.

Electrophoresis↗

PubMed1992

Genomic rearrangements in mouse C3H/10T1/2 cells transformed by X-rays, UV-C, and 3-methylcholanthrene, detected by a DNA fingerprint assay.

Genomic rearrangements occurring in C3H/10T1/2 cells transformed by X-rays were examined with a DNA fingerprint assay. Four multilocus and multiallele probes were employed (M, X, H10, and H16) that detect different families of minisatellite sequences dispersed throughout the genome. Genomic rearrangements were detectable only with probe M. This specificity may be explained by a genomic instability owing to a specific sequence or structure of DNA recognized by probe M. Genomic rearrangements were detected in 5 of 12 type III foci transformed by 600 cGy of X-rays and in all clones isolated from a previously transformed clone exposed to a second dose of 600 cGy and recloned. The latter data suggest that the stage of transformation and the occurrence of genomic rearrangement induced by X-rays may be related. An intensity shift or a complete deletion of band 2 was common to these X-ray-induced clones, as well as to clones transformed by UV-C (1 of 5) or 3-methylcholanthrene (4 of 6). This band did not hybridize to probes for the retinoblastoma gene RB or for p53. We hypothesize that the loss of band 2 may reflect a significant genetic change in the transformation of 10T1/2 cells, perhaps representing the inactivation of a tumor suppressor gene other than RB or p53. Additional rearrangements occurred in X-ray-transformed clones; these rearrangements were not observed with the other carcinogens. Aside from the changes in band 2, however, no specific pattern of genomic rearrangement was associated with X-ray transformation, and the presence or absence of rearrangements did not correlate with tumorigenicity in syngeneic nonimmunosuppressed C3H mice.

Animals↗

PubMed1996

Acute virulence in mice is associated with markers on chromosome VIII in Toxoplasma gondii.

Toxoplasma gondii has an unusual population structure consisting of three widely distributed clonal lineages. Acute virulence in mice is strictly observed in type I strains, indicating that a genetic determinant(s) unique to this lineage controls acute pathogenesis. We have analyzed several naturally occurring recombinant strains of T. gondii that carry allele 1 at the SAG1 locus; this allele is characteristic of the type I strains and was previously found to be 100% correlated with the acute virulence phenotype. Recombinant strains G622-M and ROD both had a predominantly type III genotype, with the significant exception of allele 1 at the SAG1 locus. Although these two strains had virtually identical multilocus genotypes, they differed in their virulence in mice. Strain ROD was virulent whereas strain G622-M was nonvirulent, thus demonstrating that the presence of allele 1 at SAG1 is not alone sufficient to confer acute virulence. Several sequence polymorphisms upstream of SAG1 were found to be highly correlated with the acutely virulent lineages. Collectively, these results suggest that acute virulence is regulated by a region linked to the SAG1 locus on chromosome VIII in T. gondii.

Animals↗

PubMed1990

Restriction fragment length polymorphisms among uropathogenic Escherichia coli isolates: pap-related sequences compared with rrn operons.

Among the adhesin-encoding virulence operons associated with uropathogenic Escherichia coli, only pap (pyelonephritis-associated pilus)-related gene clusters typically exhibit variation in their structure and chromosomal copy number. To access further such variability, we compared pap restriction fragment length polymorphisms (RFLPs) with those detected among rRNA (rrn) operons, which encode an essential host function unrelated to virulence. To place such findings in a phylogenetic perspective, the E. coli isolates were also characterized by using multilocus enzyme electrophoresis. Variation in the rrn RFLP profiles correlated with evolutionary divergence resolved by multilocus enzyme electrophoresis; isolates with identical rrn profiles represented the same or closely related electrophoretic types. In contrast, such isolates frequently had different pap-related RFLPs, indicating that these genetic variations have developed recently relative to the changes associated with essential rrn operons or metabolic enzymes. Despite such fluctuations, two lines of evidence indicate conditions under which the pap-related RFLPs can be stably maintained. First, for each of 20 patients with urosepsis, both the primary urinary tract isolate and the concurrent blood isolate were identical. Second, although obtained from different patients, some isolates representing the same electrophoretic type also had identical pap-related RFLPs. Thus, the genotypic diversity of this virulence adhesin operon was not generated during the course of acute infection or during laboratory manipulations. Since fecal E. coli isolates frequently carry chromosomally encoded pap-related gene clusters, these findings suggest that the intra- and interchromosomal recombination events generating the polymorphisms associated with the pap-related sequences likely occur among the E. coli of the commensal reservoir.

Base Sequence↗

PubMed2026

Genome analysis and antagonistic activity of Streptomyces sp. strain J36 against Phytophthora cactorum.

The Phytophthora blight of Panax notoginseng, caused by Phytophthora cactorum, is a devastating oomycete disease. Biocontrol strategies hold immense potential for inhibiting the spread of P. cactorum. We isolated 72 actinobacteria from soil and screened their antagonistic activity against P. cactorum. Both strain J36 and its cell-free filtrate exhibited strong antagonistic activity against P. cactorum and were therefore selected. Based on the 16S rRNA gene phylogenetic tree, strain J36 formed a well supported subclade with Streptomyces zaomyceticus NRRL B-2038 (bootstrap value 100%). However, because 16S rRNA sequences often lack sufficient resolution for species-level discrimination, we performed multilocus sequence analysis (MLSA) using three housekeeping genes (rpoB, recA, and atpD). The MLSA results consistently placed strain J36 within the same cluster as S. zaomyceticus NRRL B-2038, with a bootstrap support of 99%, indicating a close phylogenetic relationship. To further clarify the taxonomic status, we calculated the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain J36 and the type strain of S. zaomyceticus NBC-00415T. The ANI value was 90.91% and the dDDH value was 39.30%, both well below the accepted thresholds for species demarcation (ANI < 95%, dDDH < 70%). These genomic indices therefore strongly support that strain J36 represents a novel species within the genus Streptomyces. Through whole-genome sequencing and CAZymes analysis, a total of 98 carbohydrate-active enzymes (CAZymes) were detected, including 2 cellulase and 2 β-1,3-glucanases. The cell-free filtrate, which exhibited strong antagonistic activity against P. cactorum, also showed high activities of cellulase and β-1,3-glucanase, suggesting that these enzymes may be involved in its anti-oomycete activity. These findings suggest that J36 has potential as a biocontrol candidate, although further in vivo evaluation is needed to confirm its efficacy against Phytophthora blight of P. notoginseng.

Panax notoginseng↗

PubMed1998

High-level chloramphenicol resistance in Neisseria meningitidis.

BACKGROUND: Neisseria meningitidis is nearly always susceptible to the penicillins, the cephalosporins, and chloramphenicol. Between 1987 and 1996, however, chloramphenicol-resistant strains were isolated from 11 patients in Vietnam and 1 in France. METHODS: The minimal inhibitory concentration of chloramphenicol was determined for the 12 isolates. The isolates were analyzed by monoclonal-antibody-based serotyping and subtyping, pulsed-field gel electrophoresis, and multilocus enzyme electrophoresis. Bacterial DNA was analyzed by hybridization, the polymerase chain reaction, and sequencing to identify the resistance gene and determine the origin of the resistance. RESULTS: The isolates were resistant to chloramphenicol (minimal inhibitory concentration, > or =64 mg per liter) and produced an active chloramphenicol acetyltransferase. All 12 strains belonged to serogroup B but had a high degree of diversity, and 10 could not be typed with the use of monoclonal antibodies. The nucleotide sequence of the resistance gene and the flanking regions was identical to that of an internal portion of transposon Tn4451 that carries the catP gene in Clostridium perfringens. Moreover, this gene was located in the same genomic site in the chloramphenicol-resistant isolates. CONCLUSIONS: The high-level chloramphenicol resistance that we describe in N. meningitidis isolates is of great concern, since in developing countries, chloramphenicol given intramuscularly is the standard therapy for meningococcal meningitis. The resistance to chloramphenicol is due to the presence of the catP gene on a truncated transposon that has lost mobility because of internal deletions, and the transformation of genetic material between strains of N. meningitidis probably played an important part in the dissemination of the gene.

Base Sequence↗

PubMed1993

Evolutionary origin and radiation of the avian-adapted non-motile salmonellae.

Multilocus enzyme electrophoresis was employed to estimate chromosomal genotypic diversity and relationships among 131 isolates of the non-motile Salmonella biotypes Gallinarum and Pullorum (serotype 1, 9, 12:-:-) that cause fowl typhoid and pullorum disease, respectively. Thirteen electrophoretic types (ETs), marking clones, were distinguished, and construction of a neighbour-joining phylogenetic tree revealed three lineages: one consisted of five ETs of Gallinarum, a second included seven ETs of Pullorum, and a third was represented by a single ET (Ga/Pu 1) that is intermediate between those of the other two lineages in both multilocus enzyme genotype and biochemical properties. Enzyme genotype analysis and comparative nucleotide sequencing of the phase 1 flagellin gene (fliC), the hook-associated protein 1 gene (flgK), and the 6-phosphogluconate dehydrogenase gene (gnd) identified serotype Enteritidis (1, 9, 12:g, m:-) as a close relative of the non-motile salmonellae. In most strains of biotype Gallinarum, the fliC gene is complete, intact and identical in sequence to that of Enteritidis, but isolates of three ETs had a stop codon at position 495. The fliC sequences of the ETs of Pullorum differed from that of Enteritidis in having non-synonymous changes in either two or three codons and a synonymous change in one codon. The sharing of distinctive alleles at three metabolic enzyme loci and a stop codon in flgK indicates that the non-motile salmonellae are monophyletic and that their most recent common ancestor was non-motile. Since diverging from that ancestor, the Pullorum lineage has evolved more rapidly than the Gallinarum and Ga/Pu 1 lineages.

Animals↗

PubMed1988

Limited diversity of the immunoglobulin A1 protease gene (iga) among Haemophilus influenzae serotype b strains.

Immunoglobulin A1 (IgA1) proteases are thought to be important virulence factors in certain bacterial infections, including meningitis, and may have potential usage in vaccines. In this study, we compared the locations of EcoRI, BamHI, and PstI restriction endonuclease sites in the IgA1 protease gene (iga) region of whole-cell DNA from 76 Haemophilus influenzae strains. The analysis was performed by using isolated fragments of the cloned iga gene, which encodes the IgA1 protease originating from a H. influenzae serotype d strain, as probes in Southern blot experiments. All strains, including three without detectable IgA1 protease activity, had DNA sequences with a high degree of homology to the iga probes. The numbers and sizes of the DNA fragments hybridizing with the probes indicated that only three strains, none of which was of serotype b, had more than one iga gene. The iga restriction fragment length patterns of 60 clinical isolates of serotype b were of only four distinct types, which correlated with previously observed clusters of multilocus genotypes (electrophoretic types). This correlation supports the concept of the clonal population structure of H. influenzae. Three of the iga gene restriction types, which appear to represent 98% of the H. influenzae serotype b population, encode IgA1 proteases that were inhibited by antisera to any one of these types and therefore could form the basis for the development of a vaccine against H. influenzae meningitis.

Antibodies, Bacterial↗

PubMed1994

Evaluation of 13 short tandem repeat loci for use in personal identification applications.

Personal identification by using DNA typing methodologies has been an issue in the popular and scientific press for several years. We present a PCR-based DNA-typing method using 13 unlinked short tandem repeat (STR) loci. Validation of the loci and methodology has been performed to meet standards set by the forensic community and the accrediting organization for parentage testing. Extensive statistical analysis has addressed the issues surrounding the presentation of "match" statistics. We have found STR loci to provide a rapid, sensitive, and reliable method of DNA typing for parentage testing, forensic identification, and medical diagnostics. Valid statistical analysis is generally simpler than similar analysis of RFLP-VNTR results and provides powerful statistical evidence of the low frequency of random multilocus genotype matching.

Alleles↗