Typing

About: Typing is a research topic. Over the lifetime, 5010 publications have been published within this topic receiving 146539 citations.

Comparison of PCR-Ribotyping, Arbitrarily Primed PCR, and Pulsed-Field Gel Electrophoresis for Typing Clostridium difficile

Abstract: Clostridium difficile is now recognized as the major agent responsible for nosocomial diarrhea in adults. Among the genotyping methods available, arbitrarily primed PCR (AP-PCR), PCR-ribotyping, and pulsed-field gel electrophoresis (PFGE) have been widely used for investigating outbreaks of C. difficile infections. However, the comparative typing ability, reproducibility, discriminatory power, and efficiency of these methods have not been fully investigated. We compared the results of three methods—AP-PCR with three different primers (AP3, AP4, and AP5), PCR-ribotyping, and PFGE (with SmaI endonuclease)—to differentiate 99 strains of C. difficile that had been previously serogrouped. Typing abilities were 100% for PCR-ribotyping and AP-PCR with AP3 and 90% for PFGE, due to early DNA degradation in strains from serogroup G. Reproducibilities were 100% for PCR-ribotyping and PFGE but only 88% for AP-PCR with AP3, 67% for AP-PCR with AP4, and 33% for AP-PCR with AP5. Discriminatory power for unrelated strains was >0.95 for all the methods but was lower for PCR-ribotyping among serogroups D and C. PCR-based methods were easier and quicker to perform, but their fingerprints were more difficult to interpret than those of PFGE. We conclude that PCR-ribotyping offers the best combination of advantages as an initial typing tool for C. difficile.

emm typing and validation of provisional M types for group A streptococci.

Abstract: This report discusses the following issues related to typing of group A streptococci (GAS): The development and use of the 5' emm variable region sequencing (emm typing) in relation to the existing serologic typing system; the designation of emm types in relation to M types; a system for validation of new emm types; criteria for validation of provisional M types to new M-types; a list of reference type cultures for each of the M-type or emm-type strains of GAS; the results of the first culture exchange program for a quality control testing system among the national and World Health Organization collaborating centers for streptococci; and dissemination of new approaches to typing of GAS to the international streptococcal community.

Multilocus sequence typing of IncI1 plasmids carrying extended-spectrum β-lactamases in Escherichia coli and Salmonella of human and animal origin

Abstract: Received 17 January 2008; returned 11 February 2008; revised 28 February 2008; accepted 29 February 2008 Objectives: Plasmids belonging to incompatibility group I1 (IncI1) are widespread in Enterobacteriaceae and are characterized by the presence of a cluster of genes encoding the type IV pili, contributing to the virulence of Shiga-toxigenic Escherichia coli. Recently, IncI1 plasmids were identified in E. coli and Salmonella strains of animal origin as responsible for the dissemination of b-lactamase genes. Plasmid multilocus sequence typing (pMLST) was developed to discern naturally occurring IncI1 plasmids in homogeneous groups according to their allele assortment. Methods: pMLST was developed by selecting multiple target genes on the available complete IncI1 plasmid DNA sequences. Sixteen plasmids, all assigned to the IncI1 group by the PCR-based replicon typing method, were included in this study. They were analysed for b-lactamase genes and typed by restriction fragment length polymorphism (RFLP) and pMLST. Results: Sixteen plasmids identified in E. coli and Salmonella isolated from animals and humans in different countries carried blaCMY-2, blaCTX-M-15, blaCTX-M-1, blaCTX-M-14, blaTEM-52, blaSHV-12 or blaTEM-1 b-lactamase genes. These plasmids were classified by RFLP in nine different groups corresponding to the nine sequence types determined by pMLST. Conclusions: The pMLST method was suitable for rapid and easy subtyping of IncI1 plasmids. This study demonstrates that the pMLST method can contribute to the epidemiological description of circulation of specific resistance plasmids among b-lactamase producers isolated from animals and humans.

Hla typing method and cdna probes used therein

Abstract: HLA typing based on restriction length polymorphism is carried out by: digesting an individual's HLA DNA with a restriction endonuclease that produces a polymorphic digestion pattern with HLA DNA; subjecting the digest to genomic blotting using a labeled cDNA hybridization probe that is complementary to an HLA DNA sequence involved in the polymorphism; and comparing the resulting genomic blotting pattern with a standard. This technique may be adapted to make paternity or transplant or transfusion compatibility determinations or to make disease association correlations to diagnose diseases or predict susceptibility to diseases. Locus specific cDNA hybridization probes, particularly probes for genes of Class II loci (D and DR loci), for use in the typing procedure are described.

Assessment of an Optimized Mycobacterial Interspersed Repetitive- Unit-Variable-Number Tandem-Repeat Typing System Combined with Spoligotyping for Population-Based Molecular Epidemiology Studies of Tuberculosis

Abstract: An optimized set of 24 mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) loci, including a discriminatory subset of 15 loci, has recently been defined for the typing of Mycobacterium tuberculosis. Here, we evaluated the performances of this MIRU-VNTR typing system in combination with spoligotyping for the detection of transmission chains in a population-based study comprising 91% of culture-confirmed tuberculosis patients reported in 2003 in Hamburg, Germany. Of the 154 isolates investigated, more than 90% had high IS6110 copy numbers (≥6). IS6110 restriction fragment length polymorphism (RFLP) typing resulted in 13 clusters, 5 of which had a confirmed epidemiological link. All five, as well as six of the eight IS6110 clusters with no identified epidemiological link, were perfectly matched by MIRU-VNTR typing with the 24 loci. Two IS6110 clusters were split by differences into 6 to 12 MIRU-VNTR loci, clearly supporting the absence of a link, as judged by contact tracing data. In contrast, only one MIRU-VNTR cluster, grouping what were probably epidemiologically unlinked isolates, was split by IS6110 RFLP. However, these isolates were also distinguished by spoligotyping. Both the optimized 24-locus and 15-locus sets thus showed a comparable to slightly better predictive value, especially when combined with spoligotyping, than the current gold standard IS6110 RFLP for the study of tuberculosis transmission in Hamburg. Because the epidemiological characteristics of this setting are similar to those of many developed countries, these results support the wide applicability of this real-time genotyping approach for population-based studies of M. tuberculosis transmission.