Typing

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

Characterization of Isolates of Methicillin-Resistant Staphylococcus aureus from Hong Kong by Phage Typing, Pulsed-Field Gel Electrophoresis, and Fluorescent Amplified-Fragment Length Polymorphism Analysis

Abstract: The genetic relatedness of 127 methicillin-resistant Staphylococcus aureus (MRSA) isolates, belonging to five major types as identified by pulsed-field gel electrophoresis (PFGE) and antibiotic resistance profiles, was examined further using phage typing and fluorescent amplified fragment length polymorphism (FAFLP). The MRSA isolates were recovered from patients at the Prince of Wales Hospital (PWH), Hong Kong, over a 13-year period, 1988 to 2000. These strains were also compared with representatives of the well-described MRSA international clones and with epidemic MRSA strains (eMRSA) 1 to 16 from the United Kingdom. Phage typing distinguished two major “clones” at this hospital: all of the phage type 1 (PT1) isolates belonged to PFGE types A, C, D, and E, while most of the PT2 isolates were associated with PFGE type B, which exhibited a unique antibiotic resistance profile. MRSA isolates belonging to PFGE subtype A2 were indistinguishable from the British eMRSA-1, while isolates of PFGE type B were closely related to eMRSA-9 by PFGE. Based on FAFLP, all five predominant PFGE types at the PWH belonged to one group and fell into the same cluster as eMRSA-1, -4, -7, -9, and -11 isolates. Multilocus sequence typing and staphylococcal cassette chromosome mec typing classified representatives of our MRSA isolates as members of the same clone (ST239-MRSA-III). Thus, the predominant MRSA isolates frin the PWH in the last decade are closely related to early United Kingdom eMRSA clones 1, 4, and 11 and are members of a lineage that includes the Brazilian MRSA clone.

Comparison of Pulsed-Field Gel Electrophoresis and Coagulase Gene Restriction Profile Analysis Techniques in the Molecular Typing of Staphylococcus aureus

Abstract: Pulsed-field gel electrophoresis (PFGE) and coagulase gene restriction profile (CRP) analysis techniques were used to analyze 71 Staphylococcus aureus isolates recovered from nine food-borne disease outbreaks. Twenty-two PFGE profiles and 11 CRPs were identified, with discrimination indices of 0.86 and 0.72, respectively. In addition, the variable regions of the coagulase genes of 39 isolates were sequenced and showed extensive identity, indicating that this is not an efficient alternative for the molecular typing of S. aureus.

Comparison of four typing methods for Aeromonas species.

Abstract: The relative sensitivities of multi-locus enzyme electrophoresis, restriction endonuclease analysis, ribosomal DNA typing, and phage typing, in distinguishing between epidemiologically unrelated Aeromonas isolates were compared All strains were typable by multi-locus enzyme electrophoresis, restriction endonuclease analysis, and rDNA typing The analysis of 11 enzyme loci resulted in 122 distinct enzyme types among 153 strains Restriction endonuclease and rDNA patterns were different for each of 58 strains tested Identical rDNA patterns (but not restriction endonuclease patterns) were found for some strains with the same enzyme type Of the 96 strains available for phage-typing, 78 (81 %) were susceptible to at least one of the 25 phages tested and belonged to 73 distinct phage types Although phage typing may provide useful phenotypic information if used in conjunction with at least one other typing method, it is specific to the genus Aeromonas and requires materials that are not commercially available The other methods are universally applicable in bacteriology and may, therefore, be of greater importance to public health laboratories

Immunoblotting to demonstrate antigenic and immunogenic differences among nine standard strains of Clostridium difficile.

Abstract: The epidemiology of Clostridium difficile-associated disease is being elucidated with the development of typing schemes for the organism. We recently described a new typing scheme based on the incorporation of [35S]methionine into bacterial proteins followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Nine standard strains were identified. We report here some observations on the antigenic differences among these nine strains when studied by immunoblotting. Type-specific rabbit antiserum was raised against each of the nine standard strains. Immunoblotting of the strains with these antisera demonstrated, in addition to the presence of shared, common proteins, a type-specific response with homologous antisera. When [35S]methionine-labeled C. difficile proteins were immunoblotted with homologous and heterologous antisera, both the immunoblots and the autoradiographs demonstrated the same strain-specific response. These strain-specific proteins, which have been so useful for epidemiological and typing purposes, were also immunogenic. Images

Progression toward an improved DNA amplification-based typing technique in the study of Mycobacterium tuberculosis epidemiology.

Abstract: While high-copy-number IS6110-based restriction fragment length polymorphism (HCN-RFLP) is the gold standard for typing most Mycobacterium tuberculosis strains, the time taken for culturing and low throughput make it impractical for large-scale prospective typing of large numbers of isolates. The development of a new method, mycobacterial interspersed repetitive units (MIRU), a variation of the original variable-number tandem repeat (VNTR) technique, may provide a viable alternative. Panels based on the original 12-loci MIRU (12MIRU), a combination of 12MIRU and remaining ETR loci (15MIRU-VNTR), and an extended panel with an additional 10 novel regions (25VNTR) were used to study three populations with varying degrees of epidemiological data. MIRU discrimination increased with panel size and the addition of spoligotyping. Combining these two techniques enabled a reduction in the panel size from 25 to 14 loci without a significant loss in discrimination. However, 25VNTR alone or in combination with spoligotyping still possessed weaker discrimination than RFLP for high-copy-number isolates.