Topic
Typing
About: Typing is a research topic. Over the lifetime, 5010 publications have been published within this topic receiving 146539 citations.
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TL;DR: The majority of phenotypic and genotypic techniques developed for MRSA are not sufficiently discriminatory, reproducible, stable or useful in an outbreak to be acceptable.
106 citations
TL;DR: The ability to recognize and subcategorize plasmids by pDLST in homogeneous groups on the basis of their phylogenetic relatedness can be helpful to analyse their distribution in nature and to discover of their evolutionary origin.
Abstract: Objectives: IncHI2 plasmids are frequently encountered in clinical enterobacterial strains associated with the dissemination of relevant antimicrobial resistance genes. These plasmids are usually .250 kb, and technical difficulties can impair plasmid DNA purification and comparison by restriction fragment length polymorphism. We analysed the available IncHI2 whole DNA plasmid sequences to devise a rapid typing scheme to categorize the members of this plasmid family into homogeneous groups. Methods: We compared the available full IncHI2 plasmid sequences, identifying conserved and variable regions within the backbone of this plasmid family, to devise an IncHI2 typing method based on sequence typing and multiplex PCRs. A collection of IncHI2 plasmids carrying extended-spectrum b-lactamase and quinolone resistance genes, identified in strains from different sources (animals and humans) and geographical origins, was tested by these typing systems. Results: We devised a plasmid double locus sequence typing (pDLST) scheme and a multiplex PCR discriminating IncHI2 plasmid variants. These systems were tested on a collection of IncHI2 plasmids, demonstrating that the plasmids carrying blaCTX-M-2 and blaCTX-M-9 belonged to two major plasmid variants, which were highly conserved among different enterobacterial species disseminated in several European countries. Conclusions: The ability to recognize and subcategorize plasmids by pDLST in homogeneous groups on the basis of their phylogenetic relatedness can be helpful to analyse their distribution in nature and to discover of their evolutionary origin.
106 citations
TL;DR: Class I isoelectric focusing proved to be a useful adjunct to the serology and confirmed several serologically defined splits and detected splits of A15(A8), A18(A6) and A22(w49) that had not been detected by serology.
Abstract: SUMMARY
Polymorphism of the bovine DRB, DQA, DQB, DYA, DOB and DIB genes was investigated using restriction fragment length polymorphism (RFLP) analysis, isoelectric focusing (IEF), class II serology and polymerase chain reaction (PCR) based typing techniques. The simultaneous application of multiple typing techniques and the characterization of multiple genes resulted in a greatly enhanced picture of the bovine class II regions. Thirty-eight class IIa (DR-DQ) and 5 class lib (DYA-DOB-DIB) haplotypes were defined. It was found that IEF types were associated with DRB3 polymorphism defined by DRB3 PCR-RFLP and DRB3 microsatellite PCR. Serologically defined polymorphism was associated with distinct molecular/IEF motifs and, therefore, DR and DQ specificities could be tentatively distinguished. Although the DR and DQ genes are tightly linked, neither DR nor DQ typing defined all of the class IIa region polymorphism. Furthermore, even the most powerful DRB3 typing technique, DRB3 PCR-RFLP, failed to detect all expressed DRB3 polymorphism. All detected DRB3 polymorphism could, however, be distinguished with a combination of two molecular techniques: DRB3 PCR-RFLP and DRB3 microsatellite PCR. RFLP typing with transmembrane probes detected significantly less polymorphism than typing with cDNA or exon probes. However, the transmembrane probes were useful because they were locus specific. The presence of only 5 of 12 possible class lib haplotypes was unexpected and indicates that the DYA, DOB and DIB genes are tightly linked.
105 citations
TL;DR: PFGE is suggested to be the most discriminatory of the three subtvping methods examined in an epidemiological investigation of Campylobacter jejuni in the UK.
Abstract: In this study we have evaluated the ability of three typing methods, pulsed field gel electrophoresis (PFGE), phage-typing and ribotyping, to discriminate not only between strains of differing serotypes but also between strains within a single serotype, heat stable serotype 2 (HS2). Forty-five isolates derived from cases of campylobacter enteritis occurring in the Cardiff area were examined. These included 18, mostly HS2, strains associated with an outbreak. The typing results for these and a further 39 epidemiologically unrelated strains of serotype HS2 were compared. This is the first report documenting the use of PFGE in an epidemiological investigation of Campylobacter jejuni in the UK. The results presented suggest that this technique is the most discriminatory of the three subtyping methods examined.
105 citations
TL;DR: ST75-MRSA-IV appears to be unique to the region and probably evolved de novo in remote Aboriginal communities, and monthly tracking of SNP-based cc types showed a highly dynamic process.
Abstract: Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as a major public health problem in Australia, as in many other parts of the world. High rates of CA-MRSA skin and soft tissue infection have been reported from Aboriginal communities. We used a single-nucleotide polymorphism (SNP) genotyping typing system based on the multilocus sequence type (MLST) database to investigate the epidemiology of CA-MRSA and methicillin-sensitive S. aureus (MSSA) over a 12-month period in three remote Aboriginal communities of Northern Australia. This was supplemented by real-time PCR for Panton-Valentine leukocidin (PVL) genes, staphylococcal cassette chromosome mec (SCCmec) typing, and antimicrobial susceptibility testing. S. aureus was recovered from pyoderma lesions on 221 occasions and throat swabs on 44 occasions. The median monthly recovery rate of S. aureus from skin sores was 58% (interquartile range, 62 to 78%), and there was no seasonal variation. Twenty-three percent of isolates were CA-MRSA; the proportion was similar across the communities and did not vary over the study period. Erythromycin resistance was found in 47% of CA-MRSA and 21% of MSSA. SNP-based typing identified 14 different clonal complexes (cc); however, cc75 was predominant, accounting for 71% of CA-MRSA isolates. These were confirmed as ST75-like by using an additional SNP and MLST of selected isolates. All but one of the cc75 isolates had SSCmec type IV (one had type V), and all were PVL negative. Monthly tracking of SNP-based cc types showed a highly dynamic process. ST75-MRSA-IV appears to be unique to the region and probably evolved de novo in remote Aboriginal communities.
105 citations