Evaluation of emm gene types, toxin gene profiles and clonal relatedness of group A streptococci
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The aim of this study is to evaluate antibiotic susceptibilities, emm gene types, toxin gene profiles and clonal relatedness of group A streptococci (GAS) isolates obtained from patients and carriers. A total of 79 clinical isolates from patients and 60 isolates from carriers were included in the study. Emm typing, toxin gene detection for speA, speB, speC, speG and smeZ genes and pulsed-field gel electrophoresis (PFGE) was performed. Twenty-one distinct emm types were detected; the most common types were emm12, emm89, emm1, emm77, emm4 and emm3. The detection rates of both emm types and the toxin genes didn't differ significantly between patients and carriers. The presence of speA and smeZ was significantly higher in emm1 and speG was significantly lower in emm4 when compared to the other emm types. The rate of clustering obtained with PFGE wasn't significantly different in patients and carriers. As a result, twelve of the 21 emm types detected in this study were covered by the 26-valent vaccine, constituting 77.7% of the emm typeable isolates; however the emm4 type which is one of the most common types in the present study is not among this coverage.Keywords:
Group A
Food poisoning
Phage typing
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Phage typing
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Molecular methods based on sequencing, such as spa typing, have facilitated epidemiological typing of bacterial isolates compared to the gold standard pulsed-field gel electrophoresis (PFGE), a technically more demanding method. We studied methicillin-resistant Staphylococcus aureus (MRSA) in 4 Swedish counties from 2003 through 2005, and compared spa typing and PFGE results to epidemiological data. Of 280 MRSA isolates, 91 were from sporadic cases and 189 were associated with 35 outbreaks. A total of 50 spa types and 74 PFGE patterns were detected. 60 (21%) of the MRSA isolates carried the Panton-Valentine leukocidin (PVL) genes. 12 of the PVL-positive MRSA were healthcare associated. 25 of the spa types and 31 of the PFGE patterns were associated with outbreaks. In 1 of the outbreaks we found isolates with different but closely related spa types, and in 6 of the outbreaks we observed isolates with different but related PFGE patterns. In this low-endemic setting, with outbreaks limited in time and place, we found spa typing to be a useful tool for epidemiological typing of MRSA, due to its rapidity, accessibility, ease of use, and standardized nomenclature.
Molecular Epidemiology
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Sequence-Based spa Typing as a Rapid Screening Method for the Areal and Nosocomial Outbreaks of MRSA
Methicillin-resistant Staphylococcus aureus (MRSA) is the leading cause of nosocomial infection and MRSA outbreaks have become a major problem. Therefore, the rapid and accurate typing of MRSA isolates is important for epidemiological surveys and nosocomial infection control. Pulsed-field gel electrophoresis (PFGE) is considered as the gold standard technique for MRSA typing, because of its high discriminatory power, but its procedure is rather complicated and time-consuming. The spa gene encodes a cell wall component of Staphylococcus aureus protein A, and exhibits polymorphism. Sequencing the spa gene is expected superior to PFGE in speed and data interpretation. In the present study, we evaluated whether spa typing of MRSA is useful for nosocomial outbreak analysis and epidemiological investigations. We analyzed 19 nosocomial outbreak isolates from 4 separate hospitals and 26 isolates from outpatients of Toyama University Hospital. Either PFGE or spa typing revealed a single nosocomial strain that appears unique to each hospital. Indeed, spa typing confirmed the four different strains, but PFGE demonstrated only 3 strains. With the total 45 isolates, PFGE showed 16 different patterns and spa typing showed 12 patterns. Moreover, we were able to analyze the spa gene in about 2 days, from sampling to obtaining the results, whereas it took about 7 days with PFGE. In conclusion, sequence-based spa typing shows comparable sensitivities to PFGE, and is a rapid and easy handling method. The sequence-based spa typing can be used as the rapid screening test when MRSA outbreak is suspected in areas and hospitals.
Multilocus sequence typing
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OBJECTIVE To explore and establish fast and sensitive typing diagnostic methods on intestinal pathogen. METHODS All 29 isolates of Shigella. sonnei and 12 strains of Escherichia coli O157:H7 (EHEC O157:H7) isolated in 1999 were carried out for typing by using pulse-field gel electrophoresis (PFGE) and phage typing. RESULTS PFGE results of 4 outbreak incidents caused by Shigella. sonnei showed that the PFGE patterns of the strains isolated from the same incident were almost the same. It was also the same during analysing the 2 outbreak incidents caused by EHEC O157:H7, however, the PFGE patterns of the 3 individual strains of EHEC O157:H7 were different. Moreover, the phage typing method showed its fine typing ability while its being used in the analysing 12 strains of EHEC O157:H7. CONCLUSION The fine typing ability and reliability of PFGE was helpful for finding out the heredity background of intestinal pathogen and the infectious resource of the outbreak. And the epidemic situation might thus be effectively prevented from spreading.
Phage typing
Shigella sonnei
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Ribotyping
Bacteremia
Molecular Epidemiology
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Summary Bacteriophage typing is currently the recognised methodology for the typing of methicillin-resistant Staphylococcus aureus (MRSA) in the UK. Bacteriophage typing is less discriminatory and does not type all isolates compared with some molecular methods for typing MRSA. Chromosomal genotyping by pulsed-field gel electrophoresis (PFGE) is increasingly recognised as an improved method for typing MRSA, providing increased discrimination and typability. In this study the results of a comparison of bacteriophage typing and PFGE typing and subtyping are presented for a large collection of isolates from the North-West of England. Isolates belonging to the most frequently isolated epidemic methicillin-resistant Staphylococcus aureus (EMRSA) bacteriophage types 15 and 16 were typed by PFGE with further discrimination of common PFGE types possible into a number of subtypes. These results for a large collection of isolates demonstrate the improved typing of MRSA with PFGE. The widespread acceptance of PFGE for typing MRSA isolates has been hampered by the lack of standardised methodologies. Recently, a standardised PFGE strain typing system, known as the GenePath system has become available. The results of an inter-laboratory comparison of PFGE typing for a collection of isolates demonstrated good reproducibility with this system.
Subtyping
Phage typing
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Laboratory-based surveillance of methicillin-resistant Staphylococcus aureus (MRSA) monitors the baseline occurrence of different genotypes and identifies strains and transmission chains responsible for outbreaks. The consequences of substituting pulsed-field gel electrophoresis (PFGE) with spa typing as a first-line typing method were analyzed by typing 589 strains isolated between 1997 and 2006, with a focus on both short- and long-term correspondence between the PFGE and spa typing results. The study, covering these ten years, included all Finnish MRSA blood isolates and representatives of the two most prevalent MRSA strains (PFGE types FIN-4 and FIN-16) in Finland. In addition, all sporadic isolates from 2006 were included. spa typing was more expensive but approximately four times faster to perform than PFGE. Nearly 90% of FIN-4 and FIN-16 isolates showed consistent spa types, t172 and t067, respectively. spa typing predicted the PFGE result of the blood isolates by a Wallace coefficient of 0.9009, recognized internationally successful strains (t041, t067) to be common also in Finland, and identified a separate cluster of isolates, also related in time and place among the FIN-4 strains. Additional typing by another method was needed to provide adequate discrimination or to characterize isolates with a newly recognized spa type in Finland.
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