Dataset Information

Multilocus sequence typing reveals a lack of diversity among Escherichia coli O157:H7 isolates that are distinct by pulsed-field gel electrophoresis.

ABSTRACT: Escherichia coli O157:H7 is a major cause of foodborne illness in the United States. Pulsed-field gel electrophoresis (PFGE) is the molecular epidemiologic method mostly commonly used to identify food-borne outbreaks. Although PFGE is a powerful epidemiologic tool, it has disadvantages that make a DNA sequence-based approach potentially attractive. Multilocus sequence typing (MLST) analyzes the internal fragments of housekeeping genes to establish genetic relatedness between isolates. We sequenced selected portions of seven housekeeping genes and two membrane protein genes (ompA and espA) of 77 isolates that were diverse by PFGE to determine whether there was sufficient sequence variation to be useful as an epidemiologic tool. There was no DNA sequence diversity in the sequenced portions of the seven housekeeping genes and espA. For ompA, all but five isolates had sequence identical to that of the reference strains. E. coli O157:H7 has a striking lack of genetic diversity in the genes we explored, even among isolates that are clearly distinct by PFGE. Other approaches to identify improved molecular subtyping methods for E. coli 0157:H7 are needed.

SUBMITTER: Noller AC

PROVIDER: S-EPMC149678 | biostudies-literature | 2003 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Multilocus sequence typing reveals a lack of diversity among Escherichia coli O157:H7 isolates that are distinct by pulsed-field gel electrophoresis.

Noller Anna C AC McEllistrem M Catherine MC Stine O Colin OC Morris J Glenn JG Boxrud David J DJ Dixon Bruce B Harrison Lee H LH

Journal of clinical microbiology 20030201 2

Escherichia coli O157:H7 is a major cause of foodborne illness in the United States. Pulsed-field gel electrophoresis (PFGE) is the molecular epidemiologic method mostly commonly used to identify food-borne outbreaks. Although PFGE is a powerful epidemiologic tool, it has disadvantages that make a DNA sequence-based approach potentially attractive. Multilocus sequence typing (MLST) analyzes the internal fragments of housekeeping genes to establish genetic relatedness between isolates. We sequenc ...[more]

PMID: 12574266

Similar Datasets

Project description:UnlabelledListeria monocytogenes is a ubiquitous bacterium that may cause the foodborne illness listeriosis. Only a small amount of data about the population genetic structure of strains isolated from food is available. This study aimed to provide an accurate view of the L. monocytogenes food strain population in France. From 1999 to 2014, 1,894 L. monocytogenes strains were isolated from food at the French National Reference Laboratory for L. monocytogenes and classified according to the five risk food matrices defined by the European Food Safety Authority (EFSA). A total of 396 strains were selected on the basis of different pulsed-field gel electrophoresis (PFGE) clusters, serotypes, and strain origins and typed by multilocus sequence typing (MLST), and the MLST results were supplemented with MLST data available from Institut Pasteur, representing human and additional food strains from France. The distribution of sequence types (STs) was compared between food and clinical strains on a panel of 675 strains. High congruence between PFGE and MLST was found. Out of 73 PFGE clusters, the two most prevalent corresponded to ST9 and ST121. Using original statistical analysis, we demonstrated that (i) there was not a clear association between ST9 and ST121 and the food matrices, (ii) serotype IIc, ST8, and ST4 were associated with meat products, and (iii) ST13 was associated with dairy products. Of the two major STs, ST121 was the ST that included the fewest clinical strains, which might indicate lower virulence. This observation may be directly relevant for refining risk analysis models for the better management of food safety.ImportanceThis study showed a very useful backward compatibility between PFGE and MLST for surveillance. The results enabled better understanding of the population structure of L. monocytogenes strains isolated from food and management of the health risks associated with L. monocytogenes food strains. Moreover, this work provided an accurate view of L. monocytogenes strain populations associated with specific food matrices. We clearly showed that some STs were associated with food matrices, such as meat, meat products, and dairy products. We opened the way to source attribution modeling in order to quantify the relative importance of the main food matrices.

Project description:Salmonella enterica serovar Typhimurium (S. Typhimurium) is a common serovar associated with non-typhoidal salmonellosis globally. However, there is insufficient data on molecular characterization of S. Typhimurium isolates from India. This study was undertaken to determine the antimicrobial resistance (AMR), plasmid, virulence profiles and molecular subtypes of S. Typhimurium Indian isolates (n = 70) of clinical and environmental origin isolated during 2010-2017. Antimicrobial susceptibility and minimum inhibitory concentrations were determined by disc diffusion and E-test methods respectively. Plasmid extraction was done following standard protocol. AMR genes, virulence genes and plasmid incompatibility types were detected by PCR; Pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) were used for molecular subtyping. Majority (57%) of the study isolates was pan susceptible; five AMR profiles were observed among the resistant (43%) isolates. AMR was significantly (p = 0.004) associated with extra-intestinal isolates than intestinal isolates.The class 1 integron and plasmid-mediated quinolone resistance genes (qnrB1, qnrS1) in the resistant isolates were transferable by conjugation. Plasmids (≥1) ranging from 1.9 to 254kb size and of IncFIIS and/or FIB type were found in most isolates. A total of 39 pulsotypes by PFGE and four sequence types by MLST like ST36 (55.7%), ST19 (32.9%), ST313 (10%) and ST213 (1.4%) were observed. ST36 and ST19 were found circulating in both clinical and environmental host, while ST313 isolates had an exclusive clinical origin. All ST19 isolates (100%) were drug-resistant, while isolates belonging to ST313 (100%), ST213 (100%) and ST36 (82%) were pan susceptible. The virulence plasmid (VP) genes (spvB- spvC) were present in all genotypes except ST36. The VP was significantly (p<0.001) associated with extra-intestinal than intestinal isolates. Some environmental and clinical isolates were clonal indicating their zoonotic transmission. Knowledge on the molecular subtypes and AMR profiles of locally prevalent Salmonella serotypes is important for effective control of spread of resistant organisms. The MLST of S. Typhimurium isolates and its association with AMR, virulence profiles was not reported earlier from India.

Project description:Pulsed-field gel electrophoresis (PFGE) characterization of 335 temporally and spatially matched clinical, bovine, and human Salmonella enterica subsp. enterica isolates revealed 167 XbaI PFGE patterns. These isolates were previously classified into 51 serotypes and 73 sequence types, as determined by multilocus sequence typing. Discriminatory power of PFGE (Simpson's index, D = 0.991) was considerably higher than that of multilocus sequence typing (D = 0.920) or serotyping (D = 0.913). Although 128 PFGE types each only represented a single isolate, 8 PFGE types represented >4 isolates, including (i) three serotype Enteritidis and Heidelberg patterns that were only identified among human isolates, (ii) two PFGE patterns (each representing serotypes Bardo and Newport) that were significantly more common among bovine isolates as compared with human isolates; (iii) two PFGE types that each includes two serotypes (4,5,12:i:- and Typhimurium; Thompson and 1,7:-:1,5); and (iv) one PFGE type that includes eight Typhimurium isolates from humans and cattle. Characterization of isolates collected over multiple farm visits indicated that given specific PFGE types persisted over time on 11 farms. On an additional seven farms, isolates with a given sequence type represented multiple PFGE type, which typically only differed by <3 bands, suggesting PFGE type diversification during strain persistence. Sixteen PFGE types were isolated from 2 or more farms, including two widely distributed serotype Newport-associated PFGE types each found on 10 farms. In six instances two or three human isolates collected in the same county in the same or consecutive months represented the same subtypes, suggesting small human case clusters. PFGE-based characterization and surveillance of human and animal isolates can provide improved understanding of Salmonella diversity and epidemiology, including identification of possible host-associated and common, widely distributed PFGE types.

Dataset Information

Multilocus sequence typing reveals a lack of diversity among Escherichia coli O157:H7 isolates that are distinct by pulsed-field gel electrophoresis.

Publications

Multilocus sequence typing reveals a lack of diversity among Escherichia coli O157:H7 isolates that are distinct by pulsed-field gel electrophoresis.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets