Typing

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

Source attribution of human Campylobacter isolates by MLST and fla-typing and association of genotypes with quinolone resistance.

Abstract: Campylobacteriosis is the most frequent zoonosis in developed countries and various domestic animals can function as reservoir for the main pathogens Campylobacter jejuni and Campylobacter coli. In the present study we compared population structures of 730 C. jejuni and C. coli from human cases, 610 chicken, 159 dog, 360 pig and 23 cattle isolates collected between 2001 and 2012 in Switzerland. All isolates had been typed with multi locus sequence typing (MLST) and flaB-typing and their genotypic resistance to quinolones was determined. We used complementary approaches by testing for differences between isolates from different hosts with the proportion similarity as well as the fixation index and by attributing the source of the human isolates with Bayesian assignment using the software STRUCTURE. Analyses were done with MLST and flaB data in parallel and both typing methods were tested for associations of genotypes with quinolone resistance. Results obtained with MLST and flaB data corresponded remarkably well, both indicating chickens as the main source for human infection for both Campylobacter species. Based on MLST, 70.9% of the human cases were attributed to chickens, 19.3% to cattle, 8.6% to dogs and 1.2% to pigs. Furthermore we found a host independent association between sequence type (ST) and quinolone resistance. The most notable were ST-45, all isolates of which were susceptible, while for ST-464 all were resistant.

Multilocus Sequence Typing and Antigen Gene Sequencing in the Investigation of a Meningococcal Disease Outbreak

Abstract: Multilocus sequence typing and antigen gene sequencing were used to investigate an outbreak of meningococcal disease in a university in the United Kingdom. The data obtained showed that five distinct Neisseria meningitidis strains belonging to the ET-37 complex were present in the student population during the outbreak. Three of these strains were not associated with invasive disease, and two distinct strains caused invasive disease, including several fatalities. The initial case of the disease cluster was caused by a strain distinct from that responsible for at least two subsequent cases and two cases remote from the university, which were epidemiologically linked to the outbreak. These observations were consistent with pulsed-field gel electrophoresis data, but the sequence data alone were sufficient to resolve the strains involved in the disease cluster. Interpretation of the nucleotide sequence data was more straightforward than interpretation of the fingerprint patterns, and the sequence data provided information on the genetic differences among the isolates.

Sequence-based typing of Legionella pneumophila serogroup 1 offers the potential for true portability in legionellosis outbreak investigation.

Abstract: Seven gene loci of Legionella pneumophila serogroup 1 were analyzed as potential epidemiological typing markers to aid in the investigation of legionella outbreaks. The genes chosen included four likely to be selectively neutral (acn, groES, groEL, and recA) and three likely to be under selective pressure (flaA, mompS, and proA). Oligonucleotide primers were designed to amplify 279- to 763-bp fragments from each gene. Initial sequence analysis of the seven loci from 10 well-characterized isolates of L. pneumophila serogroup 1 gave excellent reproducibility (R) and epidemiological concordance (E) values (R = 1.00; E = 1.00). The three loci showing greatest discrimination and nucleotide variation, flaA, mompS, and proA, were chosen for further study. Indices of discrimination (D) were calculated using a panel of 79 unrelated isolates. Single loci gave D values ranging from 0.767 to 0.857, and a combination of all three loci resulted in a D value of 0.924. When all three loci were combined with monoclonal antibody subgrouping, the D value was 0.971. Sequence-based typing of L. pneumophila serogroup 1 using only three loci is epidemiologically concordant and highly discriminatory and has the potential to become the new "gold standard" for the epidemiological typing of L. pneumophila.

Development of a bacteriophage typing system for Campylobacter jejuni and Campylobacter coli.

Abstract: A bacteriophage typing system for Campylobacter jejuni and Campylobacter coli was developed with phages isolated from poultry feces. Data for phage selection were generated from a set of isolates of C. jejuni and C. coli from humans in Illinois. Selection of 14 phages from the 47 phages available was assisted by determination of the Sneath-Jaccard similarity coefficients and subsequent unweighted pair-group arithmetic averaging cluster analysis. The typing set was reproducible and stable in the 255 isolates from Illinois. Of these isolates, 94.5% were typable, with 46% represented by the four most common phage patterns. In a set of 51 isolates from humans outside of Illinois, 88.1% of the C. jejuni isolates were typable. Phage typing for C. jejuni and C. coli has excellent epidemiologic potential and should serve as a useful adjunct or alternative to serotyping systems in current use.