a comparison of our results with published population - based 7-locus mlst studies showed that the relative abundance of different clonal complexes in northwestern england from april 2003 through march 2004 was similar ( 7 ) , presumably reflecting widely distributed foods in the united kingdom . an exception was st-574 complex , the central genotype , which represented > 5% of cases in oxfordshire but was absent from northwestern england . the clonal complex distribution of 171 isolates collected in new south wales , australia ( 8) , was distinct from the 2 english datasets , although many clonal complexes were present in all 3 datasets . fewer clonal complexes , with different relative abundances , were present in a dataset from curaao ( 9 ) , likely because of different infection sources in the dutch west indies ( figure 1 ) . relative abundance of clonal complexes of campylobacter spp . detected in oxfordshire , united kingdom , during a 1-year study compared with clonal complexes detected in 3 other studies of human campylobacter spp . infections in northwestern england ( 7 ) , new south wales , australia ( 8) , and curaao ( 9 ) . the differences in relative abundance of clonal complexes were mirrored by fst values calculated from concatenated nucleotide sequences of the mlst loci , which indicated that the australian dataset was 3.6% differentiated and the curaao set 9.9% differentiated from the oxfordshire dataset . one clonal complex detected in curaao was absent in the united kingdom ( st-41 complex ) and 13 of the clonal complexes detected in the united kingdom were absent in curaao . the antigen loci added further resolution to the oxfordshire dataset : 575 ( 98.6% of isolates ) flaa svr sequences contained 130 distinct svr alleles , and 567 ( 97.1% ) flab sequences contained 111 svr alleles . the allele fragment 630bp used for pora typing was amplified and sequenced with primers momp-1 ( 5-gat ggt tta act cta gct gc-3 ) or momp-3 ( 5-gat ggt tta gtw ggm aca gg-3 ) and momp-2 ( 5-tga gaa gtt aag ttt tgg ag ag-3 ) . pora allele and variant numbers were assigned and sequences were deposited in a database ( http://hercules.medawar.ox.ac.uk/momp ) . a description of amplification conditions is also available at this website . of the 558 ( 95.5% of the isolates ) pora sequences assigned , 1 occurred in 65 isolates whereas 135 alleles occurred only once . the discriminatory index ( di ) ( 10 ) was calculated for various subsets of these data . the combination of flaa svr and flab svr ( di  = 0.976 ) provide a similar level of discrimination as pora ( di  = 0.972 ) . the di obtained with the pora gene fragment alone was similar to that obtained previously with a larger fragment of the same gene ( di  = 0.973 ) ( 11 ) . the 10-locus combination provided a degree of discrimination ( di  = 0.992 ) higher than those published for pulsed - field gel electrophoresis fingerprinting , antigen typing , or mlst ( 4,6,9,12,13 ) . these studies calculated di , ignoring the fact that some isolates probably shared a common source and may have underestimated the true di , the capacity to discriminate between epidemiologically unrelated isolates . for the same reason , there were 68 groups of > 2 isolates with identical 10-locus types , ranging in size from 2 to 34 isolates and accounting for 283 ( 48.5% ) of the independent isolates . of the remaining isolates , 290 ( 49.7% ) had unique types , typing data were incomplete for the remaining 10 isolates ( 1.7% ) . a permutation test with 283 isolates belonging to a cluster showed highly significant temporal clustering of campylobacter spp . of 16 groups of > 5 identical isolates , 5 exhibited significant temporal clustering ( table , figure 2 ) . isolates belonging to the largest of these groups , comprising 34 isolates of st-257 , flaa 16 , flab 301 , and pora 1 , were submitted mainly in the last part of the study year with a peak of 5 isolates in week 39 ( figure 2 ) . the second largest group , comprising 13 isolates , shared st-51 and an identical pora type with a genotypic group comprising 7 isolates , but the 2 groups were distinct at both flaa and flab loci . of the 12 isolates comprising the third largest group , all but 1 were isolated over a 17-week period ( week 2 through week 18 ) at the beginning of the year ( figure 2 ) . the smallest group of isolates to show evidence for temporal clustering comprised 5 identical isolates obtained during weeks 1829 . some of the other genotypic groups were seen throughout the year , with no evidence for temporal clustering ; for others , weak evidence of clustering was found ( table ) . * st , sequence type ; svr , short variable region . clusters of related 10-locus types of campylobacter spp . detected in oxfordshire , united kingdom , during a 1-year study . five groups of isolates with identical genotypes show statistically significant clustering in time ( p values are shown in the table ) . white bars indicate other isolates that share the same sequence type ( st ) but that are differentiated by their different antigen type . numbers of isolates of each genotype are shown on a weekly basis ; week 1 corresponds to the start of the study on september 15 , 2003 . clusters were detected by this method but represented a small part of the overall disease incidence ( 14 ) . further epidemiologic information unavailable to this study , which was based solely on laboratory isolates , would be needed to confirm or refute this possibility . the clusters occurred over periods longer than the typical duration of outbreaks of gastroenteritis , which was consistent with episodes of contamination entering the food chain rather than single proximate - point source events . these findings indicated that many of these clusters may be associated with widely distributed foods . the observed temporal association of groups of identical isolates could also be caused by certain genotypes having different seasonality or environmental sources from sporadic cases . in either scenario , the data supported the interpretation that cases sharing an identical genotype were more likely to be epidemiologically linked than those infected with different genotypes . in conclusion , the 10-locus typing scheme is highly discriminatory for c. jejuni and c. coli isolates and provides information that can be used flexibly to support long - range comparisons and short - term epidemiology . the scheme can be applied in real time or near real time , enabling the data to be used to identify outbreaks and inform public health interventions . when combined with improved genetic methods of attributing source of bacterial isolates ( 15 ) , this approach will contribute to refining the epidemiology of these enigmatic pathogens .
supplementing campylobacter spp . 
 multilocus sequence typing with nucleotide sequence typing of 3 antigen genes increased the discriminatory index achieved from 0.975 to 0.992 among 620 clinical isolates from oxfordshire , united kingdom . 
 this enhanced typing scheme enabled identification of clusters and retained data required for long - range epidemiologic comparisons of isolates .