Aims: Multilocus sequence typing (MLST) was used to examine the diversity and population structure of Campylobacter jejuni isolates associated with sporadic cases of gastroenteritis in Australia, and to compare these isolates with those from elsewhere.
Methods and results: A total of 153 Camp. jejuni isolates were genotyped. Forty sequence types (STs) were found, 19 of which were previously undescribed and 21 identified in other countries. The 19 newly described STs accounted for 43% of isolates, 16 of which were assigned to known clonal complexes. Eighty-eight percent of isolates were assigned to a total of 15 clonal complexes. Of these, four clonal complexes accounted for 60% of isolates. Three STs accounted for nearly 40% of all isolates and appeared to be endemic, while 21 STs were represented by more than one isolate. Seven infections were acquired during international travel, and the associated isolates all had different STs, three of which were exclusive to the travel-acquired cases. Comparison of serotypes among isolates from clonal complexes revealed further diversity. Eight serotypes were identified among isolates from more than one clonal complex, while isolates from six clonal complexes displayed serotypes not previously associated with those clonal complexes.
Conclusions: Multilocus sequence typing is a useful tool for the discrimination of subtypes and examination of the population structure of Camp. jejuni associated with sporadic infections.
Significance and impact of the study: This study highlights the genotypic diversity of Camp. jejuni in Australia, demonstrating that STs causing disease have both a global and a local distribution evident from the typing of domestically and internationally acquired Camp. jejuni isolates.