Clonal Distribution and Virulence of Campylobacter jejuni Isolates in Blood

Benjamin Feodoroff¹

, Caroline P.A. de Haan, Patrik Ellström, Seppo Sarna, Marja-Liisa Hänninen, and Hilpi Rautelin

Author affiliations: University of Helsinki, Helsinki, Finland (B. Feodoroff, C.P.A. de Haan, S. Sarna, M.-L. Hänninen); University of Uppsala, Uppsala, Sweden (P. Ellström, H. Rautelin)

Abstract

Campylobacter jejuni bacteria are highly diverse enteropathogens. Seventy-three C. jejuni isolates from blood collected in Finland were analyzed by multilocus sequence typing and serum resistance. Approximately half of the isolates belonged to the otherwise uncommon sequence type 677 clonal complex. Isolates of this clonal complex were more resistant than other isolates to human serum.

The most common bacterial enteropathogen in industrialized countries is Campylobacter jejuni. This bacterium typically causes watery diarrhea with fever and abdominal pain (1,2). Complications, such as bacteremia, Guillain-Barré syndrome, and reactive arthritis, might also occur (3).
Multilocus sequence typing (MLST) has shown that C. jejuni is weakly clonal and highly diverse (4,5). Several MLST studies have identified particular niches for certain genetically related MLST lineages (6,7). Thus, MLST is robust in population genetics and source attribution studies.
Susceptibility to human serum varies between different species of Campylobacter; C. fetus is typically resistant, and C. jejuni is believed to be sensitive (8). Because serum resistance might contribute to spread of C. jejuni in the bloodstream, systemic isolates have been studied for their survival in human serum. However, numbers of isolates studied have been limited, and results compared with those for fecal isolates have not been distinctive (8,9).
In a recent nationwide study over a 10-year period, we collected blood culture isolates of C. jejuni and C. coli and obtained clinical features of corresponding bacteremic episodes and characteristics of patients throughout Finland (10). Our results showed that patients were moderately young and mostly without any underlying diseases (10). In the present study, we characterized C. jejuni blood culture isolates with respect to their clonal distribution and serum resistance.