Escherichia coli O104:H4 Infections and International Travel

David C. Alexander, Weilong Hao, Matthew W. Gilmour, Sandra Zittermann, Alicia Sarabia, Roberto G. Melano, Analyn Peralta, Marina Lombos, Keisha Warren, Yuri Amatnieks, Evangeline Virey, Jennifer H. Ma, Frances B. Jamieson, Donald E. Low, and Vanessa G. Allen

Author affiliations: Public Health Ontario, Toronto, Ontario, Canada (D.C. Alexander, W. Hao, S. Zittermann, R.G. Melano, A. Peralta, M. Lombos, K. Warren, J.H. Ma, F.B. Jamieson, D.E. Low, V.G. Allen); University of Toronto, Toronto (D.C. Alexander, W. Hao, R.G. Melano, F.B. Jamieson, D.E. Low, V.G. Allen); Mount Sinai Hospital, Toronto (W. Hao, K. Warren, D.E. Low); Public Health Agency of Canada, Winnipeg, Manitoba, Canada (M.W. Gilmour); Credit Valley Hospital, Mississauga, Ontario, Canada (A. Sarabia, Y. Amatnieks, E. Virey)

Abstract

We analyzed travel-associated clinical isolates of Escherichia coli O104:H4, including 1 from the 2011 German outbreak and 1 from a patient who returned from the Philippines in 2010, by genome sequencing and optical mapping. Despite extensive genomic similarity between these strains, key differences included the distribution of toxin and antimicrobial drug–resistance determinants.

In May 2011, officials in northern Germany reported a sudden surge in illness due to Shiga-toxigenic Escherichia coli (STEC). Symptoms of infection ranged from self-limiting episodes of diarrhea to life-threatening hemolytic-uremic syndrome (HUS). As of July 21, 2011, >4,075 persons in 16 countries had become ill. The outbreak was associated with an unprecedented rate of HUS (908 [22.2%] of 4,075 STEC-infected persons), and 50 persons died (1).

STEC are foodborne and waterborne pathogens. Human illness is most often associated with E. coli O157:H7, but non-O157 serogroups are also being recognized as key agents of STEC disease (2–5). The recent German outbreak was caused by E. coli O104:H4. Unlike E. coli O157:H7, which has a characteristic, sorbitol nonfermenting phenotype that is readily detected by routine laboratory testing, non-O157 E. coli strains are difficult to distinguish from the nonpathogenic E. coli strains commonly found in stool specimens, and frontline laboratories in Canada do not routinely screen for them.

This study describes 2 cases of E. coli O104:H4 infection that were imported to Canada. One case was caused by a 2011 isolate associated with the recent German outbreak. The second isolate was identified in 2010. Phenotypic and genotypic features of these 2 strains are described.