Differences in risk factors for transmission among Shiga toxin-producing Escherichia coli serogroups and stx profiles

Objectives: Trends in the incidence of O157 and non-O157 serogroups of Shiga toxin-producing Escherichia coli (STEC) infections have markedly diverged. Here, we estimate the extent to which STEC serogroups share the same transmission routes and risk factors, potentially explaining these trends. Methods: With 3048 STEC cases reported in Minnesota from 2010 to 2019, we used lasso penalized regression to estimate pooled odds ratios (pOR) for the association between STEC risk factors and specific STEC serogroups and Shiga toxin gene profiles. We used random forests as a confirmatory analysis. Results: Across an extended period of time, we found evidence for person-to-person transmission associated with the O26 serogroup, relative to other serogroups (pOR = 1.32 for contact with an individual with diarrhea). Rurality was less associated with non-O157 serogroups than O157 (pOR = 1.21 for each increasing level of rurality). We also found an association between unpasteurized juice and strains carrying only stx1 (pOR = 1.41). Conclusions: Collectively, these results show differences in risk factors across STEC types, which suggest differences in the most effective routes of transmission. Serogroup-specific disease control strategies should be explored. Specifically, preventative measures for non-O157 STEC need to extend beyond those we have employed for O157 STEC.