Molecular Characterization of Environmental Escherichia coli Isolates from Public Restrooms in the Minneapolis-St. Paul Area
Methods: We previously reported our recovery of 26 E. coli isolates from 1120 total environmental samples, as collected from 56 diverse public restrooms in the Minneapolis-St. Paul area (IDWeek 2013, abstract #39914). Here, PCR, DNA sequencing, and pulsed-field gel electrophoresis (PFGE) were used to further characterize these isolates as to major E. coli phylogenetic group, virulence gene (VG) profile, ExPEC status (presence of ≥ 2 of 5 key VGs), sequence type (ST), and pulsotype.
Results: Overall, the 26 E. coli isolates from public restrooms were distributed fairly evenly by phylogenetic group, i.e., B2 (27%), D (27%), A (23%), and B1 (23%). Nine isolates (35%) qualified as ExPEC. Compared with the 17 non-ExPEC isolates, the 9 ExPEC isolates were more commonly from group B2 (56%, vs. 12%: P = .03), had a higher prevalence of 13 VGs other than those used to define ExPEC status (i.e., iha, sat, cdtB, fyuA, iroN, ireA, traT, iss, ibeA, ompT, usp, malX, and H7 fliC), and had much higher VG scores (median, 10 [range 6-13] vs. 2 [range 0-8]: P < .001). Two isolates represented the classic ExPEC lineages ST95 (group B2; O1/O2:K1:H7) and ST69 (group D; "clonal group A"). All PFGE profiles were unique (≤ 80% similar) except for two pairs of indistinguishable profiles, within each of which the paired isolates were from the same or adjacent (mens vs. womens) restrooms. The ST95 strain's PFGE profile closely matched those of multiple ST95 clinical isolates in a large private PFGE database.
Conclusion: Public restrooms are contaminated sporadicically with ExPEC, some of which exhibit extensive VG profiles, represent classic human-associated STs, and by PFGE closely resemble known human pathogens. Such public restroom-source ExPEC, which likely reflect human fecal contamination, could contribute to ExPEC transmission within the population.
K. Owens, None
A. Gajewski, None
M. A. Kuskowski, None
C. Clabots, None
P. Thuras, None