Comparison of Escherichia coli ST131 pulsotypes, by epidemiologic traits, 1967-2009

Abstract

Escherichia coli sequence type 131 (ST131), an emerging disseminated public health threat, causes multidrug-resistant extraintestinal infections. Among 579 diverse E. coli ST131 isolates from 1967-2009, we compared pulsotypes (>94% similar XbaI pulsed-field gel electrophoresis profiles) by collection year, geographic origin, source, and antimicrobial drug-resistance traits. Of 170 pulsotypes, 65 had >2 isolates and accounted for 85% of isolates. Although extensively dispersed geographically, pulsotypes were significantly source specific (e.g., had little commonality between humans vs. foods and food animals). The most prevalent pulsotypes were associated with recent isolation, humans, and antimicrobial drug resistance. Predominant pulsotype 968 was associated specifically with fluoroquinolone resistance but not with extended-spectrum β-lactamase production or bla(CTX-M-15). Thus, several highly successful antimicrobial drug-resistant lineages within E. coli ST131 have recently emerged and diffused extensively among locales while maintaining a comparatively restricted host/source range. Identification of factors contributing to this behavior of ST131 could help protect public health.

Figure

Prevalence over time of 12 high-prevalence XbaI pulsotypes among 579 Escherichia coli ST131 isolates. High-prevalence pulsotypes are those with >6 isolates (>1% of population) each. Years before 2003 are combined into 3 groups because of the small numbers of isolates. On the x-axis, the number of isolates for the particular period is shown in parentheses below the dates. y-axis prevalence values are based on the total number of isolates in the particular period.

Figure A1

Pulsed-field gel electrophoresis profile dendrogram of 87 diverse isolates of Escherichia coli ST131. Isolates for the dendrogram, which represent a 15% subsample of the total population (n = 579), were selected randomly after deliberate inclusion of 2 representatives of each pulsotype with >6 members (indicated by brackets) plus the earliest previously reported isolate (from 1985) and the earliest present isolate (from 1967). YEAR, year of isolation or submission to reference laboratory; FQ-R, fluoroquinolone-resistant; ESBL, extended-spectrum β-lactamase; CTX-M-15, presence of bla_CTX-M-15 (as detected by PCR); POS, positive (i.e., trait present); 2008–2009, interval during which isolate was collected. Scale is percent profile similarity.