Temporal Trends in Antimicrobial Resistance and Virulence-Associated Traits within the Escherichia coli Sequence Type 131 Clonal Group and ItsH30 andH30-Rx Subclones, 1968 to 2012

Abstract

ABSTRACTTo identify possible explanations for the recent global emergence ofEscherichia colisequence type (ST) 131 (ST131), we analyzed temporal trends within ST131 O25 for antimicrobial resistance, virulence genes, biofilm formation, and theH30 andH30-Rx subclones. For this, we surveyed the WHOE. coliandKlebsiellaCentre'sE. colicollection (1957 to 2011) for ST131 isolates, characterized them extensively, and assessed them for temporal trends. Overall, antimicrobial resistance increased temporally in prevalence and extent, due mainly to the recent appearance of theH30 (1997) andH30-Rx (2005) ST131 subclones. In contrast, neither the total virulence gene content nor the prevalence of biofilm production increased temporally, although non-H30 isolates increasingly qualified as extraintestinal pathogenicE. coli(ExPEC). Whereas virotype D occurred from 1968 forward, virotypes A and C occurred only after 2000 and 2002, respectively, in association with theH30andH30-Rx subclones, which were characterized by multidrug resistance (including extended-spectrum-beta-lactamase [ESBL] production:H30-Rx) and absence of biofilm production. Capsular antigen K100 occurred exclusively amongH30-Rx isolates (55% prevalence). Pulsotypes corresponded broadly with subclones and virotypes. Thus, ST131 should be regarded not as a unitary entity but as a group of distinctive subclones, with its increasing antimicrobial resistance having a strong clonal basis, i.e., the emergence of theH30 andH30-Rx ST131 subclones, rather than representing acquisition of resistance by diverse ST131 strains. Distinctive characteristics of theH30-Rx subclone—including specific virulence genes (iutA,afaanddra,kpsII), the K100 capsule, multidrug resistance, and ESBL production—possibly contributed to epidemiologic success, and some (e.g., K100) might serve as vaccine targets.