Johnston, Brian

In total, 50 Escherichia coli bloodstream isolates from the clinical laboratory and 12 E. coli isolates referred for pulsed-field gel electrophoresis (PFGE) were sequenced, assessed for clonality using core genome multilocus sequence typing (cgMLST), and evaluated for genomic susceptibility predictions using ARESdb. Results of sequence typing using whole-genome sequencing (WGS)-based MLST and sequence type (ST)-specific PCR were identical.

Escherichia colibacteremia is caused mainly by sequence type complex 131 (STc131) and two clades within its fluoroquinolone-resistance-associatedH30 subclone,H30R1 andH30Rx. We examined clinical and molecular correlates ofE. colibacteremia in two geographically distinct centers.

Abstract Background. Within-household sharing of strains from the resistance-associated H30R1 and H30Rx subclones of Escherichia coli sequence type 131 (ST131) has been inferred based on conventional typing data, but it has been assessed minimally using whole genome sequence (WGS) analysis. Methods. Thirty-three clinical and fecal isolates of ST131-H30R1 and ST131-H30Rx, from 20 humans and pets in 6 households, underwent WGS analysis for comparison with 52 published ST131 genomes. Phylogenetic relationships were inferred using a bootstrapped maximum likelihood tree based on core genome sequence polymorphisms. Accessory traits were compared between phylogenetically similar isolates. Results. In the WGS-based phylogeny, isolates clustered strictly by household, in clades that were distributed widely across the phylogeny, interspersed between H30R1 and H30Rx comparison genomes. For only 1 household did the core genome phylogeny place epidemiologically unlinked isolates together with household isolates, but even there multiple differences in accessory genome content clearly differentiated these 2 groups. The core genome phylogeny supported within-household strain sharing, fecal-urethral urinary tract infection pathogenesis (with the entire household potentially providing the fecal reservoir), and instances of host-specific microevolution. In 1 instance, the household's index strain persisted for 6 years before causing a new infection in a different household member. Conclusions. Within-household sharing of E coli ST131 strains was confirmed extensively at the genome level, as was long-term colonization and repeated infections due to an ST131-H30Rx strain. Future efforts toward surveillance and decolonization may need to address not just the affected patient but also other human and animal household members.

Abstract Background. Emerging data implicate long-term care facilities (LTCFs) as reservoirs of fluoroquinolone-resistant (FQ-R) Escherichia coli of sequence type 131 (ST131). We screened for ST131 among LTCF residents, characterized isolates molecularly, and identified risk factors for colonization. Methods. We conducted a cross-sectional study using a single perianal swab or stool sample per resident in 2 LTCFs in Olmsted County, Minnesota, from April to July 2013. Confirmed FQ-R E. coli isolates underwent polymerase chain reaction-based phylotyping, detection of ST131 and its H30 and H30-Rx subclones, extended virulence genotyping, and pulsed-field gel electrophoresis (PFGE) analysis. Epidemiological data were collected from medical records. Results. Of 133 fecal samples, 33 (25%) yielded FQ-R E. coli, 32 (97%) of which were ST131. The overall proportion with ST131 intestinal colonization was 32 of 133 (24%), which differed by facility: 17 of 41 (42%) in facility 1 vs 15 of 92 (16%) in facility 2 (P = .002). All ST131 isolates represented the H30 subclone, with virulence gene and PFGE profiles resembling those of previously described ST131 clinical isolates. By PFGE, certain isolates clustered both within and across LTCFs. Multivariable predictors of ST131 colonization included inability to sign consent (odds ratio [OR], 4.16 [P = .005]), decubitus ulcer (OR, 4.87 [ P = .04]), and fecal incontinence (OR, 2.59 [P = .06]). Conclusions. Approximately one fourth of LTCF residents carried FQ-R ST131 E. coli resembling ST131 clinical isolates. Pulsed-field gel electrophoresis suggested intra- and interfacility transmission. The identified risk factors suggest that LTCF residents who require increased nursing care are at greatest risk for ST131 colonization, possibly due to healthcare-associated transmission.

ABSTRACT We assessed Escherichia coli ST131 and its H30 and H30-Rx subclones for virulence genes, antimicrobial resistance, and extended-spectrum beta-lactamase (ESBL) type. Although both subclones were associated with ESBL production, H30-Rx isolates had higher resistance scores and were associated specifically with CTX-M-15. Three virulence genes ( iha , sat , and iutA ) were more prevalent among H30 than non-H30 ST131 isolates. Thus, the H30 and H30-Rx subclones are more antimicrobial resistant and have virulence profiles that are distinct from those of non-H30 ST131 isolates.

ABSTRACT The clonal distribution of Escherichia coli across an unselected population in the current era of widespread antimicrobial resistance is incompletely defined. In this study, we used a newly described clonal typing strategy based on sequencing of fum C and fim H (i.e., CH typing) to infer multilocus sequence types (STs) for 299 consecutive, nonduplicate extraintestinal E. coli isolates from all cultures submitted to Olmsted County, MN, laboratories in February and March 2011 and then compared STs with epidemiological data. Forty-seven different STs were identified, most commonly ST131 (27%), ST95 (11%), ST73 (8%), ST127 (6%), and ST69 (5%). Isolates from these five STs comprised two-thirds of health care-associated (HA) isolates but only half of community-associated (CA) isolates. ST131 was represented overwhelmingly (88%) by a single recently expanded H30 subclone, which was the most extensively antimicrobial-resistant subclone overall and was especially predominant in HA infections and among adults >50 years old. In contrast, among patients 11 to 50 years old, ST69, -95, and -73 were more common. Because of the preponderance of the H30 subclone of ST131, ST diversity was lower among HA than CA isolates, and among antimicrobial-resistant than antimicrobial-susceptible isolates, which otherwise had similar ST distributions. In conclusion, in this U.S. Midwest region, the distribution and diversity of STs among extraintestinal E. coli clinical isolates vary by patient age, type of infection, and resistance phenotype. ST131 predominates among young children and the elderly, HA infections, and antimicrobial-resistant isolates, whereas other well-known pathogenic lineages are more common among adolescents and young adults, CA infections, and antimicrobial-susceptible isolates.