Molecularly defined extraintestinal pathogenic Escherichia coli status predicts virulence in a murine sepsis model better than does virotype, individual virulence genes, or clonal subset among E. coli ST131 isolates.

BACKGROUND: Escherichia coli ST131, mainly its H30 clade, is the leading cause of extraintestinal E. coli infections but its correlates of virulence are undefined. MATERIALS AND METHODS: We tested in a murine sepsis model 84 ST131 isolates that differed by country of origin (Spain vs. USA), clonal subset, resistance markers, and virulence genes (VGs). Virulence outcomes, including illness severity score (ISS) and "killer" status (>80% mouse lethality), were compared statistically with clonal subset, individual and combined VGs, molecularly defined extraintestinal and uropathogenic E. coli (ExPEC, UPEC) status, and country of origin. RESULTS: Virulence varied widely by strain. Univariable correlates of median ISS and percent "killer" (outcomes if variable present vs. absent) included pap (ISS, 4.4 vs. 3.8; "killer", 71% vs. 46%), kpsMII (4.1 vs. 2.3; 59% vs. 25%), K2/K100 (4.4 vs. 3.2; 77% vs. 41%), ExPEC (4.2 vs. 2.2; 62% vs. 17%), Spanish origin (4.3 vs. 3.1; 65% vs. 36%), and H30R1 subset (2.5 vs. 4.1; 35% vs. 59%). With multivariable adjustment, ExPEC status was the only consistently significantly predictive variable. CONCLUSION: Within ST131 the strongest predictor of experimental virulence was molecularly defined ExPEC status. Clonal subsets seemed to behave differently in the murine sepsis model by country of origin.

Contribution of yersiniabactin to the virulence of an Escherichia coli sequence type 69 ("clonal group A") cystitis isolate in murine models of urinary tract infection and sepsis.

Escherichia coli sequence type 69 (ST69; "clonal group A") is an important extraintestinal pathogen. To clarify the yersiniabactin siderophore system's role in ST69's extraintestinal virulence we compared a wild-type ST69 cystitis isolate, isogenic irp2 (yersiniabactin) mutants, and irp2-complemented mutants in murine models of sepsis and urinary tract infection (UTI). irp2 mutants were attenuated mildly in the UTI model and profoundly in the sepsis model. In both models, complementation with a functional copy of irp2 restored full parental virulence. These findings suggest that in ST69 the yersiniabactin system has a minor role in urovirulence and a major role in sepsis causation.

Clinical and microbiological determinants of infection after transrectal prostate biopsy.

BACKGROUND: Increasing numbers of infections following transrectal prostate biopsy (TPB) at our hospital led us to investigate clinical and bacterial risk factors to determine if the colonizing rectal Escherichia coli population is the source. METHODS: We performed an observational cohort study of men undergoing TPB (1 January 2010-6 February 2014) at the San Diego Veterans Affairs Medical Center. The primary outcome was clinically significant post-TPB infection. Rectal swabs were collected immediately before the biopsy and cultured selectively for fluoroquinolone-resistant gram-negative bacilli. Fluoroquinolone-resistant clinical and rectal E. coli isolates were compared using phylotyping, pulsed-field gel electrophoresis (PFGE) analysis, sequence typing, and virulence gene profiling. RESULTS: Rectal colonization with fluoroquinolone-resistant organisms (98% E. coli) was detected in 121 of 764 subjects (15.8%). Post-TPB infection was more common among fluoroquinolone-resistant-colonized subjects than noncolonized subjects (13/121 [10.7%] vs 8/649 [1.2%]; P < .001). Presence of fluoroquinolone-resistant colonizing E. coli was the most significant host characteristic associated with post-TPB infection (odds ratio, 4.5 [95% confidence interval, 1.2-18.2]; P = .03). Escherichia coli infection isolates (n = 18) did not differ from E. coli rectal culture isolates (n = 68) for any of 49 virulence genes or ST131 status (all P > .05). The rectal and clinical isolates of all 9 men with paired isolates had indistinguishable PFGE patterns and identical antimicrobial susceptibility profiles. CONCLUSIONS: The rectal colonizing E. coli population is the source for most fluoroquinolone-resistant post-TPB infections, regardless of clonal background or virulence traits. Screening cultures can identify nearly all patients at risk for fluoroquinolone-resistant post-TPB infection.

Abrupt emergence of a single dominant multidrug-resistant strain of Escherichia coli.

BACKGROUND: Fluoroquinolone-resistant Escherichia coli are increasingly prevalent. Their clonal origins--potentially critical for control efforts--remain undefined. METHODS: Antimicrobial resistance profiles and fine clonal structure were determined for 236 diverse-source historical (1967-2009) E. coli isolates representing sequence type ST131 and 853 recent (2010-2011) consecutive E. coli isolates from 5 clinical laboratories in Seattle, Washington, and Minneapolis, Minnesota. Clonal structure was resolved based on fimH sequence (fimbrial adhesin gene: H subclone assignments), multilocus sequence typing, gyrA and parC sequence (fluoroquinolone resistance-determining loci), and pulsed-field gel electrophoresis. RESULTS: Of the recent fluoroquinolone-resistant clinical isolates, 52% represented a single ST131 subclonal lineage, H30, which expanded abruptly after 2000. This subclone had a unique and conserved gyrA/parC allele combination, supporting its tight clonality. Unlike other ST131 subclones, H30 was significantly associated with fluoroquinolone resistance and was the most prevalent subclone among current E. coli clinical isolates, overall (10.4%) and within every resistance category (11%-52%). CONCLUSIONS: Most current fluoroquinolone-resistant E. coli clinical isolates, and the largest share of multidrug-resistant isolates, represent a highly clonal subgroup that likely originated from a single rapidly expanded and disseminated ST131 strain. Focused attention to this strain will be required to control the fluoroquinolone and multidrug-resistant E. coli epidemic.

Post-prostate biopsy infection with Escherichia coli ST131 leading to epididymo-orchitis and meningitis caused by Gram-negative bacilli.

A 57-year-old man who had recently undergone a transrectal prostate biopsy for a rising prostate-specific antigen level developed postbiopsy necrotizing epididymo-orchitis (requiring orchiectomy) and then Gram-negative meningitis, despite fluoroquinolone administration for periprocedural prophylaxis and subsequent therapy. The causative organism proved to be a fluoroquinolone-resistant Escherichia coli strain from sequence type ST131.

Multiple-host sharing, long-term persistence, and virulence of Escherichia coli clones from human and animal household members.

During a 3-year surveillance, six household members (five humans and the family dog) yielded 14 Escherichia coli clones. Virulence genes, group B2, and having caused cystitis (in the mother or dog) corresponded to colonization endpoints (number of samples, colonies, hosts, and dates). The dog's cystitis clone was the most extensively recovered clone.

Sharing of virulent Escherichia coli clones among household members of a woman with acute cystitis.

BACKGROUND: Within-household transmission of extraintestinal pathogenic Escherichia coli (ExPEC) may contribute to the pathogenesis of urinary tract infection (UTI), but this is poorly understood. METHODS: A woman with acute UTI, 4 human household members who cohabited with her, and the family's pet dog underwent prospective longitudinal surveillance for colonizing E. coli for 7-9 weeks after the woman's UTI episode. Unique clones were resolved by random amplified polymorphic DNA and pulsed-field gel electrophoresis analysis. Virulence genes, phylogenetic group, and O types were defined by PCR. Comparisons with reference strains were made using random amplified polymorphic DNA profiling. RESULTS: Serial fecal and urine samples from the 6 household members yielded 7 unique E. coli clones (4 of which were ExPEC and 3 of which were non-ExPEC). For 3 clones, extensive among-host sharing was evident in patterns suggesting host-to-host transmission. The mother's UTI clone, which represented E. coli O1:K1:H7, was the clone that was most extensively shared (in 5 hosts, including the dog) and most frequently recovered (in 45% of samples and at all 3 time points). The other 3 ExPEC clones corresponded with E. coli O6:K2:H1, O1:K1:H7, and O2:F10,F48. CONCLUSIONS: E. coli clones, including ExPEC, can be extensively shared among human and animal household members in the absence of sexual contact and in patterns suggesting host-to-host transmission.

Phylogenetic relationships among clonal groups of extraintestinal pathogenic Escherichia coli as assessed by multi-locus sequence analysis.

The evolutionary origins of extraintestinal pathogenic Escherichia coli (ExPEC) remain uncertain despite these organisms' relevance to human disease. A valid understanding of ExPEC phylogeny is needed as a framework against which the observed distribution of virulence factors and clinical associations can be analyzed. Accordingly, phylogenetic relationships were defined by multi-locus sequence analysis among 44 representatives of selected ExPEC clonal groups and the E. coli Reference (ECOR) collection. Recombination, which significantly obscured the phylogenetic signal for several strains, was dealt with by excluding strains or specific sequences. Conflicting overall phylogenies, and internal phylogenies for virulence-associated phylogenetic group B2, were inferred depending on the specific dataset (i.e., how extensively purged of recombination), outgroup (Salmonella enterica and/or Escherichia fergusonii), and analysis method (neighbor joining, maximum parsimony, maximum likelihood, or Bayesian likelihood). Nonetheless, the major E. coli phylogenetic groups A, B1, and B2 were consistently well resolved, as was a major sub-component of group D and an ECOR 37-O157:H7 clade. Moreover, nine important ExPEC clonal groups within groups B2 and D, characterized by serotypes O6:K2:H1, O18:K1:H7, O6:H31, and O4:K+:H+ (from group B2), and O1:K1:H-, O7:K1:H-, O157:K+:H (non-7), O15:K52:H1, and O11/17/77:K52:H18 ("clonal group A") (from group D), were consistently well resolved, regardless of clinical background (cystitis, pyelonephritis, neonatal meningitis, sepsis, or fecal), host group, geographical origin, and virulence profile. Among the group B2-derived clonal groups the O6:K2:H1 clade appeared basal. Within group D, "clonal group A" and the O15:K52:H1 clonal group were consistently placed with ECOR 47 and ECOR 44, respectively, as nearest neighbors. These findings clarify phylogenetic relationships among key ExPEC clonal groups but also emphasize that recombination appears to obscure the oldest evolutionary relationships, despite extensive targeted sequencing and use of a wide range of analysis techniques.

The IrgA homologue adhesin Iha is an Escherichia coli virulence factor in murine urinary tract infection.

The role of the Escherichia coli iron-regulated gene homologue adhesin (Iha) in the pathogenesis of urinary tract infections (UTIs) is unknown. We performed a series of complementary analyses to confirm or refute the hypothesis that Iha is a virulence factor in uropathogenic E. coli. Fecal E. coli isolates exhibited significantly lower prevalences of iha (range, 14 to 22%) than did clinical isolates from cases of pediatric cystitis or pyelonephritis, adult pyelonephritis or urosepsis, or bacteremia (range, 38 to 74%). Recombinant Iha from E. coli pyelonephritis isolate CFT073 conferred upon nonadherent E. coli ORN172 the ability to adhere to cultured T-24 human uroepithelial cells. In a well-established mouse model of ascending UTI, CFT073 and its derivative UPEC76 (a pap [P fimbriae] mutant version of strain CFT073) each significantly outcompeted their respective iha deletion mutants in CBA/J mice 48 h after bladder challenge (P < 0.03 for urine, both kidneys, and bladders of both constructs, except for bladders of mice challenged with UPEC76 and its deletion mutant, where P = 0.11). These data suggest that Iha(CFT073) is a virulence factor and might be a target for anti-UTI interventions.