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The objective of this study was to evaluate molecular and epidemiologic factors associated with Escherichia coli sequence type 131 (ST131) among long-term care facility (LTCF) residents who acquired gastrointestinal tract colonization with fluoroquinolone-resistant E. coli (FQREC). Colonizing isolates from 37 residents who newly developed FQREC colonization at three LTCFs from 2006 to 2008 were evaluated. Twenty-nine (78%) of 37 total FQREC colonizing isolates were ST131. Most ST131 isolates had a distinctive combination of gyrA and parC replacement mutations. The ST131 and non-ST131 isolates differed significantly for the prevalence of many individual virulence factors but not for the proportion that qualified molecularly as extraintestinal pathogenic E. coli (ExPEC) or aggregate virulence factor scores. E. coli ST131 was highly prevalent among LTCF residents with FQREC colonization. Future studies should determine the risk factors for infection among ST131-colonized residents, and assess the potential for increased transmissibility of ST131 in the long-term care setting., (Copyright © 2016 Elsevier Inc. All rights reserved.)

A case-control study to determine risk factors for clinical infection with Escherichia coli was conducted among nursing home residents colonized with fluoroquinolone-resistant E. coli. Among 94 subjects, 11 (12%) developed infections with E. coli. Risk factors included the presence of a urinary catheter or tracheostomy, diabetes mellitus, and trimethoprim-sulfamethoxazole exposure.

This study examined molecular and epidemiologic factors associated with Escherichia coli sequence type 131 (ST131) among hospitalized patients colonized intestinally with fluoroquinolone (FQ)-resistant E. coli between 2002 and 2004. Among 86 patients, 21 (24%) were colonized with ST131. The proportion of ST131 isolates among colonizing isolates increased significantly over time, from 8% in 2002 to 50% in 2004 (P = 0.003). Furthermore, all 19 clonally related isolates were ST131. Future studies should identify potential transmissibility differences between ST131 and non-ST131 strains., (Copyright © 2014, American Society for Microbiology. All Rights Reserved.)

Background: The objective of this study was to assess risk factors for the development of fluoroquinolone (FQ)-resistant Escherichia coli gastrointestinal tract colonization in long-term care facility (LTCF) residents., Methods: A prospective cohort study was conducted from 2006 to 2008 at 3 LTCFs. Residents initially colonized with FQ-susceptible E. coli were followed by means of serial fecal sampling for new FQ-resistant E. coli colonization for up to 12 months or until discharge or death. A Cox proportional hazards regression model was developed to identify risk factors for new FQ-resistant E. coli colonization, with antibiotic and device exposures modeled as time-varying covariates., Results: Fifty-seven (47.5%) of 120 residents became newly colonized with FQ-resistant E. coli, with a median time to colonization of 57 days. Fecal incontinence (hazard ratio [HR], 1.78; 95% confidence interval [CI], 1.04-3.06; P = .04) was significantly associated with FQ-resistant E. coli acquisition. Receipt of amoxicillin-clavulanate (HR, 6.48; 95% CI, 1.43-29.4; P = .02) and the presence of a urinary catheter (HR, 3.81; 95% CI, 1.06-13.8; P = .04) during LTCF stay increased the risk of new FQ-resistant E. coli colonization., Conclusions: Acquisition of FQ-resistant E. coli was common, with nearly half of LTCF residents developing new FQ-resistant E. coli colonization. Further studies are needed on interventions to limit the emergence of FQ-resistant E. coli in LTCFs.

Objective: Optimal strategies for limiting the transmission of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella spp (ESBL-EK) in the hospital setting remain unclear. The objective of this study was to evaluate the impact of a urine culture screening strategy on the incidence of ESBL-EK., Design: Prospective quasi-experimental study., Setting: Two intervention hospitals and one control hospital within a university health system from 2005 to 2009., Patients and Intervention: All clinical urine cultures with E. coli or Klebsiella spp were screened for ESBL-EK. Patients determined to be colonized or infected with ESBL-EK were placed in a private room with contact precautions. The primary outcome of interest was nosocomial ESBL-EK incidence in nonurinary clinical cultures (cases occurring more than 48 hours after admission). Changes in monthly ESBL-EK incidence rates were evaluated with mixed-effects Poisson regression models, with adjustment for institution-level characteristics (eg, total admissions)., Results: The overall incidence of ESBL-EK increased from 1.42/10,000 patient-days to 2.16/10,000 patient-days during the study period. The incidence of community-acquired ESBL-EK increased nearly 3-fold, from 0.33/10,000 patient-days to 0.92/10,000 patient-days (P < .001). On multivariable analysis, the intervention was not significantly associated with a reduction in nosocomial ESBL-EK incidence (incidence rate ratio, 1.38 [95% confidence interval, 0.83-2.31]; P - .21)., Conclusions: Universal screening of clinical urine cultures for ESBL-EK did not result in a reduction in nosocomial ESBL-EK incidence rates, most likely because of increases in importation of ESBL-EK cases from the community. Further studies are needed on elucidating optimal infection control interventions to limit spread of ESBL-producing organisms in the hospital setting.

Objective: Infections due to fluoroquinolone-resistant Escherichia coli (FQREC) are associated with significant morbidity and mortality. Fluoroquinolone resistance likely arises at the level of gastrointestinal colonization. The objective of this study was to identify risk factors for the development of FQREC gastrointestinal tract colonization in hospitalized patients, including the impact of antibiotics prescribed during hospitalization., Design: A prospective cohort study was conducted from 2002 to 2004 within a university health system., Methods: Hospitalized patients initially colonized with fluoroquinolone-susceptible E. coli were followed up with serial fecal sampling for new FQREC colonization or until hospital discharge or death. A Cox proportional hazards regression model was developed to identify risk factors for new FQREC colonization, with antibiotic exposure modeled as time-varying covariates., Results: Of 395 subjects, 73 (18.5%) became newly colonized with FQREC. Length of stay before sampling (hazard ratio [HR], 1.02 [95% confidence interval (CI), 1.1-1.03]; P = .003) and malignancy (HR, 0.37 [95% CI, 0.21-0.67]; P = .001) were significantly associated with the development of FQREC colonization. In addition, receipt of a first-generation cephalosporin (HR, 1.19 [95% CI, 1.10-1.29]; P < .001) or cefepime (HR, 1.05 [95% CI, 1.00-1.10]; P = .048) during hospitalization increased the risk of new FQREC colonization., Conclusions: The acquisition of FQREC in the hospital setting is complex, and antimicrobial stewardship programs should take into account patterns of antibiotic use in implementing strategies to reduce the development of new FQREC colonization. Future studies are needed to identify risk factors for infection in hospitalized patients newly colonized with FQREC.

The objective of this study was to characterize the temporal variability of fluoroquinolone resistance mechanisms among Escherichia coli colonizing the gastrointestinal tract of hospitalized patients. Patients with new fluoroquinolone-resistant E. coli (FQREC) colonization were followed with serial fecal sampling until discharge or death. Genetic mechanism(s) of resistance for all FQREC isolates was characterized, including mutations in gyrA and parC and efflux pump overexpression. Of 451 subjects, 73 (16.2%) became newly colonized with FQREC. There was significant variability in regard to temporal changes in resistance mechanisms and levofloxacin MICs among isolates from individual patients. Compared to patients with transient colonization, patients with persistent colonization were more likely to have a urinary catheter (P = 0.04), diarrhea (P = 0.04), and a longer duration of hospitalization (22 and 9.0 mean days, respectively; P = 0.01) prior to sampling. Our data demonstrate the significant variability of resistance mechanisms in colonizing E. coli isolates among hospitalized patients., (Copyright © 2013 Elsevier Inc. All rights reserved.)

We describe the prevalence of and risk factors for colonization with extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella species (ESBL-EK) in hospitalized patients. The prevalence of colonization with ESBL-EK was 2.6%. Colonization was associated with cirrhosis, longer duration of hospital stay prior to surveillance, and prior exposure to clindamycin or meropenem.

Background: We conducted a case-control study to identify risk factors for efflux overexpression, an important mechanism of fluoroquinolone resistance, among patients with fluoroquinolone-resistant Escherichia coli (FQREC) gastrointestinal tract colonization., Methods: Three annual fecal surveillance surveys were performed hospital-wide, and all patients colonized with FQREC (levofloxacin minimum inhibitory concentration, ≥8 μg/mL) were included in the study. Cases and controls were defined on the basis of overexpression of the AcrAB efflux pump, as measured by the organic solvent tolerance (OST) assay. A multivariable logistic regression model was developed to identify risk factors for OST positivity among patients with FQREC colonization., Results: Eighty-nine patients were colonized with FQREC: 44 (49.4%) and 45 (50.6%) patients had isolates that were OST-positive and OST-negative, respectively. On multivariable analyses, location on the surgical service was significantly associated with recovery of an OST-positive isolate (odds ratio, 7.36; 95% confidence interval, 1.82-29.7; P = .005). Furthermore, patients who had received a first-generation cephalosporin in the 30 days prior to sampling were less likely to have an OST-positive isolate (odds ratio, 0.20; 95% confidence interval, .04-.94; P = .04)., Conclusions: Among phenotypically identical FQREC isolates, different factors may drive the emergence of different resistance mechanisms. Further studies are needed to elucidate the relationship between antimicrobial use and specific resistance mechanisms.

Background: Fluoroquinolones are the most commonly prescribed antimicrobials. The epidemiology of fecal colonization with Escherichia coli demonstrating reduced susceptibility to fluoroquinolones remains unclear., Methods: During a 3-year period (15 September 2004 through 19 October 2007), all patients hospitalized for >3 days were approached for fecal sampling. All E. coli isolates with reduced susceptibility to fluoroquinolones (minimum inhibitory concentration [MIC] of levofloxacin, 0.125 microg/mL) were identified. We characterized gyrA and parC mutations and organic solvent tolerance. Isolates were compared using pulsed-field gel electrophoresis., Results: Of 353 patients colonized with E. coli demonstrating reduced fluoroquinolone susceptibility, 300 (85.0%) had 1 gyrA mutation, 161 (45.6%) had 1 parC mutation, and 171 (48.6%) demonstrated organic solvent tolerance. The mean numbers of total mutations (ie, gyrA and parC) for E. coli isolates with a levofloxacin MIC of 8 microg/mL versus <8.0 microg/mL were 2.70 and 0.82 (P < .001). Of the 136 E. coli isolates with a levofloxacin MIC of 8 microg/mL, 90 (66.2%) demonstrated a nalidixic acid MIC of 16 microg/mL. Significant differences were found over time in the proportion of E. coli isolates demonstrating gyrA mutation, parC mutation, and organic solvent tolerance. There was little evidence of clonal spread of isolates. Conclusions. Gastrointestinal tract colonization with E. coli demonstrating reduced susceptibility to levofloxacin is common. Although 40% of study isolates exhibited a levofloxacin MIC of <8 microg/mL (and would thus be missed by current Clinical and Laboratory Standards Institute breakpoints), nalidixic acid resistance may be a useful marker for detection of such isolates. Significant temporal changes occurred in the proportion of isolates exhibiting various resistance mechanisms.

Of 49 long-term care facility residents, 21 (43%) were colonized with 2 or more distinct strains of Escherichia coli. There were no significant risk factors for colonization with multiple strains of E. coli. These results suggest that future efforts to efficiently identify the diversity of colonizing strains will be challenging.

Objective: The prevalence of fluoroquinolone (FQ) resistance in Escherichia coli has increased markedly in recent years. Despite the important role of gastrointestinal tract colonization with FQ-resistant E. coli (FQREC), the prevalence of and risk factors for FQREC colonization among the general hospitalized patient population have not been described, to our knowledge. The objective of this study was to identify the prevalence of and risk factors for FQREC colonization among hospitalized patients., Design: Three-year case-control study. Case patients (ie, all subjects with FQREC colonization) were compared with control patients (ie, all subjects without FQREC colonization)., Setting: Two large medical centers within an academic health system., Participants: All patients hospitalized at the 2 study hospitals., Main Outcome Measure: Three annual fecal surveillance surveys were conducted. All patients colonized with FQREC (levofloxacin minimum inhibitory concentration, >or=8 microg/mL) were identified., Results: Of the 774 subjects, 89 (11.5%) were colonized with FQREC. Although there was a significant association between prior FQ use and FQREC colonization on bivariable analysis (odds ratio [OR], 2.02 [95% confidence interval {CI}, 1.14-3.46]; P=.01), there was statistically significant effect modification by year of study (P=.005). In multivariable analyses, after controlling for the hospital and for the duration of hospitalization prior to sampling, the association between FQ use and FQREC colonization was as follows: adjusted OR (aOR), 0.97 (95% CI, 0.29-3.23) in 2002; aOR, 1.41 (95% CI, 0.57-3.50) in 2003; and aOR, 9.87 (95% CI, 3.67-26.55) in 2004., Conclusions: The association between prior FQ use and FQREC colonization varied significantly by study year, suggesting that the clinical epidemiology of resistant organisms may change over time. Furthermore, in the context of recent work showing significant changes in FQREC prevalence as well as changes in FQ resistance mechanisms (specifically, efflux overexpression) over the same time period, these results suggest a previously unrecognized complexity in the relationship between the clinical and molecular epidemiology of FQ resistance.

Of 49 subjects, 21 were colonized with more than one strain of Escherichia coli and 12 subjects had at least one strain present in fewer than 20% of colonies. The ability to accurately characterize E. coli strain diversity is directly related to the number of colonies sampled and the underlying prevalence of the strain.

We assessed the rate of recovery of fluoroquinolone-resistant and fluoroquinolone-susceptible Escherichia coli isolates from culture of frozen perirectal swab samples compared with the results for culture of the same specimen before freezing. Recovery rates for these 2 classes of E. coli were 91% and 83%, respectively. The majority of distinct strains recovered from the initial sample were also recovered from the frozen sample. The strains that were not recovered were typically present only in low numbers in the initial sample. These findings emphasize the utility of frozen surveillance samples.

Among 10 subjects colonized with Escherichia coli isolates with reduced susceptibility to fluoroquinolones, the median duration of colonization following hospital discharge was 80 days (range, 8 to 172 days). Colonization was longer for isolates demonstrating organic-solvent tolerance than for isolates that were not organic-solvent tolerant (151 versus 29 days, respectively; P = 0.07) but was not associated with other resistance mechanisms, demographics, or antibiotic use.

Background: The prevalence of fecal colonization with Escherichia coli that has reduced susceptibility to fluoroquinolones is unknown. A detailed characterization of such isolates is limited., Methods: We conducted 3 annual fecal surveillance initiatives at 2 hospitals from 2002 to 2004. All E. coli isolates with reduced susceptibility to fluoroquinolones (minimum inhibitory concentration [MIC] to levofloxacin, > or = 0.125 microg/mL) were identified. We characterized gyrA and parC mutations and organic solvent tolerance (OST). Isolates were compared using pulsed-field gel electrophoresis., Results: Of 789 fecal samples, 149 (18.9%) revealed E. coli with reduced susceptibility to fluoroquinolones. Of 149 isolates, 102 (68.5%) had a MIC > or = 8 microg/mL, 138 (92.6%) had > or = 1 gyrA mutation, 101 (67.8%) had > or = 1 parC mutation, and 59 (39.6%) demonstrated OST. Isolates with a MIC > or = 8 versus <8 microg/mL had more target mutations (median, 3 vs. 1; P<.001) and more often exhibited OST (51% vs. 15%; P<.001). Of 149 isolates, 144 (96.6%) demonstrated a MIC > or = 16 microg/mL to nalidixic acid. The prevalence of OST differed across study years (P = .01). There was no clonal spread of isolates., Conclusions: Colonization by E. coli with reduced fluoroquinolone susceptibility is common, and fluoroquinolone-resistance characteristics differ significantly over time. Resistance to nalidixic acid may be useful in the identification of E. coli with early resistance mutations.

Among 63 patients enrolled in a prospective cohort study of gut colonization with fluoroquinolone-resistant Escherichia coli, the sensitivity of perirectal swab compared to stool sample was 90% (95% confidence interval [CI], 70 to 99%) and the specificity was 100% (95% CI, 91 to 100%). For rectal swab, the sensitivity was 90% (95% CI, 68 to 99%) and the specificity was 100% (95% CI, 91 to 100%).