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We describe the rapid and ongoing emergence across multiple US cities of a new multidrug-resistant Escherichia coli clone-sequence type (ST) 1193-resistant to fluoroquinolones (100%), trimethoprim-sulfamethoxazole (55%), and tetracycline (53%). ST1193 is associated with younger adults (age

Background. Although long treatment courses of outpatient antimicrobials are often used in pediatric patients, few data exist regarding the frequency of adverse events (AEs) associated with these medications. Methods. We performed a retrospective cohort study of all patients seen in the Infectious Diseases clinic at a tertiary referral children’s hospital from August 1, 2009 to August 1, 2011. We included patients who received 14 days of oral or intravenous antibiotic, antiviral, or antifungal medications. Patients receiving only prophylactic medications or human immunodeficiency virus treatment were excluded. Results. Three hundred thirty-five subjects met inclusion criteria, with a median age of 7.4 years at start of therapy. The cohort was predominantly male (60%), white (54%), and previously healthy (59%). A majority (88.4%) of subjects were treated for bacterial infections. β-Lactam agents were the most commonly used antimicrobial class (210 subjects; 62.7%), followed by clindamycin (86; 25.7%), rifampin (76; 22.7%), and vancomycin (62; 18.5%). Overall, 107 (31.9%) subjects experienced 151 distinct AEs. The most common individual AE noted was diarrhea (44; 29.1% of all AEs). Serious AEs developed in 42 (12.5%) subjects, including allergic reactions (15; 11.3% of all AEs), venous catheter-related complications (14; 13.0% of those with catheters), neutropenia (9; 3.0%), renal insufficiency (7; 2.5%), and hepatotoxicity (3; 1.1%). Rates of AEs were similar between those on oral and intravenous antimicrobials. Conclusions. In our study population, patients on prolonged oral or intravenous outpatient antimicrobials experienced AEs frequently. These findings support the need for close monitoring of pediatric patients on prolonged antimicrobial therapy and vigilance for unwanted effects of these medications.

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.