Duration of Outpatient Fecal Colonization Due to Escherichia coli Isolates with Decreased Susceptibility to Fluoroquinolones: Longitudinal Study of Patients Recently Discharged from the Hospital

Abstract

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 organicsolvent tolerant (151 versus 29 days, respectively; P ‫؍‬ 0.07) but was not associated with other resistance mechanisms, demographics, or antibiotic use.Significant increases in the prevalence of fluoroquinolone (FQ) resistance in Escherichia coli isolates have been noted in recent years (6). Approximately 20% of hospitalized patients are colonized with E. coli isolates exhibiting reduced susceptibility to FQs (4). Elucidating the duration of colonization with such organisms is vital because the human gastrointestinal (GI) tract serves as a major natural reservoir for E. coli and clinical E. coli isolates are usually derived from an organism colonizing the GI tract (3). In addition, the GI tract may serve as the primary source from which E. coli can spread through the population.Few studies have addressed the duration of fecal colonization with E. coli isolates demonstrating reduced susceptibility to FQs (1,8,9,11). These studies have been limited by focusing on only patients with specific chronic conditions (e.g., cancer or prostatitis) or patients who reside in long-term-care facilities (1,8,9,11), including only subjects receiving FQ therapy (1, 9, 11), and utilizing infrequent fecal sampling (i.e., Ն1-month intervals) (8, 11). Furthermore, the impact of FQ resistance phenotype and/or genotype on duration of colonization has not been studied.The goal of this study was to identify the duration of fecal colonization due to E. coli isolates with reduced susceptibility to FQs among patients recently discharged from the hospital. Furthermore, we sought to identify variables associated with prolonged colonization and characterize changes in the FQ resistance genotype and phenotype of isolates over time.The study was performed at the Hospital of the University of Pennsylvania, a 625-bed academic tertiary-care medical center.Eligible study subjects were identified from an ongoing prospective study of patients who, while hospitalized, developed new GI tract colonization due to E. coli isolates demonstrating reduced susceptibility to FQs (4, 5). From this larger study, a convenience sample of consecutively identified colonized subjects was enrolled. Subjects were sampled using a perirectal swab technique (5), with all in-hospital swabs collected by the same research nurse. Patients whose swabs demonstrated growth of E. coli isolates with reduced susceptibility to FQs were then prospectively monitored as outpatients. Following hospital discharge, each subject continued to collect fecal samples every 2 weeks (using a swab to collect a sample of a freshly passed bowel movement). Subjects were asked to send in fecal samples for 6 months after discharge.At the time of hospital discharge, inpatient medical...

Bacterial Colonization: Can We Live With It?

“…This carriage rate is in line with recently reported rates of carriage of selected gram-negative bacteria among newly hospitalized patients (7%) [3], healthy vegetarians (14%) [3], and Saudi Arabian inpatients (26%) [4]. The persistence of these strains is also not unexpected, given published evidence regarding long-term persistence of strains of Escherichia coli [5][6][7]. The authors do not discuss the 80% of subjects who were not carrying MDRGNB, but one might surmise that the majority of them were colonized with other gram-negative bacteria, as are most humans, and that the natural history of their colonization might be similar.…”

Colonization with Multidrug‐Resistant Gram‐Negative Bacteria: Prolonged Duration and Frequent Cocolonization

“…They showed that, among a cohort of 10 colonized outpatients, the median duration of colonization was 80 days (range, 8-172 days). They further showed that prolonged colonization was more common among species that overexpressed the AcrAB efflux pump [19]. Future studies will need to determine whether certain antimicrobial resistance characteristics among P. mirabilis also promote persistent colonization.…”

“…Lastly, among the 15 multidrug-resistant P. mirabilis isolates, 13 represented genetically unrelated strains, and therefore, acquisition of a potential outbreak strain would not explain persistent colonization. Lautenbach et al [19] analyzed potential factors associated with persistent colonization among E. coli strains with reduced susceptibility to fluoroquinolones. They showed that, among a cohort of 10 colonized outpatients, the median duration of colonization was 80 days (range, 8-172 days).…”

Epidemiology of Multidrug-Resistant Microorganisms among Nursing Home Residents in Belgium

“…: transient versus chronic carriage) is still poorly known and the cross-sectional design of our survey did not address the dynamics of ESBLE carriage [38]. Data from prior studies have suggested that gut colonization could change over time and that it may be markedly influenced through antibiotic selection pressure [39].…”