title: Clonal composition and community clustering of drug-susceptible and -resistant Escherichia coli isolates from bloodstream infections.
abstract: Multidrug-resistant Escherichia coli strains belonging to a single lineage frequently account for a large proportion of extraintestinal E. coli infections in many parts of the world. However, limited information exists on the community prevalence and clonal composition of drug-susceptible E. coli strains. Between July 2007 and September 2010, we analyzed all consecutively collected Gram-negative bacterial isolates from patients with bloodstream infection (BSI) admitted to a public hospital in San Francisco for drug susceptibility and associated drug resistance genes. The E. coli isolates were genotyped for fimH single nucleotide polymorphisms (SNPs) and multilocus sequence types (MLSTs). Among 539 isolates, E. coli accounted for 249 (46%); 74 (30%) of them were susceptible to all tested drugs, and 129 (52%) were multidrug resistant (MDR). Only five MLST genotypes accounted for two-thirds of the E. coli isolates; the most common were ST131 (23%) and ST95 (18%). Forty-seven (92%) of 51 ST131 isolates, as opposed to only 8 (20%) of 40 ST95 isolates, were MDR (P < 0.0001). The Simpson's diversity index for drug-susceptible ST genotypes was 87%, while the index for MDR ST genotypes was 81%. ST95 strains were comprised of four fimH types, and one of these (f-6) accounted for 67% of the 21 susceptible isolates (P < 0.003). A large proportion (>70%) of both MDR and susceptible E. coli BSI isolates represented community-onset infections. These observations show that factors other than the selective pressures of antimicrobial agents used in hospitals contribute to community-onset extraintestinal infections caused by clonal groups of E. coli regardless of their drug resistance.
authors.affiliation: School of Public Health, Division of Infectious Diseases and Vaccinology, University of California, Berkeley, Berkeley, California, USA.
authors.forename: Sheila
authors.initials: S
authors.lastname: Adams-Sapper
authors.forename: Binh An
authors.initials: BA
authors.lastname: Diep
authors.forename: Francoise
authors.initials: F
authors.lastname: Perdreau-Remington
authors.forename: Lee W
authors.initials: LW
authors.lastname: Riley
mesh_terms: D018830:Adhesins, Escherichia coli / Q000145:classification / Q000235:genetics*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000188:drug therapy* / Q000382:microbiology; D002999:Clone Cells; D017714:Community-Acquired Infections / Q000188:drug therapy* / Q000382:microbiology; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000188:drug therapy* / Q000382:microbiology; D036781:Fimbriae Proteins / Q000145:classification / Q000235:genetics*; D006801:Humans; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D020641:Polymorphism, Single Nucleotide
chemical_list: D018830:Adhesins, Escherichia coli; D000900:Anti-Bacterial Agents; C058769:fimH protein, E coli; D036781:Fimbriae Proteins