Glutathione-S-transferase FosA6 of Klebsiella pneumoniae origin conferring fosfomycin resistance in ESBL-producing Escherichia coli.
The objectives of this study were to elucidate the genetic context of a novel plasmid-mediated fosA variant, fosA6, conferring fosfomycin resistance and to characterize the kinetic properties of FosA6.



The genome of fosfomycin-resistant Escherichia coli strain YD786 was sequenced. Homologues of FosA6 were identified through BLAST searches. FosA6 and FosA(ST258) were purified and characterized using a steady-state kinetic approach. Inhibition of FosA activity was examined with sodium phosphonoformate.



Plasmid-encoded glutathione-S-transferase (GST) FosA6 conferring high-level fosfomycin resistance was identified in a CTX-M-2-producing E. coli clinical strain at a US hospital. fosA6 was carried on a self-conjugative, 69 kb IncFII plasmid. The ΔlysR-fosA6-ΔyjiR_1 fragment, located between IS10R and ΔIS26, was nearly identical to those on the chromosomes of some Klebsiella pneumoniae strains (MGH78578, PMK1 and KPPR1). FosA6 shared >99% identity with chromosomally encoded FosA(PMK1) in K. pneumoniae of various STs and 98% identity with FosA(ST258), which is commonly found in K. pneumoniae clonal complex (CC) 258 including ST258. FosA6 and FosA(ST258) demonstrated robust GST activities that were comparable to each other. Sodium phosphonoformate, a GST inhibitor, reduced the fosfomycin MICs by 6- to 24-fold for K. pneumoniae and E. coli strains carrying fosA genes on the chromosomes and plasmids, respectively.



fosA6, probably captured from the chromosome of K. pneumoniae, conferred high-level fosfomycin resistance in E. coli. FosA6 functioned as a GST and inactivated fosfomycin efficiently. K. pneumoniae may serve as a reservoir of fosfomycin resistance for E. coli.
Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China Key Laboratory of Clinical Pharmacology of Antibiotics, Ministry of Health, Shanghai, China.
Qinglan
Q
Guo
Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Adam D
AD
Tomich
Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Christi L
CL
McElheny
Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Vaughn S
VS
Cooper
Modernizing Medical Microbiology Consortium, Nuffield Department of Clinical Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK.
Nicole
N
Stoesser
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China Key Laboratory of Clinical Pharmacology of Antibiotics, Ministry of Health, Shanghai, China.
Minggui
M
Wang
Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Nicolas
N
Sluis-Cremer
Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA yod4@pitt.edu.
Yohei
Y
Doi
D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D004791:Enzyme Inhibitors / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D017245:Foscarnet / Q000378:metabolism; D005578:Fosfomycin / Q000494:pharmacology*; D016680:Genome, Bacterial; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000032:analysis; D017422:Sequence Analysis, DNA; D014556:Urine / Q000382:microbiology; D001618:beta-Lactamases / Q000378:metabolism
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; D005578:Fosfomycin; D017245:Foscarnet; D005982:Glutathione Transferase; D001618:beta-Lactamases