title: Diversity of moxifloxacin resistance during a nosocomial outbreak of a predominantly ribotype ARU 027 Clostridium difficile diarrhea.
abstract: To characterize the extent and diversity of moxifloxacin resistance among Clostridium difficile isolates recovered during a predominantly Anaerobe Reference Unit (ARU) ribotype 027-associated nosocomial outbreak of antibiotic associated diarrhea we measured the susceptibility of 34 field isolates and 6 laboratory strains of C. difficile to moxifloxacin. We ribotyped the isolates as well as assaying them by PCR for the metabolic gene, gdh, and the virulence genes, tcdA, tcdB, tcdC, cdtA and cdtB. All the laboratory isolates, including the historical ARU 027 isolate Cd196, were susceptible to moxifloxacin (<or=2 microg/mL). 13 field isolates were susceptible to <or=2 microg/mL. Five were resistant to from 4 to 12 microg/mL (moderate resistance); 16 were resistant to >or=16 microg/mL (high resistance). We sequenced the quinolone resistance determining regions of gyrA (position 71-460) and gyrB (position 1059-1448) from two susceptible laboratory strains, all five isolates with moderate resistance and two highly resistant isolates. Two highly resistant isolates (Pitt 40, ribotype ARU 027 and Pitt 33, ribotype ARU 001) had the same C245T (Thr(82)Delta Ile) mutation. No other changes were seen. Amplification with primer pairs specific for the C245T mutant gyrA and for the wild type gene respectively confirmed all 16 highly resistant ARU 027 isolates, as well as the highly resistant isolates from other ribotypes, had the C245T mutation and that the mutation was absent from all other isolates. Among the five isolates with moderate resistance we found combinations of mutations within gyrA (T128A, Val(43)Delta Asp and G349T, Ala(117)Delta Ser) and gyrB (G1276A, Arg(426)Delta Asn). The G1396A (Glu(466)Delta Lys) mutation was not associated with increased resistance.
authors.affiliation: TechLab Inc., 2001 Kraft Drive, Blacksburg, VA 24060-6358, USA. rjcarman@techlab.com
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Carman
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Genheimer
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Rafii
authors.forename: Miseon
authors.initials: M
authors.lastname: Park
authors.forename: Megan F
authors.initials: MF
authors.lastname: Hiltonsmith
authors.forename: David M
authors.initials: DM
authors.lastname: Lyerly
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001372:Aza Compounds / Q000494:pharmacology*; D016360:Clostridioides difficile / Q000187:drug effects*; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D027081:DNA Gyrase / Q000235:genetics; D003967:Diarrhea / Q000453:epidemiology* / Q000382:microbiology; D004196:Disease Outbreaks; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004761:Enterocolitis, Pseudomembranous / Q000453:epidemiology / Q000382:microbiology; D024841:Fluoroquinolones; D014644:Genetic Variation; D006801:Humans; D008826:Microbial Sensitivity Tests; D000077266:Moxifloxacin; D009154:Mutation; D016133:Polymerase Chain Reaction; D011804:Quinolines / Q000494:pharmacology*; D021521:Ribotyping
chemical_list: D000900:Anti-Bacterial Agents; D001372:Aza Compounds; D024841:Fluoroquinolones; D011804:Quinolines; D027081:DNA Gyrase; D000077266:Moxifloxacin