title: Antimicrobial resistance characteristics and fitness of Gram-negative fecal bacteria from volunteers treated with minocycline or amoxicillin.
abstract: A yearlong study was performed to examine the effect of antibiotic administration on the bacterial gut flora. Gram-negative facultative anaerobic bacteria were recovered from the feces of healthy adult volunteers administered amoxicillin, minocycline or placebo, and changes determined in antimicrobial resistance (AMR) gene carriage. Seventy percent of the 1039 facultative anaerobic isolates recovered were identified by MALDI-TOF as Escherichia coli. A microarray used to determine virulence and resistance gene carriage demonstrated that AMR genes were widespread in all administration groups, with the most common resistance genes being bla TEM, dfr, strB, tet(A), and tet(B). Following amoxicillin administration, an increase in the proportion of amoxicillin resistant E. coli and a three-fold increase in the levels of bla TEM gene carriage was observed, an effect not observed in the other two treatment groups. Detection of virulence genes, including stx1A, indicated not all E. coli were innocuous commensals. Approximately 150 E. coli collected from 6 participants were selected for pulse field gel electrophoresis (PFGE), and a subset used for characterisation of plasmids and Phenotypic Microarrays (PM). PFGE indicated some E. coli clones had persisted in volunteers for up to 1 year, while others were transient. Although there were no unique characteristics associated with plasmids from persistent or transient isolates, PM assays showed transient isolates had greater adaptability to a range of antiseptic biocides and tetracycline; characteristics which were lost in some, but not all persistent isolates. This study indicates healthy individuals carry bacteria harboring resistance to a variety of antibiotics and biocides in their intestinal tract. Antibiotic administration can have a temporary effect of selecting bacteria, showing co-resistance to multiple antibiotics, some of which can persist within the gut for up to 1 year.
authors.affiliation: Department of Bacteriology, Animal and Plant Health Agency Addlestone, UK.
authors.forename: Miranda
authors.initials: M
authors.lastname: Kirchner
authors.affiliation: Department of Bacteriology, Animal and Plant Health Agency Addlestone, UK.
authors.forename: Muriel
authors.initials: M
authors.lastname: Mafura
authors.affiliation: Department of Bacteriology, Animal and Plant Health Agency Addlestone, UK.
authors.forename: Theresa
authors.initials: T
authors.lastname: Hunt
authors.affiliation: Department of Bacteriology, Animal and Plant Health Agency Addlestone, UK.
authors.forename: Manal
authors.initials: M
authors.lastname: Abu-Oun
authors.affiliation: Specialist Scientific Services Department, Animal and Plant Health Agency Addlestone, UK.
authors.forename: Javier
authors.initials: J
authors.lastname: Nunez-Garcia
authors.affiliation: Department of Medical Microbiology, Institute of Infection and Immunity, St. George's University of London London, UK.
authors.forename: Yanmin
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Institute for Laboratory and Transfusion Medicine at the Heart and Diabetes Centre NRW, University Hospital of the Ruhr University Bochum, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Weile
authors.affiliation: Department of Medical Microbiology, Institute of Infection and Immunity, St. George's University of London London, UK.
authors.forename: Anthony
authors.initials: A
authors.lastname: Coates
authors.affiliation: Department of Bacteriology, Animal and Plant Health Agency Addlestone, UK.
authors.forename: Roderick
authors.initials: R
authors.lastname: Card
authors.affiliation: Department of Bacteriology, Animal and Plant Health Agency Addlestone, UK.
authors.forename: Muna F
authors.initials: MF
authors.lastname: Anjum
keywords: antibiotic trial; facultative anaerobic Gram-negative bacteria; persistent; resistance genes; transient