title: Multiple resistance to betalactam antibiotics, azithromycin or moxifloxacin in implant associated bacteria.
abstract: BACKGROUND
  Antibiotics are more and more frequently prescribed in dentistry for prevention and treatment of oral diseases. Bacterial resistance to these agents is clearly increasing, including even previously susceptible micro-organisms and true pathogens. The aim of the present investigation was to examine resistant bacterial strains with respect to possible multiple antibiotic resistance.
  
  
  METHODS
  In a previous investigation, implant-associated bacteria were tested first as mixed cultures and again as pure isolates (n = 138) for resistance to one of five antibiotics (ampicillin/AM, ampicillin + sulbactam/AB, azithromycin/AZ, penicillin/PG, moxifloxacin/MX) using the Etest. The resistance of most of the pure isolates was lower than in mixed culture, but 31.2% had retained their original resistance. Subsequently, all 138 isolates were tested for resistance or susceptibility to the other four antibiotics, again using the Etest.
  
  
  RESULTS
  27.6% (38/138) of the isolates retained their original antibiotic resistance and were resistant to at least one other antibiotic (MIC > or = 128 microg/mL for AB, AM or AZ, > or = 32 microg/mL PG, > or = 24 microg/mL MX). 2.2% (3/138) strains had lost their original antibiotic resistance, but were resistant to at least one other antibiotic (MIC > 128 microg/mL for AB, AM, or AZ, > or = 32 microg/mL PG, > or = 24 microg/mL MX).
  
  
  CONCLUSIONS
  Some of the isolates belonging to the implant-associated microflora were multi-resistant, even though the patients had not received any antibiotics six weeks prior to the sampling. The exact mechanisms that lead to multiple resistance need to be examined in further studies.
authors.affiliation: Department for Oral and Maxillofacial Surgery, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany. jkarbach@uni-mainz.de
authors.forename: Julia
authors.initials: J
authors.lastname: Karbach
authors.forename: Angelika S
authors.initials: AS
authors.lastname: Callaway
authors.forename: Brita
authors.initials: B
authors.lastname: Willershausen
authors.forename: Wilfried
authors.initials: W
authors.lastname: Wagner
authors.forename: Bilal
authors.initials: B
authors.lastname: Al-Nawas
mesh_terms: D001372:Aza Compounds / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology*; D001419:Bacteria / Q000145:classification / Q000187:drug effects*; D015921:Dental Implants / Q000382:microbiology*; D004352:Drug Resistance, Microbial; D018432:Drug Resistance, Multiple; D024841:Fluoroquinolones; D006801:Humans; D008826:Microbial Sensitivity Tests; D000077266:Moxifloxacin; D011804:Quinolines / Q000494:pharmacology*; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D001372:Aza Compounds; D015921:Dental Implants; D024841:Fluoroquinolones; D011804:Quinolines; D047090:beta-Lactams; D017963:Azithromycin; D000077266:Moxifloxacin