title: Susceptibility of clinical Moraxella catarrhalis isolates in British Columbia to six empirically prescribed antibiotic agents.
abstract: BACKGROUND
  Moraxella catarrhalis is a commensal organism of the respiratory tract that has emerged as an important pathogen for a variety of upper and lower respiratory tract infections including otitis media and acute exacerbations of chronic bronchitis. Susceptibility testing of M catarrhalis is not routinely performed in most diagnostic laboratories; rather, a comment predicting susceptibility based on the literature is attached to the report. The most recent Canadian report on M catarrhalis antimicrobial susceptibility was published in 2003; therefore, a new study at this time was of interest and importance.
  
  
  OBJECTIVE
  To determine the susceptibility of M catarrhalis isolates from British Columbia to amoxicillin-clavulanate, doxycycline, clarithromycin, cefuroxime, levofloxacin and trimethoprimsulfamethoxazole.
  
  
  METHODS
  A total of 117 clinical M catarrhalis isolates were isolated and tested from five Interior hospitals and two private laboratory centres in British Columbia between January and December 2012. Antibiotic susceptibility of M catarrhalis isolates was characterized using the Etest (E-strip; bioMérieux, USA) according to Clinical Laboratory Standards Institute guidelines.
  
  
  RESULTS
  All isolates were sensitive to amoxicillin-clavulanate, doxycycline, clarithromycin, levofloxacin and trimethoprimsulfamethoxazole. One isolate was intermediately resistant to cefuroxime, representing a 99.15% sensitivity rate to the cephem agent. Cefuroxime minimum inhibitory concentrations (MICs) inhibiting 50% and 90% of organisms (MIC50 and MIC90) were highest among the antibiotics tested, and the MIC90 (3 μg/mL) of cefuroxime reached the Clinical Laboratory Standards Institute breakpoint of susceptibility.
  
  
  CONCLUSIONS
  The antibiotic susceptibility of M catarrhalis isolates evaluated in the present study largely confirms the findings of previous surveillance studies performed in Canada. Cefuroxime MICs are in the high end of the sensitive range and the MIC50 and MIC90 observed in the present study are the highest ever reported in Canada.
  
  
  CONCLUSIONS
  Although cefuroxime MICs in M catarrhalis are high, all agents tested showed antimicrobial activity, supporting their continued therapeutic and empirical use.
authors.affiliation: Department of Biological Sciences, Faculty of Science, Thompson Rivers University;
authors.forename: Tamara
authors.initials: T
authors.lastname: Bandet
authors.affiliation: Department of Pathology, Royal Inland Hospital, Kelowna General Hospital, Kelowna, British Columbia.
authors.forename: Sue
authors.initials: S
authors.lastname: Whitehead
authors.affiliation: Department of Pathology and Laboratory Medicine, Kelowna General Hospital, Kelowna, British Columbia.
authors.forename: Edith
authors.initials: E
authors.lastname: Blondel-Hill
authors.affiliation: Department of Biological Sciences, Faculty of Science, Thompson Rivers University;
authors.forename: Ken
authors.initials: K
authors.lastname: Wagner
authors.affiliation: Department of Biological Sciences, Faculty of Science, Thompson Rivers University;
authors.forename: Naowarat
authors.initials: N
authors.lastname: Cheeptham
keywords: Amoxicillin-clavulanate; Antibiotic resistance; British Columbia; Cefuroxime; Clarithromycin; Doxycycline; Levofloxacin; Moraxella catarrhalis; Regional Hospital; TMP/SMX