title: Rapid emergence of a ceftazidime-resistant Burkholderia multivorans strain in a cystic fibrosis patient.
abstract: BACKGROUND
  Burkholderia multivorans poses a serious health threat to cystic fibrosis patients due to innate resistance to multiple antibiotics and acquisition of resistance to a range of antibiotics due to the frequent use of antibiotics to treat chronic infections. Monitoring antibiotic susceptibility is crucial to managing patient care. We identified the rapid emergence of a ceftazidime-resistant strain in a single patient within four days during a hospitalization for treatment of an exacerbation.
  
  
  METHODS
  B. multivorans was isolated from expectorated sputum samples using Burkholderia cepacia selective agar. A macrodilution assay was performed on all isolates to determine the minimum inhibitory concentration of ceftazidime. Approximately 4000 colonies were scored to identify the percent of ceftazidime-resistant colonies. Extracted DNA was used to determine the total bacterial counts and abundance of B. multivorans using quantitative PCR.
  
  
  RESULTS
  An increase from no detectable B. multivorans ceftazidime-resistant colonies to over 75% of all colonies tested occurred within a four-day period. The resistant population remained dominant in 6 of the 8 samples in the following 17 months of the study. qPCR revealed an association between change in the percent of resistant colonies and abundance of B. multivorans, but not of total bacteria. No association was found between the acquisition of resistance to ceftazidime and other antibiotics commonly used to treat B. multivorans infections.
  
  
  CONCLUSIONS
  The rapid emergence of a ceftazidime-resistant by B. multivorans strain occurred during a hospitalization while under selective pressure of antibiotics. The resistant strain maintained dominance in the B. multivorans population which resulted in an overall decline in a patient health and treatment efficacy.
authors.affiliation: Department of Biology, University of North Carolina at Charlotte, Charlotte, NC 28223, United States.
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Stokell
authors.forename: Raad Z
authors.initials: RZ
authors.lastname: Gharaibeh
authors.forename: Todd R
authors.initials: TR
authors.lastname: Steck
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D019117:Burkholderia / Q000187:drug effects*; D002442:Ceftazidime / Q000494:pharmacology / Q000627:therapeutic use*; D015169:Colony Count, Microbial; D003550:Cystic Fibrosis / Q000188:drug therapy* / Q000382:microbiology; D018450:Disease Progression; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D006801:Humans; D008297:Male; D058885:Multilocus Sequence Typing; D013183:Sputum / Q000382:microbiology; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D002442:Ceftazidime
keywords: Antibiotic resistance; Bacteria; Burkholderia multivorans; Cystic Fibrosis