title: Macrolide-resistant Staphylococcus aureus colonization in cystic fibrosis patients: is there transmission to household contacts?
abstract: OBJECTIVE
  Patients with cystic fibrosis (CF) are frequently colonized by macrolide-resistant Staphylococcus aureus, a result of maintenance macrolide therapy. As transmission of S. aureus between household contacts is common, we examined the prevalence of macrolide-resistant S. aureus colonization in CF patients on maintenance azithromycin therapy and their household contacts and compared this with the S. aureus macrolide resistance prevalence in the community.
  
  
  METHODS
  Sixty-five CF patients on maintenance macrolide therapy and 194 household contacts were screened for S. aureus colonization by culturing sputa, cough swabs and nasal swabs. Resistance to macrolide, lincosamide and methicillin was determined by disc diffusion tests. The prevalence of macrolide-resistant S. aureus colonization in both groups was compared with figures from a nationwide study into S. aureus carriership and resistance. To assess possible transmission, genotyping of S. aureus was performed using the spa-typing method.
  
  
  RESULTS
  Macrolide resistance among CF patients with S. aureus colonization was 69.6%; 75% of these isolates displayed lincosamide resistance too. Among household contacts, macrolide resistance prevalence did not differ significantly from resistance prevalence in the community (9.6% versus 6.3%; P = 0.358). No methicillin resistance was observed. No identical (macrolide-resistant and -susceptible) S. aureus genotypes were observed between CF patients and their household contacts except for one household, suggesting a probable transmission.
  
  
  CONCLUSIONS
  No significant increase in macrolide-resistant S. aureus colonization was observed among household contacts of CF patients on long-term azithromycin therapy. Transmission of macrolide-resistant S. aureus could not be proved by genotyping in the majority of households.
authors.affiliation: Department of Paediatric Respiratory Medicine, Wilhelmina Children's Hospital, University Medical Centre Utrecht, The Netherlands. g.tramper@umcutrecht.nl
authors.forename: Gerdien A
authors.initials: GA
authors.lastname: Tramper-Stranders
authors.forename: Cornelis K
authors.initials: CK
authors.lastname: van der Ent
authors.forename: Susan A M
authors.initials: SA
authors.lastname: Gerritsen
authors.forename: André
authors.initials: A
authors.lastname: Fleer
authors.forename: Jan L L
authors.initials: JL
authors.lastname: Kimpen
authors.forename: Tom F W
authors.initials: TF
authors.lastname: Wolfs
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003550:Cystic Fibrosis / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D005838:Genotype; D006801:Humans; D018942:Macrolides / Q000494:pharmacology*; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D009296:Nasal Cavity / Q000382:microbiology; D009426:Netherlands; D011159:Population Surveillance; D013203:Staphylococcal Infections / Q000382:microbiology* / Q000635:transmission*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides