title: Intracellular persisting Staphylococcus aureus is the major pathogen in recurrent tonsillitis.
abstract: BACKGROUND
  The two major indications for tonsillectomy are recurrent tonsillitis (RT) and peritonsillar abscess (PTA). Unlike PTAs, which are primarily treated surgically, RT is often cured by tonsillectomy only after a series of failed drug therapy attempts. Although the bacteriological background of RT has been studied, the reason for the lack of success of conservative therapeutic approaches is not well understood.
  
  
  METHODS
  In a prospective study, tonsil specimens from 130 RT patients and 124 PTA patients were examined for the presence of extra- and intracellular bacteria using antibiotic protection assays. Staphylococcus aureus isolates from RT patients were characterized by pulsed-field gel electrophoresis (PFGE), spa-typing and MSCRAMM-gene-PCR. Their ability for biofilm formation was tested and their cell invasiveness was confirmed by a flow cytometric invasion assay (FACS), fluorescent in situ hybridization (FISH) and immunohistochemistry.
  
  
  RESULTS
  S. aureus was the predominant species (57.7%) in RT patients, whereas Streptococcus pyogenes was most prevalent (20.2%) in PTA patients. Three different assays (FACS, FISH, antibiotic protection assay) showed that nearly all RT-associated S. aureus strains were located inside tonsillar cells. Correspondingly, the results of the MSCRAMM-gene-PCRs confirmed that 87% of these S. aureus isolates were invasive strains and not mere colonizers. Based upon PFGE analyses of genomic DNA and on spa-gene typing the vast majority of the S. aureus isolates belonged to different clonal lineages.
  
  
  CONCLUSIONS
  Our results demonstrate that intracellular residing S. aureus is the most common cause of RT and indicate that S. aureus uses this location to survive the effects of antibiotics and the host immune response. A German translation of the Abstract is provided as supplementary material (Abstract S1).
authors.affiliation: Institute of Medical Microbiology, Virology and Hygiene, Rostock, Germany. azautne@gwdg.de
authors.forename: Andreas E
authors.initials: AE
authors.lastname: Zautner
authors.forename: Merit
authors.initials: M
authors.lastname: Krause
authors.forename: Gerhard
authors.initials: G
authors.lastname: Stropahl
authors.forename: Silva
authors.initials: S
authors.lastname: Holtfreter
authors.forename: Hagen
authors.initials: H
authors.lastname: Frickmann
authors.forename: Claudia
authors.initials: C
authors.lastname: Maletzki
authors.forename: Bernd
authors.initials: B
authors.lastname: Kreikemeyer
authors.forename: Hans Wilhelm
authors.initials: HW
authors.lastname: Pau
authors.forename: Andreas
authors.initials: A
authors.lastname: Podbielski
mesh_terms: D000038:Abscess / Q000378:metabolism / Q000382:microbiology*; D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D016521:Electrophoresis, Gel, Pulsed-Field / Q000379:methods; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008875:Middle Aged; D010532:Peritoneal Diseases / Q000382:microbiology / Q000473:pathology*; D011446:Prospective Studies; D013211:Staphylococcus aureus / Q000378:metabolism*; D014069:Tonsillitis / Q000378:metabolism / Q000382:microbiology*; D016896:Treatment Outcome