title: [Detection of Staphylococcus aureus resistant to methicillin (MRSA) by molecular biology (Cepheid GeneXpert IL, GeneOhm BD, Roche LightCycler, Hyplex Evigene I2A) versus screening by culture: Economic and practical strategy for the laboratory].
abstract: OBJECTIVE
  Patients admitted in cardiac surgery and cardiac ICU at the Clinic Saint-Gatien (Tours) are screened for MRSA at the entrance by nasal swab and culture on blood agar and selective chromogenic medium made by addition of cefoxitin: BBL CHROMagar MRSA-II BD (result obtained at Day +1). We wanted to assess the molecular biology techniques available to obtain a result at day 0 for the majority of patients and to define an economic and practical strategy for the laboratory.
  
  
  METHODS
  We studied four molecular biology techniques: Cepheid GeneXpert (Cepheid) GeneOhm (BD), LightCycler (Roche) and Hyplex (I2A). Upon reception, nasal swabs were treated by culture, considered as reference, and one of the techniques of molecular biology, according to the manufacturer's notice. We conducted four studies between April 2008 and February 2009 to obtain a significant sample for each of them.
  
  
  METHODS
  By screening we mean a method that allows us to exclude MRSA carriage for patients waiting for surgery, and not to change patient management: for example, lack of isolation measures specific to entrance, no modification of antibiotic prophylaxis during surgery and no isolation measures in the immediate postoperative period.
  
  
  RESULTS
  The criteria we considered for this evaluation were: (1) technician time: time to perform one or a series of sample(s) n=10 or more (about 2h for all techniques except GeneXpert 75min), level of skilled competences (no specific training for GeneXpert); (2) results: turnaround time (all molecular biology techniques), ease of reading and results interpretations (no specialized training required for GeneXpert), failure or not (12% of failure of internal controls for GeneOhm); (3) economic: cost for one or a series of sample(s) (n=10 or more), if we considered X as the reference culture cost (10 X Hyplex and LightCycler, 20 X and 40 X for GeneXpert GeneOhm); (4) NPV: 100% for GeneXpert and LightCycler.
  
  
  CONCLUSIONS
  At same sensitivity, no technique, including culture, can solve alone our problem, which is: (1) get results at day 0 for batch of samples (n<10): all molecular biology techniques; (2) beyond 10 samples: LightCycler (Roche) automated or Hyplex (I2A) manual; (3) when the result at day 1 is sufficient, the use of chromogenic agar with a reading of less than 18h as BBL CHROMagar MRSA II (BD) remains the most economical; (4) to be sure that a patient admitted at Day 0, even at night's emergency, is not carrier of MRSA: only Cepheid GeneXpert technology (IL). Furthermore, Cepheid GeneXpert (IL) allows performing several tests in parallel. The rapidity of this system can help control the transmission and make better use of antibiotics.
authors: Laboratoire Arnaud, 40, rue Jules-Simon, 37000 Tours, France. plaudat@laboarnaud.fr
authors: P
authors: P
authors: Laudat
authors: E
authors: E
authors: Demondion
authors: C
authors: C
authors: Jouannet
authors: J
authors: J
authors: Charron
authors: C
authors: C
authors: Chillou
authors: V
authors: V
authors: Salaun
authors: B
authors: B
authors: Mankikian
mesh_terms: D000465:Algorithms; D001431:Bacteriological Techniques / Q000191:economics* / Q000379:methods*; D003362:Cost-Benefit Analysis; D057166:High-Throughput Screening Assays / Q000191:economics / Q000295:instrumentation / Q000379:methods; D006801:Humans; D007755:Laboratories, Hospital / Q000191:economics; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics / Q000302:isolation & purification*; D008826:Microbial Sensitivity Tests / Q000191:economics; D008954:Models, Biological; D008967:Molecular Biology / Q000191:economics / Q000295:instrumentation / Q000379:methods; D025202:Molecular Diagnostic Techniques / Q000191:economics / Q000379:methods; D016133:Polymerase Chain Reaction / Q000191:economics / Q000295:instrumentation / Q000379:methods; D011364:Professional Practice / Q000191:economics; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000382:microbiology