Kanchana Manickam1, Andrew Walkty2, Philippe Rs Lagacé-Wiens1, Heather Adam1, Barbara Swan3, Brenda McAdam3, Peter Pieroni3, Michelle Alfa1, James A Karlowsky1. 1. Microbiology, Diagnostic Services of Manitoba; ; Department of Medical Microbiology, Faculty of Medicine, University of Manitoba; 2. Microbiology, Diagnostic Services of Manitoba; ; Department of Medical Microbiology, Faculty of Medicine, University of Manitoba; ; Department of Medicine, Health Sciences Centre, Winnipeg, Manitoba. 3. Microbiology, Diagnostic Services of Manitoba;
Abstract
INTRODUCTION: Staphylococcus aureus bacteremia is associated with considerable morbidity and mortality. In theory, reducing the turnaround time in reporting of methicillin-resistant S aureus (MRSA) among patients with bactermia could assist with the rapid optimization of antimicrobial therapy. OBJECTIVE: To evaluate the sensitivity and specificity of MRSASelect (Bio-Rad Laboratories, USA), a chromogenic medium, in the early detection of MRSA from blood cultures growing Gram-positive cocci in clusters, and to confirm that routine use of this medium would, in fact, reduce turnaround time for MRSA identification. METHODS: The present study was conducted at three microbiology laboratories in Manitoba. Between April 2010 and May 2011, positive blood cultures with Gram-positive cocci in clusters visualized on Gram stain were subcultured to both MRSASelect and routine media. MRSA isolates were identified using conventional microbiological methods from routine media and using growth with the typical colony morphology (pink colony) on MRSASelect medium. RESULTS: A total of 490 blood cultures demonstrating Gram-positive cocci in clusters on Gram stain were evaluated. S aureus was recovered from 274 blood cultures, with 51 S aureus isolates (51 of 274 [18.6%]) identified as MRSA. MRSASelect medium had a sensitivity of 98%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 99.8% for the recovery and identification of MRSA directly from positive blood culture bottles. In addition, use of MRSASelect medium was found to improve turnaround time in the detection of MRSA by almost 24 h relative to conventional methods. DISCUSSION: These data support the utility of MRSASelect medium for the rapid identification of MRSA from positive blood cultures. Further clinical studies are warranted to determine whether the improvement in turnaround time will result in a measurable reduction in suboptimal antimicrobial therapy and/or improvement in patient outcome.
INTRODUCTION:Staphylococcus aureus bacteremia is associated with considerable morbidity and mortality. In theory, reducing the turnaround time in reporting of methicillin-resistant S aureus (MRSA) among patients with bactermia could assist with the rapid optimization of antimicrobial therapy. OBJECTIVE: To evaluate the sensitivity and specificity of MRSASelect (Bio-Rad Laboratories, USA), a chromogenic medium, in the early detection of MRSA from blood cultures growing Gram-positive cocci in clusters, and to confirm that routine use of this medium would, in fact, reduce turnaround time for MRSA identification. METHODS: The present study was conducted at three microbiology laboratories in Manitoba. Between April 2010 and May 2011, positive blood cultures with Gram-positive cocci in clusters visualized on Gram stain were subcultured to both MRSASelect and routine media. MRSA isolates were identified using conventional microbiological methods from routine media and using growth with the typical colony morphology (pink colony) on MRSASelect medium. RESULTS: A total of 490 blood cultures demonstrating Gram-positive cocci in clusters on Gram stain were evaluated. S aureus was recovered from 274 blood cultures, with 51 S aureus isolates (51 of 274 [18.6%]) identified as MRSA. MRSASelect medium had a sensitivity of 98%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 99.8% for the recovery and identification of MRSA directly from positive blood culture bottles. In addition, use of MRSASelect medium was found to improve turnaround time in the detection of MRSA by almost 24 h relative to conventional methods. DISCUSSION: These data support the utility of MRSASelect medium for the rapid identification of MRSA from positive blood cultures. Further clinical studies are warranted to determine whether the improvement in turnaround time will result in a measurable reduction in suboptimal antimicrobial therapy and/or improvement in patient outcome.
Authors: Abigail M Frye; Catherine A Baker; D Leif Rustvold; Kim A Heath; Jessica Hunt; James E Leggett; Margret Oethinger Journal: J Clin Microbiol Date: 2011-11-09 Impact factor: 5.948
Authors: Jess F Peterson; Alexander A Dionisio; Katherine M Riebe; Gerri S Hall; Deborah A Wilson; Susan Whittier; Joseph R Dipersio; Nathan A Ledeboer Journal: J Clin Microbiol Date: 2010-04-14 Impact factor: 5.948
Authors: Guy E Thwaites; Jonathan D Edgeworth; Effrossyni Gkrania-Klotsas; Andrew Kirby; Robert Tilley; M Estée Török; Sarah Walker; Heiman Fl Wertheim; Peter Wilson; Martin J Llewelyn Journal: Lancet Infect Dis Date: 2011-03 Impact factor: 25.071
Authors: J O Robinson; J C Pearson; K J Christiansen; G W Coombs; R J Murray Journal: Eur J Clin Microbiol Infect Dis Date: 2008-10-11 Impact factor: 3.267
Authors: Volker Micheel; Benedikt Hogan; Thomas Köller; Philipp Warnke; Sabine Crusius; Rebecca Hinz; Ralf Matthias Hagen; Norbert Georg Schwarz; Hagen Frickmann Journal: Mil Med Res Date: 2015-07-21
Authors: Diana R Hernandez; Duane W Newton; Nathan A Ledeboer; Blake Buchan; Carol Young; Andrew E Clark; Jessica Connoly; Donna M Wolk Journal: J Clin Microbiol Date: 2015-11-18 Impact factor: 5.948