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A comparative study of antibiotic gradient devices for meropenem, ceftriaxone and clindamycin against CLSI and BSAC reference methods

Abstract number: P1873

Reed S., Crabtree D., Scopes E.

Objectives: The aim of this study was to compare the performance of meropenem, ceftriaxone and clindamycin M.I.C.Evaluator™ strips (Oxoid) and Etest™ strips (bioMérieux) against the CLSI and BSAC broth /agar dilution reference methods.

Methods: A range of clinically significant organisms were tested, including anaerobes, staphylococci, streptococci and Enterobacteriaceae. These were grown overnight on Columbia Blood Agar and a 0.5 (1.0 for anaerobes and some streptococci) McFarland suspension of each isolate was used for both the GOLD standard agar/broth dilution and plate inoculation. Both BSAC and CLSI reference methods were followed. All inoculated plates were incubated in appropriate conditions for 24 h or 48 h (anaerobes). Results were read and used to determine essential agreement (EA).

Results: Meropenem, ceftriaxone and clindamycin M.I.C.Evaluator strips achieved an EA of >90% across all groups of organisms when compared with both CLSI and BSAC reference methods. However, with the organisms groups and method tested, the Etest strips demonstrated <90% essential agreement, with 33% of meropenem, 39% ceftriaxone and 17% clindamycin falling below this figure. See Table 1.

Conclusion: Meropenem, ceftriaxone and clindamycin M.I.C.Evaluator strips, both BSAC and CLSI methods achieved an essential agreement of greater than 90%. Etest strips were not able to display the same level of essential agreement with 30% of the results falling below 90% essential agreement.

M.I.C.Evaluator strips performed consistently and significantly better than Etest strips for meropenem (p = 0.029), ceftriaxone (p = 0.002) and clindamycin (p = 0.034).

Gradient diffusion devices are a rapid, easy and reliable alternative to the reference methods for measuring organism susceptibility to meropenem, ceftriaxone and clindamycin.

Table 1. Essential agreement (%) for each antibiotic tested

  Meropenem CeftriaxoneClindamycin
  CLSIBSACCLSIBSACCLSIBSAC
EnterococciM.I.C.E.96.97100.00    
 Etest90.91100.00    
StaphylococciM.I.C.E.93.33100.0093.3396.43100100
 Etest90.00100.0086.6778.5794.9598.04
StreptococciM.I.C.E.95.2495.24100.00100.0099.2296.38
 Etest95.2447.6290.4895.2488.3393.36
PseudomonasM.I.C.E.90.4895.1297.7890.48  
 Etest86.0695.1293.3390.48  
AcinetobacterM.I.C.E.100.00100.00100.0093.75  
 Etest100.0096.77100.00100.00  
HaemophilusM.I.C.E.90.0090.00100.0094.74  
 Etest80.0085.0083.3379.00  
NeisseriaM.I.C.E.  92.31100.00  
 Etest  92.31100.00  
MoraxellaM.I.C.E.100.00100.00100.0090.00  
 Etest100.0090.0080.00100.00  
AnaerobesM.I.C.E.93.3395.4590.91100.0096.7795.59
 Etest93.3381.8286.9686.9694.6290.91
EnterobacteriaceaeM.I.C.E.97.5197.5094.2694.53  
 Etest90.7684.5780.0986.85  

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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