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
NeisseriaM.I.C.E.  92.31100.00  
 Etest  92.31100.00  

Session Details

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