Cost analysis and antimicrobial susceptibility testing comparing the E test and the agar dilution method in Campylobacter jejuni and Campylobacter coli

Abstract Although numerous reports have compared the antimicrobial susceptibility of Campylobacter spp., controversy still exists about the use of the E test as an alternative to the agar dilution method suggested by the Clinical and Laboratory Standards Institute. MICs of 8 antimicrobials were dete...

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Bibliographic Details
Published in:	Diagnostic microbiology and infectious disease Vol. 65; no. 2; pp. 168 - 174
Main Authors:	Valdivieso-García, Alfonso, Imgrund, Ryan, Deckert, Anne, Varughese, Betsy Marie, Harris, Kathleen, Bunimov, Natalie, Reid-Smith, Richard, McEwen, Scott
Format:	Journal Article
Language:	English
Published:	New York, NY Elsevier Inc 01-10-2009 Elsevier
Subjects:	Agar dilution Animals Anti-Bacterial Agents - pharmacology Antimicrobial susceptibility testing Bacteriology Biological and medical sciences Campylobacter Campylobacter coli Campylobacter coli - drug effects Campylobacter jejuni Campylobacter jejuni - drug effects Chickens - microbiology Cost analysis Costs and Cost Analysis E test Fundamental and applied biological sciences. Psychology Infectious Disease Infectious diseases Internal Medicine Meat - microbiology Medical sciences Microbial Sensitivity Tests - economics Microbial Sensitivity Tests - methods Microbiology Miscellaneous Ontario Ontario Antimicrobial susceptibility testing E test Cost analysis Agar dilution Campylobacter Microbiology Drug susceptibility test Campylobacteraceae Campylobacter coli Method Campylobacter jejuni Infection Sensitivity resistance Bacteria
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Summary:	Abstract Although numerous reports have compared the antimicrobial susceptibility of Campylobacter spp., controversy still exists about the use of the E test as an alternative to the agar dilution method suggested by the Clinical and Laboratory Standards Institute. MICs of 8 antimicrobials were determined using the E test and agar dilution methods for 103 Campylobacter jejuni and Campylobacter coli isolates from fresh chicken randomly purchased from stores in 3 southern Ontario counties. Overall, 72.6% of E test MIC values were within 1 log2 dilution and 95.7% within 2 log2 dilutions of the corresponding agar dilution MICs. For individual antimicrobials, agreement within 1 log2 dilution and 2 log2 dilutions was as follows: ampicillin ( n = 103), 90.3% and 98.1%, respectively; chloramphenicol ( n = 104), 85.6% and 99%; ciprofloxacin ( n = 99), 51.5% and 97.0%; clindamycin ( n = 99), 26.3% and 78.8%; erythromycin ( n = 99), 52.5% and 96.0%; gentamicin ( n = 99), 100% and 100%; nalidixic acid ( n = 98), 91.8% and 99.0%; and tetracycline ( n = 86), 82.6% and 97.7%. Relative to agar dilution, the E test underestimated the MIC value by a mean of 0.74 (ampicillin), 0.82 (chloramphenicol), 1.44 (ciprofloxacin), 1.94 (clindamycin), 1.40 (erythromycin), 0.21 (gentamicin), 0.94 (nalidixic acid), and 0.20 (tetracycline) log2 dilutions and by a median of 1 log2 dilution for all antimicrobials except clindamycin (2), gentamicin (0), and tetracycline (0). Cost analysis, including materials and labor, showed a 39.0% higher cost per analyte for the agar dilution method as compared with the E test. The most relevant advantage of the E test over the agar dilution method is the turnaround time because testing 99 strains by the agar dilution method takes 3.6 times longer compared with the E test using the same number of strains. The E test is an acceptable alternative for antimicrobial susceptibility testing in Campylobacter because it corresponds well with the agar dilution method although being considerably less expensive, is less labor intensive, and is more rapid. However, the relationship between E test and agar dilution MICs must be considered when interpreting E test results.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0732-8893 1879-0070
DOI:	10.1016/j.diagmicrobio.2009.07.008