Comparison of the WST-8 colorimetric method and the CLSI broth microdilution method for susceptibility testing against drug-resistant bacteria.
The minimum inhibitory concentrations (MICs) obtained from the susceptibility testing of various bacteria to antibiotics were determined by a colorimetric microbial viability assay based on reduction of a tetrazolium salt {2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-8)} via 2-methyl-1,4-napthoquinone as an electron mediator and compared with those obtained by the broth microdilution methods approved by the Clinical and Laboratory Standard Institute (CLSI). Especially for drug-resistant bacteria, the CLSI method at an incubation time of 24h tended to give lower MICs. The extension of incubation time was necessary to obtain consistent MICs for drug-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococi (VRE) and multi-drug resistant Pseudomonas aeruginosa (MDRP) in the broth microdilution method. There was excellent agreement between the MICs determined after 24h using the WST-8 colorimetric method and those obtained after 48-96 h using the broth microdilution method. The results suggest that the WST-8 colorimetric assay is a useful method for rapid determination of consistent MICs for drug-resistant bacteria.
Biotechnology and Food Research Institute, Fukuoka Industrial Technology Center, Kurume 839-0861, Japan. tukatani@fitc.pref.fukuoka.jp
Tadayuki
T
Tsukatani
Hikaru
H
Suenaga
Masanobu
M
Shiga
Katsuya
K
Noguchi
Munetaka
M
Ishiyama
Takatoshi
T
Ezoe
Kiyoshi
K
Matsumoto
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology; D003124:Colorimetry; D003470:Culture Media; D013293:Enterococcus faecalis / Q000187:drug effects / Q000254:growth & development; D006193:Haemophilus influenzae / Q000187:drug effects / Q000254:growth & development; D007201:Indicator Dilution Techniques; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000254:growth & development; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development; D008826:Microbial Sensitivity Tests / Q000379:methods*; D050296:Microbial Viability / Q000187:drug effects; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000254:growth & development; D014640:Vancomycin / Q000494:pharmacology; D020713:Vancomycin Resistance; D018440:beta-Lactam Resistance; D047090:beta-Lactams / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D003470:Culture Media; D047090:beta-Lactams; D002939:Ciprofloxacin; D014640:Vancomycin