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Microbial Viability Assay Kit-WST

Item # Unit Size
M439-01
100 tests
M439-10
500 tests

For Research Use Only Products

Bacterial and Yeast Cell Viability Detection
∼ Feature ∼
- Colorimetric microplate assay
- Wide variety of microorganism detection
- No harvesting or washing required

Contents of the Kit:


Storage Condition: 0-5ºC
Shipping Condition: ambient temperature

Required Equipment and Materials
plate reader with 450 nm filter; 96-well culture plate, 10 μl, 100-200 μl, and multi-channel pipettes; incubator
MSDS MSDS

Product Description
Viable bacterial cell detections are very important for analyzing bacteria contamination in food or evaluating the cleanliness of facilities in order to protect us from food poisoning and infections. Bacterial cell detections are also used for the screening of sanitizing agents and drug resistance detections. Generally, counting the number of colonies on an agar plate is the standard method for determining the number of viable bacterial cells in samples. However, colony formations require one to several days. Dojindo’s Microbial Viability Assay Kit-WST can be used to determine the number of viable bacterial cells in a sample by a colorimetric method and can be applied to 96-well microplate assays. The electron mediator in the kit receives electrons from viable bacterial cells and transfers the electrones to WST, one of the water-soluble tetrazolium salts developed by Dojindo. Bacterial cell viability then can be determined by monitoring the color intensity of WST formazan dye. Since several types of media used for bacterial cell cultures and components do not interfere with the assay(Fig. 5), simply add the assay solution and incubate for one to several hours to determine the initial number of viable bacterial cells in the sample(Fig. 2). This assay kit was co-developed with the Biotechnology and Food Research Institute, Fukuoka Industrial Technology Center.


Fig. 1 Bacterial cell viability detection mechanism.


Assay Data

Fig. 2 Correlation between initial number of E. coli and time-dependent O.D. increase. The initial number of viable E.coli were determined by a colony counting method.



Fig. 3 Correlation between the initial number of SA and time-dependent O.D. increase. The initial number of viable SA were determined by the colony counting method.


Comparison Chart

Fig. 5 Influence of culture media or substances used for bacterial cell culture.
The data indicated that WST is less sensitive to various culture media or substances which are used for bacterial cell culture. WST is a better tetrazolium salt than XTT for bacterial cell viability assays.
General Procedure 2
Determination of the susceptibility of Staphylococcus aureus to oxacillin
Oxacillin: antimicrobial agent: 0-64 μg/ml
Microorganism: Staphylococcus aureus (SA)
Methicillin-resistant Staphylococcus aureus (MRSA)
1. Culture SA or MRSA with Mueller-Hintonmedium containing various concentrations of Oxacillin for 6 hours at 35ºC.
2. Add Microbial Viability Assay solution equal to 1/20 the volume of the culture medium.
3. Incubate for 2 hours at 35ºC.
4. Measure the O.D. at 450 nm to determine the MIC (Minimum inhibitory concentration).



Fig. 4 Susceptibility test of SA and MRSA against Oxacillin.
The data indicated that MRSA has lower susceptibility than SA. The MICs of MRSA (32 μg/ml) and SA (0.5 μg/ml) are close to the MICs determined by the CLSI (Clinical and Laboratory Standards Institute) method.


The list of samples measured by Microbial Viability Kit
Mould Yeast
Alternaria alternata NBR+B40:B56C31805
Aspergillus flavus NBRC4295
Aspergillus fumigatus NBRC33022
Aspergillus niger NBRC105649
Aspergillus terreus NBRC6346
Aspergillus ustus NBRC4128
Aureobasidium pullulans NBRC6353
Chaetomium globosum NBRC6347z
Cladosporium cladosporioides NBRC6348
Exophiala dermatitidis NBRC6421
Paecilomyces variotii NBRC33284
Penicillium citrinum NBRC6352
Penicillium pinzophilum NBRC33285
Phoma citricarpa NBRC5287
Pseudallescheria boydii NBRC32229
Rhizopus oryzae NBRC31005
Sporothrix schenckii NBRC32961
Trichoderma virens NBRC6355
Trichophyton rubrum NBRC 5807
Candida albicans ATCC90028
Candida albicans JCM 1542
Candida albicans SC5314
Candida krusei NBRC1395
Candida parapsilosis NBRC1396
Candida utilis
Cryptococcus albidus NBRC0378
Cryptococcus neoformans ATCC66031
Saccharomyces cerevisiae NBRC2347
Trichosporon asahii NBRC103889
Trichosporon asahii M9459
Trichosporon asahii M9925
Zygosaccharomyces rouxi
Gram-positive Gram-negative
Bacillus cereus
Bacillus subtillis
Corynebacterium glutamicum
Enterococcus faecalis
Enterococcus faecalis FSCC 146002
Lactobacillus casei
Listeria monocytogenes
Micrococcus luteus
Staphylococcus aureus
Staphylococcus aureus NBRC13276
Staphylococcus aureus ATCC 25923
Staphylococcus epidermidis
Staphylococcus epidermidis ATCC 14990
Staphylococcus epidermidis FSCC 223011
Streptococcus mutans NCTC 10449
Streptococcus mutans UA 159
Acetobacter sp.
Acinetobacter baumannii ATCC 19606
Campylobacter concisus ATCC 33237
Enterobacter cloacae FSCC145003
Escherichia coli 1.1369
Escherichia coli ATCC 25922
Escherichia coli BW25113
Escherichia coli K-12
Fusobacterium nucleatum subsp. polymorphum JCM 12990
Klebsiella pneumoniae FSCC167002
Proteus mirablils
Pseudomonas aeruginosa
Pseudomonas aeruginosa NBRC13275
Pseudomonas aeruginosa ATCC 27853
Salmonella enteritidis
Salmonella typhimurium
Serratia marcescens
Stenotrophomonas maltophilia ATCC 51331
Vivrio parahaemolyticus
Yersinia enterocollica
No. Sample Reference
1) <Yeast>
・Candida albicans JCM 1542
A. Azuma, N. Akiba and S. Minakuchi, "Hydrophilic surface modification of acrylic denture base material by silica coating and its influence on Candida albicans adherence", J. Med. Dent. Sci.., 2012, 59, (1), 1-7.
2) <Gram-negative>
・Escherichia coli BW25113
H. Y. Oh, J. O. Lee and O. B. Kim, "Increase of organic solvent tolerance of Escherichia coli by the deletion of two regulator genes, fadR and marR", Appl. Microbiol. Biotechnol.., 2012, 96, (6), 1619-27.
3) <Gram-negative>
・Escherichia coli K-12
T. Nakayashiki, N. Saito, R. Takeuchi, H. Kadokura, K. Nakahigashi, B. L. Wanner and H. Mori, "The tRNA thiolation pathway modulates the intracellular redox state in Escherichia coli", J. Bacteriol.., 2013, 195, (9), 2039-49.
4) <Gram-positive>
・Streptococcus mutans UA 159
<Gram-negative>
・Escherichia coli 1.1369
S. He, P. Zhou, L. Wang, X. Xiong, Y. Zhang, Y. Deng and S. Wei, "Antibiotic-decorated titanium with enhanced antibacterial activity through adhesive polydopamine for dental/bone implant", J. R. Soc. Interface., 2014, 11, (95).
5) <Mould>
・Trichophyton rubrum NBRC 5807
S. Arai, T. Yoshino, T. Fujimura, S. Maruyama, T. Nakano, A. Mukuno, N. Sato and K. Katsuoka, "Mycostatic effect of recombinant dermcidin against Trichophyton rubrum and reduced dermcidin expression in the sweat of tinea pedis patients", J. Dermatol.., 2015, 42, (1), 70-6.
6) <Mould>
・Trichophyton rubrum
S. Arai, T. Yoshino, T. Fujimura, S. Maruyama, T. Nakano, A. Mukuno, N. Sato and K. Katsuoka, "Mycostatic effect of recombinant dermcidin against Trichophyton rubrum and reduced dermcidin expression in the sweat of tinea pedis patients", J. Dermatol.., 2015, 42, (1), 70-6.
7) <Gram-positive>
・Staphylococcus aureus NBRC13276
<Gram-negative>
・Pseudomonas aeruginosa NBRC13275
T. Tsukatani, T. Kawaguchi, H. Suenaga, M. Shiga and T. Ikegami, "RAPID AND SIMPLE DETERMINATION OF MINIMUM BIOFILM ERADICATION CONCENTRATION BY A COLORIMETRIC MICROBIAL VIABILITY ASSAY BASED ON REDUCTION OF A WATER-TETRAZOLIUM SALT AND COMBINATED EFFECT OF ANTIBIOTICS AGAINST MICROBIAL BIOFILM", J Microbiol Biotechnol Food Sci.., 2016, 6, (1), 677.
8) <Gram-positive>
・Streptococcus mutans NCTC 10449
M. Hashimoto, H. Yanagiuchi, H. Kitagawa and Y. Honda, "Inhibitory Effect of Platinum Nanoparticles on Biofilm Formation of Oral Bacteria", Nano Biomed., 2017, 9, (2), 77-82.
9) <Gram-positive>
・Enterococcus faecalis FSCC 146002
・Staphylococcus aureus ATCC 25923
・Staphylococcus epidermidis FSCC 223011
<Gram-negative>
・Acinetobacter baumannii ATCC 19606
・Enterobacter cloacae FSCC 145003
・Escherichia coli ATCC 25922
・Klebsiella pneumoniae FSCC 167002
・Pseudomonas aeruginosa ATCC 27853
・Stenotrophomonas maltophilia ATCC 51331
Z. Xu, X. Zhao, X. Chen, Z. Chen and Z. Xia, "Antimicrobial effect of gallium nitrate against bacteria encountered in burn wound infections", RSC Adv.., 2017, 7, 52266-52273.
10) <Yeast>
・Candida albicans SC5314
J. Nagao, T. Cho, M. Mitarai, K. Iohara, K. Hayama, S. Abe and Y. Tanaka, "Antifungal activity in vitro and in vivo of a salmon protamine peptide and its derived cyclic peptide against Candida albicans", FEMS Yeast Res.., 2017, 17, (1).
11) <Mould>
・Trichosporon asahii M9459
・Trichosporon asahii M9925
T. Ichikawa, C. Hirata, M. Takei, N. Tagami, H. Murasawa and R. Ikeda, "Cell surface hydrophobicity and colony morphology of Trichosporon asahii clinical isolates", Yeast., 2017, 34, (3), 129-137.
12) Soil Microorganisms M. Kamitakahara, S. Takahashi, T. Yokoi, C. Inoue and K. Ioku, "Preparation of spherical porous hydroxyapatite granules as support materials for microorganisms", JCS Japan., 2018, 126, (9), 732-735.
13) <Gram-positive>
・Staphylococcus epidermidis ATCC 14990
F. Boschetto, T. Adachi, S. Horiguchi, D. Fainozzi, F. Parmigiani, E. Marin, W. Zhu, B. McEntire, T. Yamamoto, N. Kanamura, O. Mazda, E. Ohgitani and G. Pezzotti, "Monitoring metabolic reactions in Staphylococcus epidermidis exposed to silicon nitride using in situ time-lapse Raman spectroscopy", J Biomed Opt.., 2018,(5), 1-10.
14) <Gram-negative>
・Campylobacter concisus ATCC 33237
・Fusobacterium nucleatum subsp. polymorphum JCM 12990
T. Nambu, D. Wang, C. Mashimo, H. Maruyama, K. Kashiwagi, K. Yoshikawa, K. Yamamoto and T. Okinaga, "Nitric Oxide Donor Modulates a Multispecies Oral Bacterial Community-An In Vitro Study", Microorganisms., 2019, 7, (9), 353.