• Archives of Pharmacal Research
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• v.21 no.3
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• pp.278-285
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• 1998

The microdilution assay recommended by NCCLS (National Committee for Clinical Laboratory Standards) is one of the standardized methods of antibiotic susceptibility test. This method has been widely used clinically to obtain MIC values of antibiotics on pathogenic microorganisms. It is more convenient, rapid and simple to test many samples than other test methods such as agar diffusion assay and broth macrodilution assay. The screening of antimicrobial agents from microbial extracts is too laborious in its process. Therefore, a number of screening methods having more simple procedure have been developed. In our laboratory, we applied microdilution assay for screening the antimicrobial agents. This assay showed dose-response results and was more sensitive than disc diffusion assay in our system. We tested 200 samples of microbial extracts originated from 100 microbial strains and selected several samples as potential candidates. In this report, we show that the microdilution assay is more convenient method in screeing of antibiotic susceptibility than those previously reported.

• International Journal of Oral Biology
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• v.36 no.4
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• pp.163-166
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• 2011

Oral viridans streptococci are recognized as one of the etiological agents of a variety of infectious diseases such as dental caries and infective endocarditis. Although antimicrobial susceptibility tests for these fastidious bacterial species are now established and standardized, a comparison between the broth microdilution and broth macrodilution tests has not previously been performed. This comparison was performed in the present study using the tests adopted by the Clinical and Laboratory Standards Institute (CLSI) and seven clinical isolates of oral viridans streptococcal strains. A modified broth macrodilution susceptibility test method was also included in this analysis, in which the media was not supplemented with horse blood. The susceptibility interpretation category agreements were measured at 83% (broth microdilution versus broth macrodilution) and 71% (broth microdilution versus modified broth macrodilution). The interpretation category agreement between the broth macrodilution and modified broth macrodilution tests was also 83%. These data indicate that the interpretation of antibiotic susceptibility test results for oral viridans streptococci are influenced by the methods used.

• Restorative Dentistry and Endodontics
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• v.19 no.2
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• pp.568-584
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• 1994

Bacteria have been regarded as major etiolgic factors in root canal infections. Infected root canal flora from thirteen patients who had visited to conservative department of Wonkwang dental hospital were cultured on blood agar plates. Cultued microorganisms were isolated and identified with Gram stain and biochemical tests using Vitek Systems(BioMeriux, MO, USA); Antibiotic susceptibillity was performed with disk diffusion and broth microdilution using Vitek Systems. Gram positive cocci(65 %) were predominant, which were composed of 6 Streptococcus viridans group, 5 Staph. spp., and 4 Enterococcus faecium, in the isolatd 23 strains. Gram negative rods (26 %) were the next common bacteria, which were composed of 5 non - fermentative Gram negative rods, and 1 Enterobacter cloacae. Most strains of S. viridans group and E. faecium were susceptible to antibiotics including penicillin. But strains of Staphylococcus spp. and non - fermentative Gram negative rods showed marked resistance to antibiotics except tetrancyclin and cefotaxime. Most results between disk diffusion and microdilution were all agreed, but the results of non - fermentative Gram negative rods were susceptible to cefotaxime in disk diffusion method but resistant in microdilution.

• Journal of Veterinary Clinics
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• v.18 no.1
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• pp.1-6
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• 2001

The aim of this study was to determine optimal therapeutic dose of antifungal agents for dermatophytes. Forty nine dermatophytes were isolated form dogs and cats showing skin lesions and were tested for their in vitro susceptibility to nystatin, griseofulvin, terbinafine, ketoconazole and fluconazole by broth microdilution test. Terbinafine showed the lowest MIC value among the antifungal agents tested, and MIC values ranged from 0.002 to 0.016 $\mu\textrm{g}$/ml. Fluconazole showed the highest MIC values among the antifungal agents tested, and MIC values ranged from 32 to 512 $\mu\textrm{g}$/ml. MIC values of nystatin, griseofulvin and ketoconazole ranged from 1.12 to 4.48 $\mu\textrm{g}$/ml, 0.5 to 4.0 $\mu\textrm{g}$/ml, and 1.6 to 12.8 $\mu\textrm{g}$/ml, resistant to griseofulvin, and that antifungal susceptibility test was needed to determine optimal therapeutic dose of antifungal agents for each dermatophyte.

• Biomedical Science Letters
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• v.22 no.4
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• pp.174-183
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• 2016

In the present study, a serum-based minimum inhibitory concentration (MIC) testing to caspofungin was optimized and evaluated to solve the limitations of the conventional Clinical and Laboratory Standards Institute (CLSI) guideline-based antifungal agent MIC test and the usefulness of this testing for clinical application was determined. A total of 105 Candida albicans clinical isolates were used for measuring MIC to caspofungin. Results showed that growth characteristics were different according to types of serum and the mouse serum was the most suitable for this assay. In order to measure the optimal concentration of mouse serum, 0 to 100% mouse serum were added to the media during fungal culture. The optimal concentration of serum was 50% when consideration of antifungal agent administration and inoculum size, serum components and ease of hyphae separated, and the consideration of the degree of growth. In comparison of the usefulness between the conventional Alamar-modified broth microdilution MIC assay and 50% mouse serum-based MIC testing, the range of $MIC_{80}$ of the Alamar-modified broth microdilution MIC assay was $0.13{\sim}2.0{\mu}g/mL$ (SD ${\pm}0.42{\mu}g/mL$) and that of the 50% mouse serum-based MIC assay was $2.0{\sim}32.0{\mu}g/mL$ (SD ${\pm}9.01{\mu}g/mL$). The range of $MIC_{50}$ of the Alamar-modified broth microdilution MIC assay was $0.13{\sim}2.0{\mu}g/mL$ (SD ${\pm}0.40{\mu}g/mL$) and that of the 50% mouse serum-based MIC assay was $1.0{\sim}16.0{\mu}g/mL$ (SD ${\pm}2.36{\mu}g/mL$). The MICs of 50% mouse serum-based MIC testing was increased by up to 4 to 64 times than Alamar-modified broth microdilution MIC assay. In conclusion, a 50% mouse serum-based MIC assay was more useful for measuring MIC in Candida albicans clinical isolates than conventional colorimetric broth microdilution MIC testing.

• Tuberculosis and Respiratory Diseases
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• v.64 no.6
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• pp.422-426
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• 2008

Background: Mycobacterium abscessus is the most pathogenic and drug-resistant rapid-growing mycobacterium. Clarithromycin or azithromycin are the only regular oral antimycobacterial agents that have an effect on M. abscessus. We tried to detect the clarithromycin-resistant strains from the clinical isolates of M. abscessus. Methods: We tried to isolate the clarithromycin-resistant strains from 220 clinical isolates of M. abscessus by performing using reverse hybridization assay (RHA) and the broth microdilution test (BMT). Results: Seven resistant strains (3.2%) from all the tested clinical isolates were detected by BMT. Three of these resistant strains were also detected by RHA and it was confirmed that they had point mutants. Conclusion: These results showed that clarithromycin resistance in M. abscessus clinical isolates is related to a point mutation and other unknown mechanisms.

• Korean Journal of Veterinary Research
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• v.41 no.2
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• pp.173-176
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• 2001

The present study was conducted to examine the drug susceptibility of 57 strains of Microsporum canis isolated from dogs with dermatitis in Taegu, 1999. Antifungal susceptibility test was performed by the microdilution method, using 7 antifungal drugs as follows: itraconazole(I), terbinafine(T), ketoconazole(K), griseofulvin(G), amphotericin B(A), flucytosine(5-Fc)(F), tolnaftate(To). All tester strains of M canis were highly susceptible to T, I, K and To(geometric mean $MICs{\leq}0.007{\sim}0.155{\mu}g/ml$), while those were lowly susceptible to G, A and F(geometric mean MICs $0.285{\sim}26.430{\mu}g/ml$).

• Journal of Radiation Industry
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• v.4 no.1
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• pp.39-45
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• 2010

The pollution of antibiotics is a major cause of spreading antibiotics resistant bacteria in the environment. Applications of ozonation, UV, and ${\gamma}-ray$ irradiations have been introduced to remove antibiotics in the effluents from wastewater treatment system. In this study, we compared the chemical (HPLC) and biological (antimicrobial susceptibility test, AMS) assays in measuring of the concentrations of residual antibiotics after ${\gamma}-ray$ and UV irradiation. Most samples were degraded by ${\gamma}-ray$ irradiation (1~2 kGy). However, lincomycin and tetracycline were not degraded by UV irradiation. The concentration of residual antibiotics, that was treated with ${\gamma}-ray$ and UV irradiation, measuring by bioassay was similar to HPLC. The concentrations of ${\gamma}-ray$ irradiated cephradine measured by AMS test were 2 times higher than that of HPLC assay, indicating AMS test is more sensitive than HPLC assay. These results indicate that ${\gamma}-ray$ irradiation technique is more useful than UV irradiation, and biological assay is more useful to detect the antibiotics and toxic intermediates in antibiotics degradation.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.04a
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• pp.162-162
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• 1996

새로 합성된 6-exomethylene penamsulfone derivatives 7종에 대해 In Vitro antibacterial activities를 Broth Microdilution법으로 Sulbactam-Na(SAM), Clavulanic acid-K(CLA)와 Cefotaxime-Na(CFT), Ampicillin Trihydrates(AMP), Amoxicillin-Na(AMX), Cefoperazone(CFZ)을 병용투여하여 $\beta$-lactamase 생성 균주(30 여종)에 실시, MIC를 구하였다. 균주에 따라 SAM, CLA에 비해 CH1145, CH1155 등이 우수한 효과를, CH1140, CH2150등이 유사한 효과를 보였다.

• Korean Journal of Veterinary Research
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• v.61 no.2
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• pp.16.1-16.6
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• 2021

Pseudomonas aeruginosa is one of the most common pathogenic species associated with canine otitis externa (OE). Their resilience is achieved by forming a biofilm, which allows these bacteria to evade even the harshest of treatments. This study evaluated the in vitro synergistic efficacy of N-acetylcysteine (NAC) with different antimicrobial agents against P. aeruginosa isolated from dogs with OE to develop an effective treatment against P. aeruginosa. The antimicrobial activity was evaluated by the minimum inhibitory concentration test using the microdilution method. The efficacy of antibiofilm formation was evaluated using a crystal violet stain method. The treatment solutions included NAC alone, and in synergy with enrofloxacin, polymyxin B, and gentamicin. NAC alone exhibited antimicrobial and antibiofilm abilities. On the other hand, the combination of NAC and the antibiotics did not show any significant synergistic effects against P. aeruginosa.