The aim of this study was to investigate the susceptibility of Mutans streptococci in both planktonic and biofilm states to erythrosine.S. mutans was cultured in brain-heart infusion (BHI) broth. Erythrosine was diluted in BHI broth and prepared at a concentration range of 0.02 – 10000 µg/L. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were measured using the microdilution method. After forming biofilms on 96-well plates, the minimum biofilm inhibitory concentration (MBIC) and minimum biofilm eradication concentration (MBEC) were measured.S. mutans was susceptible to erythrosine in both planktonic and biofilm states. MIC and MBC values were both 19.5 µg/L for the planktonic state, while MBIC and MBEC values were 313 µg/L and 2500 µg/L, respectively, for the biofilm state.Erythrosine (19.5 µg/L) exhibited a bactericidal effect on S. mutans (killing 99.9%) in the planktonic state. For biofilms, erythrosine inhibited biofilm growth and eradicated 99.9% of biofilm bacteria at higher concentrations than MIC and MBC. These MBIC and MBEC concentrations are much lower than known noxious doses, and the MIC, MBC, and MBIC values were even lower than clinical concentrations.
Bacteria ; Biofilms ; Erythrosine ; Methods ; Microbial Sensitivity Tests ; Plankton

Orientia tsutsugamushi causes scrub typhus, which is endemic in many countries in the Asia-Pacific region including Korea. Recent emergence of doxycycline-resistant strains from Thailand has underlined the importance of the susceptibility tests of O. tsutsugamushi to antibiotics. To improve the flow cytometric technique for the susceptibility test, we applied a monoclonal antibody (MAb) in the quantification of O. tsutsugamushi. With using MAb FS15, we determined the doxycycline susceptibility of two strains, Boryong and AFSC-4 strain which is reported to be doxycycline-sensitive and resistant, respectively. The growth of both strains was inhibited to below 10% of the control in the presence of 0.1 microgram/mL or higher concentrations of doxycycline. We suggest that our approach is more quantitative and reproducible than the conventional microscopic methods.
Orientia tsutsugamushi/*drug effects/growth & development ; Microbial Sensitivity Tests/*methods ; Flow Cytometry/*methods ; Antibodies, Monoclonal/*immunology

BACKGROUND: There is no guideline for the appropriate wavelength at which to measure the optical density (OD) value in broth microdilution antifungal susceptibility testing, although a spectrophotometric reading method is commonly used. The present study aimed to analyze the difference in the OD values over the range of visible light and to ascertain the optimal wavelength for the spectrophotometric method of microdilution testing. METHODS: We measured the OD of background blank controls of broth medium, antifungal agents, and inocula of five type strains using a Synergy HT multi-detection microplate reader at 5-nm intervals from 380 nm to 760 nm. We also estimated the OD differences between the 50% of growth control and blank control. RESULTS: The OD of the blank control showed a parabola shape with two peaks and steadily decreased at longer wavelengths. The curves of the antifungal agent were similar to those of blank controls, and the influence of each antifungal agent on the OD was minimal. For the difference in OD between 50% of growth control and the blank control, the curve was the opposite of the blank control, and the OD increased steadily at the wavelengths above 600 nm. CONCLUSIONS: The range between 600 nm and 700 nm was the optimal wavelength for broth microdilution antifungal susceptibility testing, although any wavelength within the visible light spectrum can be used.
Antifungal Agents/*chemistry ; Azoles/*chemistry ; Culture Media/*chemistry ; Flucytosine/*chemistry ; Microbial Sensitivity Tests ; Spectrophotometry/*methods

The present study was conducted to determine the antibiotic susceptibilities of local Mycoplasma hyopneumoniae (Mhp) and Mycoplasma hyorhinis (Mhr) filed isolates. Minimum inhibitory concentrations (MICs) of Mhp and Mhr field isolates (twelve each) obtained from enzootic pneumonia-like lung lesions during 2009-2011 from Korea were determined using the broth microdilution method. Tylvalosin showed the highest activity against Mhp and Mhr field isolates, with MIC90 values of 0.06 µg/mL and 0.12 µg/mL, respectively. Therefore, Korean Mhp and Mhr isolates are highly susceptible to tylvalosin.
In Vitro Techniques* ; Korea* ; Lung ; Methods ; Microbial Sensitivity Tests ; Mycoplasma hyopneumoniae* ; Mycoplasma hyorhinis* ; Mycoplasma*

BACKGROUND: There have been several reports which assessed the activity of antifungals including azoles on Malassezia furfur by agar dilution method. However, they did not differentiate M. furfur into groups. In addition, the media for growth and minimum inhibitory concentration (MIC) determination, incubation temperature and length of incubation differed from each other. OBJECTIVE: The aim of this study was to test the antifungal activities of miconazole, clotrimazole, ketoconazole and itraconazole by determining MICs for M. furfur serovars A, B and C for these drugs. METHODS: MICs were determined by the agar dilution method. Leeming & Notman's Malassezia furfur agar medium was used. RESULTS: In all strains of serovars A, B and C, the MICs for miconazole were similar to those for clotrimazole ; MICs for ketoconazole were also similar to those for itraconazole ; MICs for miconazole or clotrimazole were higher than those for ketoconazole or itraconazole. CONCLUSION: The results suggested that ketoconazole or itraconazole could be used more effectively than miconazole or clotrimazole for the treatment of the diseases caused by M. furfur.
Agar ; Azoles ; Clotrimazole ; Danazol* ; Itraconazole ; Ketoconazole ; Malassezia* ; Methods ; Miconazole ; Microbial Sensitivity Tests* ; Serogroup

Since the bacteria metabolites in the process of growth and reproduction of can lower the resistivity characteristics of the medium, the electrical impedance method can develop a rapid detection device of bacterial drug sensitivity. The device consists of micro-organisms impedance sensors, computer systems, signal generator, resistance Anti-detection circuit, the time allocation controller, constant temperature incubator and auxiliary circuits and other components. It measures the electrical impedance of the medium, and bacteria in the culture period to obtain the impedance value of the monitor into the impedance curve. Drug sensitivity of bacteria can be determined, using this form of differential impedance curve. This detection device significantly shortened the time of bacterial drug susceptibility testing, achieving rapid drug susceptibility testing of clinical medicine, drug susceptibility testing automation and intelligence.
Bacteria ; drug effects ; Electric Impedance ; Equipment Design ; Microbial Sensitivity Tests ; instrumentation ; methods

OBJECTIVETo performance susceptibility testing of antifungal agents. Due to the increasing number of resistant strains, susceptibility testing of antifungal agents is gaining importance.

METHODSWe compared the results of standard macrotube dilution reference method with two different microdilution methods, as well as the disc diffusion method in order to test the susceptibility of 150 Candida strains to fluconazole.

RESULTSOverall correlation between microdilution and macrodilution methods was 86%. It was 91% between the Minimal Inhibitory Concentrations obtained from macrodilution and disc diffusion zone diameters.

CONCLUSIONThe disc diffusion test was evaluated as a low-cost, reproducible, and efficient way of assessing the in vitro susceptibility of Candida strains to fluconazole.

Antifungal Agents ; pharmacology ; Candida ; drug effects ; Diffusion ; Fluconazole ; pharmacology ; Microbial Sensitivity Tests ; methods

BACKGROUNDDrug susceptibility assay is very important in tuberculosis therapy. Pyrazinamide is a first line antituberculosis drug and diagnosis of its resistance in Mycobacterium tuberculosis (M. tuberculosis) is difficult and time consuming by conventional methods. In this study, we aimed to evaluate the performance of the microscopic observation drug susceptibility (MODS) assay in the detection of pyrazinamide resistance in M. tuberculosis relative to the conventional Wayne assay and Lowenstein-Jensen (LJ) proportion method.

METHODSM. tuberculosis clinical isolates (n = 132) were tested by the MODS and the Wayne assay: the results were compared with those obtained by the LJ proportion method. Mutations in the gene were identified by direct sequencing of the pncA genes of all isolates in which pyrazinamide resistance was detected by any of the three methods.

RESULTSCompared to the LJ results, the sensitivity and specificity of the MODS assay were 97.8% and 96.5% respectively; the sensitivity and specificity of the Wayne assay were 87.0% and 97.7% respectively. Mutations in the pncA gene were found in 41 of 46 strains that were pyrazinamide resistant (3 tests), in 1 of the 4 strains (LJ only), in 42 of 48 strains (at least 1 test), but no mutations in 1 strain sensitive according to the MODS assay only. The MODS assay, Wayne assay and LJ proportion method provided results in a median time of 6, 7 and 26 days respectively.

CONCLUSIONSMODS assay offers a rapid, simple and reliable method for the detection of pyrazinamide resistance in M. tuberculosis and is an optimal alternative method in resource limited countries.

Antitubercular Agents ; pharmacology ; Microbial Sensitivity Tests ; Microscopy ; methods ; Mycobacterium tuberculosis ; drug effects ; Pyrazinamide ; pharmacology

OBJECTIVETo evaluate the effects of microscopic observation drug susceptibility (MODS) in detecting susceptibility of Mycobacterium tuberculosis (MTB) onto four first line anti-tuberculosis drugs.

METHODThe 24-hole cell culture plates were used to test drug susceptibility of MTB on liquid medium, and the best detecting condition of MODS assay was probed; 66 clinical isolates susceptibility to streptomycin (S), isoniazid (H), rifampin (R) and ethambutal (E) were evaluated by using MODS assay and Lowenstein-Jensen (L-J), thereafter, all the inconcordance of isolates between MODS and L-J were tested for the minimal inhibitory concentrations (MIC).

RESULTSConcordance rate of the susceptibility to S, H, R and E in 66 clinical isolates detected by MODS and L-J was 97.0%, 90.9%, 95.5% and 86.4% respectively. If the results obtained by L-J were taken as a golden standard, the sensitivity, specificity, positive and negative predictive value (PPV and NPV) as well as accuracy of susceptibility test to S detected by MODS was 96.0%, 97.6%, 96.0%, 97.6% and 97.0%; 100%, 85.4%, 81.0%, 100% and 90.9% to H; 96.2%, 95%, 92.6%, 97.4% and 95.5% to R; 73.7%, 91.5%, 77.8%, 89.6% and 86.4% to E. There were 20 inconsistent results of 16 isolates by comparing MODS with L-J, and MIC yielded 16 results of those 14 isolates showing identical results with those of the MODS, while 4 results of other 4 isolates identical with L-J.

CONCLUSIONMODS method simultaneously provides drug susceptibility to S, H, R and E. MODS might be one of the rapid tools to diagnosing multidrug-resistant tuberculosis as it is rapid, simple, inexpensive and has high concordance with L-J drug susceptibility test.

Bacteriological Techniques ; methods ; Drug Resistance, Multiple, Bacterial ; Microbial Sensitivity Tests ; methods ; Mycobacterium tuberculosis ; drug effects ; Predictive Value of Tests ; Sensitivity and Specificity ; Tuberculosis, Multidrug-Resistant ; microbiology

The feasibility of flow cytometric antifungal susceptibility testing has been studied using the fluorescent anionic membrane potential probe, bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC4(3)]. The in vitro antifungal susceptibility testing of amphotericin B was performed on 8 Candida isolates from clinical specimens and 2 ATCC strains by flow cytometry with the results compared to those of the National Committee of Clinical Laboratory Standards (NCCLS) M27-T, broth macrodilution method. The flow cytometric method is based on an increase of fluorescence given out by DiBAC4(3) in fungi when they are killed by antifungal agents. Minimum inhibitory concentration (MIC) of amphotericin B ranged from 0.25 to 1 microg/mL. All results agreed within +/-2 dilution between the flow cytometric method and the M27-T method. MIC with ATCC strains were within recommended ranges of M27-T. The new flow cytometric method revealed a clear and distinct reproducible test end point. A four hr of incubation was sufficient for the test. In conclusion, flow cytometry using DiBAC4(3) is a rapid and accurate in vitro antifungal susceptibility testing method.
Amphotericin B/pharmacology* ; Barbiturates ; Candida/drug effects* ; Flow Cytometry/methods* ; Fluorescent Dyes ; Human ; Isoxazoles ; Microbial Sensitivity Tests