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Objective@#To evaluate the in vitro activity of ceftazidime-avibactam (CAZ-AVI) alone or in combination with colistin (COL) against clinically isolated extensively drug-resistant Pseudomonas aeruginosa (XDR-PA).@*Methods@#Minimum inhibitory concentration (MIC) of 16 clinical XDR-PA isolates was determined by broth dilution method and chessboard design when CAZ-AVI and COL were used alone or in combination, then the combined inhibitory concentration index (FICI) was calculated. Class A [Klebsiella pneumoniae carbapenemase β-lactamase (blaKPC), Guiana extended-spectrum β-lactamase (blaGES)], Class B [imipenemase β-lactamase (blaIMP), Verona-Integronmetallo β-lactamase (blaVIM), New Delhi metallo β-lactamase (blaNDM), German imipenemase β-lactamase (blaGIM), Sao Paulo metallo -β- lactamase (blaSPM)], Class C [AmpC β-lactamase (blaAmpC)], Class D [oxacillinase β-lactamase (blaOXA)] β- lactamase-related resistance genes were detected by polymerase chain reaction. Drug-resistant mutation frequencies of each strain were determined on a drug-containing plate. The time kill curves of three XDR-PA were plotted by colony counting method. A biofilm model was established in vitro, and the synergistic effect of CAZ-AVI and COL on biofilm inhibition was detected by methythiazolyl tetrazolium assay (MTT).@*Results@#The MICs of 16 XDR-PA for CAZ-AVI ranged from 1 mg/L to 128 mg/L, and three of the isolates showed resistance (MIC > 8 mg/L). The FICI range of CAZ-AVI combined with COL was 0.312-1.000. Four isolates were synergistic, while the other 12 isolates were additive. Three isolates resistant to CAZ-AVI contained Class B resistance genes such as blaIMP and blaVIM, while 13 susceptible isolates carried resistance genes belonging to Class A, C or D. The logarithm values of mutation frequencies of drug resistance in CAZ-AVI group, COL group and combination group were -4.81±0.88, -7.06±0.69 and -9.70 (-9.78, -9.53), respectively. There were significant differences among the three groups (H = 33.601, P < 0.001), and between every two groups (adjusted P < 0.05). In time kill curves, the phytoplankton load of three XDR-PA decreased more than 6 log CFU/L when these two drugs were used together, and number of PA1819 planktonic bacteria decreased more than 5.1 log CFU/L compared with monotherapy group. Viable quantity in biofilm (A490) of normal saline group, CAZ-AVI group, COL group and CAZ-AVI-COL group were 0.665±0.068, 0.540±0.072, 0.494±0.642 and 0.317±0.080, respectively. There was significant difference between the other two groups (all P < 0.001), except for that between CAZ-AVI group and COL group (P = 0.109).@*Conclusions@#CAZ-AVI combined with COL can effectively improve the bactericidal effect of each drug alone on XDR-PA. The regimen can also reduce the production of drug-resistant bacteria and inhibit the formation of biofilm. Therefore, it is a potential treatment for XDR-PA infection.
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Objective To evaluate the in vitro activity of ceftazidime-avibactam (CAZ-AVI) alone or in combination with colistin (COL) against clinically isolated extensively drug-resistant Pseudomonas aeruginosa (XDR-PA). Methods Minimum inhibitory concentration (MIC) of 16 clinical XDR-PA isolates was determined by broth dilution method and chessboard design when CAZ-AVI and COL were used alone or in combination, then the combined inhibitory concentration index (FICI) was calculated. Class A [Klebsiella pneumoniae carbapenemase β-lactamase (blaKPC), Guiana extended-spectrum β-lactamase (blaGES)], Class B [imipenemase β-lactamase (blaIMP), Verona-Integronmetallo β-lactamase (blaVIM), New Delhi metallo β-lactamase (blaNDM), German imipenemase β-lactamase (blaGIM), Sao Paulo metallo -β- lactamase (blaSPM)], Class C [AmpC β-lactamase (blaAmpC)], Class D [oxacillinase β-lactamase (blaOXA)] β- lactamase-related resistance genes were detected by polymerase chain reaction. Drug-resistant mutation frequencies of each strain were determined on a drug-containing plate. The time kill curves of three XDR-PA were plotted by colony counting method. A biofilm model was established in vitro, and the synergistic effect of CAZ-AVI and COL on biofilm inhibition was detected by methythiazolyl tetrazolium assay (MTT). Results The MICs of 16 XDR-PA for CAZ-AVI ranged from 1 mg/L to 128 mg/L, and three of the isolates showed resistance (MIC > 8 mg/L). The FICI range of CAZ-AVI combined with COL was 0.312-1.000. Four isolates were synergistic, while the other 12 isolates were additive. Three isolates resistant to CAZ-AVI contained Class B resistance genes such as blaIMP and blaVIM, while 13 susceptible isolates carried resistance genes belonging to Class A, C or D. The logarithm values of mutation frequencies of drug resistance in CAZ-AVI group, COL group and combination group were -4.81±0.88, -7.06±0.69 and -9.70 (-9.78, -9.53), respectively. There were significant differences among the three groups (H = 33.601, P < 0.001), and between every two groups (adjusted P < 0.05). In time kill curves, the phytoplankton load of three XDR-PA decreased more than 6 log CFU/L when these two drugs were used together, and number of PA1819 planktonic bacteria decreased more than 5.1 log CFU/L compared with monotherapy group. Viable quantity in biofilm (A490) of normal saline group, CAZ-AVI group, COL group and CAZ-AVI-COL group were 0.665±0.068, 0.540±0.072, 0.494±0.642 and 0.317±0.080, respectively. There was significant difference between the other two groups (all P < 0.001), except for that between CAZ-AVI group and COL group (P = 0.109). Conclusions CAZ-AVI combined with COL can effectively improve the bactericidal effect of each drug alone on XDR-PA. The regimen can also reduce the production of drug-resistant bacteria and inhibit the formation of biofilm. Therefore, it is a potential treatment for XDR-PA infection.
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Objective To evaluate the in vitro activity of ceftazidime-avibactam (CAZ-AVI) alone or in combination with colistin (COL) against clinically isolated extensively drug-resistant Pseudomonas aeruginosa (XDR-PA). Methods Minimum inhibitory concentration (MIC) of 16 clinical XDR-PA isolates was determined by broth dilution method and chessboard design when CAZ-AVI and COL were used alone or in combination, then the combined inhibitory concentration index (FICI) was calculated. Class A [Klebsiella pneumoniae carbapenemase β-lactamase (blaKPC), Guiana extended-spectrum β-lactamase (blaGES)], Class B [imipenemase β-lactamase (blaIMP), Verona-Integronmetallo β-lactamase (blaVIM), New Delhi metallo β-lactamase (blaNDM), German imipenemase β-lactamase (blaGIM), Sao Paulo metallo -β- lactamase (blaSPM)], Class C [AmpC β-lactamase (blaAmpC)], Class D [oxacillinase β-lactamase (blaOXA)] β- lactamase-related resistance genes were detected by polymerase chain reaction. Drug-resistant mutation frequencies of each strain were determined on a drug-containing plate. The time kill curves of three XDR-PA were plotted by colony counting method. A biofilm model was established in vitro, and the synergistic effect of CAZ-AVI and COL on biofilm inhibition was detected by methythiazolyl tetrazolium assay (MTT). Results The MICs of 16 XDR-PA for CAZ-AVI ranged from 1 mg/L to 128 mg/L, and three of the isolates showed resistance (MIC > 8 mg/L). The FICI range of CAZ-AVI combined with COL was 0.312-1.000. Four isolates were synergistic, while the other 12 isolates were additive. Three isolates resistant to CAZ-AVI contained Class B resistance genes such as blaIMP and blaVIM, while 13 susceptible isolates carried resistance genes belonging to Class A, C or D. The logarithm values of mutation frequencies of drug resistance in CAZ-AVI group, COL group and combination group were -4.81±0.88, -7.06±0.69 and -9.70 (-9.78, -9.53), respectively. There were significant differences among the three groups (H = 33.601, P < 0.001), and between every two groups (adjusted P < 0.05). In time kill curves, the phytoplankton load of three XDR-PA decreased more than 6 log CFU/L when these two drugs were used together, and number of PA1819 planktonic bacteria decreased more than 5.1 log CFU/L compared with monotherapy group. Viable quantity in biofilm (A490) of normal saline group, CAZ-AVI group, COL group and CAZ-AVI-COL group were 0.665±0.068, 0.540±0.072, 0.494±0.642 and 0.317±0.080, respectively. There was significant difference between the other two groups (all P < 0.001), except for that between CAZ-AVI group and COL group (P = 0.109). Conclusions CAZ-AVI combined with COL can effectively improve the bactericidal effect of each drug alone on XDR-PA. The regimen can also reduce the production of drug-resistant bacteria and inhibit the formation of biofilm. Therefore, it is a potential treatment for XDR-PA infection.
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BACKGROUND: The aim of this study was to comparatively evaluate the bactericidal effects of copper, brass (copper 78%, tin 22%), and stainless steel against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VREFM), and multidrug-resistant Pseudomonas aeruginosa (MRPA). METHODS: The isolates (MRSA, VREFM, MRPA) used in this study were mixed wild type 3 strains isolated from patients treated at Uijeongbu St. Mary's Hospital in 2017. These strains showed patterns of multidrug resistance. The lyophilized strains were inoculated into and incubated for 24 hr in tryptic soy broth at 35℃. The initial bacterial inoculum concentration was adjusted to 105 CFU/mL. A 100-mL bacterial suspension was incubated in containers made of brass (copper 78%, tin 22%), copper (above 99% purity), and stainless steel at 35℃. Viable counts of bacteria strains were measured for 9 days. RESULTS: In this study, the bactericidal effects of copper and brass on MRSA, VREFM, and MRPA were verified. The bactericidal effect of stainless steel was much weaker than those of copper and brass. The bactericidal effect was stronger on MRPA than on MRSA or VREFM. CONCLUSION: To prevent cross infection of multidrug resistant bacteria in hospitals, further studies of longer duration are needed for testing of copper materials on objects such as door knobs, faucets, and bed rails.
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Humans , Bacteria , Copper , Cross Infection , Drug Resistance, Multiple , Enterococcus faecium , Methicillin-Resistant Staphylococcus aureus , Pseudomonas aeruginosa , Stainless Steel , TinABSTRACT
Polyphenon 60 refers to the mixture of catechins present in green tea. The aim of this study was to investigate the antimicrobial activities of polyphenon 60 against 4 strains of Streptococcus mutans and 2 strains of Streptococcus sorbrinus, which are the major causative bacteria of dental caries. The minimum bactericidal concentration (MBC) values of polyphenon 60 for S. mutans and S. sobrinus were determined and the effect of biofilm formation inhibition of that was evaluated. The MBC value of polyphenon 60 against the bacterial strains was 2.5 mg/ml except for one particular strain, S. mutans KCOM 1128 for which the value was 1.25 mg/ml. The results of biofilm formation inhibition assay revealed that polyphenon 60 inhibited biofilm formation more than 90% at a concentration of 2.5 mg/ml. It was apparent that polyphenon exhibited biofilm formation inhibition activity along with bactericidal effect against S. mutans and S. sobrinus. Therefore, it is proposed that polyphenon 60 as one of the components of bactericidal agents could be useful in developing oral hygiene products, toothpaste or gargling solution.
Subject(s)
Bacteria , Biofilms , Catechin , Dental Caries , Oral Hygiene , Streptococcus mutans , Streptococcus sobrinus , Streptococcus , Tea , ToothpastesABSTRACT
Enterococcus faecalis is a major causative agent of endodontic treatment failure. The purpose of this study was to investigate bactericidal effects of ethanol extract of Garcinia mangostana L. (mangosteen extract) on five strains of E. faecalis that were isolated from human oral cavities. The bactericidal effects of mangosteen extract were assessed by measurement of minimum bactericidal concentration (MBC) value. The cytotoxicity of mangosteen extract on immortalized human gingival fibroblasts, hTERT-hNOF, was determined based on cell counting method. The data revealed the MBC value of mangosteen extract against the E. faecalis strains was 4 µg/ml. Additionally, the cell viability of mangosteen extract on hTERT-hNOF was 83.7–89.1% at the 1 to 16 µg/ml. These findings indicated that mangosteen extract could be used as a root canal cleaner during management of endodontic treatment failure caused by E. faecalis.
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Humans , Cell Count , Cell Survival , Dental Pulp Cavity , Enterococcus faecalis , Enterococcus , Ethanol , Fibroblasts , Garcinia mangostana , Garcinia , Methods , Mouth , Treatment FailureABSTRACT
Objective To investigate the effects of azithromycin and clarithromycin on biofilm formation of Pseudomonas aeruginosa.Methods The minimal inhibitory concentrations (MIC) of azithromycin,clarithromycin,ceftazidime,ciprofloxacin and gentamicin against 4 strains of Pseudomonas aeruginosa (ATCC 27853,PA1,PA2 and PA3) were determined by broth microdilution method.The biofilm formation of Pseudomonas aeruginosa was identified by silver dyeing method on the biofilm model with medical microporous membranes in vitro.The effects of azithromycin and clarithromycin on the adhesion of biofilm were detected by crystal violet staining.The synergistic bactericidal effects of azithromycin and clarithromycin with ceftazidime,ciprofloxacin or gentamicin were detected by thiazolyl blue method respectively.Results The MIC values of Pseudomonas aeruginosa ATCC 27853,PA1,PA2 and PA3 for azithromycin,clarithromycin,cefiazidime,ciprofloxacin and gentamycin were 32,64,1,≤0.125 and 0.25 μg/mL;32,256,8,0.25 and 1 μg/mL;64,128,＞ 256,32 and 2 μg/mL and 64,128,8,2 and 0.25 μg/mL.The results of silver staining showed that the microfiltration membranes of all the four P.aeruginosa cultures appeared to be grayish black,thick and dense,and cotton-like.Compared with the control group in which no antibacterial drugs were added,both azithromycin and clarithromycin (1/16 or 1/4 MIC) reduced significantly the adhesion of the 4 strains of Pseudomonas aeruginosa (ATCC 27853,PA1,PA2 and PA3) on the microporous membrane (Pall ＜ 0.05).Compared with the use of 1 MIC of ceftazidime,ciprofloxacin or gentamycin alone,the combination of anyone of the four antimicrobial drug with azithromycin or clarithromycin (1/16 MIC) reduced the counts of viable bacteria on each biofilms with significant differences (P all ＜ 0.01).Conclusion Azithromycin and clarithromycin could effectively inhibit the biofilm formation of Pseudomonas aeruginosa and may present synergistic effects combined with cefiazidime,ciprofloxacin or gentamicin.
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Objective:To evaluate the cleaning ability of Er∶YAG laser against Enterococcus faecalis in root canals.Methods:The single-rooted human teeth were sterilized and inoculated with Enterococcusfaecalis and were randomly assigned into 2 groups.A group of teeth was irrigated with saline during root canal preparation while another group with NaClO.After mechanical preparation,the two groups were randomly divided into 3 subgroups according to the different treatments:Samples,laser radiation,and calcium hydroxide intracanal medication for 7 days.Bactericical effects were compared among groups.Root canal walls and dental tubules were observed under scanning electron microscope.Results:Er∶YAG laser was the most efficient way for anti-bacteria among the groups (P＜0.05),but there was no significant difference between the 2 laser groups (P＞0.05).Meanwhile the smear laser was efficiently removed by laser compared with other treatments,and the laser could open the dentinal tubules.Conclusion:Er∶YAG laser can be effectively used for root canal disinfection without NaClO and Ca(OH)2.
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Objective:To evaluate the antimicrobial effect of ozonated water on the putative periodontopathic bacteria.Methods:Pophyromonas gingivalis (P.g)ATCC33277,Haemophilus actinomycetemcomitans (H.a)ATCC29522,Fusobacterium nucleatum (F.n)ATCC1 0957 and clinically seperated strain of P.g(C -P.g)were treated by ozonated water with ozone concentration(mg/L) of 0.03,0.06 and 0.1 2 for 30,60,90 and 1 20 s respectively.The bactericidal effect was tested by bactericidal assay.H2 O2 was used as the positive control and distilled water as the negative control.Results:The antimicrobial rate of ozonated water agaist the bacteria increased with the ozone concentration increase.There was no statistic diffrence of the effect on P.g and C -P.g(P >0.05).Linear regression analysis showed that the βvalues of the concentration factor were over 0.95,that of the time factor under 0.1 1 .Conclu-sion:The ozonated water has dose-dependent bactericidal effect on P.g,H.a and F.n.
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Objective: To investigate the effect of fermentation time on antibacterial activity of Mirabilitum Praeparatum (MP) and screen the antibacterial active parts from MP with the optimal fermentation time. Methods: Using test tube in vitro antibacterial test and flat germicidal test, the pathogenic bacteria activities of MP with different fermentation time (7, 15, 22, 30, 50 d) were studied, and the optimal fermentation time was screened. The methanol extracts from MP with fermentation time of 15 d and its aqueous and 95% ethanol elution parts were prepared. The antibacterial and bactericidal effects of methanol extracts from MP and its aqueous and 95% ethanol elution parts were compared. Results: The 15 d fermentation MP had the strongest antibacterial activity. The 95% ethanol elution parts from MP had the strongest antibacterial activity on nine kinds of common pathogens, especially for the oral and upper respiratory tract pathogens. Conclusion: Fermentation time has obvious effect on antibacterial activity of MP, and 95% ethanol elution parts of macroporous adsorption resin from MP may be active parts.
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Background: Objective of current study is to determine whether near-IR, alone or combined with blue light and delivered at a low rate, could lower the dose needed to effectively inhibit Mycobacterium smegmatis in vitro. We have studied the effect of blue light on M. smegmatis and found that a bactericidal outcome can be obtained with high doses of blue light. Methods: The organism was treated in vitro with 464, 850 and combined 464 & 850nm light emitted from a supraluminous diode (SLD) array. Doses of 30, 45 and 60 J/cm2 were used. Colony counts were performed and compared to untreated controls using Student t tests, a two-way Repeated Measures ANOVA and a one-way ANOVA with Tukey post hoc analysis. Results: Statistically significant inhibition was observed for each individual wavelength and dose combination (p < 0.05). Two-way ANOVA demonstrated an interaction effect between wavelength and dose (F1, 9 = 358.585; p - 0.000). Post hoc analysis using one-way ANOVA (F2, 27 = 11.211; p = 0.00) and Tukey’s HSD identified 850nm at 45 J/cm2 to be the most effective wavelength / dose combination. Conclusions: 850nm irradiation delivered at 45 J/cm2 is a wavelength /dose combination that can be expected to produce a significant inhibition of M. smegmatis in vitro.
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BACKGROUND: Anti-inflammation, anti-bactericidal, and collagen synthesis are important for health skin conditions. However, the effect of horse oil on anti-inflammation, anti-bactericidal, and collagen synthesis is largely unknown. OBJECTIVE: The aim of this study was to evaluate the anti-bactericidal, anti-inflammatory, and synthesis of type I collagen of horse oil. METHODS: Anti-bacterial effect was evaluated by disc diffusion test. Expressions of inflammatory cytokines were studied by RT-PCR analysis, real time PCR. Type I collagen expression was evaluated by Western blot in human HaCaT kertinocytes and fibroblasts. RESULTS: Our data showed that horse oil exerted anti-bacterial effect on P.acnes and S.aureus. Expression of IL-10 was increased by horse oil-treated HaCaT cells. In addition, increased expression of type I collagen was observed in horse oil-treated human skin fibroblasts. CONCLUSION: Horse oil exerts an anti-bactericidal effect against P.acnes and S.aureus. In addition, anti-inflammatory and anti-aging effects of horse oil will be mediated by up-regulation of IL-10 and type I collagen, respectively.
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Humans , Blotting, Western , Collagen , Collagen Type I , Cytokines , Diffusion , Fibroblasts , Horses , Interleukin-10 , Keratinocytes , Real-Time Polymerase Chain Reaction , Skin , Up-RegulationABSTRACT
Objective To observe the destructive and scavenging effect of ambroxol (AMB) on the biofilm (BF) of Pseudomonas aeruginosa (P.a).To evaluate the synergistically bactericidal effect of AMB along with levofloxacin (LFX) on BF of P.a.Methods The early model (cultured for 3 d) and mature model (cultured for 7 d) of P.a wild strain (PAO1) BF were established,in vitro,respectively.The models were randomly (random number) divided into control group,AMB group and AMB + LFX group.The concentrations of AMB were 256 μg/ml and 512 μg/ml,respectively.When the early BF model and mature BF model were made,different concentrations of AMB were added in AMB group and AMB + LFX (1μg/ml) was added in AMB + LFX group.The number of viable P.a on the BF carrier was counted with the continuous dilution method 24 h after AMB or/and LFX added.Then,the BF morphological changes on the carrier surface were observed by using scanning electron microscopy (SEM).Measured data were analyzed with single factor analysis of variance (One-Way ANOVA).Results Both in the early BF model and in the mature BF model,the SEM examination showed that the BF in AMB group was significantly reduced compared to the control group,and this reduction of BF was in dose-dependent manner.LFX 1 μg/ml could reduce the number of viable bacterial in BF in both early model and mature model (P ＜ 0.05).LFX with addition of different concentrations of AMB showed stronger bactericidal effect than LFX used alone identified by more significant reduction in the number of colonv within the BF (P ＜ 0.05).Furthermore,the LFX combined with 512 μg/ml AMB reduced more significant number of colony apparently than the LFX combined with 256 μg/ml AMB (P ＜ 0.05).Conclusions AMB can destroy the early BF or mature BF partly,and LFX alone can partly reduce the number of viable P.a within BF.When LFX combined with AMB,they exert a synergistically bactericidal effect.
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The aim of this work was to investigate the disinfectant effect of electrolysis on chlorine-free water, artificially contaminated with Escherichia coli (CCT-1457) and to evaluate the bactericidal activity of electrolysis and kinetic behavior of a single-cell reactor, with a DSA (Dimensionally Stable Anode) electrode to develop a scaled-up system. A high-density E. coli suspension (10(6) CFU mL-1) was electrolyzed in this reactor at 25, 50 and 75 mA cm-2 for up to 60 min, at flow rates of 200 and 500 L h-1. Bacterial survival fell by 98.9 percent without addition of chlorinated compounds and a power consumption rate not more than 5.60 kWh m-3 at flow rate of 200 L h-1 and 75 mA cm-2. The process produced a germicidal effect that reached this inactivation rate within a relatively short contact time. Also, a solution of electrolyzed 0.08 M Na2SO4 added to the inoculum showed residual bactericidal effect. The efficiency of disinfection was regulated by both the contact time and current density applied, and a kinetic function for the survival rate was developed for the purpose of scaling up.
Água contaminada é uma das maiores origens de doenças em seres humanos. Em todo o mundo, a cloração é o método mais utilizado para promover desinfecção em águas de abastecimento devido ao seu efeito residual, quando adequadamente calculado. Contudo, se a água apresentar matéria orgânica, pode haver a geração de organoclorados, os quais são genotóxicos e carcinogênicos. Sob esta óptica, investigamos o efeito bactericida da aplicação da eletrólise em água sem cloro contaminada com Escherichia coli (CCT-1457). O objetivo deste estudo foi avaliar o poder de desinfecção e o comportamento cinético da eletrólise realizada em reator de compartimento único e usando eletrodos ADE (Anodo Dimensionalmente Estável), visando ampliação de escala. Uma suspensão contendo elevada concentração de E. coli (10(6) UFC mL-1) foi submetida ao tratamento no reator em 25, 50 e 75 mA cm-2 durante 60 min, em vazões de 200 e 50 Lh-1. A taxa de inativação foi aproximadamente 99 por cento para a solução isenta de compostos clorados, com consumo de energia elétrica menor que 5,60 kWh m-3 em 200 L h-1 e 75 mA cm-2. Uma solução de Na2SO4 0,08M eletrolisada e adicionada posteriormente ao inoculo apresentou efeito residual bactericida. A eficiência da desinfecção foi regida pelo tempo de contato e pela densidade de corrente aplicada, e foi realizado um estudo cinético que permite a ampliação de escala.
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1.The mean range was 2.54 on the hands.CONCLUSIONS These results show that Medilox has a quick and highly effective bactericidal action.
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BACKGROUND: Titanium dioxide (TiO2) thin film photocatalyst generates strong oxidizing power when illuminated with Ultra Violet (UV) light with wavelengths of less than 385 nm. In this study, we evaluated the bactericidal activity of it against Escherichia coli, Aspergillus fumigatus and Mycobacterium tuberculosis. METHODS: The TiO2 film were prepared from titanium isopropoxide solution and it was coated on either inner(test) or outer(control) side on Petri dish. annealing at 500 degrees C. The test and control suspension of E. coli, A. fumigatus and M. tuberculosis were grown in the chamber coated inner and outer side. respectively with UV light. For the blank, cell suspensions were grown in TiO2 coated Petri dishes without UV light. The bactericidal activities were estimated by survival ratio calculated from the number of viable cells which form the nutrient agar. RESULTS: In the test, the survival ratio for E. coli and M tuberculosis decreased to a negligible level (i.e., essentially complete sterilization) within 1hr and 2 hr, respectively. and that for 11. fumigatus decreased markedly to about 15% within 6 hr. In the control, the survival ratio for E. coli, A. fumigatus and M. tuberculosis decreased to 40% within 150 min. 6 he and 2 hr, respectively. In the blank, the survival ratio for E. coli and M tuberculosis decreased only about 67% within 150 min and 40% within 2hr. In A. fumigatus, TiO2 only caused little Sterilization within 4 hr. CONCLUSIONS: TiO2 photocatalysts under UV light clearly showed bactericidal activity against E. coli, A. fumigarus and M. tuberculosis. This feature render TiO2 photocatalysts to be applicable to eliminate microorganism from indoor air environment combined with ventilation.