Inhibitory effects of nano silver and titanium dioxide on the nucleic acid of staphylococcus aureus / 中华急诊医学杂志

Objective To study the effects of nano silver (Ag) and titanium dioxide (TiO2) on the content of nucleic acid in staphylococcus aureus in order to explore their antibacterial mechanisms.Methods After preparation of beef extract peptone liquid cultures,the effects of minimal inhibitory concentrations (MICs) of nano Ag and TiO2 on staphylococcus aureus strains were determined.With the 1/2 MICs nano Ag and TiO2,the contents of DNA and RNA macromolecules from staphylococcus aureus cultures were measured to determine the damage degree of staphylococcus aureus cell membranes by ultraviolet spectrophotometer,and then the fluorescence intensities of the staphylococcus aureus cells were observed under fluorescence microscope and the fluorescence values were tested by fluorescence spectrophotometer to determine the contents of nucleic acid DNA and RNA.Results The MICs of nano Ag and TiO2 were 1.6 mg/mL and 5.781 μg/mL.After treatment with the 1/2 MICs nano Ag and TiO2,nano Ag group and TiO2 group were compared with the control group (culture fluid without adding antibacterial agent),respectively,and there were no significant differences in the contents of DNA and RNA macromolecules from staphylococcus aureus cultures between n anoAg group and control group as well as between TiO2 group and control group were (P＞0.05),and there were significant decreases in fluorescence intensities and the contents of nucleic acid DNA and RNA (P＜0.01).Conclusions Nano Ag and TiO2 had obvious antibacterial effects on staphylococcus aureus and the antibacterial properties of nano Ag was stronger than that of TiO2.The antibacterial mechanisms of nano Ag and TiO2 against staphylococcus aureus may be associated with the inhibition of the synthesis of nucleic acid DNA and RNA,inhibiting protein synthesis and then bacterial growth.

Bactericidal mechanism of electrolyzed oxidizing water against Pseudomonas aeruginosa / 中国感染控制杂志

Objective To investigate the bactericidal mechanism of electrolyzed oxidizing water (EOW) against Pseudomona aeruginosa (P.aeruginosa).Methods Bactericidal mechanism of EOW against P.aeruginosa was studied through intracellular protein leakage,nucleic acid,and cell membrane calcium ion permeability,2 ％ glutaraldehyde was used as positive control group,and normal saline (NS) was used as negative control group.Results The killing rates of EOW and 2％ glutaraldehyde to P.aeruginosa were both＞99.99％ with 30-second contact time,and 100.00％ with 60-second contact time.After 60-second contact with EOW,NS,and 2％ glutaraldehyde,the protein leakage of P.aeruginosa detected by bicinchoninic acid (BCA) were (96.00 ± 7.42),(94.15 ± 7.49),and (216.97 ± 10.35)μg/mL,respectively,difference was significant(F =613.20,P＜0.01),2％ glutaraldehyde group was higher than EOW group and NS group;protein leakage did not change with the increase of contact time(all P＞0.05).Electrophoretogram of random amplified polymorphic DNA showed high intensity dense band between 500-1000 Kb in EOW group and NS group,while 2％ glutaraldehyde group was without amplified bands.The fluorescence intensity of calcium ion of EOW group and 2％ glutaraldehyde group were both lower than that of NS group.Conclusion Bactericidal mechanism of EOW may be due to the damage of membrane permeability of P.aeruginosa,which causes Ca2+ leakage,but fails to cause protein leakage,the damage to nucleic acid is not obvious,DNA may not be a bactericidal target of EOW.

Effects of Leptospira interrogans infection on the activities of NADPH oxidase and the levels of ROS in THP-1 and J774A. 1 cells / 中华微生物学和免疫学杂志

Objective To investigate the effects of Leptospira interrogans ( L. interrogans) infec-tion on the activities of NADPH oxidase ( nicotinamide adenine dinucleotide phosphate-oxidase) and the lev-els of reactive oxygen species (ROS) in THP-1 and J774A. 1 cells and to understand the bactericidal mecha-nisms of macrophages in different hosts against L. interrogans. Methods Human mononuclear macrophage cell line (THP-1 cells) and murine mononuclear macrophage cell line (J774A. 1 cells) were infected with L. interrogans strain 56601. The activities of NADPH oxidase and the levels of superoxide ion ( O-2 ) were measured with spectrophotography. Changes in the levels of ROS were detected with immunofluorescence as-say. Results Compared with the normal cells, the activities of NADPH oxidase in L. interrogans-infected J774A. 1 cells changed from 0. 619 0 μmol · min-1 · mg-1 to 0. 305 5 μmol · min-1 · mg-1 , 6. 141 5μmol·min-1 ·mg-1 , 1. 487 1μmol·min-1 ·mg-1 and 0. 964 6μmol·min-1 ·mg-1 after 2, 4, 12 and 24 hours of infection, respectively (P<0. 05), while the activities of NADPH oxidase in L. interrogans-infected THP-1 cells were up-regulated from 0. 723 5μmol·min-1 ·mg-1 to 0. 884 2μmol·min-1 ·mg-1 , 1. 897 1μmol·min-1 ·mg-1 , 1. 125 4 μmol·min-1 ·mg-1 and 0. 562 7 μmol·min-1 ·mg-1 , respectively ( P<0. 05). The levels of O-2 in L. interrogans-infected J774A. 1 cells at the time points of 2 h, 4 h, 12 h and 24 h after infection increased from 0. 189 0μmol/L to 0. 236 3μmol/L, 0. 297 7μmol/L, 0. 324 0μmol/L and 0. 305 7 μmol/L, respectively (P<0. 05), while the levels of O-2 in L. interrogans-infected THP-1 cells rose from 0. 123 7 μmol/L to 0. 149 3 μmol/ L, 0. 249 0 μmol/ L, 0. 270 0 μmol/ L and 0. 272 7μmol/L, respectively (P<0. 05). The fluorescence intensity of ROS in THP-1 and J774A. 1 cells increased gradually after infection with L. interrogans for 2 h and decreased after reaching the peak at 24 h. Conclu-sion Both the activities of NADPH oxidase and the levels of O-2 in J774A. 1 and THP-1 cells were signifi-cantly upregulated after infected with L. interrogans, especially in J774A. 1 cells. The results of this study provided references for further elucidating the bactericidal mechanisms of macrophages in different hosts against L. interrogans.

Expression of iNOS and levels of NO in THP-1 and J774A. 1 cells during Leptospira interrogans infec-tion / 中华微生物学和免疫学杂志

Objective To investigate the expression of inducible nitric oxide synthase ( iNOS) and the levels of nitric oxide (NO) in THP-1 and J774A. 1 cells during Leptospira interrogans (L. interrogans) infection for a better understanding of the mechanism of macrophages involved defense against L. interrogans strains in different hosts. Methods The human mononuclear macrophages (THP-1) and the murine mono-nuclear macrophages (J774A. 1) were infected with L. interrogans strain 56601. The expression of iNOS at mRNA and protein levels were determined by using real-time RT-PCR and flow cytometry analysis. The lev-els of NO were detected with Griess test. Results The expression of iNOS at mRNA level in J774A. 1 and THP-1 cells infected with L. interrogans strains for 2, 4, 12 and 24 hours were respectively 1. 37, 2. 82, 25. 76, 27. 47 times and 1. 59, 3. 98, 3. 89, 8. 81 times than that of cells without infection (P<0. 05). The expression rates of iNOS protein in J774A. 1 cells were increased from 34. 16% to 85. 85%, 93. 82%, 91. 77% and 93. 65% along with the increased time of infection time (P<0. 05). The expression rates of iNOS protein in THP-1 cells were up-regulated from 22. 08% to 72. 64%, 81. 33%, 80. 03% and 65. 72%after 2, 4, 12 and 24 hours of infection (P<0. 05), respectively. Results of the Griess test indicated that the levels of NO in J774A. 1 and THP-1 cells were respectively increased from 0. 1588 μmol/L to 0. 2208μmol/L, 0. 2668μmol/L, 0. 3808μmol/L, 0. 3828μmol/L and from 0. 0988μmol/L to 0. 2848μmol/L,0. 3228 μmol/L, 0. 2608μmol/L and 0. 3308μmol/L after infection with L. interrogans strains for 2, 4, 12 and 24 hours (P<0. 05). Conclusion The expression of iNOS and the levels of NO in J774A. 1 and THP-1 cells were significantly increased during L. interrogans infection. This study might help to explain the bactericidal mechanism of macrophages derived from different hosts against L. interrogans infection.

A Basic Study for the Development of Effective Preventive Measure against Vibrio vulnificus Septicemia: Bactericidal Mechanism of Osmotic Shock

The establishment of effective preventive measure against V. vulnificus septicemia is urgently required. It was reported that V. vulnificus osmotically shocked by distilled water lost viability rapidly but regain viability after appropriate resuscitation (RS) procedure. But V. vulnificus was reported to be completely killed when osmotically shocked in the presence of ethylenediaminetetraacetic acid (EDTA). This study was carried out to uncover the bactericidal mechanism of osmotic shock and the mechanism of potentiation of osmotic shock by EDTA. When about 2.0 x 10(7) CFU/ml of V. vulnificus were inoculated in distilled water, the number of viable cells abruptly decreased to 2.5 x 10(3) CFU/ml in 1 min. and slowly thereafter to 1.0 x 10(1) CFU/ml in 5 min. After RS, there was a increase in the number of surviving bacteria by 10(3) to 10(4) fold. When the bacteria were inoculated in 1 mM EDTA solution, osmotic concentration of which is about 30 mEq./1, no colony could be observed even in 1 minute. The turbidity decreased abruptly as soon as the bacteria were inoculated in distilled water or in the 1 mM EDTA solution, but rather slowly thereafter. When V. vulnificus whose cellular constituents were labeled with 3H-L-amino acid mixture was inoculated in distilled water or in the 1 mM EDTA solution, about 35% of the whole cell radioactivity was released in the 1 mM EDTA solution in 30 sec while about 6% of the whole cell radioactivity was released to the supernatant in distilled water in 5 minutes. The cell surface hydrophilicity decreased significantly by osmotic shock. The decrease was more significant when the bacteria were inoculated in 1 mM EDTA solution than in distilled water. Bacterial cell volume analysis with a flow cytometer revealed that the osmotic shock balloons V. vulnificus. The increase in the cell volume was more prominent in 1 mM EDTA solution. When the cytoplasmic RNA content in the osmotically shocked bacteria was measured by a flow cytometer, the frequency of the cells with decreased RNA content increased after osmotic shock, and the degree of increase was more prominent in 1 mM EDTA solution. Number of non-staining cells also increased after osmotic shock, and the degree of increase was more prominent in the 1 mM EDTA solution. To see whether the susceptibility to osmotic shock is unique to V. vulnificus, bactericidal kinetic curves of other Vibrio species were observed after inoculating in distilled water. V. cholerae and V. mimicus were more resistant to the osmotic shock than V. vulnificus. V. parahaemolyticus, V. furnissii, V. fluvialis, V. damsela, and V. harveyi showed similar susceptibility to osmotic shock as V. vulnificus. V. alginolyticus and V. hollisae were more susceptible than V. vulnificus. The concentration of NaCl in culture media influenced the susceptibility of V. vulnificus to osmotic shock. V. vulnificus grown in 0.5% NaCl was more resistant to the osmotic shock than that grown in 2.5% NaCl. Taken together, it was concluded that osmotic shock causes leakage of the cytoplasmic contents(ribosomes etc.). And EDTA was supposed to quantitatively potentiate the bactericidal effect of the osmotic shock. Susceptibility to osmotic shock was influenced by the osmolarity of culture media and appeared to be a phenotypic property of V. vulnificus.

The bactericidal mechanism and effect of HVEF in the air cleaner / 医疗卫生装备

The configuration of the air cleaner and operating principle of high-voltage static electrical field (HVEF) are introduced. The primary bactericidal mechanism and broad-spectrum effect are also mentioned.