The effect of mitomycin C on the pyocine typing patterns of hospital strains of Pseudomonas aeruginosa

1971 ◽  
Vol 17 (7) ◽  
pp. 829-835 ◽  
Author(s):  
G. S. Tripathy ◽  
P. Chadwick
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Mitomycin C ◽  
Incubation Period ◽  
Agar Plate ◽  
Time Required ◽  
Maximal Production ◽  
Typable Strain

With a view to shortening the time required for pyocine typing and reducing the proportion of untypable isolates, the effect of inducing strains of Pseudomonas aeruginosa by mitomycin C was studied. Detailed experiments with two strains showed that mitomycin C enhanced pyocine production by a typable strain and allowed formation of pyocine by an untypable strain. Maximal production of pyocine was achieved using mitomycin C in a concentration of 0.5 μg/ml.Three hundred and thirty-six isolates of P. aeruginosa which had been typed by Gillies and Govan's method were retyped after induction by mitomycin C. Induction and typing were performed on the same agar plate, and a 6-h incubation period at 32 °C was found sufficient for pyocine production. A similar number of typing patterns were found by both methods, but 154 isolates showed a different pattern after induction, and 23 of 38 previously untypable strains became typable. The typing patterns observed after induction were reproducible, and at least as stable epidemiologically as those obtained without induction.

scholarly journals Design of Vaccine Trials during Outbreaks with and without a Delayed Vaccination Comparator

2016 ◽  
Author(s):  
Natalie E. Dean ◽  
M. Elizabeth Halloran ◽  
Ira M. Longini
Keyword(s):  
Immune Response ◽  
Incubation Period ◽  
Vaccine Efficacy ◽  
Emerging Pathogens ◽  
Illness Onset ◽  
Efficacy Trials ◽  
Randomized Design ◽  
Time Of Infection ◽  
Cluster Randomized ◽  
Time Required

AbstractConducting vaccine efficacy trials during outbreaks of emerging pathogens poses particular challenges. The ‘Ebola ça suffit’ trial in Guinea used a novel ring vaccination cluster randomized design to target populations at highest risk of infection. Another key feature of the trial was the use of a delayed vaccination arm as a comparator, in which clusters were randomized to immediate vaccination or vaccination 21 days later. This approach, chosen to improve ethical acceptability of the trial, complicates the statistical analysis as participants in the comparison arm are eventually protected by vaccine. Furthermore, for infectious diseases, we observe time of illness onset and not time of infection, and we may not know the time required for the vaccinee to develop a protective immune response. As a result, including events observed shortly after vaccination may bias the per protocol estimate of vaccine efficacy. We provide a framework for approximating the bias and power of any given per protocol analysis period as functions of the background infection hazard rate, disease incubation period, and vaccine immune response. We use this framework to provide recommendations for designing standard vaccine efficacy trials and trials with a delayed vaccination comparator. Briefly, narrower analysis periods within the correct window can minimize or eliminate bias but may suffer from reduced power. Designs should be reasonably robust to misspecification of the incubation period and time to develop a vaccine immune response.

scholarly journals EVALUATION OF THE EFFICACY OF A HYDROGEN PEROXIDE DISINFECTANT

2018 ◽  
Vol 10 (10) ◽  
pp. 104
Author(s):  
Luz Karime Medina-cÓrdoba ◽  
Ligia Lucia Valencia-mosquera ◽  
Gretty Paola Tarazona-diaz ◽  
Janeth Del Carmen Arias-palacios
Keyword(s):  
Hydrogen Peroxide ◽  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Bacillus Subtilis ◽  
Microbial Population ◽  
Agar Plate ◽  
Minimum Level ◽  
Salmonella Choleraesuis ◽  
Bacillus Subtilis Atcc ◽  
High Level

Objective: To evaluate the efficacy of a disinfectant based on hydrogen peroxide.Methods: The method used to assess the efficacy of the disinfectant was the agar plate technique. With this procedure, it was possible to determine the percentage of inhibition of the high-level disinfectant of STERIS against four microorganisms, i.e., Pseudomonas aeruginosa ATCC 9027, Staphylococcus aureus (Beta-Hemolytic 227), Salmonella choleraesuis (Kuznedorf CMDM 074), and Bacillus subtilis (ATCC 6633). The effectiveness of five disinfectant concentrations (0.02%, 0.04%, 0.08%, 1%, and 2%) was determined and evaluated in three different times 5, 10, and 15 min, for vegetative strains and 3, 6, and 9 h for the sporulated strain.Results: According to the experimental test, the reduction of the microbial population was, on average, 100% for the disinfectant concentrations of 0.08%, 1%, and 2%.Conclusion: The results obtained demonstrated that the high-level disinfectant of STERIS based on hydrogen peroxide is 100% effective when the concentration recommended by the commercial house (2%) is used in the shortest time exposure to disinfectant. The minimum level of effectiveness was 0.08%; however, if lower concentrations are used, destruction of the microorganisms is not guaranteed.

scholarly journals PtrB of Pseudomonas aeruginosa Suppresses the Type III Secretion System under the Stress of DNA Damage

2005 ◽  
Vol 187 (17) ◽  
pp. 6058-6068 ◽  
Author(s):  
Weihui Wu ◽  
Shouguang Jin
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Dna Damage ◽  
Mitomycin C ◽  
Type Iii Secretion ◽  
Double Mutant ◽  
Type Iii Secretion System ◽  
Sos Response ◽  
Secretion System ◽  
Wild Type ◽  
Type Iii

ABSTRACT In a search for regulatory genes of the type III secretion system (TTSS) in Pseudomonas aeruginosa, transposon (Tn5) insertional mutants of the prtR gene were found defective in the TTSS. PrtR is an inhibitor of prtN, which encodes a transcriptional activator for pyocin synthesis genes. In P. aeruginosa, pyocin synthesis is activated when PrtR is degraded during the SOS response. Treatment of a wild-type P. aeruginosa strain with mitomycin C, a DNA-damaging agent, resulted in the inhibition of TTSS activation. A prtR/prtN double mutant had the same TTSS defect as the prtR mutant, and complementation by a prtR gene but not by a prtN gene restored the TTSS function. Also, overexpression of the prtN gene in wild-type PAK had no effect on the TTSS; thus, PrtN is not involved in the repression of the TTSS. To identify the PrtR-regulated TTSS repressor, another round of Tn mutagenesis was carried out in the background of a prtR/prtN double mutant. Insertion in a small gene, designated ptrB, restored the normal TTSS activity. Expression of ptrB is specifically repressed by PrtR, and mitomycin C-mediated suppression of the TTSS is also abolished in a ptrB mutant strain. Therefore, PtrB is a new TTSS repressor that coordinates TTSS repression and pyocin synthesis under the stress of DNA damage.

scholarly journals INDUCTION OF RHAMNOLIPID PRODUCTION BY PSEUDOMONAS AERUGINOSA A3 USING CHEMICAL AND PHYSICAL MUTAGENIC FACTORS

2019 ◽  
Vol 50 (4) ◽  
Author(s):  
Faqri & et al.
Keyword(s):  
Surface Tension ◽  
Pseudomonas Aeruginosa ◽  
Agar Plate ◽  
Optimum Conditions ◽  
Emulsification Index ◽  
Characterization Study ◽  
Optimum Ph ◽  
Tlc Analysis ◽  
Physical And Chemical ◽  
Layer Chromatography

This study was depend to select Pseudomonas aeruginosa A3 as a good producer of rhamnolipid (RL) biosurfactant after screening on agar plate where it was able to biosynthesize 4.3 g/L with emulsification index 52% and reducing the surface tension of water to 33.2 mN/m. Therefore, this study was aimed to increase the production of biosurfactant from selected isolate by exposure to several physical and chemical mutagenic factors like gamma radiation, nitrosoguanidine, ethyl methane sulfonate and lithium chloride. The results were shown that 0.2 g/L of nitrosoguanidine was the best mutant for increasing the production to about 2 folds (9.4 g/L) after 15 mins exposure to this material, as well as the emulsification index and surface tension of water were reached to 62% and 26.1 mN/m, respectively, comparing with non-mutant isolate. Also, the critical micelle concentration (CMC) and critical micelle dilution (CMD) of produced rhamnolipid were reached to 120 mg/L and 100 fold, respectively. The optimum conditions of RL production from mutant isolate were determined as 34ºC a best temperature, 6.5 optimum pH and incubation period of 108 h where the production was reached to 10.6 g/L and emulsification index 64% with surface tension of water 26 mN/m. characterization study of purified RL by using thin layer chromatography (TLC) analysis indicated that it was composed of a mixture of mono and di-rhamnolipid.  

scholarly journals A Comparative Evaluation and Utilization of Entrapped Bacillus sp. (Gen Bank MN 243657) and Pseudomonas aeruginosa SU-1 in Poultry Waste Degradation

2020 ◽  
Vol 2 (1) ◽  
pp. 72
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Incubation Period ◽  
Comparative Evaluation ◽  
Waste Treatment ◽  
Poultry Waste ◽  
Bacillus Sp ◽  
Waste Degradation ◽  
64 Kda Protein ◽  
Better Than

Bacillus sp. (Genbank MN243657) was obtained from the Center for Bioscience and Nanoscience Research, and P. aeruginosa SU-1 were used in this study. Initially, biomass was optimized for the incubation period, pH, and temperature, following biomass optimization with RSM. The obtained organisms were able to produce keratinase, which was found to be a 64 KDa protein and 56KDa. Now the biomass produced using the optimized condition was immobilized and checked for its ability to degrade keratinase, and efficiency was compared. Immobilized P. aeruginosa SU-1 was degrading keratin and feather better than Bacillus sp. (Genbank MN243657). It was found to reduce featherweight by 57.3% and 41%. Hence it was found that both the immobilized bacterium can be used for poultry waste treatment, and P. aeruginosa SU-1 was more efficient than Bacillus sp. (Genbank MN243657).

scholarly journals Sterilization of single-use helical stone baskets: an experimental study

2011 ◽  
Vol 9 (1) ◽  
pp. 66-69
Author(s):  
Fernando Korkes ◽  
Alex Menezes ◽  
Cely Barreto da Silva ◽  
Roni de Carvalho Fernandes ◽  
Marjo Deninson Cardenuto Perez
Keyword(s):  
Incubation Period ◽  
Safety Information ◽  
Agar Plate ◽  
Oxide System ◽  
Blood Agar Plate ◽  
E Coli ◽  
Mueller Hinton ◽  
Single Use ◽  
Sterilization Process ◽  
Functional Problems

ABSTRACT Objectives: To experimentally evaluate the efficacy of a standard sterilization protocol employed during reuse of disposable helical stone baskets. Methods: Study performed on 20 helical stone baskets: 10 were used in the initial validation process, contaminated with Escherichia coli ATCC 25922 and imprinted on Müeller-Hinton media; 10 catheters were contaminated with Geobacillus stearothermophilus ATCC 7953, processed, inoculated in TSB and incubated in a water bath at a temperature of 55°C. Bacterial growth was evaluated after 1, 3, 5 and 7 days. After sterilization, stone baskets were also opened and closed 40 times to check for functional problems. All plastic and basket parts were carefully checked for damages. Results: After the 72-hour incubation period, there was growth of E. coli ATCC 25922 in 100% of imprints. After the sterilization process and up to 7 days incubation period on a blood agar plate, there was no growth of G. stearothermophilus ATCC 7953 or any other bacteria. There were no functional problems or damage to baskets after the sterilization process. Conclusion: The ethylene oxide system is efficacious and safe for sterilization of disposable helical stone baskets. However, further clinical studies are required and should provide more safety information.

Hygroscopic Characteristics of Peanut Components and Their Influence on Growth and Aflatoxin Production by Aspergillus parasiticus

1984 ◽  
Vol 47 (10) ◽  
pp. 791-794 ◽  
Author(s):  
R. Y.-Y. CHIOU ◽  
P. E. KOEHLER ◽  
L. R. BEUCHAT
Keyword(s):  
Relative Humidity ◽  
Incubation Period ◽  
Aspergillus Parasiticus ◽  
Aflatoxin Production ◽  
Visible Growth ◽  
Atmospheric Relative Humidity ◽  
Time Required

Sound inshell runner-type peanuts, manually damaged inshell peanuts, shells, sound kernels, deskinned kernels and skins were stored in separate flasks under an atmospheric relative humidity of 100% at 28°C. After 5 d, water was adsorbed at levels of 1.2, 1.7, 3.9, 0.9, 1.0 and 9.5 g/100 g dry material, respectively. Surface disinfected components were inoculated with conidiospores of Aspergillus parasiticus NRRL 2999 and incubated under the same conditions. The time required for visible growth of the fungus was 8, 6, 4, 12, 10 and 3 d, respectively. The time for appearance of the conidiospores was 14, 10, 6, 16, 13 and 6 d. After a 3-wk incubation period, aflatoxin levels in peanut components were 111.4, 159.1, 4.4, 58.7, 99.0 and 1.5 μg/g, respectively.

scholarly journals 2,3-Dihydroxybenzoic Acid-Containing Nanofiber Wound Dressings Inhibit Biofilm Formation by Pseudomonas aeruginosa

2014 ◽  
Vol 58 (4) ◽  
pp. 2098-2104 ◽  
Author(s):  
Jayesh J. Ahire ◽  
Leon M. T. Dicks
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Iron Chelator ◽  
Wound Dressings ◽  
Tissue Destruction ◽  
Dihydroxybenzoic Acid ◽  
Chronic Infections ◽  
Content Type ◽  
Cell Numbers ◽  
Time Required

ABSTRACTPseudomonas aeruginosaforms biofilms in wounds, which often leads to chronic infections that are difficult to treat with antibiotics. Free iron enhances biofilm formation, delays wound healing, and may even be responsible for persistent inflammation, increased connective tissue destruction, and lipid peroxidation. Exposure ofP. aeruginosaXen 5 to the iron chelator 2,3-dihydroxybenzoic acid (DHBA), electrospun into a nanofiber blend of poly(d,l-lactide) (PDLLA) and poly(ethylene oxide) (PEO), referred to as DF, for 8 h decreased biofilm formation by approximately 75%. This was shown by a drastic decline in cell numbers, from 7.1 log10CFU/ml to 4.8 log10CFU/ml when biofilms were exposed to DF in the presence of 2.0 mM FeCl36H2O. A similar decline in cell numbers was recorded in the presence of 3.0 mM FeCl36H2O and DF. The cells were more mobile in the presence of DHBA, supporting the observation of less biofilm formation at lower iron concentrations. DHBA at MIC levels (1.5 mg/ml) inhibited the growth of strain Xen 5 for at least 24 h. Our findings indicate that DHBA electrospun into nanofibers inhibits cell growth for at least 4 h, which is equivalent to the time required for all DHBA to diffuse from DF. This is the first indication that DF can be developed into a wound dressing to treat topical infections caused byP. aeruginosa.

THE EFFECT OF THE INCUBATION TIME AND TEMPERATURE ON THE DETERMINATION OF PSYCHROPHILIC BACTERIA IN MILK BY THE AGAR PLATE METHOD1*

1954 ◽  
Vol 17 (12) ◽  
pp. 365-368 ◽  
Author(s):  
J. C. Boyd ◽  
C. K. Smith ◽  
G. M. Trout
Keyword(s):  
Incubation Period ◽  
Incubation Time ◽  
Incubation Temperature ◽  
Agar Plate ◽  
Psychrophilic Bacteria ◽  
Bacterial Counts ◽  
Milk Samples ◽  
Incubation Temperatures

A study has been made of the effect of incubation time and temperature on the determination of psychrophilic bacteria in milk. The incubation of agar plates at 10° C resulted in the detection of a group of thermoduric organisms which was not found when agar plates were incubated at 5° C. These organisms are not considered to be true psychrophiles. Bacterial counts on milk obtained using the 5° C and 10° C incubation temperatures did not coincide regardless of the incubation period. The counts obtained using the 10° C incubation temperature were always higher than those obtained at 5° C for a similar period. Maximum bacterial counts on milk samples stored at 5° C for 10 days or less were not obtained in less than 20 days when the agar plates were incubated at 5° C.

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