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Dealing with the invisible
Published in Brendan Curran, A Terrible Beauty is Born, 2020
Bacteria are ubiquitous, microscopically small, single-celled organisms, far too small to be seen without a microscope. Simple in structure, they reproduce by dividing in two to generate two identical cells. Some can divide every 20 minutes or so and thus, if sufficient nutrients are available (the record is about 9 minutes), can produce many billions of progeny overnight. If a number of bacteria are spread onto the surface of a nutrient jelly providing every food component they need to grow, each tiny bacterial cell will divide and divide to produce in a few hours a jumbled heap of cells in a colony which can be seen with the naked eye. The glass or plastic vessels used to grow bacteria are called Petri dishes after their inventor; microbiologists usually refer to them as ‘plates’, so spreading bacteria onto nutrient jelly is known as ‘plating’.
Aeroallergen sampling
Published in Richard F. Lockey, Dennis K. Ledford, Allergens and Allergen Immunotherapy, 2020
Estelle Levetin, Josh D. McLoud
After sampling Petri dishes are incubated, the colonies are counted and identified by microscopic examination. Concentrations are calculated and expressed as colony-forming units per cubic meter of air. When sieve impactors are used, more than one viable spore may pass through a single opening on the sieve plate, and these would likely be inaccurately counted as a single colony [25,27]. A positive-hole correction factor is used to adjust for multiple impactions.
Antimicrobial Properties of Traditional Medicinal Plants: Status and Potential
Published in Megh R. Goyal, Durgesh Nandini Chauhan, Plant- and Marine-Based Phytochemicals for Human Health, 2018
V. Duraipandiyan, T. William Raja, Naif Abdullah Al-Dhabi, Ignacimuthu Savarimuthu
The cross-streak method is helpful when rapidly screening microorganisms. A single streak of the microbial strain is placed in the middle of the agar plate and applied vertically to the petri dish. Inhibition zones are observed after the incubation period. Analysis includes evaluating the size of the inhibition zone.
Phytochemical composition, cytotoxicity, antioxidant and antimicrobial responses of Lavandula dentata L. grown under different levels of heavy metals stress condition
Published in Drug and Chemical Toxicology, 2023
Souhila Terfi, Zineb Djerrad, Soumeya Krimat, Fatma Sadi
The antibacterial activity was carried out by using the disk diffusion method according to the National Committee for Clinical Laboratory Standards (NCCLS/CLSI 2004), with slight modification. The active cultures were diluted with physiological water to achieve optical densities corresponding to 0.5 McFarland. The mediums (MHA for bacterial strains and SDA for fungal strains), sterilized in a flask, were poured into sterile Petri dishes (100 µL per 90 mmΦ), and then the tested microorganisms (100 μL of microbial suspension) were spread in these mediums using a sterile cotton swab. Subsequently, the filter paper disks (5.5 mmΦ) were individually impregnated with 10 μL of leaf ethanolic extract (50 µg/mL) and then placed onto the agar Petri dishes. After keeping these Petri dishes for 1 h at 4 °C, they were incubated at 37 °C during 24 h for bacterial strains and 48 h at 30 °C for fungal strains. Ethanol was used as negative control. Antibacterial activity was evaluated by measuring, in millimeters, the diameter of the inhibition zones. All the tests were performed in triplicate.
Endophthalmitis following Intravitreal Anti-Vascular Endothelial Growth Factor Therapy: Changes in Incidence and Outcomes over a 9-Year Period
Published in Current Eye Research, 2021
Maitri Pancholy, Philip P. Storey, Hannah J. Levin, Anthony Obeid, Samir N. Patel, Brandon Kuley, Jason Hsu, Marc J. Spirn, Mitchell Fineman, Michael A. Klufas, Omesh Gupta, Allen C. Ho, Sunir J. Garg
Endophthalmitis caused by oral-associated flora comprises a substantial subset of post-injection endophthalmitis cases, which may have a more guarded prognosis. One study analyzed the microbial spectrum of endophthalmitis after pars plana vitrectomy (PPV) and in-office IVI and found a significantly higher incidence of oral flora-associated endophthalmitis after IVI compared to PPV (9/16 cases vs. 0/8 cases, respectively; p = .01).32 Oral flora, including viridans group streptococci and Enterococcus species, tend to cause worse visual decline after infection compared to other organisms. A separate study found that endophthalmitis caused by viridans group streptococci resulted in VA of hand motion or poorer in all cases, compared to only about 10% of cases caused by coagulase-negative staphylococci.33 A previous study analyzing bacterial colonization of petri dishes found less contamination with no talking or face mask compared to no limitations on talking or lack of facemask use.34
Effect of particle morphology on performance of an electrostatic air–liquid interface cell exposure system for nanotoxicology studies
Published in Nanotoxicology, 2021
Ta-Chih Hsiao, Hsiao-Chi Chuang, Jing-Chi Lin, Tsun-Jen Cheng, Li-Ti Chou
The ESP-ALI exposure system used in this study comprised two cylinders of insulating materials. To avoid turbulent flow, the inside configuration of the upper cylinder was gradually expanded. A porous metal mesh was placed at the bottom of the upper cylinder; it dispersed the aerosol flow homogeneously and acted as the upper electrode for creating the electric field. A circular metal plate was placed atop the lower cylinder; it acted as the lower electrode (Figure 2). When operating the ESP-ALI, a negative DC voltage was applied to the collecting metal plate through a high-voltage power supply (BERTAN, series 230), and the porous metal mesh was grounded. A petri dish without culture medium was seated on the collecting metal plate. The ranges of applied voltage were set at 0-0.25 and 0-1.5 kV for ultrafine particles (NPs) and fine particles, respectively, and the uniform electric field was created between the porous metal mesh and collecting metal plate. The operational flow rate of 0.3, 0.6, and 1.5 lpm were tested. The experimental time was about 35 min and the range of particle concentration was from 104 to 109 particles/cm3 depending on operating conditions. Moreover, the variations of particle concentrations were less than 5% in the triple repeat measurements.