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Infectious Disease
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Susanna J. Dunachie, Hanif Esmail, Ruth Corrigan, Maria Dudareva
Bacteria are identified or speciated by using a series of physical characteristics (see Figure 3.8). Some of these are listed below. Gram reaction to staining with crystal violet: Gram-positive bacteria stain purple due to their thick layer of peptidoglycan in the cell wall retaining the dye, while Gram-negative bacteria stain red, because their thinner peptidoglycan wall does not retain the crystal violet dye during the decolouring process. Gram-positive and Gram-negative bacteria respond differently to antibiotics.Cell shape: Bacteria can be cocci, bacilli or spirals.Atmospheric preference: Organisms are aerobic, requiring oxygen, or anaerobic, requiring an atmosphere with very little or no oxygen. Organisms that grow in either atmosphere are known as facultative anaerobes.Requirement for special media or intracellular growth.
Therapeutic Approaches Targeting Endotoxin-Derived Mediators
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Jean-Daniel Baumgartner, Didier Heumann, Michel Pierre Glauser
Among pro-inflammatory cytokines, TNF stands as the most toxic molecule, and the pioneering work of Beutler and colleagues has opened a new avenue in the limited repertoire of therapies for septic shock, since this work was the first demonstration that anticytokine therapies might be a useful approach to treat the disease (2). Since this work, many attempts have been made to confirm the role played by TNF in animal models. Models have been parenteral injections of LPS or of gram-negative bacteria. In a few studies, gram-positive bacteria were also evaluated.
Understanding Microbiology Culture Results
Published in Firza Alexander Gronthoud, Practical Clinical Microbiology and Infectious Diseases, 2020
Microbes can be directly visualized in bodily fluids and tissue samples with microscopy. The Gram stain is used for detection of bacteria. Bacteria can be classified as Gram positive or Gram negative based on their ability to retain crystal violet after decolourization with alcohol. Gram-positive bacteria retain crystal violet in their cell wall and have a purple colour. In contrast, in Gram-negative bacteria, the alcohol has removed the crystal violet (a process called decolourization) and a counterstain is used to make them visible and pink coloured. Counterstains used are safranin and carbol fuchsin. Counterstains are weaker stains than crystal violet and Gram-positive bacteria remain purple coloured. Gram stain can also be used to visualize common fungi such as Candida species, which are Gram positive.
Development and characterization of lyophilized cefpodoxime proxetil-Pluronic® F127/polyvinylpyrrolidone K30 solid dispersions with improved dissolution and enhanced antibacterial activity
Published in Pharmaceutical Development and Technology, 2021
The antibacterial activity of the pure CEF and CEF loaded P127/PVP-SDs against S. aureus (Gram positive), E. coli (Gram negative), and K. pneumoniae (Gram negative) were investigated. The MIC values were obtained after 24-h incubation with CEF and CEF loaded P127/PVP-SDs were reported in Table 2. All microorganisms (S. aureus E. coli, and K. pneumoniae) were found to be susceptible for CEF loaded P127/PVP SDs. In case of S. aureus, E. coli, and K. pneumoniae, P127/PVP SDs showed less MIC values as compared to pure CEF. It was found that MIC values of the P127/PVP SDs were 2–8-fold lower than the pure CEF similar to the aqueous solubility test results. The differences in antimicrobial properties of CEF loaded P127/PVP SDs may be owing to the variation in membrane characteristic and wall structure of Gram-positive and Gram-negative bacteria. Gram-negative bacteria have a thin peptidoglycan segment by comparison with the Gram-positive bacteria. Owing to its lower peptidoglycan composition, CEF loaded P127/PVP SDs can easily destabilise and break down bacterial cell walls. Therefore, we observed a strong antibacterial action P127 and PVP-derived SDs against Gram-negative bacteria were noted in this study in the presence of CEF (Alves et al. 2018).
In vitro and ex vivo expression of serum amyloid A3 in mouse lung epithelia
Published in Experimental Lung Research, 2020
Haruka Kawasaki, Tomoaki Murakami, Yassien Badr, Sato Kamiya, Kaori Shimizu, Ayaka Okada, Yasuo Inoshima
SAA3 mRNA expression was stronger in cells treated with LPS than in those treated with LTA (Figures 1A and 1B). Our findings using Clara C22 cells are in high accordance with previous observations using alveolar type II epithelial cells.20 In both studies, LPS induced SAA3 mRNA expression by much lower dose than LTA, though different types of cultured pulmonary epithelial cells were used in each study, suggesting a general higher sensitivity of the respiratory epithelium to LPS than LTA stimulation. Gram-positive bacteria—such as Staphylococcus aureus, a common component of the skin flora,22 and Bacillus subtilis, an indigenous environmental species23—are often inhaled through the airways into the lungs.16 Furthermore, gram-positive bacteria cause bacterial community-acquired pneumonia more frequently than gram-negative bacteria,16,24 leading to frequent exposure of the lung to the gram-positive bacteria. Therefore, the pulmonary epithelium might respond more sensitively to gram-negative bacteria, to which they are less frequently exposed, than to gram-positive bacteria.
Gut microbiota profiles of autism spectrum disorder and attention deficit/hyperactivity disorder: A systematic literature review.
Published in Gut Microbes, 2020
Caspar Bundgaard-Nielsen, Julie Knudsen, Peter D. C. Leutscher, Marlene B. Lauritsen, Mette Nyegaard, Søren Hagstrøm, Suzette Sørensen
While sequencing enables highly sensitive determination of the microbiota composition, several factors in conjunction with handling of samples may influence data output.99,100 Among the studies included in this systematic review, several different storage techniques were utilized, ranging from lowered temperature to the use of storage buffers. While gut microbiota is robust, differences in storage can lead to growth or disruption of susceptible bacteria, and thus result in differences in bacterial composition between studies.99,101,102 Extraction of DNA from gram-positive bacteria is problematic, due to the presence of a thick cell wall, that can prevent effective bacterial lysis during DNA extraction.100,103 This can lead to underrepresentation of gram-positive bacteria in studies investigating gut microbiota.100 Only half the studies included in this systematic review took steps to increase DNA extraction from gram-positive bacteria. Despite this, we did not detect a clear pattern in differences in bacteria known to be difficult to extract, like the Streptococcus genera,103 and the impact is thus uncertain. Finally, most of the included studies investigated microbiota composition by sequencing the different hypervariable regions of the 16 S rRNA gene. However, primers targeting different regions have different affinities to specific bacteria, and thus may capture different bacteria in the same samples.100 This makes comparison of studies using primers targeting different regions problematic.