BACTERIAL LIPIDS AND THE GRAM STAINING REACTION

1964 ◽  
Vol 42 (8) ◽  
pp. 1141-1151 ◽  
Author(s):  
A. K. Bergh ◽  
S. J. Webb ◽  
C. S. McArthur
Keyword(s):  
Staphylococcus Epidermidis ◽  
Staining Reaction ◽  
Bacterial Cells ◽  
Polar Solvents ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Staining ◽  
A Cell ◽  
Gram Negative Organisms ◽  
High Polarity

In this study, no correlation was found between the Gram staining reaction of bacterial cells and the kinds of fatty acids in the lipids. The polar solvent (usually alcohol) used to wash out the stain from Gram-negative organisms removes much more lipid from these than from Gram-positive forms. The extractability of lipids from cells of Staphylococcus epidermidis increased when they became Gram-negative through aging. The infrared spectrum of the lipids extracted from these Gram-negative Staphylococci remained the same as that of the Gram-positive cells. It was further noted that high polarity characteristics and mutual miscibility in aqueous and lipid solvents are requirements of the decolorizing solvent.The Gram staining reaction of a cell appears to be related to the manner in which some of its lipids are bound to other components of the cell and the ease or difficulty with which the lipids are separated from lipoprotein and other complexes by certain polar solvents.

COMPARATIVE STUDIES ON THE GROWTH OF MYXOBACTERIA ON BACTERIAL SUSPENSIONS

1963 ◽  
Vol 9 (4) ◽  
pp. 577-584 ◽  
Author(s):  
B. Kletter ◽  
Y. Henis
Keyword(s):  
Growth Medium ◽  
Test Organism ◽  
Growth Media ◽  
Multiplication Rate ◽  
Bacterial Cells ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Negative Organisms ◽  
Myxococcus Virescens ◽  
Number Of Bacteria

The growth of Myxococcus fulvus and Myxococcus virescens on a number of bacteria was followed in a liquid medium. Multiplication of the myxobacteria was accompanied by their adsorption on the bacterial cells, by their coagglutination, and by their adsorption on the glass surface of the culture flask. Lysis of the agglutinated bacterial cells and release of their proteins to the growth medium took place prior to an increase in the lytic activity of the growth medium towards the tested bacteria. Soluble proteins reached a higher level in media containing Gram-negative than in those containing the Gram-positive organisms. No difference was observed in the multiplication rate, sporulation, or pigmentation of the myxobacteria tested, when grown on either Gram-positive or Gram-negative organisms. Using Staphylococcus aureus as a test organism, no antibiotic activity in any of the growth media could be detected.

Gram staining v1

2021 ◽  
Author(s):  
lydiariver not provided
Keyword(s):  
Cell Walls ◽  
Group B Streptococcus ◽  
Gram Negative Bacteria ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Staining ◽  
Acetone Treatment ◽  
Gram Negative Organisms ◽  
Group B ◽  
Gram Positive Cocci

Gram staining is one of the first techniques used for the identification of group B Streptococcus agalactiae and one would expect to see gram-positive cocci under the microscope. The technique consists of applying a series of colorants and bleaches (acetone), which interact with the lipids of the membranes of gram-positive and gram-negative bacteria. The cell walls of gram-positive organisms retain the dye after acetone treatment and appear purple in color, whereas gram-negative organisms become discolored after acetone treatment and appear pink.

scholarly journals Simultaneous Fluorescent Gram Staining and Activity Assessment of Activated Sludge Bacteria

2002 ◽  
Vol 68 (10) ◽  
pp. 4772-4779 ◽  
Author(s):  
Scott Forster ◽  
Jason R. Snape ◽  
Hilary M. Lappin-Scott ◽  
Jonathan Porter
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
Flow Cytometric Analysis ◽  
Quantitative Measure ◽  
Bacterial Cells ◽  
Gram Positive ◽  
Gram Negative ◽  
Highly Active ◽  
Gram Staining

ABSTRACT Wastewater treatment is one of the most important commercial biotechnological processes, and yet the component bacterial populations and their associated metabolic activities are poorly understood. The novel fluorescent dye hexidium iodide allows assessment of Gram status by differential absorption through bacterial cell walls. Differentiation between gram-positive and gram-negative wastewater bacteria was achieved after flow cytometric analysis. This study shows that the relative proportions of gram-positive and gram-negative bacterial cells identified by traditional microscopy and hexidium iodide staining were not significantly different. Dual staining of cells for Gram status and activity proved effective in analyzing mixtures of cultured bacteria and wastewater populations. Levels of highly active organisms at two wastewater treatment plants, both gram positive and gram negative, ranged from 1.5% in activated sludge flocs to 16% in the activated sludge fluid. Gram-positive organisms comprised <5% of the total bacterial numbers but accounted for 19 and 55% of the highly active organisms within flocs at the two plants. Assessment of Gram status and activity within activated sludge samples over a 4-day period showed significant differences over time. This method provides a rapid, quantitative measure of Gram status linked with in situ activity within wastewater systems.

scholarly journals Assessing Gram-stain error rates within the pharmaceutical microbiology laboratory

2020 ◽  
Author(s):  
Tim Sandle
Keyword(s):  
Error Rates ◽  
Microbiology Laboratory ◽  
Gram Stain ◽  
Clinical Context ◽  
Determinative Bacteriology ◽  
Gram Positive ◽  
Gram Negative ◽  
Microbial Identification ◽  
Gram Staining ◽  
Gram Negative Organisms

Gram-staining remains the fundamental method for determinative bacteriology, dividing bacteria into Gram-positive and Gram-negative organisms. This test provides information as to the origin of any contamination and is a pre-requisite for many microbial identification methods. Despite the longevity of the test, the test is highly reliant upon analyst technique and therefore errors occur. While there are a few studies looking at errors in the clinical context, research has not been extended to the pharmaceutical microbiology laboratory context. In this study, we present a review of over 6,000 Gram-stains and establish an error rate of around 3%, with the most common reason for error being an over-decolourisation step resulting in organisms that should be Gram-positive appearing as Gram-negative. The analysis enables others to benchmark their facilities against.

scholarly journals Quorum sensing: A molecular cell communication in bacterial cells

2019 ◽  
Vol 5 (2) ◽  
pp. 23-34
Author(s):  
Geethanjali ◽  
V. Dinesh Kumar ◽  
N. Raghu ◽  
T.S. Gopenath ◽  
S. Veerana Gowda ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Cell Density ◽  
Vibrio Fischeri ◽  
Cell Communication ◽  
Eukaryotic Cell ◽  
Bacterial Cells ◽  
Gram Positive ◽  
Gram Negative ◽  
Gene Level ◽  
A Cell

Background: Quorum sensing is a cell-to-cell communication, which is extensively observed in bacteria. This process allows the cell to detect, analyze, share and act upon various environmental stimuli based on cell density. The molecular aspect of this process is the secretion and detection of chemical signaling molecules called autoinducers (AIs), which act upon the gene expression. The quorum sensing signaling pathway is specifically observed only bulk population or in other words, the quorum sensing is effective only in high cell density. The quorum sensing circuit in the bacterial population is widely studied under the following heading; quorum sensing in Gram positive bacterium, Quorum sensing in Gram negative bacterium and the Quorum sensing with respect to Interkingdom communication. These models are studied using the widely studied models like Vibrio fischeri in Gram negative QS circuit, Staphylococcus aureus in Gram positive QS circuit and Vibrio harveyi. This review paper details the introduction of quorum sensing and their gene level explanation and how they effect on the virulence of a particular species of bacteria. This paper also throws light on the realization that the bacteria has the capable of performing coordinated activities that was so long contributed to the eukaryotic cell performance.

scholarly journals Causative organisms in microbial keratitis, their sensitivity pattern and treatment outcome in western Nepal

1970 ◽  
Vol 4 (1) ◽  
pp. 119-127 ◽  
Author(s):  
K Dhakwa ◽  
MK Sharma ◽  
S Bajimaya ◽  
AK Dwivedi ◽  
S KC Rai
Keyword(s):  
Treatment Outcome ◽  
Staphylococcus Epidermidis ◽  
Microbial Keratitis ◽  
Gram Positive ◽  
Gram Negative ◽  
Corneal Ulcers ◽  
Sensitivity Pattern ◽  
Gram Negative Organisms ◽  
Pattern Sensitivity ◽  
Epidemiological Characteristics

Introduction: Corneal infection is one of the major causes of monocular blindness in developing countries. Objective: To determine the epidemiological characteristics, predisposing factors, microbiological pattern, sensitivity pattern and treatment outcome of microbial keratitis. Materials and methods: A retrospective analysis of hospital records of 414 patients with diagnosed infective keratitis was done. The outcome measures were microbial isolates, their sensitivity to therapeutic agents and treatment outcome. Results: Of the total, 312 (75.4 %) patients were farmers by profession, 138 (33.3 %) had a history of ocular trauma and 17(4.1 %) were using topical corticosteroids. Among the 138 cases of the corneal ulcer with trauma, 52 (37.68 %) had fungi isolated in culture (RR=0.54, 95% CI = 0.44 – 0.68) and 32 (23.19 %) had a bacterial growth. Cultures were positive in 300 (72.5 %) cases, having 138 (33.3 %) patients with pure fungal infection, 121 (29.2 %) with pure bacterial and 41 (9.9 %) with mixed infection. Fusarium spp was the most common fungal pathogen while Staphylococcus epidermidis was the commonest bacterial isolate. The most sensitive antibiotics for the Gram positive bacteria was cephazolin (84.92 %), while for Gram negative, ciprofloxacin and ofloxacin were the most effective (79.31 %). Of 414 cases of corneal ulcers, 363 (87.7 %) cases healed completely. Conclusion: Microbial keratitis is mostly seen in farmers in this part of the world. Fusarium and Staphylococcus epidermidis were the most common isolates. Cephazoline and ofloxacin were the most effective antibiotics for Gram positive and Gram negative organisms respectively. DOI: http://dx.doi.org/10.3126/nepjoph.v4i1.5863 NEPJOPH 2012; 4(1): 119-127

scholarly journals Linearized esculentin-2EM shows pH dependent antibacterial activity with an alkaline optimum

2021 ◽  
Author(s):  
Erum Malik ◽  
David A. Phoenix ◽  
Timothy J. Snape ◽  
Frederick Harris ◽  
Jaipaul Singh ◽  
...  
Keyword(s):  
Helical Structure ◽  
Food Preservation ◽  
Forming Process ◽  
Gram Positive ◽  
Gram Negative ◽  
Bacterial Membranes ◽  
Gram Positive Bacteria ◽  
Alkaline Conditions ◽  
Ph Dependent ◽  
Gram Negative Organisms

AbstractHere the hypothesis that linearized esculentin 2EM (E2EM-lin) from Glandirana emeljanovi possesses pH dependent activity is investigated. The peptide showed weak activity against Gram-negative bacteria (MLCs ≥ 75.0 μM) but potent efficacy towards Gram-positive bacteria (MLCs ≤ 6.25 μM). E2EM-lin adopted an α-helical structure in the presence of bacterial membranes that increased as pH was increased from 6 to 8 (↑ 15.5–26.9%), whilst similar increases in pH enhanced the ability of the peptide to penetrate (↑ 2.3–5.1 mN m−1) and lyse (↑ 15.1–32.5%) these membranes. Theoretical analysis predicted that this membranolytic mechanism involved a tilted segment, that increased along the α-helical long axis of E2EM-lin (1–23) in the N → C direction, with −  < µH > increasing overall from circa − 0.8 to − 0.3. In combination, these data showed that E2EM-lin killed bacteria via novel mechanisms that were enhanced by alkaline conditions and involved the formation of tilted and membranolytic, α-helical structure. The preference of E2EM-lin for Gram-positive bacteria over Gram-negative organisms was primarily driven by the superior ability of phosphatidylglycerol to induce α-helical structure in the peptide as compared to phosphatidylethanolamine. These data were used to generate a novel pore-forming model for the membranolytic activity of E2EM-lin, which would appear to be the first, major reported instance of pH dependent AMPs with alkaline optima using tilted structure to drive a pore-forming process. It is proposed that E2EM-lin has the potential for development to serve purposes ranging from therapeutic usage, such as chronic wound disinfection, to food preservation by killing food spoilage organisms.

scholarly journals 1554. Epidemiology of Adult Bacterial Hand Infections at Two Urban Hospitals

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S777-S778
Author(s):  
Arsheena Yassin ◽  
Christine Stavropoulos ◽  
Krystina L Woods ◽  
Jiashan Xu ◽  
Justin Carale ◽  
...  
Keyword(s):  
New York ◽  
Staphylococcus Aureus ◽  
Antibiotic Regimen ◽  
Gram Positive ◽  
Gram Negative ◽  
Streptococcus Species ◽  
Urban Hospitals ◽  
Haemophilus Parainfluenzae ◽  
Empiric Antibiotic ◽  
Gram Negative Organisms

Abstract Background Hand infections represent a major source of morbidity, which can result in hand stiffness and amputation. Early appropriate empiric antibiotic regimen may reduce the associated morbidity, hence the importance to examine local epidemiology. The aim of this study was to define the current epidemiology of adult hand infections at two urban hospitals in New York City. Methods We performed a double center, retrospective study of adult patients hospitalized from March 2018 to May 2020. Patients with positive cultures associated with the hand infections were included. Retrospectively, 100 patients were reviewed. Data on baseline demographic, clinical, surgical, microbiology, and treatment parameters were collected. Results Of the 100 patients, 76% were male, with median age of 47.5 years (35, 58.25) and average C-reactive protein (CRP) of 50.66 mg/L (± 64.64) on admission (see Table 1). Previous hospitalization within 1 year (38%), previous surgical procedures (39%) and recent IV medication use (26%) were common. 130 bacterial isolates were identified (see Table 2). The most frequent organisms were Gram-positive, with Methicillin susceptible Staphylococcus aureus (MSSA, 25.38%), Streptococcus species (20.08%), and Methicillin resistant Staphylococcus aureus (MRSA, 15.38%) being the most common. Gram-negative organisms were infrequent, with Haemophilus parainfluenzae (3.85%), Enterobacter cloacae (3.85) and Pseudomonas aeruginosa (3.08%) being the most prevalent. Of the 100 patients, 27% had polymicrobial infections, associated with trauma (6%), illicit IV use (6%) and unknown (7%) etiologies. Table 1: Baseline demographics and co-morbid conditions Table 2: Types and numbers of organisms in relation to etiologies Conclusion Within our population, the most common organisms associated with hand infections were Gram-positive, with Staphylococcus aureus and Streptococcus species being the most prevalent. Gram-negative pathogens were infrequently isolated. The results within this study can provide guidance to clinicians on assessing the appropriate empiric antibiotic regimen in patients with hand infections, and can serve as a basis for further studies identifying risk factors associated with isolation of organisms associated with hand infections. Disclosures All Authors: No reported disclosures

scholarly journals Evaluation of MicroScan Bacterial Identification Panels for Low-Resource Settings

Diagnostics ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 349
Author(s):  
Sien Ombelet ◽  
Alessandra Natale ◽  
Jean-Baptiste Ronat ◽  
Olivier Vandenberg ◽  
Liselotte Hardy ◽  
...  
Keyword(s):  
Bacterial Species ◽  
Ease Of Use ◽  
Bacterial Identification ◽  
Gram Positive ◽  
Gram Negative ◽  
Low Resource Settings ◽  
Low Resource ◽  
Bacillus Spp ◽  
Gram Negative Organisms ◽  
Instructions For Use

Bacterial identification is challenging in low-resource settings (LRS). We evaluated the MicroScan identification panels (Beckman Coulter, Brea, CA, USA) as part of Médecins Sans Frontières’ Mini-lab Project. The MicroScan Dried Overnight Positive ID Type 3 (PID3) panels for Gram-positive organisms and Dried Overnight Negative ID Type 2 (NID2) panels for Gram-negative organisms were assessed with 367 clinical isolates from LRS. Robustness was studied by inoculating Gram-negative species on the Gram-positive panel and vice versa. The ease of use of the panels and readability of the instructions for use (IFU) were evaluated. Of species represented in the MicroScan database, 94.6% (185/195) of Gram-negative and 85.9% (110/128) of Gram-positive isolates were correctly identified up to species level. Of species not represented in the database (e.g., Streptococcus suis and Bacillus spp.), 53.1% out of 49 isolates were incorrectly identified as non-related bacterial species. Testing of Gram-positive isolates on Gram-negative panels and vice versa (n = 144) resulted in incorrect identifications for 38.2% of tested isolates. The readability level of the IFU was considered too high for LRS. Inoculation of the panels was favorably evaluated, whereas the visual reading of the panels was considered error-prone. In conclusion, the accuracy of the MicroScan identification panels was excellent for Gram-negative species and good for Gram-positive species. Improvements in stability, robustness, and ease of use have been identified to assure adaptation to LRS constraints.

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