GRAM + bakteerit ovat joko kokkeja, basilleja tai haaroittuneita filamentteja sisältäviä sauvoja, joiden soluseinämä on paksua peptidoglykaania

 https://www.ncbi.nlm.nih.gov/books/NBK470553/

Gram Positive Bacteria

Omeed Sizar; Stephen W. Leslie; Chandrashekhar G. Unakal. Author Information and AffiliationsLast Update: February 19, 2023. Go to:

Continuing Education Activity

Gram-positive organisms have highly variable growth and resistance patterns. The SCOPE project (Surveillance and Control of Pathogens of Epidemiologic Importance) found that in those with an underlying malignancy, gram-positive organisms accounted for 62 percent of all bloodstream infections in 1995 and 76 percent in 2000 while gram-negative organisms accounted for 22 percent in 1995 and 14 percent in 2000. This activity reviews the evaluation and management of gram-positive bacterial infections and explains the role of the interprofessional team in improving care for affected patients.

Objectives:

• Explain how to evaluate for a gram-positive bacterial infection.
• Identify common infections caused by gram-positive bacteria.
• Describe treatment strategies for gram-positive bacterial infections.
• Outline interprofessional team strategies to improve care coordination and communication to provide quality care to patients with gram-positive bacterial infections.

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Introduction

Health professionals need to understand the important difference between gram-positive and gram-negative bacteria. Gram-positive bacteria are bacteria classified by the color they turn in the staining method. Hans Christian Gram developed the staining method in 1884. The staining method uses crystal violet dye, which is retained by the thick peptidoglycan cell wall found in gram-positive organisms. This reaction gives gram-positive organisms a blue color when viewed under a microscope. Although gram-negative organisms classically have an outer membrane, they have a thinner peptidoglycan layer, which does not hold the blue dye used in the initial dying process. Other information used to differentiate bacteria is the shape. Gram-positive bacteria comprise cocci, bacilli, or branching filaments.

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Etiology

Gram-positive cocci include Staphylococcus (catalase-positive), which grows clusters, and Streptococcus (catalase-negative), which grows in chains. The staphylococci further subdivide into coagulase-positive (S. aureus) and coagulase-negative (S. epidermidis and S. saprophyticus) species. Streptococcus bacteria subdivide into Strep. pyogenes (Group A), Strep. agalactiae (Group B), enterococci (Group D), Strep viridans, and Strep pneumonia.

Gram-positive bacilli (rods) subdivide according to their ability to produce spores. Bacillus and Clostridia are spore-forming rods while Listeria and Corynebacterium are not. Spore-forming rods that produce spores can survive in environments for many years. Also, the branching filament rods encompass Nocardia and actinomyces. 

Gram-positive organisms have a thicker peptidoglycan cell wall compared with gram-negative bacteria. It is a 20 to 80 nm thick polymer while the peptidoglycan layer of the gram-negative cell wall is 2 to 3 nm thick and covered with an outer lipid bilayer membrane.