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You are watching: Can iodine be added before the primary stain

StatPearls . Sweetheart Island (FL): StatPearls Publishing; 2021 Jan-.


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Introduction

The Gram staining is just one of the most an essential staining techniques in microbiology. It it s okay its name from the Danish bacteriologist Hans Christian Gram who very first introduced the in 1882, greatly to recognize organisms resulting in pneumonia.<1> Often the first test performed, gram staining requires the usage of decision violet or methylene blue together the major color.<2> The term for organisms the retain the main color and also appear purple-brown under a microscopic lense is Gram-positive organisms. The biology that perform not take it up main stain appear red under a microscope and are Gram-negative organisms.

 The very first step in gram staining is the use of decision violet dye for the slide"s early staining. The following step, likewise known as addressing the dye, entails using iodine to kind crystal violet- iodine complex to protect against easy remove of dye. Subsequently, a decolorizer, frequently solvent of ethanol and acetone, is used to eliminate the dye. The basic principle that gram staining entails the ability of the bacter cell wall to maintain the crystal violet dye throughout solvent treatment.<3> Gram-positive microbe have higher peptidoglycan content, vice versa, gram-negative organisms have higher lipid content.<4> 

Initially, all bacteria take it up decision violet dye; however, with the use of solvent, the lipid layer indigenous gram-negative organisms is dissolved. V the resolution of the lipid layer, gram negatives lose the major stain. In contrast, solvent dehydrates the gram-positive cabinet walls with the closure of pores staying clear of diffusion that violet-iodine complex, and also thus, bacteria continue to be stained.<5> The size of decolorization is a crucial step in gram staining as prolonged exposure come a decolorizing agent deserve to remove every the stains indigenous both species of bacteria.<6>

The final step in gram staining is come use basic fuchsin stain to provide decolorized gram-negative bacteria pink shade for much easier identification. It is also known together counterstain. Some laboratories use safranin together a counterstain; however, basic fuchsin stains gram-negative organisms an ext intensely than safranin. Similarly, Hemophilus spp., Legionella app, and some anaerobic bacteria stain poorly through safranin.

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Specimen Collection

Various clinical specimens can be provided to carry out Gram staining. Few of the frequently used specimens are sputum, blood, cerebrospinal fluid, ascitic fluid, synovial fluid, pleural fluid, and also urine, etc. Swabs native nostrils, throat, rectum, wound, and cervix, etc. Can additionally be used. The repertoire of specimens should constantly be in sterile containers.