Equis ISSN 2398-2977

Staining techniques: Gram stain

Synonym(s): Gram

Contributor(s): Tony Bacon, Annalisa Barrelet, Kathleen P Freeman, Karen L Gerber, T Scrivener, Malcolm J Wheeler

Introduction

Rationale
  • Gram-positive bacteria retain the crystal violet - iodine complex and stain purple-blue (cell wall prevents dilution of violet by solvent).
  • Gram-negative bacteria are decolorized and are stained red by the counter-stain.

Uses

  • Preliminary method of identifying bacteria by light microscopy together with morphological features, to implement appropriate antibiotic therapy, before culture results (48 h).

Pros

  • Quick.

technique

  • Technician: minimum training to identify gram-positive and gram-negative bacteria.

Work time

  • 8 min - depending on efficiency of technician.

Preparation

  • 6 min - apply stain, components kept premixed on staining bench, next to sink.

Procedure

  • +/- 2 min microscope identification.

Requirements

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Method

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Storage

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Errors

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Further Reading

Publications

Refereed papers

Other sources of information

  • Pratt P W (1997) Laboratory Procedures for Veternary Technicians. 3rd edn. Mosby. pp 168,169 + 172.
  • Quin P J et al (1994) Clinical Veterinary Microbiology. Mosby. pp 21-22.


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