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Gram Stain

This is a method (named after the Danish bacteriologist, Hans Christian Gram) for staining and identifying bacteria.

PubMed Health Glossary
(Source: NIH - National Cancer Institute)

About Gram Stains

The Gram stain test, developed in the 1800s by Hans Christian Gram, is a method for classifying different types of bacteria using a chemical stain and viewing through a microscope the results on the bacteria's protective cell wall.

Most bacteria are classified into two groups—Gram-positive or Gram-negative—depending on whether they retain a specific stain color.

Gram-positive bacteria retain a purple-colored stain, while Gram-negative bacteria appear pinkish or red. NIH - National Institute of Allergy and Infectious Diseases

What works? Research summarized

Evidence reviews

Antenatal Care: Routine Care for the Healthy Pregnant Woman

The original antenatal care guideline was published by NICE in 2003. Since then a number of important pieces of evidence have become available, particularly concerning gestational diabetes, haemoglobinopathy and ultrasound, so that the update was initiated. This update has also provided an opportunity to look at a number of aspects of antenatal care: the development of a method to assess women for whom additional care is necessary (the ‘antenatal assessment tool’), information giving to women, lifestyle (vitamin D supplementation, alcohol consumption), screening for the baby (use of ultrasound for gestational age assessment and screening for fetal abnormalities, methods for determining normal fetal growth, placenta praevia), and screening for the mother (haemoglobinopathy screening, gestational diabetes, pre-eclampsia and preterm labour, chlamydia).

MALDI-TOF Mass Spectrometry for Pathogen Identification: A Review of Accuracy and Clinical Effectiveness [Internet]

This Rapid Response report reviews the accuracy and clinical impact of Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-TOF) mass spectrometry (MS) for the identification of microbial pathogens. This report was reviewed by experts in clinical microbiology and bacteriology and mycology.

Intrapartum Care: Care of Healthy Women and Their Babies During Childbirth

The guideline is intended to cover the care of healthy women with uncomplicated pregnancies entering labour at low risk of developing intrapartum complications. In addition, recommendations are included that address the care of women who start labour as ‘low risk’ but who go on to develop complications. These include the care of women with prelabour rupture of membranes at term, care of the woman and baby when meconium is present, indications for continuous cardiotocography, interpretation of cardiotocography traces, and management of retained placenta and postpartum haemorrhage. Aspects of intrapartum care for women at risk of developing intrapartum complications are covered by a range of guidelines on specific conditions (see section 1.8) and a further guideline is planned on intrapartum care of women ‘at high risk’ of complications during pregnancy and the intrapartum period.

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Summaries for consumers

The effects of antimicrobial treatment on bacterial vaginosis in non‐pregnant women  

Bacterial vaginosis (BV) is a very common cause of symptomatic and asymptomatic vaginal infection. It has been associated with a high incidence of obstetric and gynaecologic complications and an increased risk of transmission of HIV (human immunodeficiency virus). This review evaluated the effectiveness and adverse effects of antimicrobial agents used to treat BV in non‐pregnant women. Twenty‐four trials involving 4422 women were reviewed. With regard to less treatment failure, clindamycin was superior to placebo but comparable to metronidazole, irrespective of the dose regimen. Metronidazole tended to cause a higher rate of adverse events, such as metallic taste and nausea and vomiting, than did clindamycin. Oral lactobacillus combined with metronidazole was more effective than metronidazole alone. Administered in an intravaginal gelatin tablet, lactobacillus was also more effective than oral metronidazole. Triple sulfonamide cream was less effective compared with clindamycin. Hydrogen peroxide douche was not as effective as a single 2 g dose of metronidazole yet caused more harms. Only one trial involved asymptomatic women and the result was not conclusive. There was insufficient evidence to reach a conclusion on the effectiveness of other promising drugs. Drugs effective for bacterial vaginosis include clindamycin preparations, oral metronidazole, and oral and intravaginal tablets of lactobacillus. Adverse effects of metronidazole include metallic taste, and nausea and vomiting. Information on possible side effects of lactobacillus preparations is required.

Terms to know

A large group of single-cell microorganisms. Some cause infections and disease in animals and humans. The singular of bacteria is bacterium.
The basic subunit of any living organism; the simplest unit capable of independent life. Although there are some single-celled organisms, such as bacteria, most organisms consist of many cells that are specialized for particular functions.
Gram-negative Bacteria
Bacteria that show up as pink (negative) when treated by the gram-staining method.
Gram-positive Bacteria
Infections caused by bacteria that retain the crystal violet stain (positive) when treated by the gram-staining method.

More about Gram Stain

Photo of a young adult

Also called: Gram stain method, Gram staining method, Gram stain test

See Also: Bacterial Infections

Other terms to know: See all 4
Bacteria, Cells, Gram-negative Bacteria

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