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Dr.T.V.Rao MD
The observation of the Gram stain continues to be primary...
The presence of intracellular gram-negative diplococci on a smear made from a purulent urethral
discharge from a male can ...
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Reading of a gram stain in diagnostic microbiology


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Reading of a gram stain in diagnostic microbiology

  1. 1. READING OF A GRAM STAIN IN DIAGNOSTIC MICROBIOLOGY Dr.T.V.Rao MD The observation of the Gram stain continues to be primary skill among the Microbiologists, many times performed by junior staff and the senior microbiologists scrutinize the results. However it is one of the tests survived more than century of its discovery by Christian Gram in 1884. Minimal quality assurances are recommended doing the staining with standard strains available for the both gram positive and gram negative organism, Learnto define a direct smear. Describe several ways that Gram stained direct smears are clinically useful. And educating the junior staff to realise the importance of the tests, or else theyare done causally and discarded. Understand examination of direct smears with respect to: control smears, macroscopic appearance, and characteristics of appropriate microscopic fields. Discuss the identification of common nonbacterial elements with respect to: purpose, size, shape, differentiating characteristics, and Gram stain reaction. Many times the artefacts are interpreted as rare type microbes by the over confident microbiologists Identify the following types of bacteria found in Gram stained direct smears: Gram-positive cocci, gram-negative cocci, gram-positive bacilli, gram-negative bacilli, gram negative diplococci .Pleomorphism Discuss with staff procedure for reading Gram stained direct smears with respect to: principle, procedure, and sources of error. It is important the Microbiologists should be familiar to interpret the results of CSF and other important specimens from body fluids and to be reported promptly. Provide the Clinician with Same-Day Information Regarding Possible Pathogens, Information from Gram stained direct smears may help the physician make a preliminary diagnosis when the Gram stain information is combination with clinical findings. Microbiologists should be familiar to report the following bacteria Bacteria in Direct Smears Gram-positive Diplococci Gram-positive Cocci Gram-negative Cocci Intracellular Bacteria Gram-negative Diplococci Special Considerations for Genital Smears Gram-positive Bacilli Gram-negative Bacilli Significance of Specific Findings when the bacteria in the slide are gram-negative cocci.
  2. 2. The presence of intracellular gram-negative diplococci on a smear made from a purulent urethral discharge from a male can be confirmatory of the diagnosis of Gonorrhoeal infection. All the nonbacterial elements and artefacts’ should be read with caution and reported with wisdom Nonbacterial Cells in Direct Smears Size and Appearance of Nonbacterial Cellular Elements on Gram Stained Smear Match the Gram stain reaction for each of the following nonbacterial elements. Which of the following cells are about the same size as red blood cells? What nonbacterial structures are present in this microscopic field of a Gram-stained smear? This Gram stain was prepared from a sputum specimen and is viewed under oil immersion (1000X). Never forget to interpret the observation of sputum smear with culture reports; however my experience proves it is difficult to interpret the Sputum and Wound specimen with precision and accuracy Unless clearly associated with neutrophils or seen intracellular, the various organisms of normal flora need not necessarily be reported individually. In we report the Normal fora, may be confusing and misleading to the clinician who may interpret these organisms as potential pathogens simply because “the laboratory reported it.” However, if any single morphotype (even one that is considered normal flora) is closely associated with neutrophils, its presence should be reported, one should realise the presence of Moraxella in sputum cultures with confluent growth in association with observation of many Neutrophils. If the laboratories’ interpretation is not consistent with the guidelines presented in the interpretation should be reconsidered or consultation should be sought. Possibly over or under decolourization has occurred. Al though these guidelines give objective criteria for interpreting the most commonly encountered Gram stains, there will be exceptions. The quality of the reports and confidence in the reports will improve if consultation with an-other technologist occurs before reporting such findings Never forget the importance of Gram’s stain; it continues to be most rapid method in Diagnostic Microbiology or even more than molecular diagnostic advances. Dr.T.V.Rao MD Professor of Microbiology Freelancewriter.