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Diplococci Information and Courses from MediaLab, Inc.

These are the MediaLab courses that cover Diplococci and links to relevant pages within the course.

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Body Fluid Differential Tutorial
Intracellular and Extracellular Diplococci

This is a CSF sample from a patient diagnosed with bacterial meningitis.Note the intracellular and extracellular bacteria present on this smear (see arrows).Notice the white blood cells clumps around the bacteria. This is not simply an artifact of the preparation, but rather a response to the presence of the actual bacteria. WBC clumping can be a great clue to the presence of bacteria, so laboratorians should always scan any clumps present for infectious organisms.

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Intracellular Diplococci

When intracellular bacteria are present in a body fluid cytospin, they classically appear within neutrophils (see arrows). When the bacterial burden is high, they may also be found in monocytes/histiocytes. It is important to note that monocytes are the less effective phagocytes of these two cell types, so they will never contain intracellular organisms if the neutrophils do not do so as well. If you think you are seeing bacteria in a monocyte/macrophage, and the neutrophils do not display intracellular bacteria, you may actually be observing granules of hemosiderin within the macrophages. Hemosiderin usually stains more green-blue or black than bacteria, and the granules are less regular in size than ingested bacteria. Comparing the Wright stain to the Gram stain, and performing an iron stain, will help with this distinction.

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Case Studies in Clinical Microbiology
The carbohydrate utilization reaction seen in the QuadFerm system shown in the image provides a definitive identification of N. gonorrhoeae.View Page
Review 1

Smith KR, Fisher HC III, Hook, EW III: Prevalence of fluorescent monoclonal antibody-nonreactive Neisseria gonorrhoeae in five North American sexually transmitted disease clinics. J Clin Microbiol 34:1551-1552, 1996 We compared a direct fluorescent monoclonal antibody (DFA) test with alternative enzymatic and fermention tests for identifying presumptive gonococcal isolates in a systematic sample from patients attending five sexually transmitted disease clinics in five cities. Fourteen (2.5%) of 556 isolates from three clinics were nonreactive with the DFA confirmatory reagent and reactive by both the Quad-Ferm and Rapid NH tests. The prevalence of DFA-nonreactive Neisseria gonorrhoeae isolates varies geographically and is independent of local methods for the identification of possible gonococci. On the basis of our findings, we recommend that for use in medicolegal and other instances in which a diagnosis of gonorrhea has the potential to have far-reaching effects, it is appropriate to test DFA reagent-nonreactive, oxidase-positive, gram-negative diplococci by alternative methods of gonococcal confirmation. Although the prevalence of such isolates could change, the fluorescent monoclonal antibody confirmation reagents remain useful for many clinical situations. Their ease of use and ready applicability for screening large numbers of isolates make them useful for many laboratories.

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Reading and Reporting Gram Stained Direct Smears
Provide the Clinician With Same-Day Information Regarding Possible Pathogens

Cultures often require 24 or more hours before a pathogen can be recovered. A Gram stain can give preliminary information about the type of bacterial and/or fungal organisms that are present. A rapid diagnosis of bacterial meningitis, made after examining a gram-stained smear of the patient's cerebrospinal fluid, allows the physician to begin treatment immediately. Intracellular gram-negative diplococci observed in a male urethral specimen may be confirmatory of the diagnosis of gonorrhea. Cultures may not even be needed unless susceptibilities are required. (In the female genital specimen, the presence of gram-negative diplococci is not specific enough to confirm the diagnosis, and a culture or other confirmatory testing must be performed).

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Gram-negative Diplococci

When gram-negative diplococci with flattened, adjacent sides are observed within white cells, it may indicate the presence of Neisseria. Examples are indicated by the arrows.

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Gram-positive Diplococci

Cocci that occur in pairs are referred to as diplococci. Image 2 contains many gram-positive diplococci.Image 2Lancet-shaped gram-positive diplococci from a lower respiratory tract specimen could indicate Streptococcus pneumoniae. Organisms that may be harbored in the upper respiratory tract gain access to the alveolar spaces by aspiration or inhalation. Image 3 is a Gram stain made from a lower respiratory tract specimen. The gram-positive diplococci can be presumptively identified as Streptococcus pneumoniae. Image 3

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Special Considerations for Genital Smears

Gram-negative cocci that occur in pairs with their adjacent sides flattened, giving them a "coffee bean" appearance, are typical of the genus Neisseria. 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 gonorrhea. In this case, cultures may not even be needed unless susceptibilities are required. However, if the genital specimen is from a female (cervical specimen), the presence of gram-negative diplococci is not specific enough to confirm the diagnosis, and a culture or other confirmatory testing must be performed. Organisms such as Acinetobacter sp. and Moraxella sp. may mimic the appearance of N. gonorrhoeae and can lead to false-positive results.Direct smears read specifically for the presence of Neisseria gonorrhea should include a direct reference to gram-negative intracellular diplococci.

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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 gonorrhea.View Page

Reading Gram Stained Direct Smears
The presence of Gram negative intracellular diplococci in a female is diagnostic of gonorrhea.View Page
Identification of bacteria

Identification of bacteria in direct smears may be of lifesaving importance. For example, a rapid diagnosis of bacterial meningitis, made after examining a gram-stained smear of the patient's cerebrospinal fluid, allows the physician to begin treatment immediately. The appearance of bacteria on gram-stained smears is suggestive of a certain species, but identification may not be made on the basis of the stain alone. An exception to this rule is the presence of gram-negative intracellular diplococci from a male urogenital specimen, which is presumptive identification of Neisseria gonorrhoeae. In addition, culture results can be correlated with the direct smear report.

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Gram negative diplococci

When gram negative diplococci with flattened, adjacent sides are seen within white cells, it may indicate the presence of Neisseria. An example of diplococci with flattened adjacent sides, probably representing Neisseria is shown by the arrows.

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Reporting Genital Smears

Direct smears read specifically for the presence of gonococci should include a direct reference to gram negative intracellular diplococci.

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In a male with a purulent urethral exudate, a presumptive diagnosis of gonorrhea is made by finding Gram negative intracellular diplococci in a direct smear of the exudate.View Page

Reading Gram Stained Smears From Cultures (retired 2/12/2013)
Which of the following appear as budding organisms?View Page


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