| A 25 year-old female presented in the emergency room with an acute urethral discharge of 2 days duration. A smear for gram stain was obtained (see accompanying image). Many polymorphonuclear leukocytes and intracellular and extracellular gram negative diplococci were observed.
Based on the clinical history and the gram stain observation, a diagnosis of gonorrhea can be made. | View Page |
| The positive oxidase reaction as shown in the photograph (yellow arrow) rules out the following two look-alike organisms of N. gonorrhoeae: | View Page |
| The carbohydrate utilization reaction seen in the QuadFerm system shown in the picture provides a definitive identification of N. gonorrhoeae: | View Page |
| Acute Onset Pneumonia A 70-year-old transient with productive cough, pleuritic chest pain radiating to the mid back, fever, and chills was seen in the emergency room. Expectorated sputum was sent to the laboratory for gram stain and culture. (Continue on next page) | View Page |
| The Gram stain report to be issued based on the microscopic characteristics seen in the accompanying picture would most correctly be, "many wbc with".. | View Page |
| Based on the gram stain morphology observed before, the possible presumptive identifications might include "gram positive cocci consistent with... | View Page |
| PYR Differential As mentioned before, the spot PYR test is commonly performed to separate Enterococcus species (positive reaction) from the Group D streptococci (S. bovis, S. equinus), which are negative.It should be remembered that Streptococcus pyogenes (group A) also produces PYR; therefore, additional characteristics such as beta hemolysis are important.Some species of Aerococcus and Gemella are also PYR-positive; however, they can be suspected if large cocci in tetrads or clusters are observed on gram stain.These species are rare isolates in most clinical practices. | View Page |
| Enterococcus ID Illustrated in this composite photograph is the gram stain of Enterococcus species (upper), illustrating gram positive cocci arranged in pairs and short chains.The viridans streptococci generally form gram positive cocci in long chains; the gram-positive cells of S. pneumoniae, on the other hand, may appear similar in gram stain.In the lower right is shown a 6.5% NaCl tube. The turbidity indicates growth, a unique characteristic for Enterococcus species.In the lower left frame is a picture of a bile esculin hydrolysis slant, showing a positive reaction (black pigment) characteristic of Enterococcus species. The streptococci are uniformly negative.Some strains of Leuconostoc species and Pediococcus species can grow in 6.5% NaCl and are bile-esculin positive; however, they should be ruled out because of the negative PYR reaction. | View Page |
| Gas gangrene may be seen in infections with all the following clostridia except: | View Page |
| The gram stain shown in the photograph was prepared from a positive anaerobic blood culture bottle after 36 hours incubation. Based on the morphology of the bacterial cells (some with spores--blue arrows), the most likely identification is: | View Page |
| A gram stain of the serous exudate is shown in the photograph. The appropriate report would read: | View Page |
| Staph on BA The photomicrograph of the surface of a 5% sheep blood agar illustrates the colonies that grew out of the foot drainage after 24 hours at 35C. They are entire, convex, smooth, and have a slight yellow pigmentation. Hemolysis is not observed. A gram stain was prepared from one of the isolated colonies. | View Page |
| The Gram stain prepared from the positive blood culture is shown in the photograph. The appropriate report is: | View Page |
| Listeria gram stain Photomicrograph of a gram stain prepared from an 18 hour old broth culture.The organism is a small, non-spore-forming bacillus measuring between 0.4 to 0.5um by 1.0 to 3.5um.Coccobacillary forms, diplobacilli, and bacilli in short chains or in diphtheroidal clusters (upper right in photograph) may all be observed in gram stain preparations.When found in the CSF, the organism may be found both intracellularly and extracellulary. | View Page |
| The test(s) which may be performed to establish a presumptive differential identification between group B streptococci and L. monocytogenes is/are: | View Page |
| Shown in the photograph are three tubes-(1) motility agar (note subsurface flare--see arrows); (2) esculin hydrolysis (+), and (3) VP (+). The reactions illustrated here are sufficient to rule out Erysipelothrix rhusiopathiae. | View Page |
| In regards to reporting gram stains, which of the following are true: | View Page |
| In a properly decolorized area, epithelial cells, red blood cells, white blood cells and most background material will stain pink or red. It is in this area that the gram stain reaction of the bacteria can be correctly interpreted. | View Page |
| Culture results are not correlated with direct gram stain results. | View Page |
| Cellular elements The gram stain reaction and appearance can be used to identify most cellular material seen in a direct smear. Identification of cellular elements present in a direct clinical smear is important because most of these elements play an important role in the disease process. For example, the quality of a sputum sample can be assessed by determining the relative numbers of squamous epithelial cells and polymorphonuclear leukocytes (segmented neutrophils) present.
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| Fungal hyphae Tubular filaments of fungi called hyphae may also be seen in a direct smear. Hyphae stain Gram positive and may branch or intertwine. Parasites can also be identified with the Gram stain, although it is not as sensitive as the special stains used for parasites. The Gram stain reaction and appearance can be used to identify most cellular material seen in a direct smear. The crystal violet may precipitate and can be seen on the slide. If the stain has precipitated, it must be refiltered before use.
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| Match the Gram stain reaction for each of the following nonbacterial elements. | View Page |
| Recording Bacterial Characteristics The Gram stain reaction, shape, and arrangement of bacteria, and the presence or absence of intracellular organisms must be noted on the worksheet.Examples:Gram positive cocci in chains are present.Gram negative diplococci, intracellular, are present within white blood cells.Quantitate by approximating the average number of each cell type seen in 10 oil immersion fields, and record as:Many = More than 15/fieldModerate = 4-15/fieldFew = 1-3/fieldOccasional = 2-10/10 fieldsRare = 0-2/10 fields | View Page |
| Contaminated Gram Stain Solution Contamination of the staining solutions rarely occurs, but should be suspected when smears repeatedly contain the same organisms, and these organisms do not grow or are inconsistent with the clinical picture. Yeast and gram negative rods can occur as stain contaminants. | View Page |
| Summary It is important to note the Gram stain reaction, shape, and cellular arrangement when examining culture smears. This information may be useful to the physician in making a presumptive identification. | View Page |
| Gram Stain The Gram stain provides a fundamental differentiation between types of bacteria. Gram positive bacteria retain the primary stain and are deep violet in color. Gram negative organisms are those that decolorize during the staining process and, after counterstaining, are pink in color. Bacteria have two basic shapes:cocci (round)bacilli (rod-shape) | View Page |
| Principle The culture smear is used to determine the staining characteristic and shape of the unknown organism since this data helps the microbiologist to decide on additional culture and identification methods. By correlating the Gram stain reaction, colony morphology and growth requirements, the microbiologist may be able to tentatively identify the organism, which the physician may use to modify treatment, until definitive culture and antibiotic susceptibility results become available. | View Page |