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A Gram stain of mixed Staphylococcus aureus (S. aureus ATCC 25923, gram-positive cocci, in purple) and Escherichia coli (E. coli ATCC 11775, gram-negative bacilli, in red), the most common Gram stain reference bacteria. Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups ...
Sputum Gram stain at 1000x magnification. The sputum is from a person with Haemophilus influenzae pneumonia, and the Gram negative coccobacilli are visible with a background of neutrophils. Haemophilus influenzae requires hemin and NAD for growth.
The best sputum samples contain very little saliva, [2] as saliva contaminates the sample with oral bacteria. This is especially true for samples for laboratory testing in cytology or microbiology. Specimen adequacy is assessed by the laboratory technologists by examining a Gram stain or cytology stain of the sputum.
A Gram stain is first performed to guide the way, which should show typical gram-positive bacteria, cocci, in clusters. Second, the isolate is cultured on mannitol salt agar , which is a selective medium with 7.5% NaCl that allows S. aureus to grow, producing yellow-colored colonies as a result of mannitol fermentation and subsequent drop in ...
A sputum culture is a test to detect and identify bacteria [1] or fungi that infect the lungs or breathing passages. Sputum is a thick fluid produced in the lungs and in the adjacent airways. Normally, fresh morning sample is preferred for the bacteriological examination of sputum. [ 2 ]
Corynebacterium diphtheriae Gram stain. The purple colour of the bacterium is indicative of the thin peptidoglycan wall surrounding the bacterium. The 'club-like' structure can be observed. This an example of a Coryneform bacterium. Corynebacterium striatum is a gram-positive bacterium. It has a thin external peptidoglycan cell wall structure.
Both gram-positive and gram-negative bacteria commonly have a surface layer called an S-layer. In gram-positive bacteria, the S-layer is attached to the peptidoglycan layer. Gram-negative bacteria's S-layer is attached directly to the outer membrane. Specific to gram-positive bacteria is the presence of teichoic acids in the cell wall. Some of ...
Sputum Gram staining and culture can also reveal the causative microorganism. In severe cases, bronchoscopy can collect fluid for culture. Special tests, such as urinalysis, can be performed if an uncommon microorganism is suspected.