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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 ...
In Berlin, in 1884, Gram developed a method for distinguishing between two major classes of bacteria. [1] This technique, known as Gram staining, continues to be a standard procedure of medical microbiology. This work gained Gram an international reputation. The staining method later played a major role in classifying bacteria. Gram was a ...
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.
A Ziehl–Neelsen stain is an acid-fast stain used to stain species of Mycobacterium tuberculosis that do not stain with the standard laboratory staining procedures such as Gram staining. This stain is performed through the use of both red coloured carbol fuchsin that stains the bacteria and a counter stain such as methylene blue.
Helicobacter pylori is a species of gram-negative bacteria in the Helicobacter genus. [23] About half the world's population is infected with H. pylori but only a few strains are pathogenic . H pylori is a helical bacterium having a predominantly helical shape , also often described as having a spiral or S shape.
This coating makes the cells impervious to Gram staining, and as a result, M. tuberculosis can appear weakly Gram-positive. [3] Acid-fast stains such as Ziehl–Neelsen, or fluorescent stains such as auramine are used instead to identify M. tuberculosis with a microscope.
Methicillin-resistant Staphylococcus aureus (MRSA) is a group of gram-positive bacteria that are genetically distinct from other strains of Staphylococcus aureus. MRSA is responsible for several difficult-to-treat infections in humans. It caused more than 100,000 deaths worldwide attributable to antimicrobial resistance in 2019.
A Gram stain is performed to show Gram-positive cocci in chains. Then, the organism is cultured on blood agar . The rapid pyrrolidonyl arylamidase (PYR) test is commonly used, wherein a positive reaction confers a presumptive identification of group A beta-hemolytic streptococci if the appearance and clinical context is consistent.