What is the Gram stain for Streptococcus pneumoniae?

Streptococcus pneumoniae are lancet-shaped, gram-positive, facultative anaerobic bacteria with more than 100 known serotypes.

Is Streptococcus pneumoniae a quellung reaction?

The quellung reaction, also called the Neufeld reaction, is a biochemical reaction in which antibodies bind to the bacterial capsule of Streptococcus pneumoniae, Klebsiella pneumoniae, Neisseria meningitidis, Bacillus anthracis, Haemophilus influenzae, Escherichia coli, and Salmonella.

What is a positive quellung reaction?

A positive quellung reaction is observed when the capsule appears as a sharply demarcated halo around the dark blue stained cell. A negative quelling reaction is observed when there is no appearance of a clear, enlarged halo surrounding the stained cell.

What is quellung reaction test?

The Quellung reaction is the gold standard method for pneumococcal capsular serotyping. The method involves testing a pneumococcal cell suspension with pooled and specific antisera directed against the capsular polysaccharide. The antigen-antibody reactions are observed microscopically.

Is pneumonia gram-positive or negative?

Abstract. Gram-positive pneumonia is a leading cause of morbidity and mortality throughout the world. Of the gram-positive pathogens that cause pneumonia, Streptococcus pneumoniae and Staphylococcus aureus are the most common.

What is Quellung phenomenon?

Definition. A biochemical reaction in which anticapsular antibodies bind to the capsule of a bacterium, resulting in the capsule to swell or become more visible, especially through the microscope.

Is Strep pyogenes Quellung reaction positive?

The conventional serotyping method is the Quellung reaction, whereby pneumococci are mixed with polyclonal rabbit anti-capsule typing serum and examined under the microscope. If the bacteria appear swollen, this is a positive reaction.

What other tests for gram-positive cocci is very useful in differentiating S Viridans from S. pneumoniae?

The catalase test is primarily used to differentiate between gram-positive cocci.

How is gram negative pneumonia diagnosed?

Although gram staining of sputum may provide immediate etiologic clues, the diagnosis is proven only by isolation of the pathogen from blood or pleural fluid or by various invasive techniques since expectorated specimens from highly susceptible patients are often contaminated with aerobic gram-negative bacilli …

Which gram negative bacteria causes pneumonia?

Recent findings: The high rate of respiratory infections due to Gram-negative bacteria in late-onset ventilator-associated pneumonia has been repeatedly documented. The predominant pathogens are Pseudomonas aeruginosa and Acinetobacter baumannii.

What is bile solubility test?

Bile Solubility Test is the test which differentiate Streptococcus pneumoniae (positive- soluble) from alpha-hemolytic streptococci (negative- insoluble). Streptococcus pneumoniae is bile soluble whereas all other alpha-hemolytic streptococci are bile resistant.

What is capsule swelling test?

A positive test result, the quellung reaction, occurs when the type-specific antibody combines with capsular polysaccharide, resulting in swelling of the capsule with a refractile halo surrounding the bacterial cell.

What test differentiates the Streptococcus pneumoniae from Streptococcus viridans?

Bile solubility
Bile solubility is a rapid, confirmatory test often used to differentiate S. pneumoniae from viridans streptococci, in which a drop of 10% deoxycholate is placed on an area of growth.

What is the confirmatory test for Streptococcus pneumoniae?

S. pneumoniae can be identified using Gram stain, catalase, and optochin tests simultaneously, with bile solubility as a confirmatory test. If these tests indicate that the isolate is S. pneumoniae, serological tests to identify the serotype can be performed.

How do you know if gram-positive or gram-negative?

A Gram stain is colored purple. When the stain combines with bacteria in a sample, the bacteria will either stay purple or turn pink or red. If the bacteria stays purple, they are Gram-positive. If the bacteria turns pink or red, they are Gram-negative.

Which test is specific for Streptococcus pneumoniae?

How can you distinguish between gram-positive Staphylococcus and Streptococcus?

Staphylococci and Streptococci are grouped as Gram-positive cocci. Staphylococci form clumps, whereas Streptococci grow in chains. They can be discriminated by catalase test because Staphylococci have the capability to produce catalase [2].