What is the clinical significance of quellung test?
The quellung reaction has been used to identify the 93 known capsular serotypes of Streptococcus pneumoniae in diagnostic settings, but in recent years it has been challenged by the latex agglutination method, and further by molecular typing techniques such as the polymerase chain reaction, which detect DNA and …
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.
What is the Quellung reaction How might it be used to rapidly identify certain bacteria directly in clinical specimens?
The specific pneumococcal type is identified with pooled typing sera and microscopy. 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 is the positive reaction or result in Quellung test?
A positive Quellung reaction occurs when type-specific antibody binds to the capsule of the pneumococcus, leading to a change in its refractive index10. When viewed under a microscope, the bacteria appear ‘swollen’ and more visible14.
Is Streptococcus pneumoniae a normal flora?
S. pneumoniae is part of the normal bacterial flora of the upper respiratory tract of humans, and is mainly found in the nasopharynx.
What are Draughtsman colonies?
Draughtsman Colonies— also called carrom coin colonies— are the result of prolonged incubation of inoculating samples onto blood agar. The incubation time majorly ranges from 24 – 48 hours.
What does a positive Quellung reaction indicate?
What is capsular swelling test?
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.
What is capsular swelling?
The capsular swelling or quellung reaction was reported almost 100 years ago and described the effect of Abs on the appearance of microbial capsules. Despite widespread use to assess Ab binding to capsules, relatively little is known as to the mechanism of this effect or its biological consequences.
What bacteria causes pneumonia?
Common Causes of Pneumonia A common cause of bacterial pneumonia is Streptococcus pneumoniae (pneumococcus). However, clinicians are not always able to find out which germ caused someone to get sick with pneumonia. Community-acquired pneumonia is when someone develops pneumonia in the community (not in a hospital).