From the Guidelines

The condition associated with the K-capsular antigen is Klebsiella pneumoniae infection.

The K-capsular antigen is a type of polysaccharide capsule found on the surface of certain bacteria, including Klebsiella pneumoniae.
This capsule plays a major role in the virulence of the bacterium, helping it to evade the host's immune system and cause infection.
However, the provided evidence does not directly mention the K-capsular antigen or its association with a specific condition.
The evidence primarily discusses Streptococcus pneumoniae and its capsular polysaccharides, as well as the use of pneumococcal vaccines in preventing infection 1.
In the context of real-life clinical medicine, it is essential to consider the most likely cause of infection and the appropriate prevention or treatment strategies.
While the evidence does not provide a direct answer to the question, it highlights the importance of understanding the capsular antigens of various bacteria and their role in infection and disease.
In general, capsular antigens like the K-capsular antigen are critical for the identification and characterization of bacterial pathogens, and their study can inform the development of effective vaccines and treatments 1.

From the Research

The K-capsular antigen is associated with Klebsiella infections, particularly with the severity of infection and poor prognosis 2.

The presence of detectable KCA in the serum of patients infected with Klebsiella appeared to correlate with severity of infection, persistence of active foci, and a poorer prognosis than in those patients who had no detectable antigen 2.
The K antigen capsule of K. pneumoniae is involved in the expression of the serotype-specific K (capsular) antigen, and the rcsA gene is widely distributed among different Klebsiella K serotypes 3.
Klebsiella strains possessing capsule type K7 are found predominantly in respiratory secretions and are less toxic for mice than K2 strains 4.

Various types of K-capsular antigens have been identified, including K1, K2, K5, K7, K13, K14, K16, K20, and K55 5, 6, 3, 4.
The most commonly encountered somatic antigen is antigen 01, followed by antigen 03 5.

The detection of KCA in serum, cerebrospinal fluid, urine, empyema fluid, and abscess drainage can aid in the diagnosis of Klebsiella infections 2.
The presence of detectable KCA in the serum of patients infected with Klebsiella is associated with a poorer prognosis than in those patients who had no detectable antigen 2.