Serology of primary atypical pneumonia Individuals with primary atypical pneumonia characteristically develop agglutinins against which historical test organism/antigen?

Introduction / Context:
Primary atypical pneumonia (often due to Mycoplasma pneumoniae) is associated with serologic phenomena including cold agglutinins and historical agglutination against “Streptococcus MG.” Recognizing these associations aids exam recall and historical perspective on diagnostics.

Given Data / Assumptions:

• Question refers to classic agglutinin responses in atypical pneumonia.
• Options list several streptococcal species; only one is associated with the eponymous test.

Concept / Approach:

Patients with Mycoplasma pneumoniae infection may produce cold-reactive IgM that agglutinates human type O erythrocytes and historically agglutinated the “Streptococcus MG” strain. Although modern diagnostics use PCR/ELISA, this eponym persists in test banks.

Step-by-Step Solution:

Verification / Alternative check:

Cold agglutinin titers rise in early Mycoplasma infections; older literature and classical exam items pair this with Streptococcus MG agglutination.

Why Other Options Are Wrong:

• S. avium, S. mutans, E. faecalis: not linked to atypical pneumonia agglutinin tests.
• Mycobacterium bovis: unrelated to atypical pneumonia serology.

Common Pitfalls:

• Confusing cold agglutination of human RBCs with bacterial agglutination; exam items may reference either.

Final Answer:

Streptococcus MG