**Question:** All are true regarding Chlamydia psittaci except:

A. Chlamydia psittaci is a Gram-negative bacterium
B. Chlamydia psittaci is a causative agent of psittacosis in humans
C. Chlamydia pneumoniae is the primary cause of community-acquired pneumonia
D. Chlamydia trachomatis is responsible for urogenital infections in humans

**Correct Answer:** C. Chlamydia pneumoniae is the primary cause of community-acquired pneumonia

**Core Concept:** Chlamydia psittaci is a Gram-negative bacterium that is a causative agent of psittacosis in humans. It belongs to the Chlamydiaceae family and is characterized by its unique biphasic life cycle involving an elementary body (EB) and a reticulate body (RB). Chlamydia pneumoniae and Chlamydia trachomatis are also Chlamydiaceae family members, but they are responsible for different clinical manifestations:

**Option A:** Chlamydia psittaci is a Gram-negative bacterium. This statement is true as it describes the basic characteristics of Chlamydia psittaci, which is known for its Gram-negative staining pattern due to its unique lipopolysaccharide composition.

**Option B:** Chlamydia psittaci is a causative agent of psittacosis in humans. Again, this statement is correct, as psittacosis is an illness resulting from infection with Chlamydia psittaci, which can cause respiratory tract infections in humans after being transmitted from infected birds, particularly parrots and cockatiels.

**Option C:** Chlamydia pneumoniae is the primary cause of community-acquired pneumonia (CAP). While Chlamydia pneumoniae can indeed cause CAP, Chlamydia psittaci is not primarily responsible for this condition. CAP is primarily caused by various pathogens, including Streptococcus pneumoniae, Haemophilus influenzae, and Mycoplasma pneumoniae.

**Option D:** Chlamydia trachomatis is responsible for urogenital infections in humans. Chlamydia trachomatis is indeed known to cause urogenital infections, including urethritis, cervicitis, and pelvic inflammatory disease (PID). In contrast, Chlamydia psittaci primarily causes respiratory tract infections, as mentioned above, while Chlamydia pneumoniae is associated with community-acquired pneumonia.

**Core Concept:** Chlamydia pneumoniae is a primary cause of community-acquired pneumonia (CAP). Chlamydia pneumoniae is a Gram-negative bacterium that belongs to the Chlamydiaceae family. It is known for causing respiratory infections, such as pneumonia, bronchitis, and bronchiolitis, and is often associated with exacerbation of asthma and chronic obstructive pulmonary disease (COPD).

**Explanation of the wrong options:**

**Option A:** Chlamydia pneumoniae causes respiratory tract infections, which is consistent with the statement "Chlamydia psittaci is a primary cause of respiratory tract infections." However, this statement specifically