Coxiella

Coxiella is a genus of bacteria in the family Coxiellaceae. The most notable species within this genus is Coxiella burnetii, the causative agent of Q fever. These bacteria are obligate intracellular pathogens, meaning they can only replicate within the cells of a host organism.

Characteristics

Coxiella are small, Gram-negative bacteria that exhibit a pleomorphic shape, meaning they can alter their shape or size in response to environmental conditions. They are known for their ability to survive in harsh conditions, including acidic environments and within phagolysosomes of host cells. This resilience is partly due to their unique lipopolysaccharide (LPS) structure, which helps them evade the host's immune system.

Life Cycle

The life cycle of Coxiella burnetii includes two distinct forms: the small cell variant (SCV) and the large cell variant (LCV). The SCV is the infectious form that can survive outside the host cell and is resistant to environmental stresses. Once inside the host, the SCV transforms into the LCV, which is the replicative form. The LCV multiplies within the host cell's phagolysosome, eventually converting back to SCVs to infect new cells.

Pathogenesis

Coxiella burnetii primarily infects mammals, including humans, and is transmitted through inhalation of contaminated aerosols. The bacteria can also be transmitted via tick bites, although this is less common. Once inside the host, C. burnetii targets macrophages and other immune cells, where it can replicate and cause disease. The primary disease associated with C. burnetii infection is Q fever, which can present as an acute or chronic illness. Symptoms of acute Q fever include high fever, severe headache, and muscle pain, while chronic Q fever can lead to more severe complications such as endocarditis.

Diagnosis and Treatment

Diagnosis of Coxiella infection is typically done through serological tests, such as the immunofluorescence assay (IFA) or enzyme-linked immunosorbent assay (ELISA), which detect antibodies against C. burnetii. Polymerase chain reaction (PCR) can also be used to detect bacterial DNA. Treatment usually involves antibiotics such as doxycycline or hydroxychloroquine, especially in cases of chronic Q fever.

Prevention

Preventive measures for Coxiella infection include proper handling of animals and animal products, as well as vaccination for high-risk populations. The Q fever vaccine is available in some countries and is recommended for individuals who work with livestock or in laboratories where C. burnetii is present.

Related Pages

• Q fever
• Coxiella burnetii
• Gram-negative bacteria
• Intracellular pathogen
• Lipopolysaccharide
• Immunofluorescence assay
• Polymerase chain reaction
• Doxycycline
• Hydroxychloroquine