Haemophilus influenzae type B

A bacterium responsible for various infections

Haemophilus influenzae type B

Haemophilus influenzae type B Resources
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Haemophilus influenzae type b, often abbreviated as Hib, is a bacterium that can cause a range of serious infections, particularly in young children. It is a type of Haemophilus influenzae, a small, pleomorphic, gram-negative coccobacillus.

History

Haemophilus influenzae was first described in 1892 by Richard Pfeiffer during an influenza pandemic, leading to the initial belief that it was the causative agent of influenza. However, it was later discovered that influenza is caused by a virus, and H. influenzae is responsible for secondary bacterial infections.

Pathogenesis

Haemophilus influenzae type b is encapsulated, which enhances its virulence by preventing phagocytosis by the host's immune cells. The capsule is composed of polyribosylribitol phosphate (PRP), a polysaccharide that is a key virulence factor. The bacterium can colonize the nasopharynx and, under certain conditions, invade the bloodstream, leading to systemic infections.

Diseases Caused

Hib is known to cause several serious diseases, including:

• Meningitis: Inflammation of the protective membranes covering the brain and spinal cord.
• Epiglottitis: Inflammation of the epiglottis, which can lead to life-threatening airway obstruction.
• Pneumonia: Infection of the lungs.
• Septic arthritis: Infection of the joints.
• Cellulitis: A bacterial skin infection.

Epidemiology

Before the introduction of the Hib vaccine, Haemophilus influenzae type b was a leading cause of bacterial meningitis in children under five years of age. The incidence of Hib infections has dramatically decreased in countries with widespread vaccination programs.

Diagnosis

Diagnosis of Hib infections can be made by isolating the bacterium from normally sterile body fluids such as blood, cerebrospinal fluid, or joint fluid. Laboratory techniques include culture, polymerase chain reaction (PCR), and antigen detection methods.

Prevention

The most effective way to prevent Hib infections is through vaccination. The Hib vaccine is typically administered to infants starting at two months of age. The vaccine is highly effective and has led to a significant reduction in the incidence of Hib-related diseases.

Treatment

Hib infections are treated with antibiotics. Commonly used antibiotics include ceftriaxone, cefotaxime, and ampicillin. Early diagnosis and treatment are crucial to prevent serious complications.

Also see

• Haemophilus influenzae
• Bacterial meningitis
• Vaccination
• Gram-negative bacteria