Haemophilus influenzae are gram-negative bacteria that can cause infection in the respiratory tract, which can spread to other organs.
- Infection is spread through sneezing, coughing, or touching.
- The bacteria can cause middle ear infections, sinusitis, and more serious infections, including meningitis and epiglottitis, as well as respiratory infections.
- Identifying the bacteria in a sample taken from blood or from infected tissue confirms the diagnosis.
- Children are routinely given a vaccine that effectively prevents infections due to Haemophilus influenzae type b.
- Infections are treated with antibiotics given by mouth or, for serious infections, intravenously.
(See also Overview of Bacteria.)
Many species of Haemophilus normally reside in the upper airways of children and adults and rarely cause disease. One species causes chancroid, a sexually transmitted disease. Other species cause infections of heart valves (endocarditis) and, rarely, collections of pus (abscesses) in the brain, lungs, and liver. The species responsible for the most infections is Haemophilus influenzae.
Haemophilus influenzae can cause infections in children and sometimes in adults.
Risk of getting a Haemophilus influenzae infection is increased in the following:
- Children (particularly boys)
- Native Americans
- People who attend or work at a day care center
- People who live in overcrowded conditions
- People with an immunodeficiency disorder, no spleen, or sickle cell disease
Infection is spread by sneezing, coughing, or touching infected people.
One type of Haemophilus influenzae, called type b, is more likely to cause serious infections.
In children, Haemophilus influenzae type b (Hib) can spread through the bloodstream (causing bacteremia) and infect the joints, bones, lungs, skin of the face and neck, eyes, urinary tract, and other organs.
The bacteria may cause two severe, often fatal infections:
Some strains cause infection of the middle ear in children, the sinuses in children and adults, and the lungs in adults, especially those with chronic obstructive pulmonary disease (COPD) or AIDS.
Symptoms vary depending on the part of the body affected.
- Culture of a sample of blood or other body fluids
- Sometimes examination of a sample of cerebrospinal fluid (obtained by spinal tap)
To diagnose the infection, doctors take a sample of blood, pus, or other body fluids and send it to a laboratory to grow (culture) the bacteria. If people have symptoms of meningitis, doctors do a spinal tap (lumbar puncture) to obtain a sample of the fluid that surrounds the brain and spinal cord (cerebrospinal fluid). Identifying the bacteria in a sample confirms the diagnosis.
After the bacteria are identified, they may be tested to see which antibiotics are effective (a process called susceptibility testing).
Children are routinely vaccinated against Haemophilus influenzae type b (see Table: Routine Vaccinations for Infants, Children, and Adolescents). The vaccine has greatly reduced the number of serious Haemophilus influenzae type b infections, such as meningitis, epiglottitis, and bacteremia.
If the household of a person with a serious Haemophilus influenzae type b infection includes a child who is under 4 years old and is not fully immunized against Haemophilus influenzae type b, the child should be vaccinated. Also, all members of the household, except pregnant women, should be given the antibiotic rifampin to prevent infection.
If two or more children in a nursery or day care center have Haemophilus influenzae type b infection within a 60-day period, adults and children who were in contact with them should be given an antibiotic.
Haemophilus influenzae infections are treated with antibiotics. Which ones are used depends on the severity and location of the infection and results of susceptibility tests.
If children have a serious infection, they are hospitalized and kept in isolation to prevent other people from being exposed to infected droplets in the air (called respiratory isolation) for 24 hours after antibiotics are started.
Meningitis must be treated as soon as possible. An antibiotic—usually, ceftriaxone or cefotaxime—is given intravenously. Corticosteroids may help prevent brain damage.
Epiglottitis must also be treated as soon as possible. People may need help breathing. An artificial airway, such as a breathing tube, may be inserted or, rarely, an opening may be made in the windpipe (a procedure called tracheostomy). An antibiotic, such as ceftriaxone, cefotaxime, or cefuroxime, is given.
Other infections due to Haemophilus influenzae are treated with various antibiotics given by mouth. They include amoxicillin/clavulanate, azithromycin, cephalosporins, fluoroquinolones, and clarithromycin.
- Centers for Disease Control and Prevention: Haemophilus influenzae
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