Haemophilus influenzae Infection

What is Haemophilus influenzae Infection?

Haemophilus influenzae disease is an infection caused by a bacterium named Haemophilus influenzae. The bacteria come in two types: one is encapsulated, meaning it has a protective outer layer, and the other is non-encapsulated, without this layer. The encapsulated type has subcategories, labeled ‘a’ to ‘f’, based on the type of outer layer it possesses. The most common form that causes illness is H. influenzae type b (Hib), often affecting children and people with weakened immune systems. Other forms like type ‘a’, ‘e’, and ‘f’ are less common. Types ‘c’ and ‘d’ are exceptionally rare.

This bacteria, especially type ‘b’, is often the cause of serious infections of the lower respiratory tract, like pneumonia, and other severe conditions such as bacterial meningitis (a serious infection around the brain and spinal cord), epiglottitis (inflammation of the tissue that covers the windpipe), cellulitis (a common bacterial skin infection), septic arthritis (infection in the joints), and even empyema (accumulation of pus in a body cavity) and bacteremia (bacteria present in the blood).

Fortunately, the Hib conjugate vaccine, a type of immunization, is quite effective in protecting against type ‘b’ by prompting our body to build immunity. This vaccine has considerably lowered the rate of Hib infections. However, in those who have received the vaccine, the majority of Haemophilus influenzae-related illnesses – like ear infections, sinusitis, and pneumonia – are now caused by the non-encapsulated type of the bacteria, also known as non-typeable H. influenzae (NTHi). These infections are usually spread by breathing in droplets from the respiratory secretions of infected individuals or by getting very close to them.

What Causes Haemophilus influenzae Infection?

Haemophilus influenzae is a small type of bacteria that can only live in very specific conditions requiring factors found in red blood cells. Sometimes referred to as “H. influenzae,” it grows well on a medium called chocolate agar. They come in six distinct groups labeled a, b, c, d, e, and f. These groups are established according to their reaction with special serum, which is a component of blood.

Type b, or “Hib,” is especially important to note because it’s responsible for most of the invasive diseases caused by this bacteria in kids and more than half in adults. It has a special coating called a polyribosyl ribitol phosphate (PRP) capsule, which makes it particularly aggressive.

Other types of H. influenzae are less common causes of infection. Many strains are classified as “non-typeable” (NTHi), which means they don’t have a detectable coating of special carbohydrates, or polysaccharides, around their cell wall. Techniques like polymerase chain reaction (PCR) and a precise mass measurement technique (MALDI-TOF MS) are used to tell these apart more definitively. These tests are also used to tell the difference between true NTHi strains and closely related bacteria.

Humans are the only known host for this bacteria, and some strains are even considered a normal part of the microbial community in our respiratory and genital tracts and eyes.

Risk Factors and Frequency for Haemophilus influenzae Infection

After the Hib conjugate vaccine’s introduction in 1987 and 1990 for children and infants respectively in the US, cases of Hib disease in children under 5 years have notably reduced. Now, in the US, the disease is mostly caused by non-typeable H. Influenzae (NTHi), regardless of age. Interestingly, despite vaccination, the disease rates remain higher among native Alaskan children when compared to other races. Typically, the disease is seen in kids who haven’t been vaccinated or newborns who haven’t completed their vaccination schedule.

In 2017, the incidence rates per 100,000 kids under 5 years were 0.18 for Hib, 1.7 for non-b H. Influenzae, and 1.7 for NTHi. Among adults aged 65 and older, the incidence of NTHi was 6.2 per 100,000. In approximately 40% of cases, NTHi is responsible for acute ear and sinus infections in children. It’s also a factor in recurring ear infections in this age group. In developing countries where vaccination is not common, healthy children can carry H. Influenzae in the nasopharynx and throat. At the age of 1, about 20% of kids carry it, and this number increases to over 50% for 5-year-olds.

Signs and Symptoms of Haemophilus influenzae Infection

H. influenzae is a type of bacteria that can cause various health issues. The exact time it takes for symptoms to show after exposure is unclear, but it may be within a few days. People more prone to these infections include babies, children under 5 years of age, and adults aged 65 and above. Other vulnerable groups include American Indians, native Alaskans, and people with certain health conditions, such as sickle cell disease, HIV, asplenia, antibody and complement deficiencies, cancer patients undergoing chemotherapy or radiotherapy, and those who have had a bone marrow transplant.

This bacterium can lead to two types of infections: invasive and non-invasive. Children under the age of 5 are typically the ones affected by invasive H. influenzae infections, which can lead to serious health problems like pneumonia and meningitis. Less frequently, it can also cause conditions like eye infections, urinary tract infections, abscesses, infections of the bone or heart. Non-invasive infections primarily affect the surfaces of the body and are caused by a strain of H. influenzae known as NTHi. These infections can include middle ear and sinus infections, pneumonia in older people, and flare-ups of chronic obstructive pulmonary disease (COPD) in adults and the elderly.

What symptoms a person experiences depends on what part of their body is infected. Some of the more common symptoms include:

High fever
Chills
Coughing up mucus
Shortness of breath
Chest pain
Tiredness and generalized body aches

If the infection involves the meninges (the layers covering the brain and spinal cord), then symptoms can also include fever, headaches, altered consciousness, sensitivity to light, nausea, vomiting, and stiff neck. In babies, such an infection may cause irritability, drowsiness, poor feeding, and vomiting. In worst cases, an infection of H. influenzae can get into the bloodstream and show systemic symptoms like high fever, chills, extreme fatigue, stomach ache, nausea, vomiting, diarrhea, difficulty breathing, and confusion.

On another note, in pregnant women, NTHi strains can cause problems during pregnancy such as low birth weight babies, premature births, premature breaking of the water, and infection of the amniotic fluid. There’s also a risk that the infection can be passed from the mother to the newborn, leading to H. influenzae disease soon after birth. Mothers can also develop infections after delivery.

NTHi usually causes infections like otitis media (middle ear infection), conjunctivitis (pink eye), and sinusitis. Those with chronic obstructive pulmonary disease (COPD) can have flare-ups due to NTHi infection, with symptoms like a mild fever, increasing shortness of breath, worsening cough, and more mucus production. Rarely, H. influenzae can also cause septic arthritis, an infection of the joints, typically affecting large joints like the knee, ankle, hip, or elbow. It may affect one or many joints, and symptoms include redness, warmth, tenderness, swelling, and less movement in the joint.

Testing for Haemophilus influenzae Infection

When a doctor suspects an infection, they may run a variety of tests using samples from body fluids. One common test is the Gram stain, which can identify certain types of bacteria. If the bacteria in question are found—coccobacilli—then this may confirm the presence of a specific organism causing the infection. Other specialized testing methods such as cultures of blood and body fluids also help in the confirmation process. These tests may be carried out on special substances, like chocolate agar and BVCCA.

For certain infections, doctors may use a method called serotyping. This involves “typing” the bacteria sample, which means identifying its unique properties. This can be done using techniques like agglutination with antiserum or polymerase chain reaction (PCR). Other methods that provide a faster diagnosis include immunoelectrophoresis, latex particle agglutination, and enzyme-linked immunosorbent assay. These methods help identify specific elements in the bacteria.

The exact tests a doctor might order can depend on the location and nature of the infection. For example, if a doctor suspects meningitis— an infection of the protective membranes covering the brain and spinal cord—they will likely perform a lumbar puncture. This procedure involves taking a small sample of cerebrospinal fluid (CSF) from your spinal canal for testing. In the case of Hemophilus influenzae type b (Hib) meningitis, these tests commonly show a high amount of cells—particularly neutrophils—in the CSF, reduced glucose levels, and increased protein levels.

On the other hand, if a patient has pneumonia— inflammation of the lung tissue— a doctor might start with a chest x-ray. Then they would further test the patient’s coughed-up mucus for definitive diagnosis.

Diagnostic techniques are evolving, and newer methods are becoming popular. For instance, a type of PCR test helps correctly distinguish non-typable Haemophilus influenzae (NTHi) from other similar-looking but harmless bacteria. Some tests even allow detecting multiple pathogens at the same time, thus speeding up the diagnosis process.

Different imaging methods, such as computed tomography (CT) scans and X-rays, are also crucial. They help visualize the extent of certain diseases. For example, a CT scan of the head can reveal complications from meningitis, while a chest X-ray can give a closer look at the state of pneumonia. In some cases, invasive procedures, such as bronchoscopy and trans-tracheal aspiration, may be necessary to collect samples and definitively diagnose conditions.

Remember, diagnostic methods vary significantly, and the choice depends on the specifics of each patient’s case and the judgement of the healthcare professionals involved.

Treatment Options for Haemophilus influenzae Infection

In the case where H. influenzae bacteria is suspected to have infected the protective layers of the brain or spinal cord, called meningitis, specific antibiotics are suggested. These include ceftriaxone, ceftazidime, cefotaxime, and others. Some other antibiotics are usually avoided because of the risk of antibiotic resistance or side effects. For instance, cefuroxime may delay sterilization, a process of killing bacteria, and chloramphenicol might negatively impact the bone marrow, leading to life-threatening conditions.

Further treatments for meningitis may include dexamethasone, a medication which can reduce inflammation and swelling in the brain, and subsequently reduce complications such as hearing loss and other neurological problems. To be effective, dexamethasone needs to be administered before or at the same time the antibiotic treatment starts. Supportive therapy and proper management of complications like honey-like inflammation of tissue, excessive secretion of an antidiuretic hormone, seizures, and pus-filled bumps are carried out to decrease the risk to mortality.

In children experiencing breathing difficulty from a throat infection, the main concern is ensuring a clear airway and subsequent management goes from providing oxygen, nebulized epinephrine, multiple doses of steroids and antibiotics. The choice of antibiotic can vary based on the test result of tissue fluids and response to the treatment. If patients are allergic to the first-line antibiotics, then vancomycin and ciprofloxacin are used. Chest X-rays, blood cultures, and analysis of fluids around the spinal cord are recommended to determine the infection location.

Mucosal infections, which occur in the moist lining of certain parts of the body by NTHi, are typically treated with oral antibiotics such as amoxicillin or a combination of amoxicillin and clavulanate. If there is an allergy to penicillin, then alternative medicines such as erythromycin-sulfisoxazole or cefaclor might be prescribed. Treatment duration can vary depending on the child’s age and severity of the disease. For example, children under 2 years with severe infection might need treatment for a total of 10 days, whereas children older than 6 years with mild symptoms might require 5 to 7 days of treatment.

In severe cases of the infection spreading to certain body parts or fluids, surgical procedures might be required. These might involve draining fluids from affected areas or repeated aspirations, which is drawing out fluid using suction, and passing a camera into a joint (arthroscopy) with the placement of a surgical drain to relieve pressure and reduce the chances of complications such as disrupted blood supply to the hip joint.

When a patient shows symptoms common to illnesses such as meningitis and pneumonia, it could be due to a bacterial infection like H. influenzae. However, these symptoms can also be identical to other diseases. To correctly identify the cause, doctors obtain a sample of the patient’s sputum, or mucus, and then perform a test known as a gram-stain followed by a culture.

Bronchitis, defined as inflammation of the airways, shows similar indications to bacterial pneumonia. However, specific signs like fever and productive cough suggest that H. influenzae pneumonia is the cause.

For H.influenzae epiglottitis, a type of throat infection, one clue linking it to parainfluenza virus infection (also known as croup) is the ‘steeple sign’ spotted on a neck X-ray. Typically, illnesses related to the parainfluenza virus particularly affect children aged between 6 months and 3 years. Classic signs of this type of virus include a distinct barking cough that sounds like a seal and a harsh, high-pitched wheezing sound when breathing in.

What to expect with Haemophilus influenzae Infection

Diagnosing and treating meningitis early can lead to good health outcomes. Starting antibiotics as soon as possible and conducting blood tests to guide treatment is the best way to keep the disease under control. Age and the amount of certain types of bacteria in the body can also affect outcomes.

Two types of pneumonia, Hib pneumonia without complications and pneumonia caused by nonencapsulated H. influenzae, generally have better outcomes than serious or invasive Hib disease. Hib is a type of bacteria that can cause various serious infections including meningitis and pneumonia.

Possible Complications When Diagnosed with Haemophilus influenzae Infection

Meningitis is a severe type of infection that has a series of potential complications. These can include hearing loss, seizures, pus-filled areas in the body, brain abscesses, swelling of the brain, fluid build-up under the skull, incorrect hormone release, fluid accumulation in the brain, and a condition where the brain pushes against the skull.

Meningitis can be fatal and may cause partial paralysis, coma, or even death in a short period of time if it’s not treated promptly. A type of pneumonia caused by H.influenzae bacteria can worsen into a full body infection or lead to localized pus-filled areas and heart membrane inflammation.

Additionally, ear and sinus infections can progress to complex conditions like an infection of the bone behind the ear and abscesses near the covering of the brain. Lastly, a severe form of sore throat, known as epiglottitis, can block the airway if not treated, thus requiring medical intervention such as an endotracheal tube or tracheostomy to retain air entry.

Common Consequences:

Hearing loss
Seizures
Pus-filled areas in the body
Brain abscesses
Swelling of the brain
Fluid build-up under the skull
Incorrect hormone release
Fluid accumulation in the brain
Condition where the brain pushes against the skull
Partial paralysis
Coma
Potential death
Worsening into a full body infection
Heart membrane inflammation
Infection of the bone behind the ear
Abscesses near the covering of the brain
Blockage of the airway

Preventing Haemophilus influenzae Infection

The Hib conjugate vaccine is a shot that is typically given to babies after they are born. It is effective at stopping Hib disease in about 98% of kids who are under the age of 5. The vaccine works by helping the body create antibodies, which can fight off the disease. It also helps to reduce the ability of certain bacteria to live in the back of the throat. The vaccine is made up of a specific type of substance (known as PRP capsular polysaccharide) that is attached to a protein.

The Hib vaccine can be given on its own, or it can be combined with other vaccines, like the hepatitis B vaccine, and the DTaP-Hib vaccine, which protects against diphtheria, tetanus, and acellular pertussis (whooping cough), in addition to Haemophilus influenzae type b (Hib). These combination vaccines are approved for use in babies. The first shot is usually given when the baby is 2 months old, and then again every two months for a total of three shots. A booster shot is given after the baby turns one, usually between 12 to 15 months old.

It’s important for parents or caregivers to understand what Hib disease looks like in order to quickly recognize any signs and symptoms. If a child who has been in close contact with someone who has Hib disease (like at a daycare or school) starts to show similar symptoms, it’s important that they would be checked for the disease as well.

Frequently asked questions

Haemophilus influenzae infection is an infection caused by a bacterium named Haemophilus influenzae. It can cause serious infections of the lower respiratory tract, bacterial meningitis, epiglottitis, cellulitis, septic arthritis, empyema, and bacteremia. The most common form that causes illness is H. influenzae type b (Hib), but there are also non-encapsulated types of the bacteria.

Haemophilus influenzae infection is common, particularly in children.

Signs and symptoms of Haemophilus influenzae infection can vary depending on which part of the body is affected. Some common symptoms include: - High fever - Chills - Coughing up mucus - Shortness of breath - Chest pain - Tiredness and generalized body aches If the infection involves the meninges (the layers covering the brain and spinal cord), additional symptoms may include fever, headaches, altered consciousness, sensitivity to light, nausea, vomiting, and a stiff neck. In babies, an infection of the meninges may cause irritability, drowsiness, poor feeding, and vomiting. In severe cases, H. influenzae infection can enter the bloodstream and cause systemic symptoms such as high fever, chills, extreme fatigue, stomach ache, nausea, vomiting, diarrhea, difficulty breathing, and confusion. In pregnant women, certain strains of H. influenzae can lead to complications during pregnancy, including low birth weight babies, premature births, premature breaking of the water, and infection of the amniotic fluid. There is also a risk of transmitting the infection from the mother to the newborn, resulting in H. influenzae disease soon after birth. Mothers can also develop infections after delivery. Other specific symptoms and conditions associated with H. influenzae infection include: - Eye infections - Urinary tract infections - Abscesses - Infections of the bone or heart - Otitis media (middle ear infection) - Conjunctivitis (pink eye) - Sinusitis - Pneumonia in older people - Flare-ups of chronic obstructive pulmonary disease (COPD) in adults and the elderly - Septic arthritis, which can cause redness, warmth, tenderness, swelling, and limited movement in the affected joint.

Haemophilus influenzae infection can be acquired through exposure to respiratory droplets from an infected person, especially through close contact such as coughing, sneezing, or sharing personal items.

When diagnosing Haemophilus influenzae infection, a doctor needs to rule out the following conditions: 1. Other types of bacterial infections, such as bronchitis and pneumonia. 2. Parainfluenza virus infection (croup) in the case of H. influenzae epiglottitis. 3. Other diseases with similar symptoms, such as meningitis and pneumonia, which can be caused by different pathogens. 4. Harmless bacteria that may have similar characteristics to non-typable Haemophilus influenzae (NTHi).

The types of tests that may be needed for Haemophilus influenzae infection include: - Gram stain to identify certain types of bacteria - Cultures of blood and body fluids to confirm the presence of the bacteria causing the infection - Serotyping to identify the unique properties of the bacteria sample, which can be done through techniques like agglutination with antiserum or polymerase chain reaction (PCR) - Specialized tests like immunoelectrophoresis, latex particle agglutination, and enzyme-linked immunosorbent assay to identify specific elements in the bacteria - Lumbar puncture to test cerebrospinal fluid (CSF) in cases of suspected meningitis - Chest x-ray to diagnose pneumonia - Computed tomography (CT) scans and X-rays to visualize the extent of certain diseases - Invasive procedures like bronchoscopy and trans-tracheal aspiration to collect samples for definitive diagnosis.

Doctors mainly treat H. influenzae infections with antibiotics and general health management strategies. The first antibiotic doctors usually choose is a type of medicine called a "third-generation cephalosporin." After testing the specific strain of bacteria, doctors might alter the antibiotic choice depending on the test's results. Regular check-ups are done to monitor the impact of the treatment and changes in the antibiotic choice might be needed. The length of the antibiotic treatment varies depending on the infection site and how well the bodies react to the treatment. In specific cases, such as meningitis, different antibiotics like ceftriaxone, ceftazidime, and cefotaxime are suggested. Other treatments may include dexamethasone to reduce inflammation and swelling in the brain, supportive therapy, and proper management of complications. In mucosal infections, oral antibiotics like amoxicillin or a combination of amoxicillin and clavulanate are typically used. In severe cases, surgical procedures might be required.

The side effects when treating Haemophilus influenzae infection can include: - Delayed sterilization with cefuroxime - Negative impact on bone marrow with chloramphenicol - Potential allergic reactions to antibiotics - Side effects from dexamethasone, such as increased risk of infection or impaired wound healing

The prognosis for Haemophilus influenzae infection depends on several factors, including the type of infection and the age of the individual. Generally, two types of pneumonia caused by Haemophilus influenzae have better outcomes compared to serious or invasive Hib disease. Early diagnosis and treatment, including the use of antibiotics, can help improve health outcomes. However, the prognosis can be influenced by factors such as age and the amount of certain types of bacteria in the body.

You should see an infectious disease specialist or a primary care physician for Haemophilus influenzae infection.