Bacterial Pneumonia (Pneumonia)

What is Bacterial Pneumonia (Pneumonia)?

Bacterial pneumonia is an infection that causes inflammation in the lungs. It’s caused by different types of bacteria, which interact with the body’s immune system in complex ways. Symptoms of this condition can include fever, cough, trouble breathing, and chest pain. In some cases, it can lead to severe issues like necrotizing pneumonia, empyema, meningitis, sepsis, and multi-organ failure. It can even cause long-term effects on lung function and overall quality of life.

Pneumonia, a term that originates from the Greek word for lung, generally signifies a “lung disease”. It’s an inflammation of certain parts of the lung, triggered mainly by infections, although not exclusively. Infections could be caused by bacteria, viruses, fungi, and parasites, with bacterial pneumonia being a key contributor to overall sickness and death rates in those suffering from pneumonia.

There are different ways to classify pneumonia, with one popular system by the National Institutes of Health. This categorizes pneumonia as being community-acquired, hospital-acquired, or atypical, and decides severity accordingly. More classifications include healthcare-acquired pneumonia (HCAP), which includes pneumonia obtained in places like hospitals, dialysis units, and long-term care facilities. However, HCAP isn’t included in American guidelines due to insufficient evidence about microbiological differences with community-acquired pneumonia.

Here are some definitions for different types of bacterial pneumonia:

• Community-acquired pneumonia refers to a lung infection someone gets in their community or within the first two days of being in the hospital.
• Hospital-acquired pneumonia describes a lung infection that a nonintubated patient develops two days after being hospitalized.
• Atypical pneumonia is an infection caused by an uncommon pathogen that can’t be detected through standard testing methods.
• Ventilator-associated pneumonia refers to a lung infection that a patient develops two days or more after being put on a mechanical ventilator.

What Causes Bacterial Pneumonia (Pneumonia)?

Community-acquired pneumonia, or CAP, can be caused by a wide variety of factors, from bacteria and viruses to fungi and even parasites. But, for this explanation, we’re focusing mainly on pneumonia caused by bacteria. Bacteria can be split into two groups: typical and atypical. The difference is that typical bacteria can be identified through common lab tests, while atypical bacteria can’t be easily pinpointed using these methods.

Pneumonia can be “typical” if it’s mainly caused by certain types of bacteria, like Streptococcus pneumoniae or Staphylococcus aureus to name a couple. Also, sometimes pneumonia can be due to inhaling food or drink, which is also regarded as typical, because it often involves certain common bacteria.

On the other hand, “atypical” pneumonia can be caused by different types of bacteria like Legionella or Mycoplasma pneumoniae. Additionally, certain pneumonia cases are due to what we call “opportunistic” infections, caused by organisms like Mycobacterium tuberculosis.

Globally, the leading cause of CAP is Streptococcus pneumoniae, both in children and adults. Haemophilus influenzae is also frequently named as a common cause. However, the prevalence of other bacteria causing pneumonia can change depending on where you are in the world and the local health conditions. For example, in some regions, bacteria such as Klebsiella pneumoniae or Pseudomonas aeruginosa could also contribute to developing pneumonia.

Pneumonia that is contracted in a hospital or healthcare facility can be attributed to diverse bacteria, many of which are also causing ventilator-associated pneumonia. These include resistant bacteria, like MRSA, and non-resistant bacteria, like Streptococcus pneumoniae or Haemophilus influenzae.

Risk Factors and Frequency for Bacterial Pneumonia (Pneumonia)

Community-acquired pneumonia (CAP) is a global concern with an astounding 450 million cases reported annually around the world. Most of these cases, approximately 95%, happen in developing countries and contribute to around 4 million deaths each year. In Europe, the incident rate varies between 206 and 470 per 100,000 patients per year, while in China, it ranges from 298 to 2210 cases per 100,000 patient-years. In the United States, lower respiratory tract infections, including CAP, exceed all other infections concerning sickness and death rates. Approximately 649 to 847 CAP cases per 100,000 patient years end up in the hospital and these cases predominantly affect low-income and minority groups.

The rate of CAP is particularly high in specific age groups, particularly children under 4 years old and adults aged 65 or older. The United States records an estimated 2.2 to 8 million hospitalized cases of CAP each year. However, some other estimates suggest there might be as many as 5 million or more CAP cases annually. Considering the bacterial predominance, the annual frequency of M pneumoniae, C pneumoniae, and Legionella species cases in the U.S. is estimated at 108,000, 49,700, and 18,000, respectively.

Annually, about 100,000 CAP-related deaths occur in the U.S. The global mortality rate for CAP varies from 2.6% to 18.5% at the time of hospitalization and can rise to 31% to 44.5% within a year of hospitalization. Patients admitted to the intensive care unit (ICU) due to CAP are at an increased risk of death. Despite these severe outcomes, up to 90% of CAP cases are effectively treated outside the hospital. Reasons for hospitalization usually include other health conditions and the progression of CAP. The mortality rate is low, at about 0.1%, for CAP cases handled outside the hospital.

Signs and Symptoms of Bacterial Pneumonia (Pneumonia)

When a clinician examines a patient thought to have bacterial pneumonia, it’s crucial to look into the patient’s exposure history, risk factors, overall health status, and symptoms. The patient’s history with conditions like heart or lung disease, neurological impairments, HIV, kidney or liver disease, as well as age, sex, smoking habits, alcohol consumption, and dental hygiene, can all affect their risk for pneumonia. Vaccination history also needs to be reviewed, as this may signal susceptibility to specific infections. Intravenous drug use could also increase the risk for certain types of pneumonia. Therefore, every component of a patient’s health history and potential risk factors should be investigated.

Exposure history refers to the possible sources of infection a patient may have been exposed to. This can include:

• Legionella pneumonia, associated with being a smoker, or exposure to contaminated air-conditioning systems or water systems, such as those on cruise ships and hotels.
• Pneumonia in crowded spaces, typically found in jails or shelters, and potentially caused by a variety of bacteria including S pneumoniae, Mycobacteria species, M pneumoniae, and C pneumonia.
• Psittacosis, associated with exposure to birds like chickens, turkeys, and ducks. This is caused by C psittaci.
• Tularemia, associated with exposure to infected rabbits, possums, arthropods, and rodents. This is caused by Francisella tularensis.
• Leptospirosis and plague, associated with exposure to infected rodents, and could be due to either Leptospira species or Yersinia pestis.
• Q fever, associated with exposure to macropods, cats, sheep, and cattle. This is caused by Coxiella burnetii.
• Melioidosis, associated with inhaling proximity to disrupted soils in endemic areas. This is caused by B pseudomallei.
• Immunocompromised pneumonia, potentially caused by hospitalization, corticosteroid or cytotoxic therapy, or neutropenia. This is commonly caused by P aeruginosa.

There are also certain risk factors that could lead to increased chances of pneumonia due to aspiration, including altered mental status, multiple medications, trouble swallowing, acid reflux, daily supplemental oxygen therapy, dependency on oral care, decayed teeth, reliance on feeding supports, suctioning of sputum, smoking, and urinary catheterization.

Having a broader patient history such as asthma, chronic obstructive pulmonary disease (COPD), smoking, and being immunocompromised could hint towards a H influenzae infection, which tends to be more common in the winter season. Other aspects of a patient’s history, including social, sexual, medication, and family history, could help pinpoint the cause of illness. For example, individuals with advanced HIV with low CD4 counts are more likely to develop bacterial pneumonia and various opportunistic infections, like pulmonary tuberculosis and pulmonary cryptococcosis.

The symptoms of bacterial pneumonia can vary in different patients. Some commonly reported symptoms include fever, racing heart, chills, sweats, cough (sometimes productive of sputum which could have different characteristics depending on the infecting organism), chest pain, breathlessness, fatigue, headache, muscle ache, and joint pain.

The physical examination findings depend upon the severity of the infection, type of infecting organism, extent of infection, patient factors, and presence or absence of fluid buildup in the lungs. Some common findings may include fever or hypothermia, fast breathing, fast or slow heartbeat, bluish discoloration of the skin or mucous membranes, decreased chest expansion, tracheal deviation, altered percussion sounds, increased vocal resonance, and certain changes during auscultation, amongst others. The presentation might be different in infants, children, older adults, or those who are critically ill.

Certain physical exam findings are specific to particular infections. For example, slow heart rate often points towards infection by Legionella species, dental issues suggest infection by anaerobes, impaired gag reflex and difficulty swallowing hint towards aspiration pneumonia, cutaneous nodules imply nocardiosis, infection of the middle ear by Mycoplasma species, neck mass and spinal deformity signal tuberculosis, while bone infection and lower lobe pneumonia are suggestive of actinomycosis.

Testing for Bacterial Pneumonia (Pneumonia)

To diagnose pneumonia, doctors take into account the patient’s overall health, laboratory test results, and results from a radiological evaluation.

Clinical Evaluation

The clinical evaluation involves a detailed review of the patient’s health history and a thorough physical examination to assess for signs and symptoms of pneumonia. Doctors often use scoring systems like the CURB-65, CORB, SMART-COP, and the Pneumonia Severity Index to gauge the severity of the condition and predict potential complications. But these scoring systems are not replacements for a doctor’s professional judgement.

For example, the CURB-65 score takes into account the following factors:

• C: Confusion
• U: Uremia (Higher than normal amount of urea in the blood)
• R: Respiratory rate (More than 30 breaths per minute)
• B: Blood Pressure ( systolic blood pressure less than 90 or diastolic blood pressure 60 or below)
• Age: older than 65 years

A score of 0 to 1 suggests outpatient treatment, 2 or higher suggests hospital admission, and 3 or higher indicates ICU admission.

Laboratory Evaluation

Laboratory tests contribute significantly to the diagnostic process for pneumonia. This may involve checking the complete blood count, inflammatory markers, blood cultures, sputum (mucus) analysis, or conducting other tests to detect specific bacteria. An arterial blood gas analysis can show whether the patient has low oxygen levels or a respiratory acidosis (a condition that occurs when the lungs can’t remove all of the carbon dioxide).

Blood cultures are usually taken before starting antibiotics, especially in severe cases. Good quality sputum evaluation may reveal the presence of bacteria, and tests can be performed to differentiate between similar types of bacteria. Antimicrobial susceptibility testing helps doctors choose the right antibiotic for bacterial pneumonia.

In some cases, there may be specific chemical evidence present. For example, a bacterial infection called Legionella may be associated with a low sodium level (hyponatremia) and small amounts of blood in the urine (microhematuria).

Radiological Evaluation

X-rays and other imaging tests are key in the evaluation of pneumonia. A chest X-ray is often the initial imaging test used, as it can reveal abnormal areas or infiltrates in the lungs which, when combined with lab results and clinical features, can confirm the diagnosis of pneumonia.

Different bacteria can produce different patterns on an X-ray. For instance:

• Staphylococcus aureus pneumonia may show patchy opaque areas and cavities (possibly indicating abscesses).
• Haemophilus influenza infections may show changes that indicate bronchial pneumonia.
• Pseudomonas aeruginosa pneumonia might display patchy opacities with abscess formation, much like Burkholderia pseudomallei pneumonia.

In complex cases, or when the lungs have structural disease, a CT scan of the chest may be done. In some circumstances, a sample of fluid may be taken from the lungs for further analysis.

Treatment Options for Bacterial Pneumonia (Pneumonia)

Once a diagnosis of pneumonia is confirmed, doctors use a risk assessment to decide whether the patient should be treated at home or admitted in the hospital. For serious cases of bacterial pneumonia, it’s essential to start antibiotics as soon as possible to prevent sepsis, a serious condition that can lead to intensive care or even death.

Various tools can help doctors assess the patient’s risk, but it’s ultimately up to the doctor to make this call. The antibiotic prescribed depends on the bacteria commonly found in the local area. Some possible drugs include benzylpenicillin for S. pneumoniae bacteria, macrolides for Legionella, and carbapenems for B. pseudomallei, varying by geographic location.

To administer these antibiotics, benzylpenicillin is mixed with water for injection, while ceftriaxone is mixed with water for intravenous and muscle administration. In the US, respiratory fluoroquinolones or a combo of beta-lactam antibiotics with macrolides are usually the first line of treatment.

Once test results become available, doctors should adjust the antibiotics to best treat the specific bacteria. Certain antibiotics are recommended for different types of pneumonia and related conditions.

For patients managing pneumonia at home with no underlying health conditions, antibiotics from penicillin, macrolide, and tetracycline classes may be effective. Patients with other medical conditions may benefit from a respiratory fluoroquinolone or a combo of amoxicillin/clavulanate with a macrolide. In serious cases that require hospital care, the doctors will usually obtain a microbiological sample from the patient’s sputum or blood to guide the antibiotic treatment. However, outpatients may not need these tests.

Antipyretics, medicines that lower the body temperature, are typically recommended to ease symptoms and reduce fever. Once the test results come back positive, the treatment should be adjusted according to the resistance observed in the specific bacteria. Short treatments, as brief as 5 days, can effectively treat bacterial pneumonia in patients without any complications or underlying respiratory diseases like bronchiectasis.

The use of corticoids in bacterial pneumonia remains a subject of debate, with some situations favouring their use. There’s growing support for corticoids’ use in ICU patients, showing benefits in preventing worsening condition, reducing the need for a ventilator, and lowering the death rate if used within 24 hours of severe disease onset. The use of non-invasive ventilation in bacterial pneumonia is still controversial, particularly for patients who don’t have respiratory failure.

Aside from drug treatments, other ways of managing bacterial pneumonia include advising smokers to quit, providing counselling support, and recommending vaccines against flu, COVID-19, and pneumococcus. Doctors also encourage treating swallowing issues and addressing other medical conditions.

For those getting treated at home, a check-up within 2-3 days is recommended to watch for any pneumonia-related complications. For those recently discharged from the hospital, it’s a good idea to follow up within 7 days to see if there’s a need for continued antibiotics or rehydration.

While the role of physiotherapy in pneumonia remains unclear, some studies suggest it might help reduce the length of hospital stay and the need for ventilators. As a result, most guidelines don’t recommend traditional chest-clearing methods for pneumonia patients. These patients are rather encouraged to sit out of bed for at least 20 minutes within the first 24 hours of hospital admission and increase mobility each day. Other supportive measures for pneumonia include hydration, pulse oximetry monitoring, mechanical support for severe respiratory distress, good nutrition, and getting up and moving around as soon as possible.

What else can Bacterial Pneumonia (Pneumonia) be?

Telling pneumonia apart from other lung-related conditions can be quite tricky, especially when a patient already suffers from certain lung diseases. The conditions we consider to potentially mimic pneumonia symptoms change depending on whether we’re examining a child or an adult:

For children, these conditions may include:

• Asthma or severe reaction of the airways
• Bronchiolitis (inflamed small airways in the lungs)
• Croup (a common respiratory problem in young children)
• Respiratory distress syndrome (a breathing disorder in newborns)
• Epiglottitis (inflamed windpipe flap)

Meanwhile, adults could confuse their pneumonia symptoms with those of conditions like:

• Acute and chronic bronchitis (inflamed bronchial tubes)
• Acute pulmonary edema (fluid in lungs)
• Acute respiratory distress syndrome (severe lung condition)
• Swallowing a foreign body
• Severe asthma
• Atelectasis (collapsed lung)
• Bronchiectasis (damage to the airways)
• Bronchiolitis (inflamed small airways)
• Chronic obstructive pulmonary disease (long-term lung disease)
• Fungal lung infection (including a specific type named Pneumocystis jiroveci pneumonia)
• Interstitial lung disease (a group of lung disorders)
• Lung abscess (pus-filled cavity)
• Organizing pneumonia (lung inflammation)
• Respiratory failure
• Viral lung infection

What to expect with Bacterial Pneumonia (Pneumonia)

The future health outcomes of pneumonia can be affected by various factors, including a person’s age, mental clarity, additional illnesses (including cancer and chronic lung diseases), a suppressed immune system, chronic alcohol misuse, the type of healthcare setting (hospital inpatient or outpatient), and the need for help in breathing using a ventilator.

Generally, patients who are in overall good health tend to have a better prognosis if they contract bacterial pneumonia. However, the elderly may experience worse outcomes compared to younger patients. In fact, studies have shown that patients aged 65 and older with a type of lung infection caused by S pneumoniae bacteria had greater death rates within 30 days from the initial infection, even after considering whether they were vaccinated.

The mortality rate in bacterial pneumonia can also depend on the type of bacteria involved. For instance, S pneumoniae is a common cause of death, but certain types of bacteria such as Pseudomonas species, S aureus, and infections caused by multiple bacteria have higher death rates.

If pneumonia is not treated, it can result in a death rate of up to 30%. Various factors such as high levels of inflammation markers, anemia, confusion, and elevated blood urea nitrogen can make the treatment of bacterial pneumonia less successful. Moreover, failure of early treatment can be shown by persistent rapid breathing, low oxygen, confusion, and high levels of blood acidosis within the first three days of pneumonia treatment.

Furthermore, having a higher score on specific health evaluation scales that assess severity of a disease increases the risk of death, especially if the elevated score continues a week after diagnosis. The risk of death also rises when bacterial pneumonia coincides with viral respiratory infections like the flu and COVID-19 – this highlights the importance of getting vaccinated, especially for those more likely to fall seriously ill.

Increasing global resistance to antibiotics, partly due to their widespread use in healthcare and farming, can limit local options for treatment of bacterial pneumonia, which increases healthcare costs and makes patient outcomes worse.

In the long term, patients who acquire bacterial pneumonia in hospitals are more likely to die within a year of falling ill – this risk is higher particularly amongst elderly patients living in care homes. In this group, poor nutrition, ongoing use of steroids, and pre-existing other health conditions are associated with worse health outcomes. As such, it’s crucial to keep up regular and suitable check-ins with such at-risk groups after they’ve recovered from bacterial pneumonia.

Possible Complications When Diagnosed with Bacterial Pneumonia (Pneumonia)

Bacterial pneumonia can lead to severe complications that can worsen any existing health issues. This can lead to respiratory failure and sepsis, which is a severe infection that can cause multiple organ failure and abnormal blood clotting. There are also numerous other potential complications from bacterial pneumonia:

• Lung scarring
• Destruction of lung tissue
• Pneumonia that causes tissue death
• Impaired lung function for breathing
• Formation of hollow spaces in the lungs
• Collection of pus in the chest cavity
• Abscess or pus-filled cavity in the lung
• Meningitis, an infection of the brain and spinal cord membranes
• Death

Preventing Bacterial Pneumonia (Pneumonia)

Patients should be advised to quit smoking, avoid excessive alcohol consumption, and maintain good dental hygiene. These measures can help lower the risk of developing pneumonia. Pneumonia, particularly bacterial pneumonia, can be transmitted through the sharing of objects or through droplets in the air when we cough or sneeze. That’s why good hand hygiene is key to preventing the spread of this disease.

Further, there are certain preventative measures recommended specifically for bacterial pneumonia. These include:

– Getting a pneumococcus vaccine if you’re older or have a weakened immune system
– Keeping up with annual flu shots if you fall under the at-risk groups

Finally, if you’re elderly or have a compromised immune system, it’s crucial to reach out to a healthcare professional as soon as possible if you experience symptoms such as shortness of breath, intense shivering or fever. By doing so, you can get earlier medical attention and help prevent any further complications.