Community-acquired pneumonia (CAP)

Community-acquired pneumonia (CAP) is a type of pneumonia found in people outside health care facilities. Pneumonia that occurs in patients in health care facilities such as hospitals and nursing homes or in people who recently were patients in such facilities is known as hospital-acquired pneumonia. Pneumonia is an illness that involves infection of the lungs. Pneumonia is very common in the United States, affecting millions of Americans each year. Certain people are at greater risk of pneumonia than others, including people with chronic lung diseases, people who smoke, very young children, and older adults. According to the Centers for Disease Control and Prevention (CDC), over 41,000 Americans died from pneumonia in 2022.

Background

Anyone can acquire CAP, but certain risk factors make an individual more likely to catch the illness. These risk factors include chronic lung diseases, such as asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis, and cystic fibrosis; smoking; brain disorders, including dementia, stroke, and cerebral palsy; weakened or suppressed immune system; serious medical conditions, such as heart disease, cirrhosis of the liver, or diabetes; recent surgery; and recent trauma. Furthermore, people aged two or younger and people aged sixty-five or older are at greatest risk of CAP.

Several types of pathogens can cause CAP, including bacteria, viruses, and fungi. The most common cause of CAP is the bacteria Streptococcus pneumoniae. Other bacteria that commonly cause CAP are Haemophilus influenzae and Moraxella catarrhalis. Human rhinovirus (the common cold), influenza, and the virus that causes COVID-19 are common viruses that can cause CAP. Certain fungi present in bird droppings or soil may cause CAP.

The pathogens that cause CAP may enter the lungs in various ways. Pathogens can be inhaled into the lungs through the air. Pathogens can enter the lungs on food, liquid, vomit, or saliva that is inhaled. For example, pathogens may enter the lungs when an individual chokes on a piece of food. Additionally, pathogens that live in the nose, mouth, or sinuses can spread to the lungs.

Overview

An individual who has CAP may experience various symptoms. Common symptoms of CAP include cough, fever, shortness of breath, and shaking chills. Cough may be accompanied by green, yellow, or bloody mucus. Other symptoms are sweating; clammy skin; headache; loss of appetite; fatigue; malaise; chest pain when breathing or coughing; nausea, vomiting, or diarrhea; and leukonychia, which is also known as white nail syndrome. In people who are sixty-five or older, CAP may produce confusion.

In addition to these symptoms, CAP may cause complications. Possible complications are bacteremia, which is bacteria in the bloodstream; difficulty breathing; pleural effusion, which is accumulation of fluid around the lungs; empyema, which is infected fluid around the lungs; and lung abscess, which is a cavity in the lung that is filled with pus and surrounded by inflamed tissue.

An individual experiencing any of the symptoms of CAP should see a doctor. The doctor will take a medical history and perform a physical exam, listening for any abnormal sounds in the lungs with a stethoscope. Abnormal sounds include crackling or bubbling sounds. If abnormal sounds are present, the doctor will then order tests to determine a diagnosis. Common tests include a chest X-ray, blood tests, a computed tomography (CT) scan of the chest, a sputum culture, pulse oximetry, a bronchoscopy, and a pleural fluid culture. A CT scan of the chest is an imaging procedure that provides detailed images of the chest. A sputum culture is a test that analyzes the material from the lungs after it is coughed up. Pulse oximetry is a test that measures the oxygen level in the blood. A bronchoscopy is a procedure that involves examining the bronchi with a flexible tube. A pleural fluid culture is a test that analyzes the fluid between the lungs and the chest wall, or the pleural space, after the fluid is extracted via a needle that is inserted between the ribs.

If the doctor indeed diagnoses the patient with CAP, he or she will then devise the appropriate treatment plan. The doctor will first assess the severity of the illness and determine whether the patient requires hospitalization. If a hospital stay is necessary, treatment will likely consist of intravenous (IV) medications and fluids, oxygen therapy, and, if necessary, breathing treatments. The type of medication depends on the type of pathogen that is causing the condition. Bacterial pneumonia requires antibiotics, while viral pneumonia requires antivirals or similar medications. The most common first-line antibiotics for CAP are macrolides, a class including azithromycin, erythromycin, roxithromycin, and clarithromycin. However, S. pneumoniae has increasingly become resistant to this type of antibiotic, with nearly half of cases of S. pneumoniae resisting macrolides in most parts of the United States. Scientists have explored alternative antibiotic regimens for bacterial pneumonia, including beta-lactam antibiotics such as amoxicillin, cephalosporins such as cefdinir, and doxycycline.

If hospitalization is not necessary, the patient may be treated at home with prescription medications. Again, the type of medication depends on the type of pneumonia the patient has. The doctor will instruct the patient to rest. The doctor also may suggest using a humidifier or placing a warm, moist washcloth on the face, both of which may be effective in loosening mucus. By following such treatment, the patient should feel better within two weeks. The doctor may then send the patient for an X-ray to determine whether the lungs have cleared up. If left untreated, a severe case of CAP can be fatal, especially in older people, people with a weakened or suppressed immune system, and people with serious medical conditions.

Several steps can be taken to help prevent CAP. First and foremost, smoking should be avoided. Getting certain vaccines, including the flu vaccine and the pneumococcal vaccine, can lower the risk of CAP. Employing proper handwashing may reduce the chances of acquiring CAP. This involves washing hands with soap and warm water for at least twenty seconds, making sure to scrub all areas of the hands, including the backs of the hands and between the fingers. Proper handwashing also includes washing hands before preparing food, before eating, after using the bathroom, after blowing one’s nose, after changing a diaper, and after coming in contact with a sick person.

Bibliography

Baer, Stephanie L., et al. “Community-Acquired Pneumonia (CAP).” Medscape, 18 Apr. 2024, emedicine.medscape.com/article/234240-overview#a2. Accessed 16 Oct. 2024.

Bender, Michael T., and Michael S. Niederman. "Treatment Guidelines for Community-Acquired Pneumonia." Annals of Research Hospitals, June 2018, arh.amegroups.com/article/view/4354/5289. Accessed 27 Feb. 2019.

“Pneumonia.” Mayo Clinic, 13 June 2020, www.mayoclinic.org/diseases-conditions/pneumonia/symptoms-causes/syc-20354204. Accessed 16 Oct. 2024.

“Pneumonia.” Johns Hopkins Medicine, www.hopkinsmedicine.org/health/conditions-and-diseases/pneumonia. Accessed 16 Oct. 2024.

“Community-Acquired Pneumonia in Adults.” MedlinePlus, 31 July 2022, medlineplus.gov/ency/article/000145.htm. Accessed 16 Oct. 2024.

“About Pneumonia.” Centers for Disease Control and Prevention, US Department of Health & Human Services, 7 Oct. 2024, www.cdc.gov/pneumonia/about/index.html. Accessed 16 Oct. 2024.

“Pneumonia Symptoms and Diagnosis.” American Lung Association, 12 Aug. 2024, www.lung.org/lung-health-diseases/lung-disease-lookup/pneumonia/symptoms-and-diagnosis. Accessed 16 Oct. 2024.

Sethi, Sanjay. “Community-Acquired Pneumonia.” Merck Manual Professional Version, Feb. 2024, www.merckmanuals.com/professional/pulmonary-disorders/pneumonia/community-acquired-pneumonia. Accessed 16 Oct. 2024.