Pφ

Pneumonia is an infection of the lung parenchyma, usually occurring after aspiration of upper airway resident flora or inhalation of aerosolized material. Bacterial pneumonia is a common cause of morbidity and mortality in older adults, especially in those with comorbidities such as diabetes or congestive heart failure. A yearly influenza vaccine is important for all patients. Immunization with the 23-valent pneumococcal polysaccharide vaccine is recommended for all patients over the age of 64 years and other adults with specific risk factors. The 13-valent pneumococcal conjugate vaccine has recently been FDA approved for use in adults 50 years of age and older. The most common pathogens associated with community-acquired bacterial pneumonia are Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila, Haemophilus influenzae, and Moraxella catarrhalis.

TP

The patient with community-acquired bacterial pneumonia typically has fever, rigors, pleuritic chest pain, and cough productive of purulent sputum. In patients with atypical pneumonia the fever may be low grade, and patients may have nonproductive cough and no chest pain. However, there is variation in the initial symptoms and signs such that these presentations cannot reliably distinguish the specific infectious cause of the pneumonia. On physical exam there may be signs of consolidation, which can include the presence of localized dullness to percussion, increased tactile fremitus, and crackles. Examples of these sounds can be heard at this website: http://www.rale.ca/Repository.htm.

Dx

Chest radiographs (PA and lateral) reveal parenchymal opacities, which will establish the diagnosis in the appropriate clinical setting (i.e., leukocytosis, fever, sputum production). A CBC with differential may help determine if there is a bacterial infection, and specifically, a differential will indicate a “left shift,” or increased numbers of bands, which suggests that a bacterial etiology is likely. An ABG measurement may help determine the severity of hypoxemia and inpatient disposition (i.e., whether admission to the ICU is necessary).

Pathogen identification should be attempted before antimicrobial therapy is initiated; this is especially important whenever the result is likely to change the approach to management, especially in patients in whom drug-resistant pathogens are eventually isolated. Pretreatment blood cultures should be drawn. Sputum Gram stain and culture should be obtained in hospitalized patients, because sensitivities can help guide therapy and help tailor antibiotics toward a specific organism. Patients with severe community-acquired pneumonia should also have urinary antigen tests sent for L. pneumophila and S. pneumoniae, although the Legionella urinary antigen is positive only in cases caused by L. pneumophila serogroup I. CT of the chest is usually not necessary to establish the diagnosis but should be considered if a complicated infection is considered (e.g., post-obstructive pneumonia or empyema). HIV testing should be considered in patients who have risk factors associated with this disease. A diagnosis of HIV would be important to know so as to also consider infection caused by certain opportunistic organisms (e.g., Pneumocystis jirovecii or Mycobacterium tuberculosis).

Pφ

Bronchitis is inflammation of the respiratory system, which includes the nasal passages down to the trachea and bronchi but does not include the lung parenchyma, so the chest radiograph is clear. Acute bronchitis is most commonly a result of a viral infection that may last up to 2 weeks but occasionally may be caused by bacterial pathogens similar to those that cause community-acquired pneumonia.

TP

Patients with bronchitis usually present with a several-day history of symptoms such as fever, rhinorrhea, and cough, which may be purulent in nature. Patients may suffer from sore throat due to a pharyngeal irritation secondary to cough. Patients also may have been exposed to a sick contact.

Dx

A patient with clinical presentation of an acute onset of fever, cough, and purulent sputum, but normal chest radiograph, is most likely suffering from acute bronchitis. The Gram stain, culture, and sensitivity of the sputum may reveal the infecting pathogen but are not usually part of routine management.

Pφ

TB is an infectious disease caused by M. tuberculosis, an airborne infection that is spread through the respiratory secretions of people with active TB. Droplet nuclei travel directly to alveoli upon inspiration. Tubercle bacilli incite an inflammatory response known as granulomatous inflammation.

TP

The typical presentation of a patient with tuberculosis is cough for several weeks associated with fever, night sweats, and weight loss. The patient will often describe waking up with the bed sheets being soaked or drenched with sweat. Patients who abuse injection drugs, are incarcerated, are indigent, or are from high-incidence locations (e.g., foreign endemic areas) are at increased risk for TB.

Dx

Diagnosis can be suggested by positive sputum smears for acid-fast bacilli. Bronchoscopy for sputum is also useful in establishing the diagnosis in some cases, if acid-fast smears of expectorated sputum are negative. If the AFB smear is positive, nucleic acid amplification tests such as polymerase chain reaction (PCR) on the sample can be performed to specifically probe for M. tuberculosis. Cultures and in vitro susceptibility testing are necessary for definitive diagnosis and to guide antituberculous chemotherapy.

Pφ

Influenza results from infection with one of three basic types of influenza virus—A, B, or C. Influenza virus infection occurs after transfer of respiratory secretions from an infected individual to a person who is immunologically susceptible. If not neutralized by secretory antibodies, the virus invades airway and respiratory tract cells. Once the virus is within host cells, cellular dysfunction and degeneration occur, along with viral replication and release of viral progeny. Systemic symptoms result from inflammatory mediators, similar to other viruses.

TP

The incubation period of influenza ranges from 18 to 72 hours. Patients typically present with acute onset of fever, cough, chills, and myalgias. Patients will also have typical upper respiratory tract infection symptoms including sinus congestion, rhinorrhea, and sore throat.

Dx

The standard for diagnosing influenza A and B is viral culture of nasopharyngeal samples and/or throat samples. Rapid tests (enzyme immunoassays or nucleic acid detection–based assays) can document influenza A or B virus rapidly but have limited sensitivity (50–70%) in adults. Due to costs, sensitivity, and availability, however, most physicians make the diagnosis based on clinical suspicion. A chest radiograph may be useful in helping to exclude pneumonia.

Pφ

Bronchiectasis is irreversible dilation and destruction of large bronchi secondary to chronic infection and inflammation. This destruction is facilitated by the fact that most of the causes are related to impaired mucus clearance. The most common causes are repeated infections, cystic fibrosis, and immune defects.

TP

A patient who has developed bronchiectasis due to persistent infections may present with cough for many years and a history of recurrent pneumonia. A patient with bronchiectasis may have a similar presentation to that of a patient with pneumonia, but the patient with bronchiectasis has many recurring episodes associated with a longer course. Eliciting a history of copious sputum production on a daily basis also points to a possible diagnosis of bronchiectasis.

Dx

A diagnosis of bronchiectasis can be made on chest radiograph, where one will find the typical tram-track appearance caused by dilated, thick-walled bronchi. High-resolution CT of the chest is the test of choice, however, for defining the extent of bronchiectasis; the test is nearly 100% sensitive and specific. The CT typically shows thickening of the airways characterized by tram-track parallel lines or ring shadows representing thickened bronchial walls when imaged in cross-section.

Pφ

CF is a result of a defect in the gene encoding the CFTR protein. This protein is responsible for the flow of electrolytes across cell membranes. The abnormalities in salt and water transport across the cell membrane in patients with CF lead to a change in the composition of respiratory tract secretions, resulting in impaired mucociliary clearance, predisposition to infection, and airway obstruction. This eventually progresses to end-stage lung disease in many affected patients.

TP

Patients with CF typically present with recurring episodes of pneumonia throughout their lifetime. CF has several clinical manifestations in other organ systems, especially the gastrointestinal, endocrine, and reproductive systems. The gastrointestinal manifestations include fat malabsorption due to exocrine pancreatic insufficiency and distal intestinal obstruction syndrome (DIOS) due to thick mucus blocking bowel contents. Pancreatic damage also results in reduced insulin secretion and diabetes, while infertility is common in males due to congenital absence or obstruction of the vas deferens.

Dx

The sweat chloride test, in combination with newborn screening and/or a sibling with a known diagnosis of CF, can establish the diagnosis. The sweat chloride test must be repeated twice to be considered abnormal; in adults, a level > 60 mEq/L and a typical clinical presentation are suggestive of CF. The criteria for diagnosis are elevated sweat chloride level on two occasions or identification of mutations known to cause CF in both CFTR genes or in vivo demonstration of characteristic abnormalities in ion transport across the nasal epithelium, plus one or more phenotypical features of CF, as follows: sino-pulmonary disease, characteristic nutritional or gastrointestinal disorders, obstructive azospermia, salt loss syndrome, a sibling with CF, or positive newborn screening.