Mycoplasmal pneumonia is one of the most common types of community-acquired pneumonia in otherwise healthy people under age 40. It's caused by Mycoplasma pneumoniae, an interstitial bacterium that spreads in respiratory droplets. Unlike typical community-acquired pneumonia, which is usually caused by pneumococcal pneumonia, it's most likely to strike children and young adults age 5 to 20, and is often mistaken for asthma.
Although most patients with M. pneumoniae don't develop pneumonia, those with comorbid conditions (especially involving the lower respiratory tract) are at risk for serious respiratory distress. With community-acquired infections becoming more prevalent, it's essential to recognize the signs and symptoms early in order to treat the infection before it spreads.
Walking through the signs and symptoms
Sometimes called walking pneumonia, mycoplasmal pneumonia is most common in the summer and fall. Outbreaks in communities tend to be cyclical, occurring every 3 to 8 years. Hallmarks of the disease are a long, insidious onset and a long, gradual recovery. Wheezing and coughing are also characteristic, explaining why the illness is sometimes misdiagnosed as asthma. Most patients recover without complications in several weeks, but the infection may cause pneumonia in children and acute chest syndrome in patients with sickle-cell disease.
M. pneumoniae has a long incubation period (1 to 4 weeks).The gradual onset and length of the illness reflect M.
pneumoniae's distinctive properties:
* its affinity for both ciliary and nonciliary epithelial cells of the respiratory tract
* its ability to produce the damaging oxygen free radicals hydrogen peroxide and superoxide, which damage cells and cause inflammation.
Ciliary paralysis, cell damage, and inflammation of the respiratory tract lead to coughing and may result in lower respiratory tract infection.
Recognizing mycoplasmal pneumonia
When assessing a patient for possible M. pneumoniae infection, look for the following.
* upper respiratory tract signs and symptoms: pharyngitis, rhinorrhea
* lower respiratory tract signs and symptoms: crackles, rhonchi, wheezes, dyspnea, nonproductive cough, chest pain
* fever, chills, otalgia, and malaise.
Fever typically lasts more than 3 days. A prolonged fever, combined with the patient's history and other signs and symptoms, helps identify mycoplasmal pneumonia, especially when illnesses such as strep throat, acute otitis media, and sinusitis have been ruled out.
Keep in mind, however, that disease presentation is variable: 50% to 75% of patients with M. pneumoniae infection may develop only pharyngitis, otalgia, rhinorrhea, and fever.
Otalgia associated with M. pneumoniae may be caused by bullous myringitis, which is manifested as a lesion on the tympanic membrane. This lesion is a confirmatory finding of M. pneumoniae infection.
On physical exam, other clinical findings may include a nontoxic appearance, pharyngeal erythema without exudates, negative cervical adenopathy, or negative frontal and maxillary sinus tenderness.
X-ray and lab test findings
Early on, physical assessment findings may include clear breath sounds; wheezes, rhonchi, and/or crackles without evidence of consolidation on chest X-ray.
Unique findings on chest X-ray that can help confirm a diagnosis of mycoplasmal pneumonia include an absence of lobar consolidation, platelike atelectasis (seen on the lateral chest view as a thin, flat area of collapsed lung), nodular infiltration, and hilar adenopathy.
High-resolution computerized tomography scans of the chest are more sensitive than chest X-rays in identifying mycoplasmal pneumonia, but lack of availability and cost constraints limit their use.
Along with patient history, clinical findings, and chest X-ray, a serum cold agglutinin test may be performed to confirm the diagnosis. However, cold agglutinin tests are positive in only 50% to 70% of cases when performed 7 to 10 days after infection, so negative test results don't rule out M. pneumoniae infection.
Other diagnostic tests include complement fixation (CF) and enzyme-linked immunosorbent assay (ELISA). CF titers don't peak until 4 to 6 weeks after infection begins and may persist for up to a year. ELISA checks for immunoglobulin M, is specific and sensitive, and can be used to test for acute infection.3 Polymerase chain reaction testing may allow quicker diagnosis but isn't widely available.1,6 Respiratory secretions can be checked via a radiolabeled DNA probe to detect M. pneumoniae ribosomal DNA and is 90% sensitive, but also may not be widely available.1 Sputum stains are helpful only to rule out other diagnoses.
Antibiotic options
Macrolides are the antibiotics of choice for mycoplasmal pneumonia. Antibiotics that inhibit cell wall synthesis, such as penicillins, cephalosporins, and carbapenems, are ineffective with M. pneumoniae because the bacteria lack a cell wall.Antibiotics that work against M. pneumoniae, which are bacteriostatic rather than bactericidal, act on RNA-dependent protein synthesis needed for cell replication.
Macrolides most often prescribed for mycoplasmal pneumonia include erythromycin, clarithromycin, and azithromycin. The most common adverse reactions to these macrolides include nausea, vomiting, and diarrhea.
Tetracyclines such as doxycycline can also be used but are contraindicated in pregnant women and children under age 8. Fluoroquinolones such as levofloxacin and moxifloxacin are an option for some patients if macrolides or tetracyclines are contraindicated, but they shouldn't be used in patients under age 18.
Serious complications from mycoplasmal pneumonia are rare, but a cough may persist for 4 to 6 weeks after treatment.For more about possible complications, see When the course gets complicated.
Outpatient care
Most patients with mycoplasmal pneumonia are treated as outpatients. To manage coughing, the healthcare provider may recommend over-the-counter cough preparations containing dextromethorphan or prescribe cough medications with opiates, such as codeine or hydrocodone. Inform patients using opiates not to drive or operate heavy machinery. Advise them not to take cough preparations concurrently with other central nervous system depressants such as opioid analgesics, barbiturates, and alcohol. If an opiate is prescribed for a child, tell the parents to monitor closely for respiratory depression.
Coughing from airway hyperreactivity may respond well to beta2-agonists such as albuterol or levalbuterol. If these are prescribed for your patient, provide instruction on proper inhaler use with or without a spacer and/or nebulizer use.
Teach patients with mycoplasmal pneumonia about pain and fever management, including the proper use of acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs); both acetaminophen and NSAIDs can be combined in many over-the-counter drugs as well as prescription medications. Advise patients to read package labels and follow directions exactly to prevent unintentional overdose.
Inform patients that their cough may continue for up to 6 weeks after the illness has ended, but it doesn't mean they need more antibiotics or are still ill. Explain that the cough may worsen during exercise or cold temperature exposure and that using an inhaler, warming up before exercise, or covering the mouth and nose when exposed to cold air may help reduce cough and shortness of breath.
Also inform patients about the signs and symptoms of a worsening condition that require further intervention. Even though complications from mycoplasmal pneumonia are rare, 7% to 10% of patients may experience cardiovascular or neurologic complications, and some patients experience dermatologic complications. Advise patients to seek immediate emergency help if they experience any chest pain, especially pain at rest that's not associated with coughing; ascending weakness (which may be a sign of Guillain-Barr� syndrome); or increasing headache (especially associated with photophobia), nausea and vomiting, and nuchal rigidity, which may indicate meningitis or encephalitis. Skin manifestations that their healthcare provider should evaluate include painful nodules and target lesions involving the skin, oral mucosa, or conjunctiva.
ICU care
About 30% of patients with community-acquired pneumonia require hospitalization. Most patients admitted to the ICU need treatment for respiratory distress related to lower respiratory infection signs and symptoms and worsening pneumonia. Monitor vital signs and respiratory status and assess for cardiovascular, neurologic, or dermatologic complications. Keep in mind that patients with hemoglobinopathies, such as sickle-cell disease, are at increased risk for worsening respiratory signs and symptoms as well as hematologic complications.
Preventing transmission
Help patients prevent future transmission of mycoplasmal pneumonia by advocating good hygiene. Teach them to wash hands or use an alcohol-based hand sanitizer frequently, keep their hands away from the face (especially the mouth, eyes, and nose), cough or sneeze into the elbow or upper arm rather than the hand, stay away from others when ill (especially when febrile), keep phones clean, and avoid sharing drinking or eating utensils.
Early intervention is key
Infection with M. pneumoniae is generally self-limiting and mortality is low. Besides prevention, the best defense is prompt recognition and early intervention with appropriate antibiotics and supportive care.
When the course gets complicated
Common complications in patients with mycoplasmal pneumonia include pleural effusion, empyema, respiratory distress syndrome, and respiratory failure.
Other complications include:
* cardiovascular: endocarditis, myocarditis, or pericarditis
* neurologic: aseptic meningitis, encephalitis, Guillain-Barr� syndrome, transverse myelitis
* dermatologic: erythema multiforme, erythema nodosum, Stevens-Johnson syndrome, urticaria
* hematologic: patients with sickle-cell disease are at increased risk for hemolytic anemia and thrombocytopenia.
African American and Asian patients with hemoglobinopathies are also at risk for severe pleural effusions and marked respiratory distress as well as marked dermatologic problems such as digital necrosis.
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