WORKUP	Section 5 of 9
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Lab Studies:

• The WBC count generally is not helpful, since results may be normal or elevated. Hemolytic anemia has been described, but it is rare.

• Sputum Gram stains and cultures usually are not helpful, except in excluding other pathogens.

• Elevated erythrocyte sedimentation rates may be present.

Imaging Studies:

• Radiographic findings are variable, but 4 distinct patterns have been described frequently in mycoplasmal pneumonia.

• Bronchopneumonia often involves a single lower lobe. Lobar consolidation is rare.

• Platelike atelectasis is noted as thin, flat areas of collapsed lung and often is seen on a lateral image of the chest.

• Nodular infiltration may resemble that associated with other diseases with granulomatous pathology, such as tuberculosis, mycoses, and sarcoidosis.

• Hilar adenopathy sometimes is mistaken for malignancy.

• Pleural effusions can be seen rarely on lateral decubitus films.

• High-resolution CT scans have been shown in small series to be more sensitive than chest radiography in demonstrating lung disease.

Other Tests:

• Serology tests that demonstrate a 4-fold or greater increase or decrease in paired sera titers or a single titer greater than or equal to 1:32

• Serum cold agglutination is a nonspecific test for M pneumoniae, but findings are positive in 50-70% of patients after 7-10 days of infection. A negative result does not exclude infection, and this test may be affected by cross-reactions with other pathogens, such as adenovirus, Epstein-Barr, and measles viruses. A quick bedside test can be performed by partially filling a purple-top tube with blood and placing it in ice; a positive finding is one in which "grains of sand" appear on the glass portion of the tube.

• Other serological tests include complement fixation, enzyme-linked immunoassay, and indirect hemagglutination. All of these have acceptable sensitivity and specificity.

• Polymerase chain reaction

• Polymerase chain reaction (PCR) has been shown to accurately diagnose atypical pneumonia and has been used for epidemiologic studies, but it is currently not used in most clinical settings.

• A radiolabeled DNA probe detects M pneumoniae ribosomal RNA in respiratory secretions with 90% sensitivity.

	TREATMENT	Section 6 of 9
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Emergency Department Care: In general, mycoplasmal pneumonia is a diagnosis that does not need emergency treatment. However, various pulmonary and extrapulmonary complications may occur and may require emergent attention.

	MEDICATION	Section 7 of 9
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Several antimicrobials are effective in reducing the length of illness due to mycoplasmal pneumonia.

Drug Category: Antibiotics -- Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting. In the treatment of mycoplasmal pneumonia, antimicrobials against M pneumoniae are bacteriostatic, not bactericidal.

Drug Name	Erythromycin (EES, Erythrocin, E-mycin) -- Inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes and causing RNA-dependent protein synthesis to arrest; for treatment of staphylococcal and streptococcal infections.
Adult Dose	500 mg PO qid for 7-10 d
Pediatric Dose	7.5-12.5 mg/kg/dose PO qid for 7-10 d
Contraindications	Documented hypersensitivity; hepatic impairment
Interactions	Coadministration may increase toxicity of theophylline, digoxin, carbamazepine, and cyclosporine; may potentiate anticoagulant effects of warfarin; coadministration with lovastatin and simvastatin increases risk of rhabdomyolysis
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Caution in liver disease; estolate formulation may cause cholestatic jaundice; GI adverse effects are common (give doses pc); discontinue use if nausea, vomiting, malaise, abdominal colic, or fever occur

Drug Name	Azithromycin (Zithromax) -- One of the newer macrolides; very effective against M pneumoniae. Perhaps the most common agent used to treat M pneumoniae given its ease of administration.
Adult Dose	Day 1: 500 mg PO Days 2-5: 250 mg/d PO
Pediatric Dose	<6 months: Not established >6 months: day 1: 10 mg/kg PO once; not to exceed 500 mg/d; days 2-5: 5 mg/kg/d PO; not to exceed 250 mg/d
Contraindications	Documented hypersensitivity; hepatic impairment; do not administer with pimozide
Interactions	May increase toxicity of theophylline, warfarin, and digoxin; effects are reduced with coadministration of aluminum and/or magnesium antacids; nephrotoxicity and neurotoxicity may occur when coadministered with cyclosporine
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Site reactions can occur with IV route; bacterial or fungal overgrowth may result with prolonged antibiotic use; may increase hepatic enzymes and cholestatic jaundice; caution in patients with impaired hepatic function, prolonged QT intervals, or pneumonia; caution in hospitalized, geriatric, or debilitated patients

Drug Name	Clarithromycin (Biaxin) -- Reversibly binds to the P site of the 50S ribosomal subunit of susceptible organisms and may inhibit RNA-dependent protein synthesis by stimulating the dissociation of peptidyl tRNA from ribosomes; result is bacterial growth inhibition.
Adult Dose	250 mg PO bid for 7-14 d
Pediatric Dose	<6 months: Not established >6 months: 7.5 mg/kg/dose PO bid for 10 d
Contraindications	Documented hypersensitivity; coadministration of pimozide
Interactions	Toxicity increases with coadministration of fluconazole and pimozide; effects decrease and GI adverse effects may increase with coadministration of rifabutin or rifampin; may increase toxicity of anticoagulants, cyclosporine, tacrolimus, digoxin, omeprazole, carbamazepine, ergot alkaloids, triazolam, HMG CoA-reductase inhibitors; plasma levels of certain benzodiazepines may increase, prolonging CNS depression; arrhythmias and increase in QTc intervals occur with disopyramide; coadministration with omeprazole may increase plasma levels of both
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Coadministration with ranitidine or bismuth citrate is not recommended with CrCl <25 mL/min; give half dose or increase dosing interval if CrCl <30 mL/min; diarrhea may be sign of pseudomembranous colitis; superinfections may occur with prolonged or repeated antibiotic therapies

Drug Name	Tetracycline (Sumycin) -- Treats susceptible bacterial infections of both gram-positive and gram-negative organisms, as well as infections caused by Mycoplasma, Chlamydia, and Rickettsia organisms; inhibits bacterial protein synthesis by binding with the 30S subunit and possibly the 50S ribosomal subunit of susceptible bacteria; as effective as erythromycin and other macrolides in the treatment of M pneumoniae infection.
Adult Dose	500 mg PO bid for 1-4 wk
Pediatric Dose	<8 years: Not recommended >8 years: 10-20 mg/lb (25-50 mg/kg) PO divided bid/qid
Contraindications	Documented hypersensitivity; severe hepatic dysfunction
Interactions	Do not give with dairy products or with any divalent cations (eg, Fe++, Ca++, Mg++); can increase hypoprothrombinemic effects of anticoagulants (monitor PT in patients taking both medications); coadministration can decrease the pharmacologic effects of oral contraceptives, causing breakthrough bleeding and increased risk of pregnancy
Pregnancy	D - Unsafe in pregnancy
Precautions	Photosensitivity may occur with prolonged exposure to sunlight or tanning equipment; reduce dose in renal impairment; consider determining drug serum levels in prolonged therapy; tetracycline use during tooth development (last half of gestation through age 8 y) can cause permanent discoloration of teeth; Fanconi-like syndrome may occur with outdated tetracyclines

	FOLLOW-UP	Section 8 of 9
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Further Inpatient Care:

• If patients with pneumonia due to M pneumoniae require admission, use of standard and droplet precautions are recommended for the duration of the illness.

Further Outpatient Care:

• Antibiotic prophylaxis for exposed contacts is not routinely recommended. However, macrolide or tetracycline prophylaxis should be used in households in which patients with underlying conditions may be predisposed to severe mycoplasmal infection (eg, those with sickle cell disease or antibody deficiencies).

Complications:

• Lobar consolidation

• Abscess

• Bronchiolitis obliterans

• Necrotizing pneumonitis

• Acute respiratory distress syndrome

• Respiratory failure

• Extremely rare extrapulmonary complications include the following: pericarditis, arthritis, Stevens-Johnson syndrome, hemolytic anemia, thrombocytopenia, CNS infections, Guillain-Barré syndrome, peripheral neuropathy, other neurologic manifestations, and ocular complications. Recently, an association has been proposed between M pneumoniae infection and Tourette syndrome, but this association has not been extensively studied.

Prognosis:

• With proper treatment, a full recovery is expected.

	BIBLIOGRAPHY	Section 9 of 9
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• Oermann C, Sockrider MM, Langston C: Severe necrotizing pneumonitis in a child with Mycoplasma pneumoniae infection. Pediatric Pulmonology 1997; 24: 61-65[Medline].
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• Reimann HA: An acute infection of the respiratory tract with atypical pneumonia: a disease entity probably caused by a filtrable virus. JAMA 1938; 111: 2377-2384.
• Reittner P, Müller NL, Heyneman L, et al: Mycoplasma pneumoniae pneumonia: radiographic and high-resolution CT features in 28 patients. AJR Am J Roentgenol 2000 Jan; 174(1): 37-41[Medline].
• Tay YK, Huff JC, Weston WL: Mycoplasma pneumoniae infection is associated with Stevens-Johnson syndrome, not erythema multiforme (von Hebra). J Am Acad Dermatol 1996 Nov; 35(5 Pt 1): 757-60[Medline].
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Pneumonia, Mycoplasma excerpt