Suspect legionella pneumonia in pneumonia patient who is on a cruise where the water was contaminated. Cardinal symptoms of legionnaire's disease are cough, fever, gastrointestinal symptoms, and confusion. Diagnose with the urine antigen test or urine culture. Treat with azithromycin or levofloxacin.
Along with mycoplasma and chlamydia, legionella forms the third most common pathogen implicated in atypical pneumonias. Legionella pneumonia is common in transplant patients, patients with renal failure, COPD, and smokers, but less common in healthy adults and children. In this clinical vignette, the patient is a setup for legionnaire’s disease. She has multiple comorbidities (COPD from longstanding smoking and chronic renal insufficiency from longstanding hypertension), she is an elderly individual, and she has a significant exposure having been on a cruise ship with a single water supply that can become contaminated. The urinary antigen assay is very sensitive, and the antigen may persist in the urine for weeks even after treatment has begun. As shown in this vignette, patients may also present with a transaminitis, gastrointestinal symptoms, and hypovolemic hyponatremia secondary to diarrhea. Treatment centers around a quinolone such as levofloxacin or a macrolide such as azithromycin.
Thibodeau and Viera discuss atypical pathogens in community acquired pneumonia such as mycoplasma, chlamydia, and legionella. Antibiotic treatment is empiric and includes coverage for both typical and atypical organisms. Doxycycline, a fluoroquinolone with enhanced activity against Streptococcus pneumoniae, or a macrolide is appropriate for outpatient treatment of immunocompetent adult patients. Hospitalized adults should be treated with cefotaxime or ceftriaxone plus a macrolide, or with a fluoroquinolone alone.
Decker and Palmore discuss the role of water in healthcare-associated infections. Legionella can colonize a hospital water system and infect patients even with use of preventative disinfectants. Other water sources that may be contaminated include sinks, room humidifiers, and fountains. Gram negative pathogens may also be transmitted well in water.
Guyard and Low discuss travel associated legionella infections. Because of the propensity of this bacterium to colonize man-made water systems, legionella is frequently reported in travelers who stay in accommodations such as hotels or cruise ships, and thus this diagnosis must be considered in the differential in a patient who presents with pneumonia after travel.
Illustration A depicts the classic pattern of an atypical pneumonia such as legionella on chest X-ray. Note the interstitial bilateral infiltrates.
Answer 2: In a patient with methicillin sensitive staph aureus sepsis diagnosis is made with blood cultures, and the preferred treatment is oxicillin.
Answer 3: In a patient with sepsis secondary to a methicillin resistant staph aureus abscess diagnosis can be accomplished with blood cultures, and treatment is with intravenous vancomycin.
Answer 4: The FTA-abs is useful in diagnosis syphilis, which may be treated with penicillin.
Answer 5: Upper respiratory illnesses secondary to rhinovirus for instance may be diagnosed with a nasal swab PCR. Supportive care is all that is needed.
Thibodeau KP, Viera AJ. Atypical pathogens and challenges in community-acquired pneumonia. Am Fam Physician. 2004 Apr 1;69(7):1699-706.
PMID:15086042 (Link to Abstract)
Decker BK, Palmore TN. The role of water in healthcare-associated infections. Curr Opin Infect Dis. 2013 Aug;26(4):345-51. doi: 10.1097/QCO.0b013e3283630adf.
PMID:23806897 (Link to Abstract)
Guyard C, Low DE. Legionella infections and travel associated legionellosis. Travel Med Infect Dis. 2011 Jul;9(4):176-86. doi: 10.1016/j.tmaid.2010.05.006. Epub 2010 Jun 16.
PMID:21995862 (Link to Abstract)