Aging Begins at 30

Fitting a Newer Pneumonia Into Practice

Ian Maclean Smith, M.D.
Emeritus Professor
Department of Internal Medicine
University of Iowa Hospitals and Clinics
Creation Date: November 2002
Last Revision Date: November 2002
Peer Review Status: Internally Peer Reviewed

Legionnaires' disease is now known to cause about 9 percent of pneumonia that occurs in the community and about 20 percent of pneumonia occurring in hospitalized patients. About 500 cases are diagnosed yearly but this may only be the tip of the iceberg, as estimates from other sources say there are 15,000 cases yearly in the United States. New tests such as finding Legionella material in the urine and fluorescent antibody tests or PCR (multiplication of trace infecting material) applicable to fresh sputum, have led to the diagnosis of previously undiagnosable pneumonia patients where the sputum shows many pus cells but no obvious organisms on microscopic examination.

Think of an elderly American Legionnaire, and you will know some of the risk factors such as cigarette smoking, chronic lung disease, and age. Also those on steroid medication, immunosuppression, with recent surgery, and transplant recipients are the target groups.

The organisms were found by microbiologists at CDC using charcoal (poison inhibiting), buffered, yeast agar with antibiotics added to suppress competing organisms. It takes 3 to 5 days to grow. It is a cocco-bacillus that is found in nature in water bodies especially if they are heat polluted. It can grow inside soil amoeba. It grows in water or soil contamination in urban environments too such as cooling towers, showers, air conditioning systems, vegetable sprayers in supermarkets, drinking coolers in auto plants, hospital respiratory equipment, whirlpool and Hubbard (burn treatment) baths, stagnant water systems and in potting soils. Patients with trouble swallowing after an ear, nose, or throat operation are at special risk. Annual or more often, surveys with cleaning are necessary to keep hospitals free of these hazards. Prevention depends on it. Water temperature was often lowered to avoid scalding older patients and this encouraged Legionella growth. The organism is chlorine tolerant.

A typical patient is a 60-year-old, white, non-hispanic male who develops fever up to 105 degrees F, general discomfort, muscle aches, lack of appetite and headache in the summertime. The patient also may be a large-volume water drinker. There is mild cough without much sputum and the chest x-ray will show pneumonia. About half have a small amount of fluid in the lung cavity (pleural effusion.) A mistaken diagnosis of pulmonary embolus (loose leg clots to the lung) can be made. With chronic lung disease, the patient has lost the wave-like cilia hair in the lung tubes that removes invading organisms. Diarrhea develops in a third. About a third will have developed their disease in the hospital, a quarter will be part of a pneumonia outbreak, and about a fifth have been traveling in the two weeks before illness. The doctors may get a tip off by finding low blood sodium. Only a third of the cases are diagnosed correctly, but recent guidelines to treat pneumonia of uncertain type with erythromycin will get them properly treated.

Treatment depends on a proper diagnosis and the use of erythromycin derivatives (macrolides) such as azithromycin or with fluoroquinolones, including ciprofloxacin or both. Tetracyclines such as doxycycline are helpful in milder illnesses. The chest x-ray is slow to respond and is not helpful in following the course of the patient's illness.

Fatalities have fallen in recent years from 34 percent to 12 percent. The rapid diagnostic tests pick up sick patients sooner with better results.

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See related Patient Topics Infections, Legionnaires' Disease or Lungs and Breathing.

See related Provider Topics Infections or Lungs and Breathing.

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