The incubation period is from 2 to 10 days in the legionnaires disease. The initial symptoms of both legionnaires disease and Pontiac fever are characterized by anorexia, malaise, myalgia (muscle pain) and headache. In the term of a day, fever can appear rising quickly, with temperatures between 39 ºC and 40.5 ºC accompanied by chills. Dry cough and chest pain, occasionally pleuritic, may be prominent and when combined with hemoptysis (blood expectoration), can mistakenly suggest a pulmonary embolism. Gastrointestinal symptoms are important, especially diarrhea, which occurs between 20% and 40% of cases; the stools are more liquid than bloody.
The clinical spectrum of the disease due to Legionella species is broad and ranges from asymptomatic infection to rapidly progressive pneumonia. Legionnaires’ disease cannot be distinguished clinically or radiologically from pneumonia caused by other agents, and evidence of infection by other respiratory pathogens does not exclude the possibility of concomitant infection with Legionella.
The Diagnosis Of Legionnaires Disease Can Be Confirmed By Any Of These Methods:
-Isolation by Legionella culture in respiratory secretions or tissues.
-Microscopic visualization of the bacterium in the respiratory secretions or tissues by immunofluorescent microscopy.
-Detection of antigens in urine in the case of Legionellosis due to L. pneumophila serogroup 1 by radioimmunoassay.
-Detection of elevation of the antibody titer up to = 1: 128 in paired samples of sera by the indirect immunofluorescence test.
Because each of the legionnaires disease tests mentioned above complements each other, the completion of these, when the disease is suspected, increases the probability of confirming the diagnosis. However, since none of the laboratory tests is 100% sensitive, the diagnosis of Legionellosis is not excluded if one or more of these are negative. Of the available tests, the most specific is the isolation in the culture of the Legionella species from any sample of the respiratory tract.
Can Legionnaires Disease Be Cured?
The legionnaires disease can be cure. The treatment for legionnaires disease is based on the use of antibiotics, which should be chosen from the group of macrolides (erythromycin, clarithromycin, azithromycin…) which are widely used antibiotics in respiratory infections. Recently, another group of antibiotics (quinolones) have also shown their activity. In general, hospital admission is usually required due to the severity of the legionnaires disease.
The delay of an appropriate treatment against Legionella pneumonia contributes to significantly increase mortality from this disease; that is why a specific therapy should be initiated in the face of severe cases of community-acquired pneumonia.
Historically, the medication of choice for legionnaires disease has been Erythromycin, but gastrointestinal intolerance and ototoxicity (being toxic to the ear) caused by doses of up to 4 grams of this drug have made it in recent years considered less attractive compared to the new existing macrolides, especially Azithromycin, which is more active in vitro and penetrates more easily in lung tissue. Other antibiotics such as clarithromycin, josamycin, and roxithromycin have been effective in anecdotal reports.
The quinolones also have higher in vitro activity and higher intracellular penetration than the macrolides. Numerous cases have been successfully treated with quinolones, especially with ciprofloxacin.
Due to the pharmacological interaction of macrolides and rifampicin with immunosuppressive drugs after transplantation, ciprofloxacin or levofloxacin is recommended for cases of Legionnaires’ Disease in transplant recipients.
Other legionnaires disease drugs such as Tetracycline, minocycline, doxycycline, imipenem, trimetropim sulfamethoxazole, and ofloxacin are very effective for the treatment of this disease.
The administration of intravenous antibiotics should not be substituted by the oral route until a clinical improvement of the legionnaires disease patient is observed, which in most cases usually occurs after three days when the fever disappears.
The total duration of legionnaires disease treatment is 10 to 14 days, although it can be prolonged up to 21 days in those immunosuppressed patients or with evidence of the disease on chest radiography, for this a 5- to 10-day treatment with Azithromycin is recommended.
In general, it is possible to affirm that macrolides and quinolones are the antibiotics of choice in immunosuppressed patients, both with nosocomial pneumonia and community-acquired pneumonia, as well as in cases of pneumonia due to other pathogenic agents.