This is a common cause of pneumonia. It often occurs in patients in their teens and twenties, frequently amongst those living in boarding institutions. Generalized features such as headaches and malaise often precede the chest symptoms by 1-5 days. Cough may not be obvious initially and physical signs in the chest may be scanty. On chest X-ray, usually only one of the lower lobes is involved but sometimes there may be dramatic shadowing in both lower lobes. There is frequently no correlation between the X-ray appearances and the clinical state of the patient.
The white blood cell count is not raised. Cold agglutinins occur in half of the cases. The diagnosis is confirmed by a rising antibody titre. Treatment is with erythromycin 500 mg four times daily for 7-10 days. Tetracycline is effective.
Although most patients recover in 10-14 days. the disease can be protracted. with cough and X-ray appearance lasting for weeks and relapses occurring. Lung abscesses and pleural effusions are rare.
Extrapulmonary complications can occur at any time during the illness and occasionally dominate the clinical picture. Most are rare but they include:
• Myocarditis and pericarditis
• Rashes and erythema multiforme
• Haemolytic anaemia and thrombocytopenia
• Myalgia and arthralgia
• Meningo-encephalitis and other neurological abnormalities
• Gastrointestinal symptoms (e.g. vomiting. diarrhoea)
Viral pneumonia is uncommon in adults. bacteria being the usual cause of the pneumonia per se. Influenza A virus or adenovirus infection can occasionally produce pneumonia.
Haemophilus iniluenzae H. inJluenzae is frequently identified in the yellow-green sputum produced during exacerbation of chronic bron chitis. It is therefore not surprising that this organism may be the cause of pneumonia in people suffering from chronic bronchitis and emphysema. The pneumonia can be diffuse or confined to one lobe. There are no special features to separate it from other bacterial causes of pneumonia. It responds well to treatment with oral cefaclor 250 mg 8-hourly.
Typically the individual has been working with infected birds, especially parrots, but a history of contact is not always elicited. The incubation period is 1-2 weeks and the disease may pursue a very low-grade course over several months. Symptoms include malaise, high fever, cough and muscular pains. The liver and spleen are occasionally enlarged and scanty ‘rose spots’ may be seen on the abdomen. The chest X-ray shows segmental or a diffuse pneumonia. Occasionally the illness presents with a high, swinging fever and dramatic prostration with photophobia and neck stiffness that can be confused with meningitis. The diagnosis is confirmed by the demonstration of a rising titre of complement-fixing antibody. Erythromycin or tetracycline are the antibiotics of choice.
Chlamydia pneumoniae has only recently been recognized as a respiratory pathogen in man. Outbreaks have been reported in institutions and within families suggesting person-to-person spread without any avian or animal reservoir. Serological tests on patients admitted to hospital with community-acquired pneumonia suggest that 5- 10% may be the result of C. pneumoniae infection. Since this infection has only recently been recognized it may account for a substantial number of previous pneumonias in which no organism had been isolated. In general, disease is mild with 50% of C. pneumoniae infections presenting as pneumonia, 28% as acute bronchitis, 10% with a ‘flu-like illness and 12% with upper respiratory illnesses. Type-specific micro immunofluorescence tests are required to distinguish C. pneumoniae from C. psittaci and C. trachoma tis. Treatment is with erythromycin or tetracycline.
Staph. aureus normally only causes a pneumonia after a preceding influenza! viral illness. The infection starts in the bronchi, leading to patchy areas of consolidation in one or more lobes, which break down to form abscesses. These may appear as cysts on the chest X-ray. Pneumothorax, effusion and empyemas are frequent. Septicaemia develops with metastatic abscesses in other organs. Fulminating staphylococcal pneumonia occurring in influenza epidemics can lead to death in hours. All patients with this type of pneumonia are very ill; intravenous antibiotics must be administered promptly, but are not always effective.
Areas of pneumonia (septic infarcts) are also seen in staphylococcal septicaemia. This is frequently seen in intravenous drug abusers and also in patients with central catheters being used for parenteral nutrition. The infected puncture site is the source of the Staphylococcus. Pulmonary symptoms are often few but breathlessness and cough occur and the chest X-ray reveals areas of consolidation. Abscess formation is frequent.
Diagnosis and treatment Coxiella bumetii (Q-fever)
The patient develops systemic symptoms of fever, malaise and headache, often associated with multiple lesions on the chest X-ray. The illness may run a chronic course and is occasionally associated with endocarditis. Diagnosis is made by an increase in the titre of complement-fixing antibody, and erythromycin or tetracycline is the usual treatment.
Three epidemiological patterns of this disease are recognized:
1 Outbreaks amongst previously fit individuals staying in hotels, institutions or hospitals where the shower facilities or cooling systems have been contaminated with the organism
2 Sporadic cases occurring in many parts of the world where the source of the infection is unknown 3 Outbreaks occurring in immunocompromised patients and in middle-aged and elderly male smokers Legionella grows well in water up to 40°C in temperature, and the infection is almost certainly spread by the aerosol route. Adequate chlorination and temperature control of the water supply are important factors in the prevention of the disease.
The incubation period is 2-10 days. Males are affected twice as commonly as females. The infection may be mild, but the characteristic picture is of malaise, myalgia, headache and a fever with rigors and a pyrexia of up to 40°C. Half of the patients have gastrointestinal symptoms, with nausea, vomiting, diarrhoea and abdominal pain. Patients may be acutely ill, with mental confusion and other neurological signs. Haematuria occurs and occasionally renal failure.
The patient is tachypnoeic with initially a dry cough that later may become productive and purulent. The chest X-ray usually shows unilateral lobar and then multilobar shadowing, sometimes with a small pleural effusion.
Cavitation is rare.
A strong presumptive diagnosis of L. pneumophila infection is possible in the majority of patients if they have three of the four following features:
1 A prodromal virus-like illness
2 A dry cough, confusion or diarrhoea
3 Lymphopenia without marked leucocytosis
Hypoalbuminaemia and abnormal levels of liver enzymes are common in this disease. The diagnosis is confirmed by a change in antibody titre, but the quickest way is by the direct immunofluorescent staining of the organism in the pleural fluid, sputum or bronchial washings. A Gram stain does not detect the organism. Culture is possible but takes up to 3 weeks.
The organism is sensitive to erythromycin, which is the antibiotic of choice. Rifampicin is also being used. Mortality can be up to 30% in elderly patients but most patients recover spontaneously.
Prevention is important with chlorination and sealing of water supplies.
These are the cause of many hospital-acquired pneumonias but they are occasionally responsible for cases in the community.
Klebsiella pneumoniae. Pneumonia due to Klebsiella usually occurs in the elderly with a history of heart or lung disease, diabetes, alcohol excess or malignancy. The onset is often sudden, with severe systemic upset. The sputum is purulent, gelatinous or blood-stained. The upper lobes are more commonly affected and the consolidation
is often extensive. There is often swelling of the infected lobe so that on the lateral chest X-ray there is bulging of the fissures. The organism can be found in the sputum or in the blood. Treatment is dependent on the sensitivity of the organism, but a cephalosporin or chloramphenicol is usually required. The mortality is high, partly owing to the presence of an underlying condition. Pseudomonas aeruginosa. Pneumonia due to this organism is of considerable significance in patients with cystic fibrosis, since it correlates with a worsening clinical condition and mortality. It is also seen in patients with neutropenia following cytotoxic chemotherapy. The isolation of P. aeruginosa must be interpreted with care because the organism grows well on bacterial culture medium and may simply represent contamination from the upper airways. Pseudomonal and other Gram-negative infections respond well to treatment with the 4-quinolone antibiotic ciprofloxacin (100-200 mg i.v. over 30-60 min twice daily) or ceftazidime (2 g bolus i.v. 8-hourly). The combination of tobramycin 3-5 mg kg-l i.v. or i.m. daily in 8-hourly doses together with carbenicillin 5 g i.v. 4-6-hourly is now less commonly used. These antibiotics can however be inhaled direct into the lung via nebulizers and are still used in patients with CF.
Modifications may have to be made in the light of sensitivity testing. Tobramycin is nephrotoxic and also produces vestibular damage, so that blood levels should be monitored. Azlocillin and ticarcillin are also available. Moraxella catarrhalis. This organism, previously known as Branhamella catarrhalis, has been found to be associated with exacerbations of chronic bronchitis and occasionally with fatal pneumonia. Some strains produce a f3-lactamase capable of destroying amoxycillin. The exact role of this organism in bronchopulmonary infection remains to be determined.
Infections with these organisms usually occur in those with an underlying condition, e.g. diabetes, and are often associated with aspiration. Bacteroides is the commonest organism and is sensitrve to metronidazole. The prognosis depends largely on the precipitating cause.