TYPES OF SPECIFIC PNEUMONIA
TYPES OF SPECIFIC PNEUMONIA
It may be a primary respiratory infection or secondary to staphylococcal focus anywhere in the body. It is responsible for 5% of all pneumonias. Primary lesion in lung usually occurs as complication to influenza, otherwise it is common. It may occur in cystic fibrosis of lung as the cyst contains phydroxy-phenyl-acetic acid which increases the growth of these organisms. Haematogenous source may be seen in cases with septic thrombophlebitis, infective endocarditis or from infected intravascular device. The organism is Staphylococcus pyogenes. Onset is insidious and the temperature is remittent in type.
The lesion may be a lobar or segmental one indistinguishable from pneumococcal lesion but there may be formation of parenchymal necrosis resulting in multiple lung abscesses with thin walls (25%) . Empyema may develop in 5% of cases.
Treatment is difficult because the organisms are very frequently resistant to most of the antibiotics. Penicillinase resistant agent, e.g., Nafcillin is preferred treatment. It is better to have a culture of sputum with drug sensitivity test. Treatment is to be continued for at least 2 weeks. Longer treatment is better as it prevents relapse.
It usually occurs above 40 years of age. Organism is Klebsiella pneumoniae and this type of pneumonia is rare. It occurs in less than 1% of all pneumonias.
There is massive consolidation most commonly affecting the upper lobes along with other lobe or lobes. Profound toxaemia is present. Large amount of mucoid expectoration occurs which may have a chocolate colour. Alcoholics, diabetics and old debilitated subjects often develop this pneumonia. Resolution is extremely rare and often there is fibrosis, bronchiectasis or abscess formation. So, it is often confused with tuberculosis. Cephalosporin is usually preferred. In severe cases it should be added with Gentamycin, Tobramycin or Amikacin. The disease is fatal in 40%-60% of untreated cases but with adequate treatment the fatality rate is about 30%.
See Pulmonary tuberculosis
Primary Atypical Pneumonia (Mycoplasma pneumonia)
The main causative organism is Mycoplasma pneumonia which is the only definite mycoplasmal disease in man. This infection occurs endemically and may spread in the family through respiratory secretions. It may outburst in military barracks and schools. Tracheo-bronchitis is more common than pneumonia together with pharyngitis. Skin rash, erythema nodosum, encephalitis, myelitis, neuropathy, etc. may also develop.
Onset is gradual. Low grade fever, weakness, lassitude, headache, myalgia and cough are present. Cough is the dominant symptom which increases gradually and may sometimes come in paroxysm. Sputum is scanty and sometimes blood tinged. Chest signs are minimal and variable. X-ray finding is disproportionately greater than the clinical signs.
- Blood examination shows normal count.
- Sputum examination and culture show normal flora.
- Cold agglutinin test: 50% of the cases may develop cold agglutinin in a dilution of 1:32 or higher and agglutinate human type 0 red cells at 4°C not before 7-14 days. However, this is not helpful.
- Complement Fixation Test may also be positive.
- X-ray chest may show segmental mid or mid and lower lobe consolidation sometimes with effusion; but this is variable.
Variable-usually 3 days to 6 weeks. Slow recovery is usual.
Cefotaxime, Ceftriaxone, Ceftizoxime or Ceftazidime are preferred. If the infection is severe a combination of aminoglycoside and Cephalosporin is given.
VIRAL AND RICKETTSIAL PNEUMONIAS
Viruses of the psittacosis ornithosis group, respiratory syncytial viruses and others may produce pneumonia. Rickettsia burnettii which causes Q-fever may also produce pneumonia.
The lesion is similar to bacterial lesion but physical signs on the chest may not be prominent for few days. Constitutional symptoms are noticed first. Of these, headache and anorexia are very characteristic symptoms. Spleen may be palpable, blood picture may be normal. Cold agglutinin and agglutinin for streptococcus MG may be found in the blood. The disease is self-limiting in 5-10 days and sometimes responds to Tetracycline.
The organism of the Legionella family includes more than 40 species but about 50% are pathogens to human being. Legionella pneumophila is the most important species causing Legionellar’s disease. The organisms are present in water. Healthy individuals, patients with diseases of lungs, heart, kidney or cell mediated immunodeficiency diabetes and cancer cases suffer from this disease. Symptoms include fever, weakness, malaise, myalgia, headache, confusion, cough, dyspnoea. The disease may occur in any age but rare in children. The common age is 55 years. There may be a wide spectrum of illness starting from Flu like syndrome (Pontiac fever) to pneumonia. Cough is initially dry but later on becomes mucopurulent and sometimes there may be tinge of blood. Breathlessness depends on extent of pneumonia. Extrapulmonary features may be present but rare. Mental confusion, delirium, diarrhoea may be present. A relative bradycardia may be present in earlier stages. Hyponatremia and high ESR may be present. There may be patchy segmental or lobar non-consolidating pneumonia. The radiological shadows may aggravate inspite of antibiotics and radiological shadows may resolve very late or not at all. In immunodeficient subjects nodular lesion may be present which may cavitate.
Diagnosis is made by
a) Direct fluorescent antibody of respiratory secretion (95%).
b) Indirect fluorescent antibody testing (75%)
c) Gimenez staining of the fresh tissues and secretions.
d) Culture of the infected tissues or secretion in charcoal yeast extract media.
Erythromycin is the drug of choice. Erythromycin 500 mg IV 6 hourly may be given for 2 days and then 500 mg 6 hours orally for about 2-3 weeks. It may or may not be added with Rifampicin. Alternately Trimethoprim sulphamethoxazol, Clarithromycin or Ciprofloxacin may be given.
Pneumocystis Carinii Pneumonia
This protozoal infection occurs in association with immuno- suppression caused by Steroids rather than from cancer. This is very important in cases of AIDS. There may be fever, cough, pulmonary exudates with breathlessness. Bronchial lavage and open lung biopsy may reveal the organism. Trimethoprim sulphamethoxazole or Pentamidine may be used as treatment. Alternately Dapsone and Trimethoprim, Clindamycin and Primaquine may be given.
This occurs in 1%-5 % hospitalised patients; 60 % of ICU patients may develop this with heavy mortality. Gram negative organism from the patients’ oropharynx is the main source. To isolate the organism which is very difficult, bronchial lavage or aspirated material is required. Empirical coverage with antibiotics is required for treatment. Prognosis is bad.