Pneumonia caused by S. aureus
serious and rapidly progressive infection.
less frequent than viral or pneumococcal pneumonia.
Epidemiology.
preceded by a viral upper respiratory tract infection.
30% of all patients are younger than 3 mo
70% are younger than 1 yr.
Boys are affected more commonly than girls.
Pathogenesis.
cause confluent bronchopneumonia
often unilateral or more prominent on one side than the other
extensive areas of hemorrhagic necrosis and irregular areas of cavitation.
The pleural surface is covered by a thick layer of exudate.
Numerous abscesses occur, containing clusters of staphylococci, leukocytes,
erythrocytes, and necrotic debris.
Rupture of a small subpleural abscess may result in pyopneumothorax, which may erode
into a bronchus, producing a bronchopleural fistula.
Pneumonia due to S. aureus may be
primary (hematogenous) or
secondary after a viral infection such as influenza.
Hematogenous pneumonia may be secondary to septic emboli, right-sided endocarditis,
or the presence of intravascular devices.
Inhalation pneumonia is caused by alterations of mucociliary clearance, leukocyte
dysfunction, or bacterial adherence initiated by a viral infection.
high fever,
abdominal pain,
tachypnea, dyspnea,
localized or diffuse bronchopneumonia
lobar disease.
Staphylococci cause
necrotizing pneumonitis
empyema, pneumatoceles, pyopneumothorax,
bronchopleural fistulas
diffuse interstitial disease characterized by extreme dyspnea, tachypnea, and cyanosis.
Clinical Manifestations.
Infants younger than 1 yr are commonly affected
history of an upper respiratory tract infection for several days to 1 wk.
A rapid progression of symptoms is characteristic.
onset with high fever, cough, and evidence of respiratory distress.
Signs and symptoms
tachypnea,
grunting respirations,
sternal and subcostal retractions,
nasal flaring,
cyanosis, and
anxiety.
lethargic , irritable and toxic.
may develop severe dyspnea and a shocklike state.
gastrointestinal disturbances, = vomiting, anorexia, diarrhea, and abdominal distention
secondary to a paralytic ileus.
Physical findings depend on the stage of pneumonia.
Early
diminished breath sounds,
scattered rales, and rhonchi are commonly heard over the affected lung.
With the development of effusion, empyema, or pyopneumothorax, dullness on
percussion is noted, and breath sounds and vocal fremitus are markedly diminished.
A lag in respiratory excursion occurs on the affected side.
Results of physical examination may, , be misleading, in young infants, with findings
disproportionate to the degree of tachypnea.
Diagnosis.
Recognizing early staphylococcal pneumonia in infants is often difficult.
Abrupt onset and rapid progression of symptoms of pneumonia in infants should be
considered to be due to staphylococci until proved otherwise.
A history of furunculosis, a recent hospital admission, or maternal breast abscess should
also alert physicians to the possibility of this diagnosis.
Other bacterial pneumonias that cause empyema or pneumatoceles and thus may be
confused with staphylococcal disease include S. pneumoniae, group A Streptococcus,
Klebsiella, H. influenzae (both type b and nontypable), and primary tuberculous
pneumonia with cavitation.
Aspiration of a radiolucent foreign body followed by pulmonary abscesses may
occasionally lead to a similar clinical and radiologic picture.
LABORATORY FINDINGS.
Leukocytosis
increase primarily among the polymorphonuclear cells.
Mild to moderate anemia is common.
cultures -obtained by tracheal aspiration or pleural tap
Gram stain reveals gram-positive cocci in clusters.
The finding of staphylococci in the nasopharynx is of no diagnostic value,
blood cultures may be positive.
Pleural fluid reveals an exudate with polymorphonuclear cell counts of 300-
100,000/mm3 , protein above 2.5 g/dL, and a low glucose concentration.
ROENTGENOGRAPHIC FINDINGS.
nonspecific bronchopneumonia early in the illness.
The infiltrate may become patchy and limited in extent
may be dense and homogeneous and involve an entire lobe or hemithorax.
The right lung is involved in about 65% of cases
bilateral involvement occurs in fewer than 20% of patients
A pleural effusion or empyema
pyopneumothorax occurs in approximately 25%.
Pneumatoceles of various sizes
no roentgenographic change can be considered diagnostic
rapid progression from bronchopneumonia to effusion or pyopneumothorax with or
without pneumatoceles is highly suggestive of staphylococcal pneumonia
Chest films should be obtained at frequent intervals if the diagnosis is suspected
Clinical improvement usually precedes roentgenographic clearing by weeks,
pneumatoceles may persist for months.
Treatment.
antibiotics
drainage of collections of pus.
should be given oxygen and placed in a semireclining position to relieve cyanosis and
anxiety.
intravenous hydration and nutrition
Assisted ventilation may be needed.
A semisynthetic, penicillinase-resistant penicillin should be administered intravenously
immediately after cultures are obtained (cloxacillin,100 mg/kg/24 hr for 4 to 6 weeks
initially IV and when tolerates oral change to tablets. Infant can be given tablet after
making it powder mix with honey).
Pleural tap even if only a small empyema is present, in order to reduce the chance of
bronchopleural fistula
Generally, pus reaccumulates so rapidly and becomes so viscous or loculated that closed
drainage with a chest tube of the largest possible caliber is required
The appearance of pyopneumothorax is another indication for immediate insertion of a
catheter into the pleural space.
Once begins to improve and the lung has re-expanded, the tubes can be removed,
Complications.
empyema,
pyopneumothorax,
pneumatoceles
= are considered part of the natural course of the illness and not complications.
Septic lesions outside the respiratory tract = pericarditis, meningitis, osteomyelitis, and
metastatic abscesses in soft tissue
Prognosis.
mortality still ranges from 10-30%
Factors =
the length of illness before hospitalization
age of the patient,
adequacy of therapy,
the presence of other illness or complications.
Source:DR.NS.MANI.MD Associate Professor in Pediatrics
