A 6 year old male was referred from a rural ED for fever and possible pneumonia. He was well until three days ago when he was stung by a bee on his right forearm. He developed a moderate local reaction with edema and erythema. He saw his primary care physician the next day at which time he also complained of chest pain.
Chest radiographs were obtained that day and they were negative.
The next evening (yesterday), he developed fever and worsening of the swelling and erythema of his right forearm. He was seen at a rural ED. Cellulitis and a hypersensitivity reaction were considered. He was placed on oral cephalexin and acetaminophen with codeine. He took two doses of cephalexin.
He returned to the rural ED in the morning (today) because of abdominal pain. Chest radiographs were repeated. This was interpreted as showing a possible right lower lobe infiltrate.
A CBC at that time showed: WBC 20.4, 67% segs and 18% bands.
T38.5 (oral), P145, R44, BP 140/89, oxygen saturation 96% (room air).
He was obese, crying, agitated, and uncooperative, making examination difficult. HEENT exam significant for slightly dry oral mucosa. Neck supple.
Heart regular, tachycardic, without murmurs or gallops. Lungs coarse breath sounds with rhonchi in both bases. Abdominal guarding noted throughout with tenderness. Bowel sounds were hypoactive.
His right arm was diffusely indurated and erythematous (difficult to distinguish cellulitis from hypersensitivity).
He was given a fleet enema for suspected constipation. He passed large amounts of stool and seemed to be better in that he was less agitated and more cooperative. He was noted to be grunting at times. His abdomen was still tender. More blood studies were drawn. Radiographs of his chest and abdomen were obtained.
Although there some subtle abnormalities on his CXR, there were no definite abnormalities to account for his grunting and abdominal pain. There were some possible central infiltrates and the right hemidiaphragm appeared to be possibly elevated. The inspiratory effort shown on the film was poor. This was also noted on the CXR from the rural ED.
His abdominal radiographs showed some bowel distention, but consistent with an ileus and not a bowel obstruction.
CBC WBC 33.6, 1 meta, 29 bands, 63 segs, 5 lymphs, 2 monos, Hgb 13.1, Hct 39.0, platelet count 310,000. Na 136, K 4.0, Cl 102, Bicarb 21, glucose 142. UA SG 1.031, 0-2 WBC, 3-5 RBC.
Ultrasound and CT
An abdominal ultrasound was performed looking for an intra-abdominal abscess. This study showed a suspicious right lower quadrant mass, but it was unable to define it further. A surgical consultation was obtained.
The likelihood of acute appendicitis was felt to be low.
A CT scan of the abdomen was obtained. This study was unremarkable except for a view of the upper abdomen.
This CT cut is through the upper abdomen. It shows the liver, parts of the diaphragm, and the lower portions of the lungs. Pulmonary infiltrates are noted in the posterior portion of the right lower lobe. Note the pleural effusion adjacent to the infiltrates (arrows).
Progress on the ward
He was given IV ceftriaxone and hospitalization was arranged. Six hours after leaving the ED, house officers ordered a follow-up CXR (13 hours after the ED CXR, and 8 hours after the CT scan).
This CXR shows a large right pleural effusion. This is a significant change over the 13 hour period since the previous CXR suggesting a rapidly progressive pneumonia. This is highly suspicious for a staphylococcal pneumonia.
The source of the staph was suspected to be the cellulitis on his arm. The pleural effusion worsened, at which time it was drained through a tube thoracostomy.
Gram stain of the fluid revealed gram positive cocci. Cell counts 50,000 RBC’s, 29,000 WBC’s, 70% segs, 18% bands. Protein 5.4 grams/dl, pH 7.0, glucose 8 mg/dl. He required a second chest tube to drain a loculated empyema.
Other than this, he did remarkably well. He did not develop any pneumatoceles or a pneumothorax.
He was discharged after 6 weeks of IV antibiotics.
Teaching Points and Discussion
- Staphylococcal pneumonia is rapidly progressive in all age groups. This is a serious pulmonary infection that is associated with significant morbidity and a high potential for death.
- There are two main forms of staphylococcal pneumonia. Primary pneumonia is caused by direct inoculation through the respiratory tract. Secondary or metastatic hematogenous lung infection is due to bacteremic seeding of the lung during the course of endocarditis or septicemia associated with infection at other sites. It is not unusual to see severe impetigo associated with staphylococcal pneumonia.
- Primary staphylococcal pneumonia is a disease of infancy and childhood with three-quarters of the cases involving patients less than one-year old. Predisposing factors include cystic fibrosis, chronic lung disease, leukemia, preexisting skin infection, and viral respiratory infection (measles, influenza, adenovirus).
- The patients with staphylococcal pneumonia may present with fever, lethargy, severe respiratory distress (tachypnea, grunting, retractions, cyanosis), and gastrointestinal disturbances (anorexia, vomiting, abdominal distention). About 75% of patients present with fever, cough, and dyspnea. The rapid progression of clinical symptoms is characteristic of staphylococcal pneumonia.
- Chest radiographs in the early stage of staphylococcal pneumonia may be normal or show a minimal focal infiltrate. In general, there is a rapid progression of radiographic findings over just a few hours. The segmental bronchopneumonia pattern is usually unilateral and then expands to involve other lobes. In the case of our patient here, he presented with abdominal pain and tachypnea. A small infiltrate was noted which progressed to a large pleural effusion over a few hours.
- About 71% of pneumonias due to Staph aureus have associated pleural effusions. The effusion is on the right in 65%, on the left in 15% and bilateral 20% of the time. This frequently progresses to an empyema. Ultrasound or CT is often helpful in locating the loculated fluid.
- A pulmonary pneumatocele is a frequent complication of staphylococcal pneumonia with an incidence of greater than 85%. There are usually multiple pneumatoceles which vary in size. Pneumatoceles are believed to be caused by a partial airway obstruction by intraluminal exudate or a peribronchial abscess.
- A lung abscess is another complication of staphylococcal pneumonia. An abscess is a relatively thick-walled cavity, in contrast to a pneumatocele which is usually a thin-walled radiolucent area. Fluid levels may be present in both pneumatoceles and abscesses.
- The incidence of pneumothorax associated with staphylococcal pneumonia is between 40% to 60%. A pneumothorax may result from a pneumatocele rupture or formation of a bronchopleural fistula (localized bronchial wall necrosis). A pyopneumothorax (pneumothorax + empyema) is highly suggestive of staphylococcal pneumonia.
- Empyemas require drainage with large bore tube thoracostomies. The empyema is often rapidly progressive, which leads to compression of the lung and respiratory failure unless the empyema is drained. It is likely to reaccumulate following a thoracentesis. Chest tube thoracostomy also has the benefit of maintaining lung expansion if a pneumothorax develops.
- A pathogen is recovered from patients with pneumonia and effusions about 76% of the time. Of these, pleural fluid cultures are positive in 86% and blood cultures are positive in 10%.
- Although antibiotic coverage with anti-staphylococcal penicillins (e.g., oxacillin) or first generation cephalosporins (e.g.. cefazolin) is usually sufficient, there is a substantial rate of resistance to these drugs. Methicillin resistant staph aureus will usually be cephalosporin resistant as well. Vancomycin should be added to the anti-staphylococcal antibiotic regimen until sensitivities of the organism are determined.
- Complications of staphylococcal pneumonia include endocarditis, purulent pericarditis, osteomyelitis, deep tissue abscess, septic arthritis, and meningitis.
Chartrand SA, McCracken GH. Staphylococcal pneumonia in infants and children. Ped Infect Dis 1982;1:19-23.
Forbes GB, Emerson GL. Staphylococcal pneumonia and empyema. Pediat Clin N Amer 1957;4:215-229.
Melish ME. Staphylococcal Infections. In: Feigin RD, Cherry JD (eds). Textbook of Pediatric Infectious Diseases, 2nd edition, 1987, Philadelphia, WB Saunders Company, pp. 1260-1292.