Internal Medicine

0521779407-19 CUNY1086/Karliner 0 521 77940 7 June 6, 2007 17:50

Streptococcal Infections 1383

protein and erythrocyte sedimentation rate: nonspecific but may be

seen in acute rheumatic fever and endocarditis

■Basic urine studies:

■Hematuria may be seen in endocarditis and post-streptococcal

glomerulonephritis

➣Basic studies: gram stain (slightly elongated gram-positive cocci

in pairs and chains) or culture of blood or specimen from sus-

pected site of infection (sputum, CSF, joint fluid etc.) can confirm

the diagnosis in most cases

➣An adequate sputum expectorate (large number of PMNs, few

epithelial cells) that is analyzed promptly can lead to early diag-

nosis of pneumococcal pneumonia

➣Other studies: rapid antigen-detection tests

➣Can detect presence of group A streptococcal (carbohydrate)

antigen in minutes from throat swabs

➣Highly specific (>95%) but lower sensitivity: if clinical suspicion

is high, need to confirm negative throat swabs with culture

■Other studies: serology

➣Can be helpful in diagnosis of rheumatic fever but not specific

(three samples sent for ASO >95% sensitivity two months after

onset); can also help in poststreptococcal glomerulonephritis

Imaging

■CXR: usually infiltrates in a single lobe seen in pneumococcal

pneumonia; pleural effusion generally uncommon, but suspect

empyema if seen in pneumonia due to S. pyogenes

■Plain films, CT and MRI rarely helpful in necrotizing fasciitis and

often delay diagnosis

differential diagnosis

■Streptococcal pharyngitis can be identical to adenovirus and

Epstein-Barr virus; always think of acute HIV in the right host. Also

distinguish from diphtheria, epiglottitis, Neisseria spp and Myco-

plasma

■Streptococcal skin infections may be difficult to those caused by S.

aureus

management

What to Do First

■Empiric antibiotics in serious disease is necessary (endocarditis,

meningitis, pneumonia) before definitive diagnosis