Streptococcus pneumoniae infection laboratory findings

Streptococcus pneumoniae infection Microchapters
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Overview
Classification Community Acquired Pneumonia Endocarditis Sinusitis Bronchitis Meningitis
Cause
Laboratory Findings
Medical Therapy
Primary Prevention

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Depending on the nature of infection, an appropriate sample is collected for laboratory identification. Pneumococci are typically gram positive, cocci, seen in pairs or chains. When cultured on blood agar plates with added optochin antibiotic disk, they show alpha-hemolytic colonies and a clear zone of inhibition around the disk meaning they're sensitive to the antibiotic. Pneumococci are also bile soluble. Just like other streptococci, it's catalase negative. Quellung test to identify specific capsular polysaccharides may also be done.

Laboratory Diagnosis

Diagnosis is generally made based on clinical suspicion along with a positive culture from a sample from virtually any place in the body. An ASO Titre of >200 units is significant. S. pneumoniae is, in general, optochin sensitive, although optochin resistance has been observed.

Atromentin and leucomelone possess antibacterial activity, inhibiting the enzyme enoyl-acyl carrier protein reductase, (essential for the biosynthesis of fatty acids) in S. pneumoniae.