Pneumococcal infections laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Laboratory Findings
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, they are catalase-negative. A Quellung test can identify specific capsular polysaccharides.[1]
Pneumococcal antigen (cell wall C polysaccharide) may be detected in various body fluids. Older detection kits, based on latex agglutination, added little value above Gram staining and were occasionally false-positive. Better results are achieved with rapid immunochromatography, which has a sensitivity (identifies the cause) of 70-80% and >90% specificity (when positive identifies the actual cause) in pneumococcal infections. The test was initially validated on urine samples, but has been applied successfully to other body fluids.[1] Chest X-rays can also be conducted to confirm an infection.
References
- ↑ 1.0 1.1 Werno AM, Murdoch DR (2008). "Medical microbiology: laboratory diagnosis of invasive pneumococcal disease". Clin. Infect. Dis. 46 (6): 926–32. doi:10.1086/528798. PMID 18260752. Unknown parameter
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