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Current possibilities of laboratory diagnostics of pneumococcal infections
ČAPKOVÁ, Irena
Streptococcus pneumoniae (S. pneumoniae) can be common colonizing flora of human nasopharynx, but it also can be one of the main patogens causing invasive pneumococcal disease. It is diagnosed directly, using various methods, such as microscopy, cultivation, identification, or non-cultivation proof of antigen or deoxyribonucleic acid (DNA). First part of my thesis is dedicated to the description of the Streptococcus genus, including species S. pneumoniae. Morphology, physiology, antigenic structure, pathogenesis and pathogenicity of this bacterial race and species is described, as well as theoretical description of laboratory diagnostics methods. In methodics, the identification methods are described as they were used for diagnostics of S. pneumoniae in the Laboratory of medicinal microbiology, Department of bacteriology Nemocnice České Budějovice a.s. It also includes description of cultivation of biological samples, which was S. pneumoniae isolated from, and several identification tests which can differentiate S. pneumoniae from other viridans streptococci. Two basic, commonly used identification tests were used for diagnostics test of sensitivity to optochin and test of solubility in bile-sodium deoxycholate. Test of solubility using sodium deoxycholate is a basic test in diagnostics of S. pneumonia. Out of 127 species which were positive in the solubility test, 114 were also positively tested for sensitivity to optochin. Test of sensitivity to optochin had 89,9% accuracy. Four species primarily identified as viridans streptococci were tested using Matrix-Assisted Laser Desorption Ionisation Time of Flight Mass Spectrometry (MALDI TOF MS). This specific, fast and accurate method cannot be fully used for identification of S. pneumoniae however, because its genotype is far too similar to the one of Streptococcus oralis/mitis. Two tests were used and described to prove the antigen S. pneumoniae imunochromatographic test and latex agglutination reaction. Out of 266 examined samples, antigen was found in fifteen cases in urine and cerebrospinal fluid using the imunochromatographic test, and in seven cases, the antigen was proved using the latex agglutination reaction. These two methods are highly specific and provide fast information about the presence of the antigen S. pneumoniae in the examined sample and subsequently about the possibility of pneumococcus infection. Another highly specific test used for diagnostics of severe pneumococcus diseases is DNA proof using PCR methods, which was successful in 5 cerebrospinal fluid samples, which were examined simultaneously in the Laboratory of molecular biology and genetics of Nemocnice České Budějovice a.s.
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