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KMID : 0361319860180010109
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Korean Journal of Medical Technologists
1986 Volume.18 No. 1 p.109 ~ p.118
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Evaluation of the Presumptive Identification Tests of Group A and B β-hemolytic Streptococci
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정조원/Chung, Chowon
이동우/정윤섭/이삼열/Lee, Dongwoo/Chong, Yunsop/Lee, Samuel Y.
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Abstract
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Identification of group A and B , hemolvtic streptococci is very important not only in the aspects of epidemologic studies but also for treatment of the patients with primary infections and prevention of serious complications.
The serological group of P-hemolytic streptococci was originally classified by antigenicity of the cell. Therefore, determination of the groin A and Bwas possible only with the use of serological method. However, as the serological methods were very complicated, various alternate methods have been used. used. Simple serological methods such as cogglutination test become available, but they are very expensive. Therefore, despite of the inherent inaccuracies, several presumptive methods of identification are still avidly used.
In this study bacitracin test and sulfamethoxazo´.e- tri,_.etaopr :n(SXT) test for presumptive indentification of group A streptococci, and MA hippurate hydrolysis test for the identification of group B streptococci were evaluated. Two hundred and sixty two strains of streptococci isolated from clinical materials obtained from patients at h ung-Hee -Medical Center during July 1985 to March 1986, were used for the study. ´Serological group of the organisms were determined by coaggentinatination The following results -,sere obtained.
1. In the identification of group A streptococci, bacitracin tea showed that the sensitivity was 100 percent, specificity 72.1 percent, positive predictive value 34.0 percent, and negative predictive value 100 percent. Correlation in the identification of group A streptococci, bacitracin test and coagglutination test showed correlation coefficient value of 0.496(P<0.001).
2. In the identification of group A streptococci, bacitracin test plus SXT test showed that the sensitivity was 93.9 percent, specificity 89.1 percent, positive predicative value 55.4 percent, and negative predictive value 99.0 percent. Correlation in the identification of group A streptococci, bacitracin test plus SXT test and coagglutination test showed correla:iin coefficient value of 0.672(P<0.001).
3. In the identification of group B streptococci, MA hippurate hydrolysis test showed that the sensitivity was 97.0 percent, specificity 60.7 percent, positive predictive value 26.2 percent and negative predictive value 99.3 percent. Correlation in the identification of V )up B streptococci, MA hippurate hydrolysis test and coagglutination test showed cur-elatir,n coefficient value of 0.384(P<0.001).
4. In the identification of group B streptococci, when nonenterococcal streptococci were tested, the MA hippurate hydrolysis test showed that the sensitivity and positive predictive value were 97.0 percent respectively, specificity and nagative predictive value were 99.3 percent respectively. Correlation in the identification of group B streptococci, AIA hippurate hydrolysis test and coagglutination coefficient value of 0.963(P<0.45).
It is concluded that bacitracin or SXT test alone for the identification of group A streptococci are not accurate, but the identification can be improved when the two tested are used concomitantly. Coagglutination test might be used to confirm the identification of group A isolate when necessary. MA hippurate hydrolysis test is accurate for the identification of group B streptococci when nonenterococcal streptococci is tested and can be a good alternate test for coagglutination test.
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