Comparison of culture, direct antigen detection and PCR for diagnosis of pneumococcal pneumonia

ABSTRACT

Pneumonia due to Streptococcus pneumoniae [S.pneumoniae] is a major cause of morbidity and mortality among children and adults worldwide. Comparison of Culture, Direct Polysaccharide Antigen Detection and Polymerase chain Reaction 'PCR' for diagnosis of Pneumococcal Pneumonia. This study was conducted on 80 nasopharyngeal aspirates from children patients with community acquired pneumonia [CAP], admitted to Cairo university specialized Pediatric hospital [CUSPH]. Only samples of good quality and Significant counts of alpha haemolytic streptococci were subjected to optochin sensitivity, bile solubility test, pneumococcal antigen detection by latex and PCR. Significant counts of alpha haemolytic streptococci were isolated from-35 patients out of the original 80 patients. Out of 35 samples, 11 [31%] were optochin sensitive and bil soluble. Considering the optochin disc sensitivity test as a reference method, both Latex agglutination test and PCR had excellent sensitivity [100%] and good specificity 62.5% for latex agglutination test and 79% for PCR. Culture and optochin sensitivity remain to be the definitive diagnostic test for streptococcus pneumoniae. Pneumococcal antigen detection by latex is a rapid screening test but should be combined with culture to avoid false positive results. PCR had good sensitivity and specificity, but it is difficult to be used for routine clinical diagnosis because of its relatively high cost and its tedious work that needs skilled personnel