Comparative study between conventional blood culture method versus polymerase chain reaction assay for diagnosis of neonatal septicemia

ABSTRACT

Neonatal septicemia represents a major clinical problem in neonatology with high morbidity and mortality rates despite the progress in neonatal intensive care and antibiotics. Clinical diagnosis of septicemia in newborn infants is not easy and there is no laboratory test with 100% specificity and sensitivity with the exception of blood culture, the results of which are not available for at least 48-72 hours. The purpose of this study was to compare the utility of a 16S rRNA PCR assay to that of the conventional blood culture for detecting bacteria in blood obtained from neonates suspected of having septicemia. The present work included 50 neonates with provisional diagnosis of neonatal septicemia and 25 non infected neonates as control group. For each neonate the following was done Full history taking, full clinical diagnosis, routine investigations including complete blood cell count and C-reactive protein [CRP], conventional blood culture for isolation of the causative organism and its identification and lastly the polymerase chain reaction for detection of the 16S rRNA gene from blood of septicemic neonates. The results of this study showed that Only thirty nine neonates [78%] of those diagnosed as having or suspected to have septicemia on clinical backgrounds had given positive blood culture results. The most common isolated organisms were Klebsiella pneumonia [41.02%], coagulase negative staphylococci [CoNS] [20.51%], E. coli [10.26%] and S. aureus [10.26%]. K. pneumonia was the commonest isolated organism in early onset infection while CoNS was the commonest in late onset infection. Thirty eight of cases with positive blood culture [97.44%], two cases with negative blood culture [18.18%] and one of the control group [4%] were positive by 16S rRNA PCR. The sensitivity, specificity, positive and negative predictive values for 16S rRNA PCR in relation to blood culture were 97.4, 91.7, 92.7 and 97.1%, respectively and the accuracy was 94.7%. These values were superior to that of CRP [89.7, 83.3, 85.4 and 88.2%, respectively with accuracy of 86.7%]. Our results suggested that 16S rRNA PCR is a rapid, sensitive and specific diagnostic test for ruling out neonatal septicemia