Abstract 1608 Poster Session II, Sunday, 5/2 (poster 114)

The differentiation of sepsis in the setting of the SIRS remains a unique challenge to neonatologists due to the low sensitivity and specificity of laboratory tests. Detection of a highly conserved region of bacterial DNA by PCR may represent an extremely sensitive and specific tool to discriminate infants with bacterial sepsis at the onset of clinical signs. To determine whether 16S rRNA gene amplification and sequencing could amplify the diagnosis of bacteremia in neonates with SIRS, DNA was extracted from the blood of 51 neonates (2-68 days) who were admitted to a regional NICU and presented with SIRS and from 35 control infants (1-21 days) who had no recent illness and had a normal sepsis screening panel. The diagnosis of SIRS was based on clinical signs of sepsis and abnormalities of at least one of the following test results: C-RP, neutrophil counts, and I:T ratio. On each neonate with SIRS, cultures of the blood and whenever possible of the spinal fluid, bronchoalveolar lavage (BAL), urine, and central venous catheter (CVC) tips were performed. All SIRS infants were on antibiotic prophylaxis at the time of sample collection. PCR techniques were used to amplify a fragment of a region within the DNA encoding the 16S ribosomal RNA, which is highly conserved in gram + and -bacteria (McCabe KM, Pediatrics 1997). Of all 51 cases of SIRS, positive blood cultures were found in only 7 (14%) (S. aureus (3), S. epidermidis (2), E. coli (1), Group B streptococci (1)). However, 19 neonates (37%) had positive cultures on other sites, specifically 9 on the BAL, 3 on the urine, 1 on the spinal fluid, and 6 on the CVC tips. In addition, 2 neonates of the 25 with SIRS and negative culture results had NEC. PCR detected bacterial DNA in all of the 7 blood culture-positive sepsis cases, but in none of the control infants. Bacterial DNA was also detected in the blood of the 19 neonates who had blood culture negative results but positive cultures on other sites. Moreover, PCR revealed the presence of bacterial DNA in 5 of the 25 neonates who presented with SIRS, two of whom had NEC, but had negative culture results. Altogether, of the 51 SIRS neonates, PCR detected the presence of bacterial components in the blood of 31 (60%). Using a clinical score of severity of illness, we found that these 31 infants had a higher mean score than the remaining 20 in whom bacterial DNA was not detected by PCR. The results of this study suggest that PCR is more sensitive than blood culture for detecting bacterial components in the blood of neonates with SIRS and may be helpful in augmenting the diagnosis of bacteremia in these infants especially when they are on antibiotics. (Supp. by the Italian Dept. of Health)