Potential neonatal sepsis has been subject to expensive testing and a minimum of 48 to 72 h. of antibiotic therapy. Although several tests, risk factors, and signs have been developed to aid in diagnosis, the gold standard in diagnosing neonatal sepsis is the blood culture. This has traditionally been followed 48-72 h. before considering a change in therapy. A retrospective study (M. Pichichero & J Todd, J. Pediatrics 94: 958; 1979) found that 96% of bacteremic cultures obtained prior to antibiotics were positive by 48h., and 98% positive by 72h. With the newer techniques of culture analysis such as the BACTAC system, it may be possible to detect bacteremia in the neonate in a significantly shorter time. The BACTEC system detects the release of bacterial CO2 through florescence and it analyses the culture every 10 minutes. We hypothesized that neonatal bacteremia can be detected in less than 48 hours by this method. Methods: Our method included a retrospective review of 613 blood cultures obtained during the period 8/1/95 to 3/18/96 taken from 325 infants who had cultures drawn in conjunction with sepsis work-up and/or repeat cultures who had initial positive cultures in our NICU. Data was accumulated from chart review and microbiology computers. Comparisons were made using variables like weight, gestational age, organism grown, results of CBC (complete blood count), and positive cultures. Results: The results showed that of 325 infant blood cultures, 49 (15%) were positive. Of these, 64% were Coagulase negative Staphylococci (CNS), 14% Strept, viridens, 8% E. coli, 2% Enterobacter sp., 4% Enterococcus sp., 4% Pseudomonas sp., 2% Candida albicans and 2% Klebsiella sp. The time for culture to turn positive on blood samples taken from infants not on antibiotics was as follows: 54% were positive at 18h., 71% were positive at 24h. and 100% were positive by 36h. A single culture for Candida albicans became positive at 61 h. Detection time by organism type was as follows: Coagulase negative Staph. 21.7 h., Strept. viridens 15.6 h., E. coli 7.5 h., Enterococcus sp. 12 h., Enterobacter sp. 5 h., Klebsiella sp. 10 h. and Pseudomonas sp. 12 h. Conclusions: Our results indicate that the BACTEC system helps in early identification of neonatal bacteremia and that gram-negative organisms are detected earlier than gram-positive organisms (p<0.05). An abnormal CBC diff. with an I:T ratio of > 0.2 was significantly associated with gram-negative sepsis(p<0.001).
