Abstract 1596 Poster Session II, Sunday, 5/2 (poster 110)

Antibiotics are frequently administered to infants in the neonatal intensive care unit (NICU) and newborn nursery (NBN) while awaiting blood CX results. In an effort to decrease exposure of infants to antibiotics and minimize the risk of emergence of antibiotic-resistant pathogens, we analyzed the timing to positivity of blood CXs obtained from infants in NBN/NICU of a large, county hospital. From 1/95 - 10/31/98, there were 836 Å blood CXs that yielded at least one bacterial isolate from 458 infants. Their clinical course and laboratory values were reviewed and the decision was made as to whether the isolate(s) was responsible for the sepsis episode or represented a contaminant. The time that the microbiology laboratory received the blood CX and the time that the blood CX yielded bacterial growth were analyzed. All blood CXs were processed using the BacT/Alerta Microbial Detection System. Of the 836 Å blood CXs, 476 (57%) were assessed to represent true pathogens in 196 infants; 358(43%) were initial blood CXs and 118(14%) were follow-up CXs. Of the 358 Å blood CXs, 25 (7%) were from NBN and 333 (93%) from NICU infants. There were 47 episodes (27 group B streptococci [GBS], 12 Gram-negative bacilli, 8 other) in 47 infants with early-onset (EO) infections (0-72 hrs after birth), and 171 episodes (98 coagulase-negative staphylococci [CONS], 40 Gram-negative bacilli, 10 Staphylococcus aureus (SA), 5 GBS, 9 Enterococci, 3 methicillin-resistant SA, 6 other) of late-onset (LO) infections (>72 hrs) in 149 infants. Since many infants had 2 blood CXs performed per sepsis episode, there were more bacterial isolates than episodes of bacteremia. Overall, the time to positivity of the blood CX in the EO group was 14 ± 6 hrs (range 4-33 hrs; 99% Å by 25 hrs), while it was 16 ± 9 hrs (range 2-45 hrs) in the LO group. In the LO group, 314 (90%) were Å by £ 24 hrs, 28 (8%) by > 24 to 36 hrs while an additional 6 (2%) by > 36 hrs (maximum 45 hrs). Specifically, there were 42 GBS isolates which required 14 ± 6 hrs of incubation, 46 E. coli isolates which required 10 ± 2 hrs, and 184 CONS isolates which required 19 ± 7 hrs. In addition, there were 22 fungal isolates which required 21 ± 8 hrs of incubation to yield growth. These data suggest that the majority of bacterial blood CXs in neonates become Å within 24 hrs, and that antibiotic therapy can be discontinued by 33 hrs in infants with possible EO infection and by 45 hrs among those with suspected LO infection.