Objective To determine whether culture yield and time to positivity (TTP) differ between peripheral and central vascular catheter-derived blood cultures (BCx) in neonatal intensive care unit (NICU) patients evaluated for late-onset sepsis.

Design Single-centre, retrospective, observational study.

Setting Level IV NICU.

Participants The study included infants >72 hours old admitted to NICU in 2007–2019 with culture-confirmed bacteraemia. All episodes had simultaneous BCx drawn from a peripheral site and a vascular catheter (‘catheter culture’).

Main outcome measures Dual-site culture yield and TTP.

Results Among 179 episodes of late-onset bacteraemia (among 167 infants) with concurrently drawn peripheral and catheter BCx, the majority (67%, 120 of 179) were positive from both sites, compared with 17% (30 of 179) with positive catheter cultures only and 16% (29 of 179) with positive peripheral cultures only. 66% (19 of 29) of episodes with only positive peripheral BCx grew coagulase-negative Staphylococcus, while 34% (10 of 29) were recognised bacterial pathogens. Among 120 episodes with both peripheral and catheter BCx growth, catheter cultures demonstrated bacterial growth prior to paired peripheral cultures in 78% of episodes (93 of 120, p<0.001). The median TTP was significantly shorter in catheter compared with peripheral cultures (15.0 hours vs 16.8 hours, p<0.001). The median elapsed time between paired catheter and peripheral culture growth was 1.3 hours.

Conclusion Concurrently drawn peripheral and catheter BCx had similar yield. While a majority of episodes demonstrated dual-site BCx growth, a small but important minority of episodes grew virulent pathogens from either culture site alone. While dual-site culture practices may be useful, clinicians should balance the gain in sensitivity of bacteraemia detection against additive contamination risk.