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Late onset septicaemia in a tertiary neonatal unit in Oxford

Presented at the Neonatal Society 2010 Summer Meeting (programme).

Gupta N1, Crockett D2, Webster D2, Anthony M1

1 Neonatal Unit, John Radcliffe Hospital, Oxford, UK
2 Department of Microbiology, John Radcliffe Hospital, Oxford, UK

Background: Preterm infants are highly vulnerable to blood stream infections (BSI). BSI rates in very low birth weight preterm (VLBW) infants is as high as 25% (1), and are often thought to be associated with vascular catheters. There are few data comparing risk factors for non-CONS BSI caused by gram-positive versus gram-negative organisms in this population (2).

Aim: To describe late onset septicaemia caused by non-CONS bacteria, over a 7 year period in the neonatal unit (NNU) at John Radcliffe Hospital, Oxford. To determine the type of infecting pathogens, risk factors for disease, and the impact of infection on overall morbidity and mortality.

Methods: This data was collected as a part of retrospective audit which identified 114 VLBW infants admitted to the NNU from Jan 2002 to December 2009. All inborn neonates with late onset infection (>72 hours of life) were included. Cases were identified from the hospital microbiology database. 60 sepsis episodes were recorded in 54 neonates. Cases were compared with controls, matched for gestation (within 2 weeks) and gender. Cases with fungal infection were excluded. Data was analysed using SPSS v.17 statistical software.

Results: In our cohort of VLBW infants 8.3% had non-CONS sepsis. The mean gestation for cases and control was 27 weeks and mean birth weight 864g and 890g, respectively. 65% of cases were <28 weeks and 36% were <750 g. The mean age of infection by Gram negative organism was 35.4 days (range 8 - 146 days) and for Gram positive organism was 43.1 days (range: 4 - 151). Neonates with BSI were more likely to have been on a ventilator, had renal impairment and have had a longer mean length of stay. There was no significant difference between Gram positive and Gram negative sepsis in this respect. There were no significant differences with respect to occurrence of necrotising enterocolitis, surgery, presence of central line at or before positive culture for cases and controls or between Gram positive and Gram negative infections. In univariate analysis, duration of central line was longer in cases compare to control (Mean: 34.2 vs. 20.7 days, p = 0.018), this difference was not significant between Gram negative and Gram positive infection. In Gram positive infection, duration of central line before BSI and duration of last line before BSI was longer compared to Gram negative organism though the difference was not statistically significant. (Mean 31.3 vs. 20.5 days; 22.8 vs 12.6 days). On univariate analysis, infants with BSI are more likely to die than controls (odds ratio = 4.7, 95%CI = 1.3 – 17.5, p = 0.021). This remained significant on multivariate analysis. There was no difference in overall mortality between Gram positive and Gram negative cases (27% vs. 19%). In multivariate analysis, total time on ventilation remained significant risk factors for non-CONS blood stream infection (p = 0.015).

Conclusion: Late onset sepsis occurs predominantly in ELBW infants. Duration of ventilation is significantly associated with late onset of sepsis in our population although this relationship is likely to be complex. In our cohort, subgroup analysis between Gram positive and Gram negative infection did not show any significant difference in risk factors, impact of infection and subsequent hospital stay.

Ethical Approval: Ethical approval was not required as this was a retrospective case note study, with audit committee approval, in keeping with the organisation’s research governance policy

1. Modi N, Dore CJ, Saraswatula A: A case definition for national and international neonatal bloodstream infection surveillance. Arch Dis Child Fetal Neonatal Ed 2009; 94:8–10
2. Perlman S, Saiman L, et al: Risk factors for late-onset health care-associated bloodstream infections in patients in neonatal intensive care units. Am. J Infect Control. 2007; 35(3): 177–18

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