The changing antibiotic susceptibility of bloodstream infections in the first month of life: informing antibiotic policies for early- and late-onset neonatal sepsis

Abstract

This study describes the association between antibiotic resistance of bacteria causing neonatal bloodstream infection (BSI) and neonatal age to inform empirical antibiotic treatment guidelines. Antibiotic resistance data were analysed for 14 078 laboratory reports of bacteraemia in neonates aged 0-28 days, received by the Health Protection Agency's (now Public Health England) voluntary surveillance scheme for England and Wales between January 2005 and December 2010. Linear and restricted cubic splines were used in logistic regression models to estimate the nonlinear relationship between age and resistance; the significance of confounding variables was assessed using likelihood ratio tests. An increase in resistance in bacteria causing BSI in neonates aged <4 days was observed, which was greatest between days 2-3 and identified an age (4-8 days, depending on the antibiotic) at which antibiotic resistance plateaus to almost unchanging levels. Our results indicate important age-associated changes in antibiotic resistance and support current empirical treatment guidelines.

Fig. 1.

Bacteria isolated from blood cultures taken from neonates aged 0–6 days. Reports are shown only for the seven most frequently reported groups, which account for 90% of all reported neonatal bloodstream infections (BSI).

Fig. 2.

Models incorporating a spline or linear function of age (at which the blood culture was taken) to estimate the change in the odds of antibiotic resistance in all organisms (a–c) or excluding coagulase-negative staphylococci (d–f). Models are shown on the logit scale. AIC, Akaike's Information Criterion.