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The acquisition and persistence of antibiotic resistant Gram-negative bacilli (GNB) by babies on neonatal units

Presented at the Neonatal Society 2007 Summer Meeting (programme).

Costeloe KL1,2, Philpott A2, Wilks M3, Kempley ST3, Wiley A3, Hennessy EM1, Stacey F1,2, Millar MR3

1 Barts and the London, Queen Mary’s School of Medicine and Dentistry, London E1 2AD, UK
2 Homerton University Hospital NHS Foundation Trust, London E9 6SR, UK
3 Barts and the London NHS Trust, London E1 1BB, UK

Background: The emergence of antibiotic resistant bacteria is a major public health concern. The pattern of bowel colonisation differs in babies admitted to Neonatal Units compared with those who remain with their mothers; typically there is less bacterial diversity and more potentially pathogenic Gram-negative bacilli (GNB). In pilot studies on neonatal units at 2 hospitals we found high rates of colonisation with multi-resistant organisms (MRGNB).

Objectives: 1. To ascertain rates of colonisation with MRGNB (resistant to >2 classes of antibiotics). 2. To examine risk factors for acquisition of MRGNB. 3. To study persistence of MRGNB after discharge

Methods: Babies >14 days old were recruited on 2 tertiary neonatal units over one year. Clinical data were collected throughout the time in hospital. Stools were collected at discharge, 6 months and 1 year and subjected to quantitative microbiological analysis. Data were analysed using Fishers exact test and multiple logistic regression.

Results: 124 babies were recruited (54 at Unit 1 and 70 at Unit 2), for all of these a stool sample was obtained at discharge. At 6 months 74, and at 1 year 37 samples were available. Median birthweight was 1560g (IQR 1080-1890) and gestational age 31w (IQR 29-33). At discharge 56% (95%CI 47 – 65%), at 6m 42% (95%CI 31-53%) and at 1y 51% (95%CI 35-67%) were colonised with MRGNB.

No clinical item other than gestational age <26w (p=0.004) was significantly associated with colonisation at discharge.

The proportion of infants at discharge carrying GNB resistant to tetracycline was 84%, amoxycillin 78%, cephalosporin 31%, trimethoprim 31%, piperacillin / tazobactam 18%, chloramphenicol 15% and aminoglycosides 7%.

Many infants acquired GNB resistant to antibiotics to which they had not been directly exposed. After discharge the proportion of babies carrying strains resistant to cephalosporins, piperacillin / tazobactam and aminoglycosides fell while the proportion colonised with strains resistant to other antibiotic groups was unchanged.

Conclusion: Intestinal colonisation by MRGNB is high in babies on neonatal units and for some classes of antibiotic persists through infancy. The implications both for the health of individual babies and for the wider public are unknown.

Acknowledgements: This work was supported by a grant from the Joint Research Board of St Bartholomew’s Hospital.

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