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Effect of antibiotic use on antimicrobial antibiotic resistance and late-onset neonatal infections over 25 years in an Australian tertiary neonatal unit
  1. David Carr1,
  2. Elizabeth Helen Barnes2,
  3. Adrienne Gordon3,4,
  4. David Isaacs5,6
  1. 1Junior Medical Staff Unit, Royal North Shore Hospital, St Leonards, New South Wales, Australia
  2. 2NHMRC Clinical Trials Centre, University of Sydney, Sydney, New South Wales, Australia
  3. 3RPA Newborn Care, John Spence Neonatal Nursery, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
  4. 4Discipline of Obstetrics, Gynaecology and Neonatology, University of Sydney, Sydney, New South Wales, Australia
  5. 5Discipline of Child Health, University of Sydney, Sydney, New South Wales, Australia
  6. 6Department of Infectious Diseases & Microbiology, Children's Hospital at Westmead, Westmead, New South Wales, Australia
  1. Correspondence to Professor David Isaacs, Department of Infectious Diseases and Microbiology, Children's Hospital at Westmead, Westmead NSW 2145, Australia; david.isaacs{at}


Background Antibiotic resistance is a worldwide problem. We describe 25 years of responsible antibiotic use in a tertiary neonatal unit.

Methods Data on neonatal infections and antibiotic use were collected prospectively from 1990 to 2014 at a single tertiary Sydney neonatal intensive care unit attached to a maternity unit. There are approximately 5500 deliveries and 900 nursery admissions per year.

Results The mean annual rate of late-onset sepsis was 1.64 episodes per 100 admissions. The mean number of late-onset sepsis episodes per admission to the neonatal unit decreased by 4.0% per year (95% CI 2.6% to 5.4%; p<0.0001) and occurred particularly in infants born weighing <1500 g. No infants with negative cultures relapsed with sepsis when antibiotics were stopped after 48–72 hours. Antibiotic use decreased with time. The proportion of colonising methicillin-resistant Staphylococcus aureus isolates decreased by 7.4% per year (95% CI 0.2% to 14.1%; p=0.043). The proportion of colonising Gram-negative bacilli isolates resistant to either third-generation cephalosporins or gentamicin increased by 2.9% per year (95% CI 1.0% to 4.9%; p=0.0035). Most were cephalosporin-resistant; gentamicin resistance was rare. An average of one baby per year died from late-onset sepsis, the rate not varying significantly over time. The mortality from episodes of late-onset sepsis was 25 of 332 (7.5%).

Conclusion Stopping antibiotics after 2–3 days if neonatal systemic cultures are negative is safe. However, it does not prevent the emergence of cephalosporin-resistant Gram-negative organisms.

  • Antibiotic stewardship
  • Nosocomial infection
  • MRSA
  • Antibiotic resistance

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  • Contributors DCcollected, collated and analysed the data, performed the initial analyses and drafted the initial manuscript. EHBperformed all the statistical analyses. AGconceived the study with DI. DIconceived the study and collected the data over 25 years. All authors contributed to and approved the final manuscript as submitted.

  • Competing interests None declared.

  • Ethics approval Royal Alexandra Hospital for Children ethics committee (approval number 93060).

  • Provenance and peer review Not commissioned; externally peer reviewed.