Nosocomial infections in a Dutch neonatal intensive care unit: surveillance study with definitions for infection specifically adapted for neonates

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Summary

The incidence of nosocomial infection in neonatal intensive care units (NICUs) is high compared with other wards. However, no definitions for hospital-acquired infection are available for NICUs. The aim of this study was to measure the incidence of such infections and to identify risk factors in the NICU of the VU University Medical Center, which serves as a level III regional NICU. For this purpose, a prospective surveillance was performed in 1998–2000. We designed definitions by adjusting the current definitions of the Centers for Disease Control and Prevention (CDC) for children <1 year of age. Birth weight was stratified into four categories and other baseline risk factors were dichotomized. Analysis of risk factors was performed by Cox regression with time-dependent variables. The relationship between the Clinical Risk Index for Babies (CRIB) and nosocomial infection was investigated. Furthermore, for a random sample of cases, we determined whether bloodstream infection and pneumonia would also have been identified with the CDC definitions. Seven hundred and forty-two neonates were included in the study. One hundred and ninety-one neonates developed 264 infections. Bloodstream infection (N=138, 14.9/1000 patient-days) and pneumonia (N=69, 7.5/1000 patient-days) were the most common infections. Of bloodstream infections, 59% were caused by coagulase-negative staphylococci; in 21% of neonates, blood cultures remained negative. In 25% of pneumonias, Enterobacteriaceae were the causative micro-organisms; 26% of cultures remained negative. Compared with the Nosocomial Infections Surveillance System (NNIS) of the CDC, our device utilization ratios and device-associated nosocomial infection rates were high. The main risk factors for bloodstream infection were birth weight [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.45–2.17] and parenteral feeding with hospital-pharmacy-produced, all-in-one mixture ‘Minimix’ (HR 3.69, 95%CI 2.03–6.69); administration of intravenous antibiotics (HR 0.39, 95%CI 0.26–0.56) was a protective risk factor. The main risk factors for pneumonia were low birth weight (HR 1.37, 95%CI 1.01–1.85) and mechanical ventilation (HR 9.69, 95%CI 4.60–20.4); intravenous antibiotics were protective (HR 0.37, 95%CI 0.21–0.64). In a subcohort of 232 very-low-birthweight neonates, the CRIB was not predictive for infection. With the CDC criteria, only 75% (21/28) of bloodstream infections and 87.5% of pneumonias (21/24) would have been identified. In conclusion, our local nosocomial infection rates are high compared with those of NICUs participating in the NNIS. This can be partially explained by: (1) the use of our definitions for nosocomial infection, which are more suitable for this patient category; and (2) the high device utilization ratios.

Introduction

The incidence of nosocomial infections in neonatal intensive care units (NICUs) is high; it has been reported to occur in up to 30% of all neonates.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 Diagnosis of infection, especially in preterm neonates, is difficult because symptoms of infection are often non-specific and different from those in older infants.20, 21 In addition, as diagnostic procedures are different in the NICU, the definitions of such infections for children aged <1 year of the Centers of Disease Control and Prevention (CDC) are less suitable in this patient population.22 The lack of standardized definitions for nosocomial infection in the NICU and the huge diversity in patient mix in different NICUs makes comparison of studies on the incidence of infection in neonates difficult.23 Lacking better definitions, the National Nosocomial Infections Surveillance System (NNIS), consisting of approximately 140 American NICUs, uses the CDC definitions for children aged <1 year as the best available for surveillance.24

Diagnosis of bloodstream infection (BSI) in premature neonates is hampered by several factors, including the relatively small volume of blood that can be drawn for culture, which compromises sensitivity.25, 26 Also, the diagnosis of ventilator-associated pneumonia is more difficult in neonates than in older children because of the low sensitivity of chest X-rays.27, 28, 29

The NICU of our hospital is a level III NICU. Indications for admission are: preterm birth (<32 weeks of gestation), respiratory distress, infections, congenital malformations and birth asphyxia. The aims of this prospective surveillance study were: (1) to test the applicability of CDC definitions for children aged <1 year adjusted for neonates for detection of nosocomial infection; (2) to determine the incidence of nosocomial infection in the NICU of the VU University Medical Center, Amsterdam based on these definitions; and (3) to identify risk factors for nosocomial infection in our NICU.

Section snippets

Definitions of nosocomial infections

Definitions for infection surveillance were developed by the Department of Medical Microbiology and Infection Control and the Department of Neonatology. CDC definitions for children aged <1 year for BSI, pneumonia, meningitis, urinary tract infection (UTI), eye infection, infection of the umbilicus, and skin infection were adjusted with respect to specific neonatal symptomatology and diagnostic procedures. During the surveillance period, problems with definitions were discussed regularly. After

Surveillance

Surveillance was performed over two periods: February–November 1998 and June 1999–December 2000. A total of 742 neonates was included. We recorded 264 infections in 191 neonates. General information on the study population, the incidence of infection and the causative agents is provided in Table I, Table II, Table III, respectively. BSI and pneumonia were the most frequently occurring nosocomial infections. BSI was predominantly caused by coagulase-negative staphylococci and other Gram-positive

Discussion

CDC definitions for children aged <1 year are not suitable in some aspects for (preterm) neonates. Symptomatology of infection is different in this patient category. Irritability, apathy and grey skin colour are considered to be symptoms of possible infection, but they are difficult to assess and somewhat subjective.21 A classic symptom of infection, which is used as a defining symptom in all studies on nosocomial infections, is body temperature above 38.0 °C. Body temperature, however, acts

Acknowledgements

We are indebted to L.E.A. Boeijen-Donkers, infection control practitioner, and E.F. Ree, neonatologist, for participation in the surveillance. W.C. van der Zwet is supported by an AGIKO grant of ‘The Netherlands Organization for Scientific Research’.

References (49)

  • T.G. Emori et al.

    National Nosocomial Infections Surveillance System (NNIS); description of surveillance methods

    Am J Infect Control

    (1991)
  • R.L. Schelonka et al.

    Volume of blood required to detect common neonatal pathogens

    J Pediatr

    (1996)
  • C.G. Mayhall

    Noscomial pneumonia. Diagnosis and prevention

    Infect Dis Clin North Am

    (1997)
  • L. Cordero et al.

    Surveillance of ventilator-associated pneumonia in very-low-birth-weight infants

    Am J Infect Control

    (2002)
  • E.E.L. Wang et al.

    Ureaplasma urealyticum infections in the perinatal period

    Clin Perinatol

    (1997)
  • J.K. Ferguson et al.

    Risk-stratified nosocomial infection surveillance in a neonatal intensive care unit: report on 24 months of surveillance

    J Paediatr Child Health

    (1996)
  • E. Galanakis et al.

    Neonatal bacteremia: a population-based study

    Scand J Infect Dis

    (2002)
  • R.P. Gaynes et al.

    Nosocomial infections among neonates in high-risk nurseries in the United States

    Pediatrics

    (1996)
  • M. Hack et al.

    Very low birth weight outcomes of the National Institute of Child Health and Human Development Neonatal Network

    Pediatrics

    (1991)
  • J.M. Jason

    Infectious disease-related deaths of low birth weight infants, United States, 1968 to 1982

    Pediatrics

    (1989)
  • V. Khadilkar et al.

    A prospective study of nosocomial infection in a neonatal intensive care unit

    J Paediatr Child Health

    (1995)
  • S. Nambiar et al.

    Change in epidemiology of health care-associated infections in a neonatal intensive care unit

    Pediatr Infect Dis J

    (2002)
  • National Nosocomial Surveillance (NNIS) System Report, data summary from January 1990–May 1999, issued June 1999

    Am J Infect Control

    (1999)
  • J. Raymond et al.

    Nosocomial infections in pediatric patients: a European, multicenter prospective study

    Infect Control Hosp Epidemiol

    (2000)
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    Current address: Department of Medical Microbiology, Erasmus University Hospital, Rotterdam, The Netherlands.

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