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Colonization studies: are they of any value? The audit of a referral tertiary NICU

Maria Teresa Neto(1) (2) Daniel Virella(1) , Micaela Serelha(1)

1- Neonatal Intensive Care Unit, Hospital de Dona Estefânia. Centro Hospitalar de Lisboa Central EPE
Nova Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa. Lisbon, Portugal

Comunicação oral. 22nd European Workshop on Neonatology. Certosa dei Pontignano. 15 a 18 de Junho 2014

Background: Multidrug-resistant Gram-negative bacteria are a significant source of nosocomial infection. Active microbiological surveillance has been recommended to reduce their transmission, as it allows the adoption of isolation measures to prevent bacterial dissemination. Microbiologists disagree with colonization studies, due to alleged low sensitivity, high costs and mislead antibiotic use. Aim: To audit the practice of conducting systematic colonization screening for multi-drug resistant bacteria at admission to a tertiary medico-surgical neonatal unit. Methods: Cross-sectional study of every admission to a single NICU through 2012. Data on the results of the colonization screenings requested in the admission day and bacterial resistance patterns were collected from the intranet clinical data system. Length of stay in a previous neonatal unit (LOS) was hypothesized as the main risk exposure. The main outcomes are multi-drug resistant bacteria colonization rate, number needed to screen (NNS) depending on previous LOS, and cost for each positive screening. Cost assessment was based on the official costs of colonization screenings and estimated costs related to isolation measures. Results: Out of 174 patients admitted to the NICU, 141 were screened using samples from 244 swabs (pharynx, rectal, axilla or tracheal aspirate). Screening was positive in 41 patients (29%) and 60 isolates were obtained. There was a positive correlation between positive screening and previous LOS (r=0.957). Patients admitted with previous LOS of 29-60 days had the higher rate of positive screening (54.5%), with a NNS of 5 comparing with LOS≤7 days and 12 with LOS 8-28days. Positivity of screening from pharynx and rectal swabs was similar (21%vs.17%;p=0.263). Nine patients were colonized with multi-drug resistant bacteria, two of them admitted from home:4 Kl pn ESBL, 4 MRSA, 1 Acinetobacter baumanii. No bloodstream infections caused by these bacteria occurred. The overall cost for identification of each patient colonized with MR bacteria was about 1000€. Conclusion: Criteria for colonization screening for multi-drug resistant bacteria should be narrow, thoroughly defined and customised to each NICU. Even so, costs will be high, with scarce evident gain, even in a tertiary referral medical-surgical neonatal unit. It is difficult to calculate gains of eventually prevented nosocomial sepsis with this policy.

Keywords: Colonization, intensive care unit, newborn