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Open Access Highly Accessed Research article

Molecular epidemiology of coagulase-negative Staphylococcus carriage in neonates admitted to an intensive care unit in Brazil

Yves Mauro Ternes1, Juliana Lamaro-Cardoso1, Maria Cláudia Porfirio André1, Vicente Porfírio Pessoa2, Maria Aparecida da Silva Vieira3, Ruth Minamisava4, Ana Lúcia Andrade1 and André Kipnis1*

Author Affiliations

1 Institute of Tropical Pathology and Public Health, Federal University of Goiás, Goiânia, GO, Brazil

2 Children’s Hospital, Goiânia, Brazil

3 Pontifical Catholic University of Goiás, Goiânia, GO, Brazil

4 School of Nursing, Federal University of Goiás, Goiânia, GO, Brazil

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BMC Infectious Diseases 2013, 13:572  doi:10.1186/1471-2334-13-572

Published: 5 December 2013

Abstract

Background

Nasal colonization with coagulase-negative Staphylococcus (CoNS) has been described as a risk factor for subsequent systemic infection. In this study, we evaluated the genetic profile of CoNS isolates colonizing the nares of children admitted to a neonatal intensive care unit (NICU).

Methods

We assessed CoNS carriage at admittance and discharge among newborns admitted to a NICU from July 2007 through May 2008 in one of the major municipalities of Brazil. Isolates were screened on mannitol salt agar and tryptic soy broth and tested for susceptibility to antimicrobials using the disc diffusion method. Polymerase chain reaction (PCR) was used to determine the species, the presence of the mecA gene, and to perform SCCmec typing. S. epidermidis and S. haemolyticus isolated from the same child at both admission and discharge were characterized by PFGE.

Results

Among 429 neonates admitted to the NICU, 392 (91.4%) had nasal swabs collected at both admission and discharge. The incidence of CoNS during the hospitalization period was 55.9% (95% confidence interval [CI]: 50.9-60.7). The most frequently isolated species were S. haemolyticus (38.3%) and S.epidermidis (38.0%). Multidrug resistance (MDR) was detected in 2.2% and 29.9% of the CoNS isolates, respectively at admittance and discharge (p = 0.053). The mecA gene was more prevalent among strains isolated at discharge (83.6%) than those isolated at admission (60%); overall, SCCmec type I was isolated most frequently. The length of hospitalization was associated with colonization by MDR isolates (p < 0.005). Great genetic diversity was observed among S. epidermidis and S. haemolyticus.

Conclusions

NICU represents an environment of risk for colonization by MDR CoNS. Neonates admitted to the NICU can become a reservoir of CoNS strains with the potential to spread MDR strains into the community.

Keywords:
Coagulase-negative Staphylococcus; mecA; SCCmec; Neonatal intensive care units; Neonates