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1. Introduction
Invasive candidiasis (IC) has substantially increased in neonatal intensive care units (NICUs) over the two past decades and is still associated with a high morbidity and mortality [1, 2]. Candida albicans remains the most common causative agent even though non-albicans species have been increasingly reported for several years [3]. Acquisition of the Candida species by neonates may occur through two different modes: perinatal transmission, mother-neonate (vertical transmission), and nonperinatal transmission, environment-neonate (horizontal transmission) [4]. In hospitalized infants, exogenous origin of Candida colonization and infection is well documented. Indeed, many outbreaks of neonatal IC caused by strains originating from hospital staff, biomedical devices, parenteral nutrition, environment, or from other patients have been reported [5–8].
In order to type outbreak-related isolates and to assess their clonality and identify the source and the routes of their transmission, many molecular techniques have been used. They include electrophoretic karyotyping, southern blot hybridization, restriction fragment length polymorphism (RFLP) analysis, randomly amplified polymorphic DNA (RAPD) analysis, PCR-based fingerprinting, and multilocus sequence typing [5, 9–12].
In the NICU of our hospital, six cases of IC due to C. albicans were diagnosed within a five-week period. At the same period, two nurses working at the same unit were suffering from C. albicans onychomycosis of the fingers. Therefore, a neonatal IC outbreak originating from HCWs strains was suspected. In order to check on this hypothesis, we investigated isolates collected from infected neonates and HCWs at the molecular level by using pulsed-field gel electrophoresis (PFGE) which consisted of electrophoretic karyotyping (EK) and restriction endonuclease analysis of genomic DNA by using Sfi I (PFGE-Sfi I).
2. Material and Methods
2.1. Patients
Six cases of C. albicans IC were identified within a five-week period in the NICU of Farhat Hached University Hospital in Sousse, Tunisia. The NICU consists of one single room with a total of twelve beds. Infected neonates were hospitalized between September 1, 2006 and November 10, 2006. The periods of hospitalization of neonates overlapped and neonates were cared for by the same staff members. Treatment consisted of fluconazole administered intravenously for at least three weeks with removing of the indwelling catheter in all cases. Surgical drainage was used in one neonate with hepatic abscess. The short-term outcome was favorable for five...