Successful control of Serratia marcescens outbreak in a neonatal unit of a tertiary-care hospital in Spain

Serratia marcescens is a Gram-negative bacterium that is found in hospital environments and commonly associated with outbreaks in neonatal units. One S. marcescens isolate was detected from a bloodstream culture from a neonate in our hospital that was followed by an outbreak. The aim of this study was to describe the molecular epidemiology of a S. marcescens outbreak in the neonatal unit. In order to investigate the outbreak, weekly surveillance rectal swabs were submitted for culture from all patients admitted in this unit from August to September 2018. Environmental samples were obtained from potential sources in September 2018. Typing of isolates was performed by pulsed field gel electrophoresis (PFGE). In addition, we studied the in vitro activity of chlorhexidine against S. marcescens. During this period, 146 infants were hospitalised in our neonatal unit, of which 16 patients had a S. marcescens-positive sample. A total of 36 environmental surveillance samples were collected, and one sample from a stethoscope from an incubator of a colonized baby was positive for S. marcescens. All the 18 isolates, including the isolate from the stethoscope, belonged to a single PFGE cluster. We found that very low concentrations of chlorhexidine, even with application times close to 0 achieved significant reductions in the amount of S. marcescens. A unique clone of S. marcescens caused this outbreak, including isolates from patients and from one stethoscope. The outbreak was controlled with the early implementation of specific control measures. Serratia marcescens(S. marcescens) es una bacteria gramnegativa que se encuentra en ambientes hospitalarios y comúnmente aparece asociada a brotes en unidades neonatales. En agosto de 2018 se detectó un aislado de esta bacteria a partir de un hemocultivo de un paciente neonatal en nuestro hospital. El objetivo de este estudio fue describir la epidemiología molecular del brote de S. marcescens en la unidad neonatal. Con el fin de investigar el brote, se enviaron semanalmente para cultivo muestras rectales de todos los pacientes ingresados en estas unidades de agosto a septiembre de 2018. Asimismo, se obtuvieron muestras ambientales de potenciales orígenes del brote en septiembre de 2018. Los aislados se genotipificaron mediante electroforesis de campo pulsado (PFGE). Durante este período, 146 lactantes fueron hospitalizados en nuestra unidad neonatal, de los cuales 16 pacientes tenían una muestra positiva para S. marcescens. S