Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Fri, 09 Nov 2018 01:49:04 Colonization of the gut with Gram-negative bacilli, its association with neonatal sepsis and its clinical relevance in a developing country Parijat Das, 1 Arun K. Singh, 2 Titir Pal, 3 Sudipta Dasgupta, 2 T. Ramamurthy 1 and Sulagna Basu 1 Correspondence Sulagna Basu supabasu@yahoo.co.in or sulagnabasu@gmail.com Received 29 April 2011 Accepted 23 June 2011 1 Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India 2 Department of Neonatology, Institute of Postgraduate Medical Education & Research, SSKM Hospital, Kolkata, India 3 AbsolutData Research and Analytics, New Delhi, India This study examined the pattern of colonization of the neonatal gut by aerobic Gram-negative bacilli (GNB) and evaluated the association between gut colonization and sepsis in the developing world. This deserves attention because of the high incidence of sepsis and the differences in hygienic environments in developing countries compared with the developed world. The study was carried out on neonates in a tertiary-care government hospital. Serial gut samples were analysed (gastric aspirates and stool samples) for GNB. Blood samples of cases showing clinical signs of sepsis were also analysed for septic screening and culture positivity. Antibiograms, serotyping and PFGE were carried out to evaluate the relatedness of the gut and blood isolates. A diverse array of GNB was isolated from the gut of the neonates, Klebsiella pneumoniae being most common, followed by Escherichia coli. The rate of isolation of GNB was consistently higher in stool samples compared with gastric aspirate samples. Colonization was influenced by a stay in the neonatal intensive care unit and by the prolonged use of a feeding tube. GNB were the cause of sepsis in the majority of cases, with K. pneumoniae being the most frequently isolated GNB from the blood. Acinetobacter baumannii, Escherichia coli, Enterobacter cloacae and Burkholderia cepacia were the other GNB recovered from the blood of the neonates. Neonates with GNB in the gut had a higher incidence of clinical sepsis than those without. In 50 % of cases, the genotypes of the organisms found in the blood were indistinguishable from their gut counterpart. These results show that the neonatal gut is colonized with a diverse array of GNB, and an association between gut colonization and neonatal sepsis was observed. INTRODUCTION The gut of a neonate is colonized by bacteria immediately after birth. Among the hundreds of bacteria that colonize the gut, there are some potential pathogens (Guarner & Malagelada, 2003; Sharma et al., 2009). Whilst not all colonization leads to infection, the pathogenicity of aerobic Gram-negative bacilli (GNB) may predispose neonates towards infection (Graham et al., 2007; Pierro et al., 1998; van Saene et al., 2003). The vulnerability of the immune system and the gut barrier in neonates, particularly in those who are premature and of low birth weight, make the neonate especially prone to colonization with aerobic GNB. Studies have shown that GNB in the gut may predispose neonates to septicaemia (Pierro et al., 1998; van Saene et al., 2003). Evidence from surgical neonates shows that gut overgrowth, particularly with GNB, causes depression of the mucosal and systemic immunity leading to the development of sepsis (Donnell et al., 2002). However, the association between enteric organisms and subsequent sepsis remains, at least in humans, largely circumstantial and based on surgical cases (Donnell et al., 2002; MacFie, 2004). However, in developing countries such as India, neonatal sepsis occurs in large numbers of neonates without any surgical intervention. Although there have been studies examining patterns of colonization of the neonatal gut with GNB (Magne et al., 2005; Schwiertz et al., 2003), there are few originating from developing countries (Adlerberth et al., 1991; Bennet et al., 1991). This deserves to be studied separately because of the differences in maternal health, hygiene conditions during delivery and hospital milieu between developed and Abbreviations: GNB, Gram-negative bacilli; NICU, neonatal intensive care unit. Journal of Medical Microbiology (2011), 60, 1651–1660 DOI 10.1099/jmm.0.033803-0 033803 G 2011 SGM Printed in Great Britain 1651