Abstract
The bacterial flora of nasogastric feeding tubes and faecal samples were analysed for a low-birth weight (725 g) neonate EGA 25 weeks in intensive care. Samples were collected at age 6 and 8 weeks of life. Optical coherence tomography (OCT) was used to visualise bacterial biofilms inside the nasogastric feeding tubes. The biofilm was heterogeneously distributed along the tube lumen wall, and had a depth of up to 500 µm. The bacterial biofilm and faecal samples included Enterococcus faecalis and Enterobacter hormaechei. Representative strains, recovered from both feeding tubes and faecal samples, were whole genome sequenced using Illumina, Mi-Seq, which revealed indistinguishable strains, each with less than 28 SNP differences, of E. faecalis and E. hormaechei. The E. faecalis strains were from two sequence types (ST191 and ST211) and encoded for a number of traits related to biofilm formation (BopD), adherence (Epb pili), virulence (cps loci, gelatinase, SprE) and antibiotic resistances (IsaA, tetM). The E. hormaechei were all ST106, and encoded for blaACT-15 β–lactamase and fosfomycin resistance (fosA). This proof of concept study demonstrates that bacterial flora within the neonatal feeding tubes may influence the bacterial colonisation of the intestinal tract and can be visualised non-destructively using OCT.
Highlights
Bacteria are well known for being able to form biofilms on inert surfaces such as plastic and glass[1,2], and on medical devices including catheters, ventilator tubes, and enteral feeding tubes[3]
E. coli K1 sequence type 95 strains recovered from the feeding tubes of twelve neonates over a three week period were indistinguishable according to pulsed-field gel electrophoresis (PFGE) indicating a unidentified source of exposure, and high risk to neonatal health[13]
We demonstrate the complementary use of Optical coherence tomography (OCT) and whole genome sequencing, where the OCT was used for rapid non-invasive visualisation of bacterial biofilm structures and the whole genome sequencing analysis was used to identify and characterise the bacteria inside the feeding tubes of a preterm infant in a neonatal intensive care units (NICU)
Summary
Bacteria are well known for being able to form biofilms on inert surfaces such as plastic and glass[1,2], and on medical devices including catheters, ventilator tubes, and enteral feeding tubes[3]. The complex microbial flora included various Enterobacteriaceae species (E. coli K1, Enterobacter hormaechei, E. cancerogenus, Cronobacter sakazakii, Serratia marcescens, and Klebsiella pneumoniae), Pseudomonas fluorescens, P. luteola, staphylococci, lactic acid bacteria, as well as fungi such as Candida albicans Many of these organisms such as E. coli K1, C. sakazakii, E. hormaechei, and staphylococci are recognised as causative agents of severe neonatal infections and can be present in infant formula[14,15,16,17,18]. Colonization of neonatal feeding tubes by such organisms that can cause highly severe infections of neonates, has not been investigated thoroughly These organisms produce extracellular capsular material associated with biofilm formation, and would entrap other organisms resulting in multi-organism biofilm formation. Hurrell et al.[19] further showed that a single contaminated feed resulted in bacterial biofilm formation within the feeding tube and subsequent contamination of every following feed which would be ingested by the neonate
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