Background:
Leicester Children’s Hospital serves a population of approximately 200,000 children. There are X inpatient beds, and Y patients are treated per year. The aim of this retrospective survey was to understand the activity of the Hospital in terms of microbiological investigation of suspected invasive bacterial infections, in order to understand local epidemiology and inform future service development.
Methods:
The microbiology laboratory results database was searched for all cerebrospinal fluid (CSF) samples and blood cultures taken from paediatric patients (age <16) over a 1-year period (1 March 2016 – 28 February 2017). Samples referred for testing from other Trusts and post-mortem samples were excluded, as were any discarded samples (e.g. leaking, unidentifiable). Data recorded included demographic data, sender location and microbiology result.

Results:
777 CSF samples were obtained from 738 patients, of which 45% (352) came from general paediatrics, and 43% (336) from neonatal units, with the remainder sent by the Emergency Department and intensive care units. 53% (410) CSF samples were from babies aged ≤28 days  .
On microscopy, 59% were “clear and colourless” and 31% “blood-stained” with the remaining 10% having variable descriptions (e.g. “cloudy”). 40 samples (5.1%) had elevated white cell counts, and 9 were positive on Gram stain or culture. 2 were positive for Gram-negative bacilli, with the remaining 7 samples growing Gram-positive organisms. No CSF samples grew Neisseria meningitidis, Streptococcus pneumoniae or Group B Streptococcus, and of 9 samples sent away for meningococcal/pneumococcal PCR, there was 1 positive for Meningitis B. 8 samples had in-house 16S PCR performed, with one positive result sent away for sequencing; this was reported as “skin contaminants”.
5702 blood culture samples were received from 3879 patients, of which 38% (2139) came from general paediatrics, 31% (1766) from neonatal units, and 23% (1317) from the Emergency Department. 35% (1991) of blood cultures were from babies aged ≤28 days.
316 (5.5%) of blood cultures were positive. Of these, skin/oral commensals (potential contaminants) made up the largest group of organisms (220; 70%). The commonest pathogens were Enterobacteriaceae (n=48), Enterococci (n=17) and Staphylococcus aureus (n=11). There were 5 cases of blood-culture-proven N. meningitidis and 3 cases of Streptoccoccus pneumoniae. PCR testing of blood revealed a further 2 cases of N. meningitidis and 5 cases of S. pneumoniae.  Antimicrobial resistance in this population was not problematic; there were no MRSA or CRE cases. 
Conclusions:
The yield of significant culture-positive results from sterile sites in children is very low, with the majority of organisms isolated from paediatric CSF and blood being skin/oral commensals and thus potential contaminants. Nevertheless, the information obtained from significant positive cultures remains clinically valuable. PCR-based methods appear successful in identifying further cases, but pose logistical and financial challenges. Education aimed at reducing contamination rates should be considered.

CEREBROSPINAL FLUID AND BLOOD CULTURES IN A PAEDIATRIC POPULATION