A multi-species cluster of GES-5 carbapenemase producing Enterobacterales linked by a geographically disseminated plasmid

BACKGROUND: Early and accurate treatment of infections due to carbapenem-resistant organisms is facilitated by rapid diagnostics but rare resistance mechanisms can compromise detection. One year after a GES-5 carbapenemase-positive Klebsiella oxytoca infection was identified by whole genome sequencing (WGS) (later found to be part of a cluster of three cases), a cluster of 11 patients with GES-5-positive K. oxytoca was identified over 18 weeks in the same hospital. METHODS: Bacteria were identified by MALDI-TOF, antimicrobial susceptibility testing followed EUCAST guidelines. Ertapenem-resistant isolates were referred to Public Health England for characterization using PCR detection of GES, pulse-field gel electrophoresis (PFGE) and WGS for the second cluster. RESULTS: The identification of the first GES-5 K. oxytoca isolate was delayed, being identified on WGS. A GES-gene PCR informed the occurrence of the second cluster in real-time. In contrast to PFGE, WGS phylogenetic analysis refuted an epidemiological link between the two clusters; it also suggested a cascade of patient-to-patient transmission in the later cluster. A novel GES-5-encoding plasmid was present in K. oxytoca,E. coli and E. cloacae isolates from unlinked patients within the same hospital group and in human and wastewater isolates from three hospitals elsewhere in the UK. CONCLUSIONS: Genomic sequencing revolutionized the epidemiological understanding of the clusters, it also underlined the risk of covert plasmid propagation in healthcare settings and revealed the national distribution of the resistance-encoding plasmid. Sequencing results also informed and led to the ongoing use of enhanced diagnostic tests for detecting carbapenemases locally and nationally

Serial clustering of late onset group B streptococcal infections in the neonatal unit - a genomic re-evaluation of causality

Background. Invasive Group B streptococcus (GBS) is a major cause of serious neonatal infection. Current strategies to reduce early onset GBS disease have no impact on late onset disease (LOD). Although GBS is a normal part of the enteric microbiota in healthy term infants, LOD cases arising in the neonatal intensive care unit setting raise questions about mode of acquisition. Methods. Enhanced surveillance for any case of late onset GBS sepsis admitted to a level 3, 24-bed neonatal intensive care unit over a 2 year period was instituted following a cluster of four cases. All late onset GBS isolates were serotyped and genomes sequenced. Rectal screening of neonates for GBS was undertaken weekly. Healthcare workers and parents were not screened. Results. Over 24 months, a total of 12 late onset invasive GBS episodes were identified (incidence 0.6/1000 live births). Genomic analysis revealed that 11/12 GBS isolates (92%) were linked to at least one other LOD isolate. Four isolates from the first cluster were serotype V, resistant to macrolides and lincosamides, providing early evidence of a common source. Sequencing confirmed isolates were indistinguishable, or distinguishable by 1 SNP, from each other, and distinct from contemporary serotype V GBS. Although a common environmental source was not identified, prompt infection prevention interventions were instituted and no further serotype V GBS infections arose. Prospective surveillance identified three further clusters of LOD due to serotypes Ia, Ib, and III, leading to re-evaluation of interventions required for preventing GBS LOD. Conclusion. Acquisition routes for LOD GBS in the neonatal unit are poorly understood; such cases may not necessarily be sporadic. Within this neonatal unit, our data suggest that a single case of LOD GBS sepsis should be considered a potential nosocomial transmission event warranting prompt investigation, heightened infection prevention vigilance and action where required