Nosocomial outbreak of extended-spectrum β-lactamase-producing Enterobacter ludwigii co-harbouring CTX-M-8, SHV-12 and TEM-15 in a neonatal intensive care unit in Venezuela

Enterobacter spp. have emerged as an important group of pathogens linked to outbreaks in neonatal intensive care units (NICUs), usually involving strains expressing extended-spectrum β-lactamases (ESBLs). The aim of this study was to describe the first nosocomial bloodstream infection outbreak caused by Enterobacter ludwigii co-harbouring CTX-M-8, SHV-12 and TEM-15 in a NICU in a Venezuelan hospital. Initial bacterial identification was achieved by VITEK^®2 system and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (VITEK^® MS) and was subsequently confirmed by nucleotide sequencing of the 16S rDNA gene and hsp60 genotyping. Antimicrobial susceptibility testing was determined by AST-GN-299 VITEK^®2 system cards and Etest strips. Isolates were typed by repetitive element sequence-based PCR (rep-PCR). Detection of bla_ESBL genes was carried out by molecular methods. Plasmid analysis included Southern blot and restriction pattern analysis, with transferability of resistance genes being assessed by conjugation. ESBL-producing E. ludwigii isolates were recovered from three neonates with bloodstream infection from the NICU in a 21-day period. rep-PCR fingerprints were indistinguishable among all of the isolates, strongly suggesting spread of a clonal strain. All isolates carried an ca. 56kb conjugative plasmid harbouring the bla_CTX-M-8, bla_SHV-12 and bla_TEM-15 genes. Considering that isolation of ESBL-producing E. ludwigii remains an unusual phenomenon, not previously reported in Venezuela, the results of this study reveal the potential role of E. ludwigii as an emerging pathogen and highlight the importance of microbiological surveillance and judicious antibiotic use as measures to curb the emergence and spread of ESBL-producing bacteria.