Infection Control & Hospital Epidemiology


1267


Table 1. Typing and Antimicrobial Susceptibility Testing of 6 vanD Enterococcus faecium Isolates Identified as Part of an Outbreak in a Canadian Neurosurgical Acute Care Ward and 2 Sporadic Isolates Identified 4 Months Prior


Minimum Inhibitory Concentration (μg/mL)a PFGEb


Outbreak Cases 1


2 3 4 5 6


Sporadic Cases 7


8 ST Typec 117 117 117 117 117 AMP NIT >32 (R) 64 (I) >32 (R) 64 (I) >32 (R) 64 (I) VAN TEC ≥32 (R) 24 (I) ≥32 (R) 6 (S) ≥32 (R) 6 (S) >32 (R) 32 (S) ≥32 (R) 24 (I) >32 (R) 64 (I) 117 NC NC CIP DAP RIF TET TGC LZD ≥8 (R) 2 (S) >4 (R) ≤1 (S) ≤0.12 2 (S) ≥8 (R) 2 (S) >4 (R) ≤1 (S) ≤0.12 2 (S) ≥8 (R) 2 (S) >4 (R) ≤1 (S) ≤0.12 2 (S) ≥8 (R) 2 (S) >4 (R) ≤1 (S) ≤0.12 2 (S) ≥32 (R) 32 (R) ≥8 (R) 2 (S) >4 (R) ≤1 (S) ≤0.12 2 (S) ≥32 (R) 24 (I) ≥8 (R) 2 (S) >4 (R) ≤1 (S) ≤0.12 2 (S)


117 117


>32 (R) 64 (I) >32 (R) 64 (I)


≥32 (R) NC ≥32 (R) NC


≥8 (R) NC NC ≥8 (R) NC NC


2 (S)


0.25


2 (S) ≤1 (S) ≤0.12 2 (S) Note. AMP, ampicillin; NIT, nitrofurantoin; VAN, vancomycin; TEC, teicoplanin; CIP, ciprofloxacin; DAP, daptomycin; RIF, rifampin; TET, tetracycline; TGC, tigecycline; LZD, linezolid;


S, susceptible; I, intermediate; R, resistant; NC, not completed; ST, sequence type; PFGE, pulsed-field gel electrophoresis. aSusceptibility testing was carried out using VITEK-2 antimicrobial susceptibility cards (bioMérieux, Marcy l’Etoile, France) and an in-house prepared microbroth dilution. Interpretative


criteria provided in parentheses beside minimum inhibitory concentration values are based on CLSI M100-S27 performance standards for antimicrobial susceptibility testing. bIsolates 1, 2, 5, and 6 were indistinguishable based on PFGE analysis. cIsolate 8 was matched to ST117 with 5 of 7 matching housekeeping genes; all other isolates were matched to all housekeeping genes


E. faecium septicemia in a hematology ward reported by Star- lander et al2 identified 8 other patients (30%) with enterococci carrying the vanD gene, but no specific species were identified nor did dissemination occur.2 The prevalence of vanD enterococcal carriage in the general population is unknown but may be underestimated because most microbiology laboratories do not routinely perform genotyping on VRE-positive patients. To date, 5 distinct vanD alleles have been reported in enter-


ococci (vanD1 to vanD5). While previous vanD-carrying VRE reported in Canada have included strains N97-330 (vanD3 allele) and N03-0072 (vanD5 allele),5 this outbreak represents the first Canadian cases of vanD4-carrying VRE. The vanD4 gene was initially identified in an E. faecium (isolate 10/96A, ST281) from a 9-year-old girl with aplastic anemia in Brazil.3 The finding of 100% sequence homology with vanD4, yet different sequence types between the outbreak and the E. faecium 10/96A isolate, suggests acquisition of resistance through horizontal gene transfer rather than clonal expansion. The index case in this outbreak was a patient hospitalized for


more than a year who received multiple courses of antibiotics with no travel history to Brazil. We suspect that this patient acquired the organism from the hospital environment in the context of selective pressure. With the identification of a related vanD isolate 4 months prior, unrecognized nosocomial transmission of this strain likely took place months before the outbreak. This report describes the first documented nosocomial out-


break of vanD-carrying E. faecium. Many institutions do not routinely perform genotyping on VRE isolates; therefore, vanD transmission in hospitalized patients may be underrecognized.


Acknowledgments. We thank George Golding and David Boyd for facil- itating nucleic acid sequencing at the National Microbiology Laboratory and Nyog Inn Ng-Haing and Grace Luk for facilitating PFGE and PCR testing at our institution.


Financial support. No financial support was provided relevant to this article.


Conflicts of interest. All authors report no conflicts of interest relevant to this article.


References


1. Depardieu F, Kolbert M, Pruul H, et al. VanD-type vancomycin-resistant Enterococcus faecium and Enterococcus faecalis. Antimicrob Agents Chemother 2004;48:3892–3904.


2. Starlander G, Tellgren-Roth C, Melhus Å. Fatal acquisition of vanD gene during vancomycin treatment of septicaemia caused by Enterococcus faecium. J Hosp Infect 2016;92:408–412.


3. Camargo IL, Dalla Costa LM, Woodford N, Gilmore MS, Darini AL. Sequence analysis of Enterococcus faecium strain 10/96A (VanD4), the original vancomycin-resistant E. faecium strain in Brazil. J Clin Microbiol 2006;44:2635–2637.


4. Boyd DA, Kibsey P, Roscoe D, Mulvey MR. Enterococcus faecium N03- 0072 carries a new VanD-type vancomycin resistance determinant: characterization of the VanD5 operon. J Antimicrob Chemother 2004;54:680–683.


5. Boyd DA, Lalancette C, Lévesque S, Golding GR. Characterization of a genomic island harbouring a new vanD allele from Enterococcus faecium N15-508 isolated in Canada. J Antimicrob Chemother 2016;71: 2052–2054.


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