Methods: EFM were susceptibility (S) tested by reference methods (M07-A10) and categorized according to CLSI (M100-S26) and US-FDA (tigecycline) guidelines. Screening for oxazolidinone mechanisms including cfr, optrA and mutations in 23S rRNA, L3 and L4 proteins was performed by PCR and sequencing techniques. Isolates were subjected to NGS and epidemiological and cfr(B) genetic context information extracted.
Results: Four additional VRE LZD-R were isolated (3-blood and 1-bone culture; May 2015- Jan 2016) from immunocompromised/suppressed patients with severe underlying diseases. Index isolates and one of the four additional EFM were recovered from patients with previous LZD treatment. All isolates (these 4 plus 2 previously reported) were multidrug-resistant, and tedizolid MIC values (1 - 2 mg/ml) were eight-fold lower than LZD (8 - 16 mg/ml). G2576T in 23S rRNA was present, along with cfr(B) in all EFM. L3 and L4 proteins showed wildtype sequences, and optrA was not detected. The two index isolates belonged to ST794 (CC17), while the additional four EFM were categorized as ST794 or a close variant, ST78. cfr(B) was located on a Tn6218 structure and embedded in chromosomal DNA in all isolates.
Conclusion: NGS and analysis demonstrate that E. faecium isolates originated from a common ancestor. However, alterations in conserved MLST housekeeping gene, suggest distant temporal relationships indicating prolonged persistency within Ochsner system. Both G2576T and cfr(B) were chromosomally-located; therefore, infection control measures should be effective in minimizing the spread of these MDR EFM isolates.
L. M. Deshpande,
C. Naccari, None
A. P. Davis, None
G. Pankey, None
M. Castanheira, None
R. E. Mendes, None
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