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Correlation between Mutations in
<i>liaFSR</i>
of Enterococcus faecium and MIC of Daptomycin: Revisiting Daptomycin Breakpoints
(2012)
MUNITA SEPULVEDA, JOSE MANUEL
;
Diana Panesso
;
Lorena Diaz
;
Truc T. Tran
;
Jinnethe Reyes
Mutations in liaFSR, a three-component regulatory system controlling cell-envelope stress response, were recently linked with the emergence of daptomycin (DAP) resistance in enterococci. Our previous work showed that a liaF mutation increased the DAP MIC of a vancomycin-resistant Enterococcus faecalis strain from 1 to 3 μg/ml (the DAP breakpoint is 4 μg/ml), suggesting that mutations in the liaFSR system could be a pivotal initial event in the development of DAP resistance. With the hypothesis that clinical enterococcal isolates with DAP MICs between 3 and 4 μg/ml might harbor mutations in liaFSR, we studied 38 Enterococcus faecium bloodstream isolates, of which 8 had DAP MICs between 3 and 4 μg/ml by Etest in Mueller-Hinton agar. Interestingly, 6 of these 8 isolates had predicted amino acid changes in the LiaFSR system. Moreover, we previously showed that among 6 DAP-resistant E. faecium isolates (MICs of >4 μg/ml), 5 had mutations in liaFSR. In contrast, none of 16 E. faecium isolates with a DAP MIC of ≤2 μg/ml harbored mutations in this system (P<0.0001). All but one isolate with liaFSR changes exhibited DAP MICs of ≥16 μg/ml by Etest using brain heart infusion agar (BHIA), a medium that better supports enterococcal growth. Our findings provide a strong association between DAP MICs within the upper susceptibility range and mutations in the liaFSR system. Concomitant susceptibility testing on BHIA may be useful for identifying these E. faecium first-step mutants. Our results also suggest that the current DAP breakpoint for E. faecium may need to be reevaluated
14Scopus© Citations 104
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A liaF Codon Deletion Abolishes Daptomycin Bactericidal Activity against Vancomycin-Resistant Enterococcus faecalis
(2013)
MUNITA SEPULVEDA, JOSE MANUEL
;
Truc T. Tran
;
Lorena Diaz
;
Diana Panesso
;
Jinnethe Reyes
The genetic bases for antibiotic tolerance are obscure. Daptomycin (DAP) is a lipopeptide antibiotic with bactericidal activity against enterococci. Using time-kill assays, we provide evidence for the first time that a deletion of isoleucine in position 177 of LiaF, a member of the three-component regulatory system LiaFSR involved in the cell envelope response to antimicrobials, is directly responsible for a DAP-tolerant phenotype and is likely to negatively affect response to DAP therapy.
4Scopus© Citations 66
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Ceftaroline-Resistant, DaptomycinTolerant, and Heterogeneous Vancomycin-Intermediate MethicillinResistant Staphylococcus aureus Causing Infective Endocarditis
(2017)
Masayuki Nigo
;
Lorena Diaz
;
Lina P. Carvajal
;
Truc T. Tran
;
Rafael Rios
<jats:title>ABSTRACT</jats:title> <jats:p> We report a case of infective endocarditis (IE) caused by ceftaroline-resistant, daptomycin-tolerant, and heterogeneous vancomycin-intermediate methicillin-resistant <jats:named-content content-type="genus-species">S. aureus</jats:named-content> (MRSA). Resistance to ceftaroline emerged in the absence of drug exposure, and the E447K substitution in the active site of PBP2a previously associated with ceftaroline resistance was identified. Additionally, we present evidence of patient-to-patient transmission of the strain within the same unit. This case illustrates the difficulties in treating MRSA IE in the setting of a multidrug-resistant phenotype. </jats:p>
8 1Scopus© Citations 31

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