343. Emergence of Daptomycin (DAP) Resistance in Community-Associated MRSA USA300 Latin American Variant (USA300-LV)
Session: Poster Abstract Session: Emerging Resistance - Epidemiology and Mechanisms
Thursday, October 5, 2017
Room: Poster Hall CD
Background: The conventional detection of antibiotic resistance in clinical laboratories by automated systems might overlook resistance, including that to last resort antibiotics that could be helpful for salvage therapy of complicated infections. DAP is a lipopetide antibiotic approved for the treatment of complicated skin and soft tissue infections (cSSTI) and bacteremia and remains one of the last-line anti-staphylococcal agents. DAP resistance has not been observed in MRSA isolates in Colombia, however a DAP MIC creep has been noted since 2016 in MRSA USA300-LV isolates causing cSSTI in one hospital. We aimed to study the possible vancomycin (VAN) and DAP resistance mechanisms in a representative MRSA isolate from this hospital.

Methods: We identified a MRSA isolate recovered from a patient with cSSTI who was failing VAN and DAP therapies. The organism was reported to be susceptible to both antibiotics. We confirmed DAP and VAN MICs by E-test and broth micro dilution respectively. We performed whole genome sequencing on an Illumina platform to characterize the resistome and genetic changes potentially associated with DAP resistance, including 22 proteins associated with development of the VISA phenotype.

Results: The MRSA isolate belonged to ST2802 (Single locus variant of ST8, Clonal complex 8) and exhibited the common characteristics of the USA300-LV (SCCmecIVc-E, absence of ACME and presence of PVL and COMER elements). VAN and DAP MICs were 2 ug/ml and 4 ug/ml, respectively. The isolate tested negative for VISA using CLSI recommended screening method. The resistome only detected genes associated with B-lactam resistance genes (mecA and blaZ). We found relevant changes in four proteins associated to VISA and DAP-NS phenotypes: MprF, VraS, TcaA and in GraS.

Conclusion: We were able to confirm the emergence of DAP resistance in a representative isolate of the prevalent community-associated USA300-LV lineage in Colombia. Detection of unusual resistance by conventional methods in clinical laboratories is challenging, where a continuous surveillance and confirmatory tests are recommended. WGS is a powerful method to detect a resistance phenotypes influenced by multiple genes.

Jinnethe Reyes, PhD1,2, Ernesto Martinez, MD3, Lina Paola Carvajal, BSc2, Aura Echeverri, MSc2, Cristhian Hernández-Gómez, MSc2,4, Lorena Diaz, PhD1,2, Javier Ardila, MSc2, Rafael Rios, MSc2, David Aragon, MD3, Diego Martinez, MD3, Elsa De La Cadena, MSc2,5, Carolina Ferro, BSc2, Claudia Gonzalez, MD3, Maria Virginia Villegas, MD, MSc, FIDSA2,5 and Cesar Arias, MD, PhD, FIDSA1,2, (1)Center for Antimicrobial Resistance and Microbial Genomics (CARMiG), University of Texas McGovern Medical School, Houston, TX, (2)Molecular Genetics and Antimicrobial Resistance Unit - International Center for Microbial Genomics, Universidad El Bosque, Bogota, Colombia, (3)Clinica Farallones, Cali, Colombia, (4)Antimicrobial Resistance and Hospital Epidemiology, Universidad El Bosque, Bogota, Colombia, (5)Antimicrobial Resistance and Hospital Epidemiology, Universidad El Bosque, Bogotá, Colombia

Disclosures:

J. Reyes, None

E. Martinez, Merck Sharp & Dohme: Consultant , Consulting fee
Pfizer: Consultant , Consulting fee

L. P. Carvajal, None

A. Echeverri, None

C. Hernández-Gómez, Merck Sharp & Dohme: Consultant , Consulting fee
Pfizer: Consultant , Consulting fee

L. Diaz, None

J. Ardila, None

R. Rios, None

D. Aragon, None

D. Martinez, None

E. De La Cadena, None

C. Ferro, None

C. Gonzalez, None

M. V. Villegas, Merck Sharp & Dohme: Consultant , Consulting fee and Research support
Pfizer: Consultant , Consulting fee and Research support

C. Arias, Merck: Consultant and Speaker's Bureau , Consulting fee and Research support
Theravance: Consultant , Consulting fee and Research support
Allergan: Consultant and Speaker's Bureau , Consulting fee and Research support
The Medicines Company: Consultant and Speaker's Bureau , Consulting fee and Research support
Bayer Global: Consultant , Consulting fee

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