Browsing by Author "Castro, Betsy E."

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    Detection of heterogeneous vancomycin intermediate resistance in MRSA isolates from Latin America
    (2020-06) Castro, Betsy E.; Berrio, Maritza; Vargas, Mónica L.; Carvajal, Lina P.; Millan, Lina V.; Rios, Rafael; Hernández, Angie K.; Rincon, Sandra; Cubides, Paola; Forero, Erika; Dinh, An; Seas, Carlos; Munita, José; Arias, Cesar A.; Reyes, Jinnethe; Díaz, Lorena
    Background: Vancomycin is a common first-line option for MRSA infections. The heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) phenotype is associated with therapeutic failure. However, hVISAisolates are usually reported as vancomycin susceptible by routine susceptibility testing procedures. Objectives: To detect and characterize the hVISA phenotype in MRSA isolates causing infections in nine LatinAmerican countries. Methods: We evaluated a total of 1189 vancomycin-susceptible MRSA isolates recovered during 2006–08 and2011–14. After an initial screening of hVISA using glycopeptide-supplemented agar strategies, the detection ofhVISA was performed by Etest (GRD) and Macro-method (MET). Isolates deemed to be hVISA were subjectedto population analysis profile/AUC (PAP/AUC) and WGS for further characterization. Finally, we interrogatedalterations in predicted proteins associated with the development of the VISA phenotype in both hVISA andvancomycin-susceptible S. aureus (VSSA) genomes. Results: A total of 39 MRSA isolates (3.3%) were classified as hVISA (1.4% and 5.6% in MRSA recovered from2006–08 and 2011–14, respectively). Most of the hVISA strains (95%) belonged to clonal complex (CC) 5. Only6/39 hVISA isolates were categorized as hVISA by PAP/AUC, with 6 other isolates close (0.87–0.89) to the cut-off(0.9). The majority of the 39 hVISA isolates exhibited the Leu-14!Ile (90%) and VraT Glu-156!Gly (90%) aminoacid substitutions in WalK. Additionally, we identified 10 substitutions present only in hVISA isolates, involvingWalK, VraS, RpoB and RpoC proteins. Conclusions: The hVISA phenotype exhibits low frequency in Latin America. Aminoacid substitutions in proteinsinvolved in cell envelope homeostasis and RNA synthesis were commonly identified. Our results suggest thatEtest-based methods are an important alternative for the detection of hVISA clinical isolates
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    Multiomics characterization of methicillin-resistant Staphylococcus aureus (MRSA) isolates with heterogeneous intermediate resistance to vancomycin (hVISA) in Latin America
    (2023) Castro, Betsy E.; Ríos, Rafael; Carvajal, Lina P.; Vargas, Mónica L.; Cala, Mónica P.; León, Lizeth; Hanson, Blake; Dinh, An Q.; Ortega-Recalde, Oscar; Seas, Carlos; Munita, José; Arias, Cesar A.; Rincón, Sandra; Reyes, Jinnethe; Díaz, Lorena
    Background: Heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) compromise the clinical efficacy of vancomycin. The hVISA isolates spontaneously produce vancomycin-intermediate Staphylococcus aureus (VISA) cells generated by diverse and intriguing mechanisms. Objective: To characterize the biomolecular profile of clinical hVISA applying genomic, transcriptomic and metabolomic approaches. Methods: 39 hVISA and 305 VSSA and their genomes were included. Core genome-based Bayesian phylogenetic reconstructions were built and alterations in predicted proteins in VISA/hVISA were interrogated. Linear discriminant analysis and a Genome-Wide Association Study were performed. Differentially expressed genes were identified in hVISA-VSSA by RNA-sequencing. The undirected profiles of metabolites were determined by liquid chromatography and hydrophilic interaction in six CC5-MRSA. Results: Genomic relatedness of MRSA associated to hVISA phenotype was not detected. The change Try38 →His in Atl (autolysin) was identified in 92% of the hVISA. We identified SNPs and k-mers associated to hVISA in 11 coding regions with predicted functions in virulence, transport systems, carbohydrate metabolism and tRNA synthesis. Further, capABCDE, sdrD, esaA, esaD, essA and ssaA genes were overexpressed in hVISA, while lacABCDEFG genes were downregulated. Additionally, valine, threonine, leucine tyrosine, FAD and NADH were more abundant in VSSA, while arginine, glycine and betaine were more abundant in hVISA. Finally, we observed altered metabolic pathways in hVISA, including purine and pyrimidine pathway, CoA biosynthesis, amino acid metabolism and aminoacyl tRNA biosynthesis. Conclusions: Our results show that the mechanism of hVISA involves major changes in regulatory systems, expression of virulence factors and reduction in glycolysis via TCA cycle. This work contributes to the understanding of the development of this complex resistance mechanism in regional strains.

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