Abstract
BackgroundThe evolving antibiotic-resistant behavior of health care–associated methicillin-resistant Staphylococcus aureus (HA-MRSA) USA100 strains are of major concern. They are resistant to a broad class of antibiotics such as macrolides, aminoglycosides, fluoroquinolones, and many more.FindingsThe selection of appropriate antibiotic susceptibility examination media is very important. Thus, we use bacteriological (cation-adjusted Mueller-Hinton broth) as well as physiological (R10LB) media to determine the effect of vancomycin on USA100 strains. The study includes the profiling behavior of HA-MRSA USA100 D592 and D712 strains in the presence of vancomycin through various high-throughput assays. The US100 D592 and D712 strains were characterized at sub-inhibitory concentrations through growth curves, RNA sequencing, bacterial cytological profiling, and exo-metabolomics high throughput experiments.ConclusionsThe study reveals the vancomycin resistance behavior of HA-MRSA USA100 strains in dual media conditions using wide-ranging experiments.
Highlights
The evolving antibiotic-resistant behavior of health care–associated methicillin-resistant Staphylococcus aureus (HA-MRSA) USA100 strains are of major concern
At the same time that samples of HA-MRSA USA100 D592 and D7128 were taken for OD600 measurements, ∼400 μL was collected from each replicate of all growth conditions and syringefiltered using 0.22- μm disc filters (Millex-GV, MilliporeSigma) to remove the cells from the spent media
The data of 1.4 μg/mL subinhibitory concentration for Cation-adjusted Mueller-Hinton broth (CAMHB) on the D712 strain have been excluded from all studies because the reproducibility between the samples was too low
Summary
The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infections such as bacteremia differs around the world, and it is one of the leading causes of nosocomial infections worldwide [1]. The USA100 strain is a HA-MRSA that shows high resistance to a wide range of antibiotics such as macrolides, fluoroquinolones, and lincosamides [5, 6]. These strains are considered to display vancomycin-resistant and intermediate phenotypes [7]. For the D712 strain, the MIC value decreased from 2 μg/mL in R10LB to 0.96 μg/mL in CAMHB These MIC values fall below the clinically defined vancomycin resistance levels (MIC ≥ 16 μg/mL), vancomycin treatment was not able to clear the bacteremia caused by these isolates [10]. Our data provide an in-depth look into vancomycin response by simultaneously tracking gene expression (RNA-seq), cell morphology (BCP), and changes in the chemical composition of the media (HPLC and LC/MS)
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