Biology subjects

Silbert, S.

Publications and source records attributed to Silbert, S..

3 recordsLinked to original sources

bioRxiv2025

Genomic and Phenotypic Characterization of Mupirocin Resistant Staphylococcus aureus Clinical Isolates

BackgroundColonization with Staphylococcus aureus is a risk factor for subsequent infection. Decolonization with the topical antibiotic mupirocin is effective and reduces the risk of subsequent S. aureus infection for both methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) strains but may select for mupirocin-resistant isolates. MethodsWe characterized oxacillin and mupirocin susceptibility amongst 384 S. aureus strains isolated from clinical samples isolated 2017-2023 in Tampa, Florida, spanning strains collected before and after the onset of the COVID-19 pandemic. Whole genome sequencing of bacterial isolates was conducted in parallel and correlated with drug susceptibility profiles. ResultsMupirocin resistance (MupR) was nearly exclusively present in MRSA strains (103/106 97.1% of MupR; 103/299 34.4% of MRSA). Although our hospital protocol for decolonization shifted to povidone iodine in the Post-COVID period, the overall prevalence of MupR did not change in Pre-COVID and Post-COVID samples (28.9% vs 26%). Genotype correlated with antibiotic susceptibility with low level MupR (MupLR), linked to mutations in ileS and high level MupR (MupHR), linked to the presence of mupA. Genome analysis revealed that most MupR strains fell into three sequence types (ST) falling into two major clonal complexes (CC): CC8 ST8 (including Community-Associated MRSA strains USA300 and USA500), CC5 ST5 (associated with Healthcare-Associated MRSA such as USA100), and CC5 ST3390. ST3390 isolates had the highest prevalence of MupR (30/36 83%; MupHR 20/36 55.6%; MupLR 10/36 27.8%). ConclusionsMupirocin resistance was prevalent in our hospital MRSA strains. We also found evidence for emergence and persistence of ST3390 MRSA-MupR strains in Florida. Key pointsO_LIIn a survey of clinical isolates in Florida, 34.4% of MRSA strains were mupirocin resistant. C_LIO_LIMupirocin resistance correlated with mutations in ileS or carriage of mupA. C_LIO_LIWe found evidence for emergence of MRSA mupirocin-resistant strains that were sequence type ST3390. C_LI

microbiology↗

bioRxiv2025

Emergence of ST3390: A non-pigmented HA-MRSA clone with enhanced virulence

BackgroundOne of the most successful and widely-distributed hospital-associated lineages of MRSA is CC5. These strains are known from widespread antibiotic resistance, but less severe disease than CA-MRSA counterparts. Recently, CC5 descendant lineages have appeared globally with hypervirulent properties. MethodsHerein we use genomic analyses to study the epidemiology of a rare CC5 MRSA sequence type, ST3390, circulating within Tampa General Hospital (TGH). We employ genetic tools alongside in vitro and in vivo models of virulence to study the pathogenic capabilities of strains. ResultsTo date, there have only been 50 recorded instances of infection caused by ST3390 globally, with 36 of those occurring at TGH. Genomic analysis of strains identified numerous spa-types, with a t010 cluster found only at TGH. Exploration of AMR genes detected the presence of unique hybrid SCCmec types, with [~]90% of TGH strains possessing components of SCCmecIa, SCCmecIIa and/or SCCmecVIII. Phenotypically, all ST3390 strains lack the staphyloxanthin pigment, which is mediated by a conserved 6 aa in frame deletion within the staphyloxanthin biosynthesis protein CrtN. ST3390 strains display high levels of cytotoxicity towards human neutrophils compared to other CC5 lineages, with several isolates displaying hypervirulence in animal models of infection. ConclusionsThis is the first study to characterize the pathogenicity and genomic architecture of the rare MRSA lineage ST3390. Our work provides a deeper understanding of the clonal expansion of CC5, and the wider diversification of S. aureus isolates within patient populations.

microbiology↗

bioRxiv2020

Validation and Comparison of a Modified CDC Assay with two Commercially Available Assays for the Detection of SARS-CoV-2 in Respiratory Specimen

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19), has spread rapidly around the globe since it was first identified in December of 2019 in Wuhan, China. In a race to contain the infection, researchers and healthcare officials have developed several assays to help diagnose individuals with COVID-19. To help laboratories in deciding what assay to bring into testing lines, factors such as assay availability, cost, throughput, and TAT should be considered. Here we validated a modified version of the CDC assay and used it as a reference to evaluate the performance of the NeuMoDx SARS-CoV-2 and DiaSorin Simplexa Covid-19 Direct assays. In silico analysis and clinical sample testing showed that the primesr/probes designed by the CDC were specific to the SARS-CoV-2 as they accurately detected all reactive samples with an assay LoD of 200 copies/ml. The performance of the three assays were analyzed using 161 nasopharyngeal swabs specimen tested within 24 hours or 5 days from routine testing. A 100% agreement was observed between the commercial assays and the modified CDC SARS-CoV-2 assay. A deeper look at the Ct values showed no significant difference between NeuMoDx and the modified CDC SARS-CoV-2 assay, whereas DiaSorin had lower overall Ct values than the modified CDC SARS-CoV-2 assay. NeuMoDx and DiaSorin workflows were much easier to perform. NeuMoDx has the highest throughput and shortest TAT, whereas although the modified CDC SARS-CoV-2 assay has comparable throughput to DiaSorin, it has the longest hands-on time, and highest TAT.

microbiology↗