Biology subjects

Gomez Mejia, A.

Publications and source records attributed to Gomez Mejia, A..

3 recordsLinked to original sources

bioRxiv2021

Assessing antibiotic tolerance of Staphylococcus aureus derived directly from patients by the Replica Plating Tolerance Isolation System- REPTIS

Antibiotic tolerant Staphylococcus aureus pose a great challenge to clinicians as well as to microbiological laboratories and are one reason for treatment failure. Antibiotic tolerant strains survive transient antibiotic exposure despite being fully susceptible in vitro. Thus, fast and reliable methods to detect tolerance in the routine microbiology laboratory are urgently required. We therefore evaluated the feasibility of the replica plating tolerance isolation system (REPTIS) to detect antibiotic tolerance in S. aureus isolates derived directly from patients suffering from different types of infections and investigated possible connections to clinical presentations and patient characteristics. One hundred twenty-five S. aureus isolates were included. Replica plating of the original resistance testing plate was used to assess regrowth in the zones of inhibition, indicating antibiotic tolerance. Bacterial regrowth was assessed after 24 and 48 hours of incubation and an overall regrowth score (ORS) was assigned. Regrowth scores were compared to the clinical presentation. Bacterial regrowth was high for most antibiotics targeting protein synthesis and relatively low for antibiotics targeting other cellular functions such as DNA-replication, transcription and cell wall synthesis, with the exception of rifampicin. Isolates with a blaZ penicillinase had lower regrowth in penicillin and ampicillin. Low ORSs were more prevalent among isolates recovered from patients with immunosuppression or methicillin-resistant S. aureus (MRSA) isolates. In conclusion, REPTIS is useful to detect antibiotic tolerance in clinical microbiological routine diagnostics. Rapid detection of antibiotic tolerance offers a new diagnostic readout that might allow more tailored treatments in the future.

microbiology↗

bioRxiv2021

Ser/Thr phospho-regulation by PknB and Stp mediates bacterial quiescence and antibiotic persistence in Staphylococcus aureus

Staphylococcus aureus colonizes 30 to 50% of healthy adults and can cause a variety of diseases, ranging from superficial to life-threatening invasive infections such as bacteraemia and endocarditis. Often, these infections are chronic and difficult-to-treat despite adequate antibiotic therapy. Most antibiotics act on metabolically active bacteria in order to eradicate them. Thus, bacteria with minimized energy consumption resulting in metabolic quiescence, have increased tolerance to antibiotics. The most energy intensive process in cells - protein synthesis - is attenuated in bacteria entering into quiescence. Eukaryote-like serine/threonine kinases (STKs) and phosphatases (STPs) can fine-tune essential cellular processes, thereby enabling bacteria to quickly respond to environmental changes and to modulate quiescence. Here, we show that deletion of the only annotated functional STP, named Stp, in S. aureus leads to increased bacterial lag-phase and phenotypic heterogeneity under different stress challenges, including acidic pH, intracellular milieu and in vivo abscess environment. This growth delay was associated with reduced intracellular ATP levels and increased antibiotic persistence. Using phosphopeptide enrichment and mass spectrometry-based proteomics, we identified possible targets of Ser/Thr phosphorylation that regulate cellular processes and bacterial growth, such as ribosomal proteins including the essential translation elongation factor EF-G. Finally, we show that acid stress leads to a reduced translational activity in the stp deletion mutant indicating metabolic quiescence correlating with increased antibiotic persistence. One-sentence summaryPhospho-regulation mediates quiescence and antibiotic persistence in Staphylococcus aureus.

microbiology↗

bioRxiv2021

Atypical N-glycosylation of SARS-CoV-2 impairs the efficient binding of Spike-RBM to the human-host receptor hACE2

SARS-CoV-2 internalization by human host cells relies on the molecular binding of its spike glycoprotein (SGP) to the angiotensin-converting-enzyme-2 (hACE2) receptor. It remains unknown whether atypical N-glycosylation of SGP modulates SARS-CoV-2 tropism for infections. Here, we address this question through an extensive bioinformatics analysis of publicly available structural and genetic data. We identified two atypical sequons (sequences of N-glycosylation: NGV 481-483 and NGV 501-503), strategically located on the receptor-binding motif (RBM) of SGP and facing the hACE2 receptor. Interestingly, the cryo-electron microscopy structure of trimeric SGP in complex with potent-neutralizing antibodies from convalescent patients revealed covalently-linked N-glycans in NGV 481-483 atypical sequons. Furthermore, NGV 501-503 atypical sequon involves the asparagine-501 residue, whose highly-transmissible mutation N501Y is present in circulating variants of major concerns and affects the SGP-hACE2 binding-interface through the well-known hotspot-353. These findings suggest that atypical SGP post-translational modifications modulate the SGP-hACE2 binding-affinity affecting consequently SARS-CoV-2 transmission and pathogenesis.

molecular biology↗