Biology subjects

Jacques, N.

Publications and source records attributed to Jacques, N..

3 recordsLinked to original sources

bioRxiv2024

The Spx stress regulator confers high-level β-lactam resistance and decreases susceptibility to last-line antibiotics in methicillin resistant Staphylococcus aureus

Infections caused by methicillin resistant Staphylococcus aureus (MRSA) are a leading cause of mortality worldwide. MRSA have acquired resistance to next generation {beta}-lactam antibiotics through the horizontal acquisition of the mecA resistance gene. Development of high resistance is, however, often associated with additional mutations in a set of chromosomal core genes, known as potentiators which through poorly described mechanisms enhance resistance. The yjbH gene was recently identified as a hot spot for adaptive mutations during severe infections. Here, we show that inactivation of yjbH increased {beta}-lactam MICs up to 16-folds and transformed MRSA cells with low level of resistance to being homogenously highly resistant to {beta}-lactams. The yjbH gene encodes an adaptor protein that targets the transcriptional stress regulator Spx for degradation by the ClpXP protease. Using CRISPRi to knock down spx transcription, we unambiguously linked hyper-resistance to accumulation of Spx. Spx was previously proposed to be essential, however, our data indicate that Spx is dispensable for growth at 37{degrees}C but becomes essential in the presence of antibiotics with various targets. On the other hand, high Spx levels bypassed the role of PBP4 in {beta}-lactam resistance and broadly decreased MRSA susceptibility to compounds targeting the cell wall or the cell membrane including vancomycin, daptomycin, and nisin. Strikingly, Spx potentiated resistance independently of its redox sensing switch. Collectively, our study identifies a general stress pathway that, in addition to promoting the development of high-level, broad-spectrum {beta}-lactam resistance, also decreases MRSA susceptibility to critical antibiotics of last resort.

microbiology↗

bioRxiv2023

Novel determinant of antibiotic resistance: a clinically selected Staphylococcus aureus clpP mutant survives daptomycin treatment by reducing binding of the antibiotic and adapting a rod-shaped morphology

Daptomycin is a last-resort antibiotic used for treatment of infections caused by Gram-positive antibiotic-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA). Treatment failure is commonly linked to accumulation of point mutations, however, the contribution of single mutations to resistance and the mechanisms underlying resistance remain incompletely understood. Here we show that a single nucleotide polymorphism (SNP) selected during daptomycin therapy inactivates the highly conserved ClpP protease and is causing reduced susceptibility of MRSA to daptomycin, vancomycin, and {beta}-lactam antibiotics as well as decreased expression of virulence factors. Super-resolution microscopy demonstrated that the improved survival of the clpP mutant strain during daptomycin treatment was associated with reduced binding of daptomycin to the septal site and diminished membrane damage. In both the parental strain and the clpP strain, daptomycin inhibited the inward progression of septum synthesis eventually leading to lysis and death of the parental strain while surviving clpP cells were able to continue synthesis of the peripheral cell wall in the presence of 10 x MIC daptomycin resulting in a rod-shaped morphology. To our knowledge, this is the first demonstration that synthesis of the outer cell wall continues in the presence of daptomycin. Collectively, our data provide novel insight into the mechanisms behind bacterial killing and resistance to this important antibiotic. Also, the study emphasizes that treatment with last-line antibiotics is selective for mutations that, like the SNP in clpP, favor antibiotic resistance over virulence gene expression. IMPORTANCEThe bacterium Staphylococcus aureus is a leading cause of life-threatening infections and treatment is challenged by the worldwide dissemination of methicillin-resistant Staphylococcus aureus (MRSA) that are multi-drug resistant. Daptomycin, a cell membrane-targeting cationic lipopeptide, is one of the few antibiotics with activity against MRSA, however, the killing mechanism of daptomycin and the mechanisms leading to resistance are not fully understood. Here we show than an MRSA strain, isolated from the blood of a patient treated with daptomycin, has acquired a mutation that inactivates the ClpXP protease resulting in increased resistance to several antibiotics and diminished expression of virulence genes. Super resolution microscopy showed that the mutant avoids daptomycin-elicited killing by preventing the binding of the antibiotic to the septal site and by growing into a rod-shaped morphology. In summary, this study discloses new perspectives on the mechanism of killing and the mechanism of resistance to an antibiotic of last resort.

microbiology↗

bioRxiv2020

Effect of mechanical properties of monofilament twines on the catch efficiency of biodegradable gillnets.

Gillnets made of the biodegradable resin polybutylene succinate co-adipate-co-terephthalate (PBSAT) were tested under commercial fishing conditions to compare their fishing performance with that of conventional nylon polyamide (PA) gillnets. Both types of gillnets were made of 0.55 mm Ø monofilaments. However, since the biodegradable nets are weaker than nylon PA nets when using the same monofilament diameter, we also used biodegradable nets made of 0.60 mm Ø monofilament that had a similar tensile strength to the 0.55 mm Ø nylon PA nets. The relative catch efficiency of the different gillnet types was evaluated over the 2018 autumn fishing season for saithe and cod in northern Norway. For cod, both biodegradable gillnets (0.55 and 0.60 mm) had a significantly lower catch efficiency compared to the traditional nylon PA net (0.55 mm) with estimated catch efficiencies of 62.38% (CI: 50.55–74.04) and 54.96% (CI: 35.42–73.52) compared with the nylon PA net, respectively. Similarly for saithe, both biodegradable gillnets (0.55 and 0.60 mm) had a lower estimated catch efficiency compared to the traditional nylon PA net (0.55 mm) with estimated catch efficiencies of 83.40% (71.34–94.86) and 83.87% (66.36–104.92), compared with the nylon PA net, respectively. Tensile strength does not explain the differences in catch efficiency between the two gillnet types, since increasing the twine diameter of the biodegradable gillnets (to match the strength of nylon PA gillnets) did not yield similar catch efficiencies. However, the elasticity and stiffness of the materials may be responsible for the differences in catch efficiency between the nylon PA and biodegradable gillnets.View Full Text

scientific communication and education↗