Biology subjects

Tarnutzer, A.

Publications and source records attributed to Tarnutzer, A..

4 recordsLinked to original sources

bioRxiv2024

Inhibition of Streptococcus pyogenes biofilm by Lactiplantibacillus plantarum and Lacticaseibacillus rhamnosus

The human pathobiont Streptococcus pyogenes forms biofilms and causes invasive infections, such as pharyngotonsillitis and necrotizing fasciitis. Bacterial biofilms are more resilient to antibiotic treatment and new therapeutic strategies are needed to control biofilm-associated infections, such as recurrent pharyngotonsillitis. Lactiplantibacillus plantarum and Lacticaseibacillus rhamnosus are two bacterial commensals used for their probiotic properties. This study aimed to elucidate the anti-biofilm properties of L. plantarum and L. rhamnosus cell-free supernatants (LPSN and LRSN, respectively) on S. pyogenes biofilms grown in vitro in supplemented minimal medium. When planktonic or biofilm S. pyogenes were exposed to LPSN or LRSN, S. pyogenes survival was reduced significantly in a concentration-dependent manner and the effect was more pronounced on preformed biofilms. Enzymatic digestion of LPSN and LRSN suggested that glycolipid compounds might cause the antimicrobial effect. In conclusion, this study indicates that L. plantarum and L. rhamnosus produce glycolipid bioactive compounds that reduce S. pyogenes viability in planktonic and biofilm cultures.

microbiology↗

bioRxiv2024

Single-cell approach dissecting agr quorum sensing dynamics in Staphylococcus aureus

Staphylococcus aureus both colonizes humans and causes severe virulent infections. Virulence is regulated by the agr quorum sensing system and its autoinducing peptide (AIP), with dynamics at the single-cell level across four agr-types - each defined by distinct AIP sequences and capable of cross-inhibition - remaining elusive. Employing microfluidics, time-lapse microscopy, and deep-learning image analysis, we uncovered significant differences in AIP sensitivity among agr-types. We observed bimodal agr activation, attributed to intergenerational phenotypic stability and influenced by AIP concentration. Upon AIP stimulation, agr-III showed AIP insensitivity, while agr-II exhibited increased sensitivity and prolonged generation time. Beyond expected cross-inhibition of agr-I by heterologous AIP-II and -III, the presumably cross-activating AIP-IV also inhibited agr-I. Community interactions across different agr-type pairings revealed four main patterns: stable or switched dominance, and delayed or stable dual activation, influenced by community characteristics. These insights underscore the potential of personalized treatment strategies considering virulence and genetic diversity.

microbiology↗

bioRxiv2023

C-di-AMP levels modulate Staphylococcus aureus cell wall thickness as well as virulence and contribute to antibiotic resistance and tolerance

Beta-lactam antibiotics are widely used to treat infections caused by the important human pathogen Staphylococcus aureus. Resistance to beta-lactams, as found in methicillin-resistant S. aureus (MRSA), renders effective treatment difficult. The second messenger cyclic di-3',5'- adenosine monophosphate (c-di-AMP) promotes beta-lactam resistance in clinical S. aureus isolates. C-di-AMP plays a crucial role in the regulation of cellular processes such as virulence, cell wall homeostasis and resistance to beta-lactams in many bacterial species. In S. aureus, c-di-AMP synthesis is mediated by the diadenylate cyclase DacA, while its degradation is carried out by the phosphodiesterases GdpP and Pde2. In this work, we assessed the effect of altered c-di-AMP levels due to mutations in cacA, gdpP or gdpP/pde2 on virulence determinants. We report that a previously described growth defect in bacteria producing high c-di-AMP levels is mainly attributable to smaller cell size. High c-di-AMP levels also led to decreased survival upon oxidative stress, reduced production of the antioxidant staphyloxanthin, increased oxacillin and fosfomycin resistance and increased cell wall thickness. While resistance to ceftaroline was not affected, high c-di-AMP levels promoted tolerance to this antibiotic. In response to cell wall stress induced by antibiotics, the three-component regulatory system VraTSR mediates an increase in cell wall synthesis via the cell wall stress stimulon (CWSS). Increased c-di-AMP levels led to an activation of the CWSS. Upon deletion of vraR, resistance to oxacillin and fosfomycin as well as cell wall thickness diminished in the {Delta}gdpP mutant, indicating a contribution of the VraTSR system to the cell wall related phenotypes. ImportanceAntibiotic resistance and tolerance are substantial health-care related problems, hampering effective treatment of bacterial infections. Mutations in the phosphodiesterase GdpP, which degrades cyclic di-3', 5'-adenosine monophosphate (c-di-AMP), have recently been associated with resistance to beta-lactam antibiotics in clinical Staphylococcus aureus isolates. In this study, we show that high c-di-AMP levels decreased the cell size and increased the cell wall thickness in S. aureus mutant strains. As a consequence, an increase in resistance to cell wall targeting antibiotics such as oxacillin and fosfomycin as well as in tolerance to ceftaroline, a cephalosporine used to treat MRSA infections, were observed. These findings underline the importance of investigating the role of c-di-AMP in the development of tolerance and resistance to antibiotics in order to optimize treatment in the clinical setting.

microbiology↗

bioRxiv2022

Group A Streptococcus antibiotic tolerance in necrotizing fasciitis

ObjectivesGroup A Streptococcus (GAS) necrotizing fasciitis (NF) is a difficult-to-treat bacterial infection associated with high morbidity and mortality despite extensive surgery and targeted antibiotic treatment. Bacteria surviving prolonged antibiotic exposure without displaying genetic resistance, so-called persisters, are associated with difficult-to-treat infections, such as GAS-NF. In the present study, we investigated the presence of persistent GAS in tissue freshly debrided from three NF patients and examined more in depth the persisters phenomenon in GAS-NF clinical isolates. MethodsTime-lapse imaging of freshly isolated GAS-NF clinical isolates, the image analysis software ColTapp and antibiotic challenge-based persisters assays were used to assess the presence of persisters. ResultsWe show for the first time that GAS recovered directly from freshly debrided NF patients tissue are characterized by increased colony appearance time heterogeneity, indicating the presence of persisters. Acidic pH or nutrient stress exposure, mimicking the NF-like environment in vitro, similarly leads to phenotypic heterogeneity resulting in enhanced antibiotic survival and confirming the presence of GAS persisters. ConclusionsGAS persisters are present in the tissue freshly debrided from GAS-NF patients and might be one explanation for antibiotic treatment failure and surgery requirement in GAS-NF. Tailored treatment options, including the use of persisters-targeting drugs, need to be developed to increase GAS-NF therapy success.

microbiology↗