Biology subjects

Cattoir, V.

Publications and source records attributed to Cattoir, V..

5 recordsLinked to original sources

bioRxiv2025

Stress-Induced Iron-Sulfur Cluster Damage as a Conserved Trigger of the Stringent Response

Pathogenic bacteria rely on the stringent response to adapt to the complex and fluctuating conditions encountered within the host. However, the mechanisms by which the stringent response senses host-induced stress remain poorly understood. Here, we identify iron-sulfur (Fe-S) cluster damage as a conserved trigger of the stringent response in major Gram-negative pathogens, including Salmonella enterica, Enterobacter cloacae, and Klebsiella pneumoniae. We demonstrate that Fe-S cluster disruption--caused by oxidative stress or metal imbalance--restricts the intracellular pools of sulfur-containing and branched-chain amino acids, thereby activating the ribosome-associated (p)ppGpp synthetase RelA. Furthermore, we show that iron availability governs recovery from Fe-S cluster damage, modulating the dynamics of the stringent response. Finally, we emphasize the dual role of (p)ppGpp in transcriptional regulation, enhancing bacterial fitness during Fe-S cluster stress while simultaneously promoting virulence by upregulating the SPI-2 type III secretion system. Together, these findings uncover a conserved mechanism by which pathogenic bacteria integrate metabolic stress into adaptive gene regulation and virulence, positioning Fe-S cluster integrity as a pivotal node linking environmental sensing to transcriptional control during infection.

microbiology↗

bioRxiv2021

A cis-RNA-mediated expression regulation of the tet(M) resistance gene in Enterococcus faecium

A set of putative novel small RNAs was recently identified as expressed in Enterococcus faecium, a major opportunistic pathogen involved in numerous healthcare-associated infections and hospital outbreaks. The aim of this study was to characterize the first functional analysis of one of them, srn0030, by phenotypic, genomic and transcriptomic approaches. By genomic analysis and RACE mapping, we revealed the presence of this RNA (previously designated as Ptet) within the 5-untrasnlated region (UTR) of tet(M), a gene conferring tetracycline resistance through ribosomal protection. The regulatory mechanism has previously been described as transcriptional attenuation, but has actually been poorly characterized. Hence, we provide original additional data, especially the presence of three upstream transcripts of ~100, ~150 and ~230 nt within the 5-UTR of tet(M), suggesting an alternative regulatory mechanism. The total deletion of these three transcripts causes an unexpected decreasing of tetracycline resistance in E. faecium. The attenuation mechanism was investigated, and we confirmed that the transcriptional read-through and tet(M) overexpression induced by tetracycline addition but the function of putative peptide leader on attenuation mechanism was not supported by our data. We report here new phenotypic and transcriptomic observations in E. faecium demonstrating an alternative regulatory mechanism of tet(M) gene expression.

microbiology↗

bioRxiv2020

Rapid Detection of VanA/B-Producing Vancomycin-Resistant enterococci using Lateral Flow Immunoassay from colonies and blood culture

Vancomycin-resistant enterococci (VRE) have become one of the most important nosocomial pathogens worldwide associated with increased treatment costs, prolonged hospital stay, and high mortality. Rapid detection is crucial to reduce their spread and prevent infections and outbreaks. The lateral flow immunoassay NG-Test VanB (NG Biotech) was evaluated for the rapid detection of VanB-producing vancomycin-resistant enterococci (VanB-VRE) using 104 well-characterized enterococcal isolates. The sensitivity and specificity were both 100%, when bacterial cells were grown in the presence of vancomycin used as VanB inducer. The NG-Test VanB is an efficient, rapid, and easy to implement assay in clinical microbiology laboratories for the confirmation of VanB-VREs either from colonies or from positive blood cultures. Together with the NG-Test VanA, they could complete/replace the already existing panel of tests available for confirmation of acquired vancomycin resistance in enterococci, especially from selective media (rectal screenings) or from antibiograms (infections), with a sensitivity and specificity of both of 100%. The rapid detection in less than 15 minutes will result in more efficient management of carriers and infected patients.

microbiology↗

bioRxiv2019

Unexpected activity of oral fosfomycin against resistant strains of Escherichia coli in murine pyelonephritis.

Fosfomycin-tromethamine activity is well established for oral treatment of uncomplicated lower urinary tract infections but little is known about its potential efficacy in pyelonephritis. Ascending pyelonephritis was induced in mice infected with 6 strains of Escherichia coli (fosfomycin MICs: 1 g/ml to 256 g/ml). Urine pH was 4.5 before infection and 5.5-6.0 during infection. Animals were treated for 24h with fosfomycin (100 mg/kg subcutaneously every 4 hours) and CFU were enumerated in kidneys 24h after the last fosfomycin injection. Peak (20.5 g/ml at 1h) and trough (3.5 g/ml at 4h) levels in plasma were comparable to those obtained in human after an oral dose of 3 grams. Fosfomycin treatment significantly reduced bacterial loads in kidneys (3.65 log10CFU/g [min-max=1.83-7.03] and 1.88 log10CFU/g [1.78-5.74] in start-of-treatment control mice and treated mice, respectively, P < 10-6). However, this effect was not found to differ across the 6 study strains (P = 0.71) and between the 3 susceptible and the 3 resistant strains (P=0.09). Three phenomena may contribute to explain this unexpected in vivo activity: i) in mice, fosfomycin kidney/plasma concentrations ratio increased from 1 to 7.8 (95% CI, 5.2; 10.4) within 24 hours; in vitro, when pH decreased to 5: (ii) fosfomycin MICs for the 3 resistant strains (64-256 g/ml) decreased into the susceptible range (16-32 g/ml) and: iii) maximal growth rates significantly decreased for all strains and were the lowest in urine. These results suggest that local fosfomycin concentrations and physiological conditions may favour fosfomycin activity in pyelonephritis, even against resistant strains.

microbiology↗

bioRxiv2019

Colistin heteroresistance in Enterobacter cloacae is mediated by PmrAB-independent 4-amino-4-deoxy-l-arabinose addition to lipid A

The Enterobacter cloacae complex (ECC) consists of closely-related, but genetically distinct bacteria commonly associated with the human microbiota. ECC have been increasingly isolated from healthcare-associated infections, demonstrating that these Enterobacteriaceae are emerging nosocomial pathogens. ECC strains can rapidly acquire multidrug resistance to conventional antibiotics. Cationic antimicrobial peptides (CAMPs) have served as therapeutic alternatives because they target the highly conserved lipid A component of the Gram-negative outer membrane to lyse the bacterial cell. Many Gram-negative Enterobacteriaceae fortify their outer membrane with cationic amine-containing moieties to protect from CAMP-inflicted lysis. The PmrAB two-component system (TCS) transcriptionally activates 4-amino-4-deoxy-O_SCPCAPLC_SCPCAP-arabinose (O_SCPCAPLC_SCPCAP-Ara4N) biosynthesis to result in amine moiety addition to lipid A in many Enterobacteriaceae such as E. coli and Salmonella. In contrast, PmrAB in E. cloacae is dispensable for CAMP resistance. Instead, fitness against CAMPs presents as heteroresistance, or a subpopulation of cells that exhibit clinically significant increases in resistance levels compared to the majority population. We demonstrate that E. cloacae lipid A is modified with O_SCPCAPLC_SCPCAP-Ara4N to induce CAMP heteroresistance and that the regulatory mechanism is independent of the PmrABEcl TCS. We show that the response regulator, PhoPEcl, directly binds to the arnBEcl promoter to induce expression of O_SCPCAPLC_SCPCAP-Ara4N biosynthesis and PmrAB-independent addition to the lipid A disaccharolipid. Therefore, we have identified a mechanism of ECC colistin heteroresistance that directly involves the PhoPQ system.\n\nImportanceMembers of the Enterobacter cloacae complex (ECC) are Gram-negative nosocomial pathogens that have emerged within healthcare facilities around the world. ECC infections are associated with immunocompromised patients and infections are often life threatening. The cationic antimicrobial peptide, colistin (polymyxin E), is a last-line treatment option to combat Gram-negative multidrug resistant infections. However, many ECC intrinsically encode a colistin heteroresistance mechanism. Our analysis to characterize colistin heteroresistance in E. cloacae revealed that 4-amino-4-deoxy-O_SCPCAPLC_SCPCAP-arabinose is conjugated to the lipid A disaccharolipid to protect from colistin-mediated lysis. Additionally, this mechanism is directly regulated by the PhoPQEcl two-component system. Elucidation of outer membrane antimicrobial resistance modifications and their regulatory pathways in E. cloacae isolates will advance our understanding of CAMP heteroresistance.

microbiology↗