Mobile genetic element-encoded hypertolerance to copper protectsStaphylococcus aureusfrom killing by host phagocytes

Abstract

22Pathogens are exposed to toxic levels of copper during infection and copper tolerance 23 may be a general virulence mechanism used by bacteria to resist host defences. In support of 24 this, inactivation of copper-exporter genes has been found to reduce the virulence of bacterial 25 pathogens in vivo. Here we investigate the role of copper-hypertolerance in methicillin 26 resistant Staphylococcus aureus. We show that a copper-hypertolerance locus (copB-mco), 27 carried on a mobile genetic element, is prevalent in a collection of invasive S. aureus strains 28 and more widely among clonal complex 22, 30 and 398 strains. The copB and mco genes 29 encode a copper efflux pump and a multicopper oxidase, respectively. Isogenic mutants 30 lacking copB or mco had impaired growth in subinhibitory concentrations of copper. Transfer 31 of a copB-mco encoding plasmid to a naive clinical isolate resulted in a gain of copper-32 hypertolerance and enhanced bacterial survival inside primed macrophages. The copB and 33 mco genes were upregulated within infected macrophages and their expression was 34 dependent on the copper sensitive operon repressor CsoR. Isogenic copB and mco mutants 35were impaired in their ability to persist intracellularly in macrophages and were less resistant 36 to phagocytic killing in human blood than the parent strain. The importance of copper-37 regulated genes in resistance to phagocytic killing was further elaborated using mutants 38 expressing a copper-insensitive variant of CsoR. Our findings suggest that the gain of mobile 39 genetic elements carrying copper-hypertolerance genes contributes to the evolution of 40 virulent strains of S. aureus, better equipped to resist killing by host immune cells. 41 42 43

Pathogenicity and virulence of Staphylococcus aureus

“…Furthermore, S. aureus produces a lactate dehydrogenase, which is inducible by nitric oxide (NO), another ROS, and contributes to maintaining redox homeostasis in the phagosome [121]. Also, S. aureus can inhibit the oxidate burst by converting ADP and AMP to adenosine [122] and resist the toxicity of copper, which is imported into macrophage phagosomes and contributes to ROS production, via a mobile genetic element-encoded copper hypertolerance system [123]. Lastly, staphylococcal peroxidase inhibitor (SPIN) directly inhibits MPO [124].…”

Investigation of a Staphylococcus argenteus Strain Involved in a Chronic Prosthetic-Joint Infection

“…This extra set of proteins required for copper tolerance could likely represent an effective strategy against the copper killing mechanisms [ 30 , 31 , 32 ] used by the host cells to eradicate the bacteria or, at the opposite, could help survive the copper limitation the host could use as another defensive mechanism [ 33 ]. Notably, it could play a role similar to the copB gene, mco operon and its repressor csoR identified on a mobile genetic element in methicillin-resistant S. aureus that increase survival in human blood and resistance to killing by host immune cells [ 34 ]. We also identified the presence of the β-hemolysin gene that has been involved in the suppression of the IL-8 production and in the inhibition of the neutrophil migration [ 35 ] adding to its low inflammatory potential.…”

Staphylococcus aureus lacking a functional MntABC manganese import system has increased resistance to copper

“…CopL is an external Cu-binding lipoprotein that aids in preventing Cu from entering the cell (Rosario-Cruz et al, 2019). Some strains also encode a multicopper oxidase (Mco) and an S. aureus Δmco mutant was more sensitive to Cu than the parental strain (Zapotoczna et al, 2018). S. aureus contains csoR which encodes for a transcriptional regulator of the copBL and copAZ operons (Grossoehme et al, 2011;Purves et al, 2018).…”