The role of the msaABCR operon in implant-associated chronic osteomyelitis in Staphylococcus aureus USA300 LAC

Abstract

Background The msaABCR operon regulates several staphylococcal phenotypes such as biofilm formation, capsule production, protease production, pigmentation, antibiotic resistance, and persister cells formation. The msaABCR operon is required for maintaining the cell wall integrity via affecting peptidoglycan cross-linking. The msaABCR operon also plays a role in oxidative stress defense mechanism, which is required to facilitate persistent and recurrent staphylococcal infections. Staphylococcus aureus is the most frequent cause of chronic implant-associated osteomyelitis (OM). The CA-MRSA USA300 strains are predominant in the United States and cause severe infections, including bone and joint infections. Results The USA300 LAC strain caused significant bone damage, as evidenced by the presence of severe bone necrosis with multiple foci of sequestra and large numbers of multinucleated osteoclasts. Intraosseous survival and biofilm formation on the K-wires by USA300 LAC strains was pronounced. However, the msaABCR deletion mutant was attenuated. We observed minimal bone necrosis, with no evidence of intramedullary abscess and/or fibrosis, along reduced intraosseous bacterial population and significantly less biofilm formation on the K-wires by the msaABCR mutant. microCT analysis of infected bone showed significant bone loss and damage in the USA300 LAC and complemented strain, whereas the msaABCR mutant’s effect was reduced. In addition, we observed increased osteoblasts response and new bone formation around the K-wires in the bone infected by the msaABCR mutant. Whole-cell proteomics analysis of msaABCR mutant cells showed significant downregulation of proteins, cell adhesion factors, and virulence factors that interact with osteoblasts and are associated with chronic OM caused by S. aureus. Conclusion This study showed that deletion of msaABCR operon in USA300 LAC strain lead to defective biofilm in K-wire implants, decreased intraosseous survival, and reduced cortical bone destruction. Thus, msaABCR plays a role in implant-associated chronic osteomyelitis by regulating extracellular proteases, cell adhesions factors and virulence factors. However additional studies are required to further define the contribution of msaABCR-regulated molecules in osteomyelitis pathogenesis.

The msaABCR Operon Regulates Persister Formation by Modulating Energy Metabolism in Staphylococcus aureus

“…We have found a positive regulatory role for the msaABCR operon in biofilm development (Sahukhal et al, 2015), capsule production (Batte et al, 2018), antibiotic resistance (Bibek et al, 2019), antibiotic tolerance (Sahukhal et al, 2017), response to oxidative stress, and intracellular survival (Pandey et al, 2019). Moreover, in a recent study, we observed that an msaABCR operon mutant is attenuated in rat models of acute and chronic implant-associated osteomyelitis (Sahukhal et al, 2020).…”

Role of Animal Models to Advance Research of Bacterial Osteomyelitis

“…Biofilms are well recognized as a source of recalcitrant bacteria that can impair antibiotic treatment of osteomyelitis and cause persistent or recurrent osteomyelitis, particularly when orthopedic implants are in place ( 13 , 31 , 111 ). Two studies that have pursued the in vivo investigation of biofilm virulence factors and genetic components in rats include the investigation by Wu et al ( 107 ), which demonstrated that overexpression of AS yycG led to a reduction in biofilm formation and in vivo pathogenicity of MRSA in a model of rat tibial osteomyelitis; as well as the investigation by Sahukhal et al ( 110 ) who utilized a model of implant-associated osteomyelitis. This investigation demonstrated that deletion of the msaABCR operon of S. aureus (USA300 LAC) resulted in defective biofilm production and reduced severity of bacterial osteomyelitis.…”

Development of an anti-infective coating on the surface of intraosseous implants responsive to enzymes and bacteria

“…Staphylococcus aureus is the most common pathogens in endosseous implants infection. And the indiscriminate use of antibiotics has resulted in bacteria developing resistance to antibiotics [ 39 ]. And non-controllable drug-loaded antibacterial coatings cannot achieve the prevention of mid- and late-stage infections, and also can cause bacteria to develop resistance to antibiotics.…”