Question

May you please put this in layman's terms?

ABSTRACT

Coagulase-negative staphylococci (CoNS) and Staphylococcus aureus are part of the natural flora of humans and other mammals. We found that spent media from the CoNS species Staphylococcus caprae can inhibit agr-mediated quorum sensing by all classes of S. aureus. A biochemical assessment of the inhibitory activity suggested that the S. caprae autoinducing peptide (AIP) was responsible, and mass spectrometric analysis identified the S. caprae AIP as an eight-residue peptide (YSTCSYYF). Using a murine model of intradermal MRSA infection, the therapeutic efficacy of synthetic S. caprae AIP was evident by a dramatic reduction in both dermonecrotic injury and cutaneous bacterial burden relative to controls. Competition experiments between S. caprae and MRSA demonstrated a significant reduction in MRSA burden using murine models of both skin colonization and intradermal infection. Our findings indicate that important interactions occur between commensals that can impact disease outcomes and potentially shape the composition of the natural flora.

Answer 1

The abstract is describing the use of Autoinducing peptide (AIP) as a potential probiotic to prevent or counteract MRSA(Methicillin-Resistant Staphylococcus aureus) infections in a Mouse model.

Many bacteria utilize quorum sensing to detect the presence of competing bacteria. Quorum sensing is a phenomenon where bacteria sense the concentration of an Autoinducer molecule (AIP in this case) as an indicator of bacterial cell density to regulate their own growth rate. A high concentration of the Autoinducer indicates that there are a proportionally large number of competing bacteria, limiting the availability of resources. In the presence of high enough concentrations of the Autoinducer, bacteria do not divide, instead opting to remain dormant until Autoinducer concentrations drop.

The researchers find that media on which CoNS cells had been grown was able to inhibit agr-mediated quorum sensing by S. aureus. They later find that the inhibition of agr-mediated Quorum sensing in S. aureus is mediated by S. caprae AIP.

Next, the researchers created a mouse (murine) model of intradermal (skin layer between epidermis and hypodermis) infection and find that synthetic S. caprae AIP was able to reduce injury due to skin necrosis caused by MRSA cells and also reduce the 'cutaneous bacterial load' or concentration of bacteria on skin surface. When competition experiments were performed using S. caprae and MRSA, S. caprae reduced the concentration and intradermal cencentration of MRSA.

The researchers postulate that commensal organisms (like S. caprae) can play an important role in controlling the spread of infectious agents like MRSA.