Staph seems to love human hemoglobin best of all (that's NOT all that good!)

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Staphylococcus aureus - Antibiotics Test plate
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Staphylococcus aureus  (“staph”) is one of the most common causes of human infection.  These gram-positive  microbes can grow whether there is a shortage of oxygen or not (facultatively anaerobic), is spherically shaped (coccus-shaped),  that is found on the skin and nose of some 30% of  us.   These gram-positive microbes are lacking an outer membrane and lipoprotein layer, when compared to gram-negative type microbes. Until recently, staph were held in check via treatment with penicillin. Penicillin is a β-lactam antibiotic, which becomes incorporates into the outer lipoprotein layer of gram positive microbes, reducing their ability to grow and infect humans.  However, due to our choosing to incorporate antibiotics in animal feedstock (to improve the animal’s ability to grow) and our failure to follow the full course of antibiotic regimen, these gram positive microbes have become resistance to the penicillin treatment.  As such, S. aureus is now the leading cause of infectious heart disease, skin and soft-tissue infections- and the prime hospital acquired infection (we acquire the infection while being treated for something else in the hospital).

Now, a group of scientists at Vanderbilt under the direction of Dr. Skaar (who is now at NYU), have found that S. aureus actually prefers humans to other animals; it turns out they love our version of hemoglobin (from which it obtains the iron it needs to grow and thrive).  The microbe’s receptor, IsdB, has an augmented affinity for human hemoglobin, compared to the other species. Not only does it bind more effectively to human hemoglobin, it is more able to lyse the red blood cells and acquire the iron from human hemoglobin.  (When mice were modified to express human hemoglobin, they were found to be more susceptible to infection than conventional mice.)  It seems that other microbes have similar “affinities”   (such as Corynebacteria that cause diphtheria) for human hemoglobin

Dr. Skaar hopes to determine what, if any, variations in hemoglobin contribute to susceptibility to staph infections.  This may afford a new avenue for prophylactic treatment prior to hospital admission.

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