How has the bacterium staphylococcus aureus become so immune to antibiotics like penicillin?

Hint: Staphylococcus aureus is a Gram-positive, round-shaped bacterium that belongs to the Firmicutes family and is a common member of the body's microbiota, frequently found in the upper respiratory tract and on the skin.

Complete answer:
Staphylococcus aureus is naturally resistant to nearly every antibiotic ever developed. Resistance is frequently acquired through horizontal gene transfer from other sources, though chromosomal mutation and antibiotic selection are also important. This exquisite susceptibility of S. aureus led to the discovery of penicillin by Alexander Fleming, ushering in the “antibiotic era.”

Penicillin was truly a miracle drug, curing infections that were previously fatal. Nonetheless, by the mid-1940s, only a few years after its introduction into clinical practice, penicillin resistance was being observed in hospitals, and within a decade it had become a significant community problem. S. aureus is
remarkable in its ability to develop antibiotic resistance.

The ability of S. aureus to colonize normal people asymptomatically is a fundamental biological property. Approximately 30% of humans are asymptomatic nasal carriers of S. aureus, implying that S. aureus is a normal flora. S. aureus carriers are at a higher risk of infection and are thought to be an important source of S. aureus strain spread among individuals.

S. aureus is primarily transmitted through direct contact, typically skin-to-skin contact with a colonized or infected individual, though contact with contaminated objects and surfaces may also play a role.Various host factors, such as loss of the normal skin barrier, the presence of underlying diseases such as diabetes and acquired immunodeficiency syndrome, or neutrophil function defects, predispose to infection.

So, in this way bacterium staphylococcus aureus becomes so immune to antibiotics like penicillin.


Note: Infections caused by antibiotic-resistant strains of Staphylococcus aureus have reached epidemic proportions around the world. In many countries, the overall burden of staphylococcal disease, particularly that caused by methicillin-resistant S. aureus strains (MRSA), is rising in both healthcare and community settings.