Question

Most antimicrobials that arrest protein function are non-selective as to the microbes they affect. Why would this be? What would the effect of these agents be on human skin or tissue, if applied there?

Answer 1

Antimicrobials are drugs capable of killing or stopping the growth of a microorganism. The most common antimicrobial drugs are antibiotics. Examples of non-selective antibiotics that arrest protein function include chloramphenicol, clindamycin, oxazolidinones, streptogramins, and erythromycin, all of them inhibiting protein synthesis by binding to the 23S rRNA located in the bacterial 50S subunit. An example of how non-selective they are due to their mechanism of action can be explained with erythromycin which can be used to treat skin and respiratory infections in humans, caused by bacteria like Staphylococcus, Streptococcus, Haemophilus, and Corynebacterium.

Most antimicrobials that arrest protein function are non-selective as to the microbes they affect. Why would this be? Eukaryotic ribosome subunits contain ribosomal RNA that doesn't change between different types of eukaryotic organisms and species, therefore a single antimicrobial that arrests protein function (usually inhibiting protein synthesis by binding to rRNA of the 50S subunit) will be able to kill or stop the growth of several different bacteria species like erythromycin does.

In summary, as the sequence of the rRNA to which antimicrobials bind doesn't change between different species of bacteria, antimicrobials that inhibit protein synthesis will not be selective as to the microbes they affect.

What would the effect of these agents be on human skin or tissue, if applied there?

No effect, as prokaryotic organisms, in which humans are included, have different ribosome subunits. In terms of the difference in the ribosomal RNA, eukaryotic organisms have 3 rRNA molecules in their ribosomes (16S, 23S, and 5S), that are different to the ones that prokaryotic organisms have, which are 4 rRNA molecules (18S, 28S, 5.8S, and 5S). As antimicrobials that arrest protein function do it by binding to the 23S rRNA specifically, and we humans do not have that rRNA, the drugs will not have the arrest of protein effect on us.