What is one other way suggested by theory by which a previously sensitive bacterial strain can become resistant to penicillin?

1. Mutation in the target site of penicillin
2. Increased production of penicillinase enzyme
3. Decreased permeability of the bacterial cell wall
4. Efflux pumps to remove penicillin from the cell

Bacteria can develop resistance to penicillin through a mutation in the target site of penicillin, decreased permeability of the cell wall to antibiotics, or by using efflux pumps to expel the antibiotic from the cell.

Explanation:

Another way by which a previously sensitive bacterial strain can become resistant to penicillin, aside from increased production of penicillinase, is through a mutation in the target site of penicillin.

This occurs through spontaneous genetic changes in the genes that encode for the binding proteins targeted by penicillin, such as penicillin-binding proteins (PBPs). This leads to alterations in the structure of these proteins, resulting in reduced binding affinity for the antibiotic, thereby conferring resistance.

An example includes strains of Streptococcus pneumoniae changing their PBPs to avoid the action of ß-lactam drugs.

Decreased permeability of the bacterial cell wall is another mechanism by which bacteria achieve resistance. This can occur in bacteria like Mycobacterium, which has a cell wall that inherently blocks the entry of certain antibiotics.

Efflux pumps that actively remove penicillin from bacterial cells represent another resistance mechanism. These pumps can be specific to one drug or may be multidrug-resistance efflux pumps (MDR pumps), which expel a broad range of antibiotics out of the cell, enhancing resistance.