Question

Staphylococcus aureus has become resistant to penicillin, methicillin, and now possibly to vancomycin. Since bacteria do not sexually reproduce, genetic recombination does not introduce new alleles into the genome. Bacteria do mutate at a high rate and can also swap genetic material through horizontal gene transfer. How did S. aureus acquire resistance in each instance?

Answer 1

Answer:

S. aureus acquire resistance by :

1) Beta-lactamase production.

2) Changes in penicillin-binding protiens (PBP) (mecA genes encode these altered PBPs )

3) Genes  encoding the enzymes substituting D-lactate for D-alanine in the peptidogylcan.

Explanation:

More than 90% strains of Staphylococcus aureus contains plasmids which code for beta- lactamases which cause the enzymatic hydrolysis of the beta lactam ring resulting in the loss of antibacterial activity. (Resistance against penicillins )

Some of the strains of S.Aureus are resistant to beta lactamase resistant penicillins such as methicilin (MRSA)  and nafcillin (NRSA)  by virtue of changes in the penicillin-binding protien (PBP) in their cell membrane.

Some strains of S.Aureus are resistant to Vancomycin (VRSA) and they acquire this resistance by some genes located in a transposon on a plasmid  and encode the enzymes that substitute D-lactate for D-alanine in the peptidoglycan.