The pain you describe sounds very much like pain of the chest wall that includes the ribs, muscles, cartilage, intercostal ligaments and nerves. That is it does not sound like pain from the pleura, lung or any of the underlying organs.
The new class of drugs was known as beta-lactamase inhibitors and they worked to block the ability of the S. aureus bacteria to destroy the distinctive penicillin ring structure. The new combination drugs that are effective against Staphylococcus aureus infections are amoxicillin/clauvulante, ampicillin/sublactam, piperacillin/tazobactam and ticarcillin/clavulanate.
Initially, most Staph infections were sensitive to penicillin. In the 1950s, many infections became resistant to penicillin and methicillin (a related drug developed to treat these germs). Thus, the term methicillin-resistant Staphylococcus aureus (MRSA) was derived.