Penicillin-resistant S. aureus isolates emerged shortly after penicillin was introduced for treatment of bacterial infections during WWII and, within less than two decades, approximately 80% of S. aureus strains had developed penicillin resistance, mostly through the acquisition of the blaZ gene, which encodes beta-lactamase, an enzyme that inactivates penicillin by hydrolyzing its essential beta-lactam ring [47,85]. The gene discussed is LACTB; the disease is bacterial infectious disease.