Antimicrobial resistance (AMR) is a growing global health threat, as bacteria develop mechanisms to resist antibiotics, making infections harder to treat. The introduction of antibiotics in the 20th century initially seemed to solve infectious diseases, but resistance has since become widespread. The main resistance mechanisms include limiting drug uptake, modifying drug targets, inactivating drugs, and active efflux. These mechanisms can be intrinsic or acquired from other bacteria. Understanding these mechanisms is crucial for developing better treatments and new antimicrobial drugs. Resistance can be distinguished from persistence, where resistant bacteria have genetic changes that prevent drug binding, while persistent bacteria are not resistant but are in a dormant state. Bacteria can acquire resistance through genetic changes, horizontal gene transfer, or mutations. Factors such as overuse of antibiotics, improper prescribing, and animal feed use contribute to the spread of resistant strains. Gram-negative bacteria often use all four main resistance mechanisms, while gram-positive bacteria are less likely to limit drug uptake. Resistance mechanisms include outer membrane barriers, efflux pumps, and changes in drug targets. For example, β-lactamases break down β-lactam antibiotics, while efflux pumps expel drugs from the cell. Resistance to drugs like vancomycin and daptomycin can also occur through structural changes in bacterial proteins. The emergence of drug-resistant strains, such as MRSA and CRE, has led to increased healthcare costs and mortality. Efflux pumps, such as those in the RND family, play a significant role in antibiotic resistance. Other mechanisms include drug inactivation, modification of drug targets, and resistance to ribosomal subunits. The development of new antimicrobial agents and better stewardship practices are essential to combat AMR. Despite efforts, the challenge remains significant, with many resistant strains still difficult to treat. Continued research and innovation are needed to address this growing threat.Antimicrobial resistance (AMR) is a growing global health threat, as bacteria develop mechanisms to resist antibiotics, making infections harder to treat. The introduction of antibiotics in the 20th century initially seemed to solve infectious diseases, but resistance has since become widespread. The main resistance mechanisms include limiting drug uptake, modifying drug targets, inactivating drugs, and active efflux. These mechanisms can be intrinsic or acquired from other bacteria. Understanding these mechanisms is crucial for developing better treatments and new antimicrobial drugs. Resistance can be distinguished from persistence, where resistant bacteria have genetic changes that prevent drug binding, while persistent bacteria are not resistant but are in a dormant state. Bacteria can acquire resistance through genetic changes, horizontal gene transfer, or mutations. Factors such as overuse of antibiotics, improper prescribing, and animal feed use contribute to the spread of resistant strains. Gram-negative bacteria often use all four main resistance mechanisms, while gram-positive bacteria are less likely to limit drug uptake. Resistance mechanisms include outer membrane barriers, efflux pumps, and changes in drug targets. For example, β-lactamases break down β-lactam antibiotics, while efflux pumps expel drugs from the cell. Resistance to drugs like vancomycin and daptomycin can also occur through structural changes in bacterial proteins. The emergence of drug-resistant strains, such as MRSA and CRE, has led to increased healthcare costs and mortality. Efflux pumps, such as those in the RND family, play a significant role in antibiotic resistance. Other mechanisms include drug inactivation, modification of drug targets, and resistance to ribosomal subunits. The development of new antimicrobial agents and better stewardship practices are essential to combat AMR. Despite efforts, the challenge remains significant, with many resistant strains still difficult to treat. Continued research and innovation are needed to address this growing threat.