What bacteria cannot be killed by antibiotics?

No bacteria is completely invincible to all antibiotics, but many bacteria have developed resistance to one or more antibiotics, making them very difficult to kill, and are often called superbugs, and some are resistant to almost all available antibiotics. Bacteria that cannot be killed by common antibiotics include MRSA, methicillin-resistant Staphylococcus aureus, which resists penicillins and many other antibiotics, VRSA which resists vancomycin, drug-resistant Mycobacterium tuberculosis which resists first-line TB drugs and requires long treatment with toxic second-line drugs, CRE, carbapenem-resistant Enterobacteriaceae like resistant Klebsiella and E. coli that resist carbapenems which are last-resort antibiotics, drug-resistant Neisseria gonorrhoeae, and extensively drug-resistant Pseudomonas aeruginosa. These bacteria survive because they have evolved mechanisms like producing enzymes that destroy antibiotics, pumping antibiotics out, or changing their targets. They are not killed by standard antibiotics but may still be killed by alternative antibiotics, combinations, or newer drugs, though options are limited and treatment is more toxic and expensive. Bacteria in biofilms, such as in chronic sinus or wound infections, are also hard to kill because biofilm protects them. Prevention is critical, including proper antibiotic stewardship, completing prescribed courses, not using antibiotics for viral infections, handwashing, vaccination, and good ventilation with HEPA filtration to reduce airborne spread. Research is ongoing for phage therapy and new antimicrobials.