Antibiotics that target the bacterial cell wall (such as penicillins and cephalosporins), or cell membrane (for example, polymixins), or interfere with essential bacterial enzymes (such as quinolones and sulfonamides) have bactericidal activities.
Further categorization is based on their target specificity. "Narrow-spectrum" antibacterial antibiotics target specific types of bacteria, such as Gram-negative or Gram-positive bacteria, whereas broad-spectrum antibiotics affect a wide range of bacteria
Antibacterial-resistant strains and species, sometimes referred to as "superbugs", now contribute to the emergence of diseases which were for a while well-controlled. For example, emergent bacterial strains causing tuberculosis (TB) that are resistant to previously effective antibacterial treatments pose many therapeutic challenges. Every year, nearly half a million new cases of multidrug-resistant tuberculosis (MDR-TB) are estimated to occur worldwide. For example, NDM-1 is a newly identified enzyme conveying bacterial resistance to a broad range of beta-lactam antibacterials. United Kingdom Health Protection Agency has stated that "most isolates with NDM-1 enzyme are resistant to all standard intravenous antibiotics for treatment of severe infections."
Many antibacterials are frequently prescribed to treat symptoms or diseases that do not respond to antibacterial therapy or are likely to resolve without treatment, or incorrect or sub-optimal antibacterials are prescribed for certain bacterial infections. The overuse of antibacterials, like penicillin and erythromycin, have been associated with emerging antibacterial resistance since the 1950s. Widespread usage of antibacterial drugs in hospitals has also been associated with increases in bacterial strains and species that no longer respond to treatment with the most common antibacterials.
In agriculture, antibacterials are often used to promote weight gain in livestock animals. More...