Which resistance mechanism is common among Gram-negative ocular pathogens toward beta-lactams?

• A. Beta-lactamase production
• B. Altered penicillin-binding protein
• C. Efflux pumps
• D. Porin changes

Answer: (A)

Beta-lactamase production is the most common way Gram-negative ocular pathogens resist beta-lactam antibiotics. These enzymes hydrolyze the beta-lactam ring, inactivating the drug before it can bind to penicillin-binding proteins and block cell wall synthesis. In the eye, many Gram-negative pathogens—such as Pseudomonas, Haemophilus, Moraxella, and various Enterobacteriaceae—produce beta-lactamases that can target penicillins and often cephalosporins, and some strains carry extended-spectrum or AmpC enzymes that broaden this resistance. While other mechanisms like porin changes (reducing drug entry), altered penicillin-binding proteins, or efflux pumps can contribute to resistance, enzymatic inactivation by beta-lactamases is the most widespread driver across these organisms.