Antibiotic Resistance Mechanisms

Antibiotic resistance belongs to the bacterial population, not to the patient. An antibiotic eliminates susceptible bacteria; organisms that survive because of a defence mechanism multiply, and their resistance traits may pass to daughter cells or move to other bacteria on mobile genetic elements. Antibiotic exposure is therefore the selective pressure that accelerates resistance, especially when treatment is unnecessary, broader than needed, or longer than necessary. The mechanism predicts the clinical problem. A drug may be destroyed before reaching its target, fail to bind its altered target, be pumped out of the cell, or be unable to enter through a changed outer membrane. The laboratory result then becomes clinically useful only when interpreted with the infection site, illness severity, prior microbiology, renal function, and local susceptibility patterns. In Canada, CARSS surveillance continues to identify resistant Gram-negative organisms, including ESBL- and carbapenemase-producing Enterobacterales, among priority concerns. For the NP, the practical sequence is to assess severity and likely source, obtain appropriate specimens when this will not delay urgent treatment, use current local data to choose empiric therapy, and narrow or stop antibiotics...