Fitness of antimicrobial-resistant Campylobacter and Salmonella

Abstract

<p><em>Campylobacter</em> and <em>Salmonella</em> are the most commonly reported bacterial causes of human foodborne infections, and increasing proportions of these pathogens become resistant to medically important antimicrobial agents, imposing a burden on public health. Acquisition of resistance to antibiotics affects the adaptation and evolution of <em>Salmonella</em> and <em>Campylobacter</em> in various environments. Many resistance-conferring mutations entail a biological fitness cost, while others (e.g. fluoroquinolone resistance in <em>Campylobacter</em>) have no cost or even enhanced fitness. In <em>Salmonella</em>, the fitness disadvantage due to antimicrobial resistance can be restored by acquired compensatory mutations, which occur both in vitro and in vivo. The compensated or even enhanced fitness associated with antibiotic resistance may facilitate the spread and persistence of antimicrobial-resistant <em>Salmonella</em> and <em>Campylobacter</em> in the absence of selection pressure, creating a significant barrier for controlling antibiotic-resistant foodborne pathogens.</p>