In Vitro Therapeutic Efficacy of Furazolidone for Antimicrobial Susceptibility Testing on Campylobacter

<b>Background:</b><i>Campylobacter</i> causes gastroenteritis worldwide with increasing antimicrobial resistance. Furazolidone (FZD) shows potential in resource-poor areas but needs further study. We aimed to assess the in vitro susceptibility of <i>Campylobacter</i> spp. to FZD, ciprofloxacin (CIP), and erythromycin (ERY) in a high-risk pediatric cohort and to evaluate the clinical relevance of resistance patterns using inhibitory quotient (IQ) pharmacodynamics. <b>Methods:</b> A two-phase prospective study (2012-2013, 2014-2015) was conducted at a tertiary pediatric hospital in Lima, Peru. Stool samples from children ≤24 months were cultured on selective media, with <i>Campylobacter</i> isolates identified via conventional bacteriological methods. Antimicrobial susceptibility was determined using Kirby-Bauer disk diffusion and regression-derived minimum inhibitory concentrations (MICs). IQ analysis correlated inhibition zones with therapeutic outcomes. <b>Results:</b> Among 194 <i>Campylobacter</i> isolates (<i>C. jejuni</i>: 28%; <i>C. coli</i>: 72%), resistance to CIP declined from 97.7% (2012-2013) to 83% (2014-2015), while ERY resistance rose from 2.3% to 9.4% (<i>p</i>= 0.002). No FZD resistance was observed, with mean inhibition zones of 52 ± 8 mm (2012-2013) and 43 ± 10.5 mm (2014-2015). MICs for FZD were predominantly <0.125 μg/mL, and all susceptible isolates demonstrated favorable IQ outcomes. Multidrug resistance (≥2 drugs) increased to 6.2% (2014-2015), though all MDR strains retained FZD susceptibility. CLSI and EUCAST breakpoints showed concordance for ERY (<i>p</i> = 0.724) but discordance for CIP (<i>p</i> = 0.022 vs. 0.008). <b>Conclusions:</b> FZD exhibits sustained in vitro efficacy against <i>Campylobacter</i> spp., even among MDR strains, contrasting with escalating fluoroquinolone and macrolide resistance.