In VitroStudy of the Susceptibility of Clinical Isolates ofTrichomonas vaginalisto Metronidazole and Secnidazole
ABSTRACTNitroimidazoles (metronidazole [MTZ] and tinidazole [TNZ]) are the only drugs recommended for treatment ofTrichomonas vaginalisinfections. MTZ resistance occurs in 4% to 10% of cases of vaginal trichomoniasis (R. D. Kirkcaldy et al., Emerg Infect Dis 18:939–943, 2012; J. R. Schwebke and F. J. Barrientes, Antimicrob Agents Chemother 50:4209–4210, 2006) and TNZ resistance in 1% of cases (J. R. Schwebke and F. J. Barrientes, Antimicrob Agents Chemother 50:4209–4210, 2006). Emerging nitroimidazole-resistant trichomoniasis is concerning, because few alternatives to standard therapy exist. We assessed the prevalence ofin vitroaerobic MTZ and secnidazole resistance amongT. vaginalisisolates collected in 2015 to 2016 from 100 women in Birmingham, Alabama, with positive cultures. Archived specimens were treated with secnidazole or MTZ (0.2 to 400 μg/ml) for 48 h, according to U.S. Centers for Disease Control and Prevention protocols. Ninety-six (96%) of the 100 clinicalTrichomonasisolates tested demonstrated lower minimum lethal concentrations for secnidazole than for MTZ, suggesting that secnidazole has betterin vitroactivity than MTZ.