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Prevalence of metronidazole-resistant Trichomonas vaginalis
in a gynecology clinic.
Journal of Reproductive Medicine 2001;46(6):545-549.
Schmid G, Narcisi E, Mosure D, Secor WE, Higgins J, Moreno H.
Abstract
OBJECTIVE: To determine the prevalence of in vitro resistance to metronidazole
among unselected isolates of Trichomonas vaginalis and correlate in vitro
findings with response to metronidazole therapy. STUDY DESIGN: Vaginal fluid
from women attending a gynecology clinic at an urban hospital was cultured,
isolates were tested for in vitro resistance to metronidazole, and these
results were correlated with therapeutic outcome. RESULTS: Among 911 women,
T vaginalis was detected by culture in 82 (9.0%). Of the 82 isolates, 2 (2.4%;
95% CI, 0.3-8.5%) had low-level in vitro resistance (minimum lethal concentration,
50 micrograms/mL). Women with positive wet mount examinations were treated
with metronidazole, 2 g, once and asked to return in one week. Of the 42
infected women agreeing to return for a repeat examination and culture, 26
(61.9%) did, and all (including one woman with a resistant isolate) were
cured. CONCLUSION: Isolates of T vaginalis resistant to metronidazole occur
widely throughout the United States. Although the in vitro susceptibility
of T vaginalis to metronidazole has been very poorly studied, our study is
consistent with a decade-old prevalence estimate of in vitro resistance (5%),
and suggests that high-level resistance is uncommon. This study confirmed,
in the absence of reinfection, the continuing clinical effectiveness of single-dose
metronidazole for the large majority of trichomoniasis cases.