Mycoplasma hominis infection of Trichomonas vaginalis is not associated with metronidazole-resistant trichomoniasis in clinical isolates from the United States

Abstract

Trichomonas vaginalis is a protozoan parasite that is the cause of the most common non-viral sexually transmitted disease, trichomoniasis. Metronidazole and tinidazole are the only drugs approved for treatment of T. vaginalis infections in the USA. However, drug resistance exists and some patients are allergic to these medications. Furthermore, the exact mechanism of metronidazole resistance remains undefined and current testing methods require several weeks before results are available. Identification of the mechanism of drug resistance may lead to the development of molecular tools to detect drug resistance, and quicker results for clinical treatment. In a recent study, Chinese T. vaginalis isolates that were polymerase chain reaction (PCR) positive for Mycoplasma hominis DNA demonstrated greater in vitro resistance to metronidazole than isolates with no evidence of M. hominis infection. To evaluate this finding in isolates from a distinct epidemiologic setting, we tested 55 T. vaginalis isolates collected from patients in the USA through the Centers for Disease Control and Prevention metronidazole susceptibility testing service. One half of the isolates demonstrated resistance to metronidazole by an in vitro sensitivity assay. Of the metronidazole-resistant T. vaginalis isolates, 18% were PCR positive for M. hominis, as were 22% of the metronidazole-susceptible T. vaginalis isolates (p = 0.746). We also observed no change in metronidazole sensitivity of two infected T. vaginalis isolates after they were cleared of their M. hominis infection by culturing the isolates in antibiotics. Thus, M. hominis infection of USA T. vaginalis isolates did not correlate with in vitro resistance to metronidazole.

High rates of double-stranded RNA viruses and Mycoplasma hominis in Trichomonas vaginalis clinical isolates in South Brazil

“…After incubation, the plates were examined using an inverted microscope to determine the MIC (minimum inhibitory concentration), the lowest drug concentration at which no motile trichomonads were observed at the end of the incubation period. Low-level resistance was defined as an anaerobic MIC 30-60 µM, moderate-level resistance as 60-120 µM, and high-level resistance as 235 µM or greater as previously described by Butler et al (2010). The end point was confirmed by the failure of non-motile parasites to grow after re-inoculation into drug-free medium (Rabiee et al, 2012).…”

“…A strong relationship between M. hominis coinfection and metronidazole resistance in vitro was proposed (Xiao et al, 2006). In contrast, a lack of correlation in this association was described (Butler et al, 2010).…”

Anti-Trichomonas vaginalisproperties of the oil ofAmomum tsao-koand its major component, geraniol

“…Although the cure rate was high, these drugs demonstrated treatment failure which was normally related to non-compliance because of side effects such as headache, dry mouth, metallic taste, glossitis, and urticaria caused by lengthy treatment or high doses (Garduño-Espinosa et al, 1992;Kapoor et al, 1999;Oxberry et al, 1994), or reinfection (Rocha et al, 2012). Moreover, an increasing number of metronidazole-resistant T. vaginalis isolates have been reported since metronidazole was introduced for the treatment of trichomoniasis in 1959 (Blaha et al, 2006;Butler et al, 2010;Durel et al, 1967;Narcisi & Secor, 1996;Schmid et al, 2001; Upcroft et al, 2006). In addition, the metronidazole-resistant isolates were cross-resistant to other members of the 5-nitrothiazole compounds including ornidazole, tinidazole, nitazoxanide, and furazolidone (Wright et al, 2010).…”

Trichomonas vaginalis Metronidazole Resistance Is Associated with Single Nucleotide Polymorphisms in the Nitroreductase Genes ntr4 Tv and ntr6 Tv

“…Additionally, metronidazole resistance does occur in isolates with intact ntr4 Tv and ntr6 Tv genes, indicating that multiple resistance mechanisms may be responsible for resistance. For example, one study linked resistance to infection of T. vaginalis by Mycoplasma (16); however, the mechanism by which infection would impart resistance is unclear, and this association was not found in a subsequent study (17). Another study found that infection by a double-stranded RNA virus was associated with a lower mean metronidazole MLC value (2); however, the virus is also strongly associated with population 1, being present in 73% of isolates in this population compared to only 2.5% of isolates in population 2 (18).…”