Determination of the In Vitro Susceptibility of Feline Tritrichomonas foetus to 5 Antimicrobial Agents

Gut microbiota and Tritrichomonas foetus infection: A study of prevalence and risk factors based on pet cats

Tritrichomonas foetus (T. foetus) is a protozoal pathogen that infects cats and constitutes a significant cause of chronic colitis and diarrhea. Perturbations in the gut microbiota (GM) are affected by Trichomonas infection. Furthermore, dysregulation of the host GM enhances Trichomonas pathogenicity. However, it remains unclear whether the occurrence of diarrhea is associated with a dysregulation in GM following T. foetus infection in cats. Hence, the primary objective of this investigation was to explore the correlation between T. foetus infection and dysregulation in GM by analyzing fecal samples obtained from pet cats in Henan Province, central China. We randomly collected 898 fecal samples from pet cats living in 11 prefectural cities within Henan Province, and T. foetus was screened with polymerase chain reaction (PCR) amplification based on the 18 S rRNA gene. Subsequently, six T. foetus-positive and six T. foetus-negative samples underwent analysis through 16 S rRNA gene sequencing to evaluate the gut microbiota's composition. The overall prevalence of T. foetus infection among the collected samples was found to be 6.01% (54/898). Notably, a higher prevalence of infection was observed in young, undewormed, unimmunized, and diarrheic pet cats. T. foetus infection was found to significantly alter the composition of the pet cat fecal microbiota, leading to dysfunctions. Moreover, it resulted in a substantial increase in the abundance of Bacteroidetes, Proteobacteria, and Phascolarctobacterium spp., while decreasing the ratio of Firmicutes to Bacteroidetes (F/B) and the abundance of Actinobacteria, Clostridiaceae_Clostridium spp., Phascolarctobacterium spp., SMB53 spp., and Blautia spp. We constructed ROC curves to assess the diagnostic value of specific bacterial taxa in discriminating T. foetus infection. The analysis revealed that Proteobacteria and Clostridiaceae_Clostridium spp. were the most reliable single predictors for T. foetus infection. This finding suggests that alterations in the GM may be strongly associated with T. foetus infections.

Assessment of in vitro efficacy for common surface disinfectants and antiseptics against Tritrichomonas foetus trophozoites

The protozoan Tritrichomonas foetus causes early embryonic death in cattle, there are no legal options for treating this parasite in the United States, and there are few developed protocols for cleaning veterinary and obstetrical equipment that may have been contaminated with trophozoites. In this study, we evaluated bleach, ethanol, acetic acid, chlorhexidine gluconate, and hydrogen peroxide solutions for the ability to kill trophozoites in vitro. Our findings suggested that ethanol and bleach could adequately disinfect tools and equipment. Acetic acid, chlorhexidine, and hydrogen peroxide had applications as surface disinfectants in addition to potential as local topical treatments due to their past uses in veterinary theriogenology. Chlorhexidine gluconate demonstrated trophocidal effects by damaging parasite cell membranes and had the lowest effective concentration 50 (EC50) of any compound tested and was in the micromolar range. These findings, in conjunction with accepted clinical uses of chlorhexidine gluconate suggest that this is a convenient agent for disinfecting equipment. In addition, topical use of chlorhexidine is relatively common, setting the stage for further investigation of this compound as a topical therapeutic option for bovine trichomonosis.

Evaluation of the susceptibility of Tritrichomonas foetus to extracts of Lantana camara (Verbenaceae) by flow cytometry

Bovine Trichomonosis (BT), a sexually transmitted disease endemic in countries with extensive cattle farming and natural service, is one of the most common causes of reproductive failure. 5-nitroimidazoles and their derivatives are used for its treatment, mainly metronidazole. The emergence of drug resistance mechanisms and treatment failures raise the need to investigate the effectiveness of new active compounds that contribute to parasite control. In this regard, extracts of Lantana camara (Verbenacea) have shown high biocidal potential against isolates of Trypanosoma cruzi and Leishmania braziliensis in vitro assays, although their effect on Tritrichomonas foetus has not been demonstrated yet. The available information on in vitro susceptibility of trichomonicidal drugs comes from the use of a diversity of methodologies and criteria, especially the observation of parasite motility under the optical microscope to assess their viability. Recently, in our laboratory, the use of flow cytometry has been described for the first time as a rapid and efficient method to evaluate the viability of T. foetus against metronidazole. The present study aimed to evaluate the cytostatic effect of L. camara extracts against T. foetus isolates by flow cytometry. Under aerobic conditions, IC50 values of 22.60 µg/mL were obtained on average. Under anaerobic conditions, the IC50 oscilated around 29.04 µg/mL. The results obtained allowed describing the susceptibility exhibited by these protozoa, being a valuable information for the development of potential BT treatments.

Evidence of self-resolution of feline trichomonosis in a pair of single household cats due to ronidazole-resistant Tritrichomonas foetus

Tritrichomonas foetus causes chronic large-bowel diarrhoea in cats, complicated not only by its chronicity but for its difficulty to treat, with few registered or effective products available, subsequently resulting in ronidazole frequently used off-label. The extent of T. foetus resistance to ronidazole is unknown. To demonstrate in vitro resistance of feline T. foetus to ronidazole and the self-resolution of the infection, we isolated novel T. foetus "feline" genotype strains from two cats in 2017 from the same household and monitored these cats over a three-year period. Axenic cultures of T. foetus from the cats were tested for in vitro resistance to metronidazole and ronidazole using anaerobic and aerobic culture assays. The minimum lethal concentration for the novel strains after incubation in aerobic conditions for 48 h were 50-100 μg/ml and 6.25-12.50 μg/ml for metronidazole and ronidazole, respectively. For susceptible T. foetus strains, the minimum lethal concentrations ranged from 1.56-12.50 μg/ml for metronidazole, and 0.39-3.13 μg/ml for ronidazole. The self-resolution of the infection was assessed using repeat diagnostic qPCR and culture. Whilst positive in 2018, the cat samples are no longer returning positive qPCR results in 2020 and 2021, indicating self-resolution over this period. This study demonstrated resistance to ronidazole for the first time in Australian cats and infection self-resolution without antimicrobial intervention is demonstrated. This study provides clinicians with the evidence to reduce the use of off-label ronidazole, and advice on the resolution timeframe for cats in single households.

Dysbiosis of fecal microbiota in cats with naturally occurring and experimentally induced Tritrichomonas foetus infection

The protozoal pathogen Tritrichomonas foetus infects the colon of domestic cats and is a major cause of chronic colitis and diarrhea. Treatment failure is common, but antibiotics may improve clinical signs in a subset of cats, leading researchers to question involvement of the colonic microbiota in disease pathogenesis. Studies performed in women with venereal Trichomonas vaginalis infections have revealed that dysbiosis of host microbiota contributes to pathogenicity with similar findings also found in mice with intestinal Tritrichomonas musculis The aim of this study was to characterize differences in the fecal microbiota of cats with and without naturally occurring T. foetus infection and in a group of kittens prior to and after experimentally induced infection. Archived fecal DNA from cats undergoing testing for T. foetus infection (n = 89) and experimentally infected kittens (n = 4; at pre-, 2 weeks, and 9 weeks post-infection) were analyzed by sequencing of 16S rRNA genes. Amongst the naturally infected population, the genera Megamonas and Helicobacter were significantly increased in prevalence and abundance in cats testing positive for T. foetus infection. In the group of four experimentally infected kittens, fecal samples post-infection had significantly lower abundance of genus Dialister and Megamonas and greater abundance of the class Betaproteobacteria and family Succinivibrionaceae. We hypothesize that T. foetus promotes dysbiosis by competition for fermentable substrates used by these bacteria and that metabolic byproducts may contribute to the pathogenesis of colonic inflammation and diarrhea. Future studies are warranted for the measurement of fecal concentrations of microbial and protozoal metabolites in cats with T. foetus infection for the identification of potential therapeutic targets.

TriTOX: A novel Trichomonas vaginalis assay platform for high-throughput screening of compound libraries

Trichomonas vaginalis is a neglected urogenital parasitic protist that causes 170 million cases of trichomoniasis annually, making it the most prevalent non-viral, sexually transmitted disease. Trichomoniasis treatment relies on nitroheterocyclics, such as metronidazole. However, with increasing drug-resistance, there is an urgent need for novel anti-trichomonals. Little progress has been made to translate anti-trichomonal research into commercialised therapeutics, and the absence of a standardised compound-screening platform is the immediate stumbling block for drug-discovery. Herein, we describe a simple, cost-effective growth assay for T. vaginalis and the related Tritrichomonas foetus. Tracking changes in pH were a valid indicator of trichomonad growth (T. vaginalis and T. foetus), allowing development of a miniaturised, chromogenic growth assay based on the phenol red indicator in 96- and 384-well microtiter plate formats. The outputs of this assay can be quantitatively and qualitatively assessed, with consistent dynamic ranges based on Z' values of 0.741 and 0.870 across medium- and high-throughput formats, respectively. We applied this high-throughput format within the largest pure-compound microbial metabolite screen (812 compounds) for T. vaginalis and identified 43 hit compounds. We compared these identified compounds to mammalian cell lines, and highlighted extensive overlaps between anti-trichomonal and anti-tumour activity. Lastly, observing nanomolar inhibition of T. vaginalis by fumagillin, and noting this compound has reported activity in other protists, we performed in silico analyses of the interaction of fumagillin with its molecular target methionine aminopeptidase 2 for T. vaginalis, Giardia lamblia and Entamoeba histolytica, highlighting potential for fumagillin as a broad-spectrum anti-protistal against microaerophilic protists. Together, this new platform will accelerate drug-discovery efforts, underpin drug-resistance screening in trichomonads, and contributing to a growing body of evidence highlighting the potential of microbial natural products as novel anti-protistals.

Repurposing the open access malaria box reveals compounds with activity against Tritrichomonas foetus trophozoites

The protozoan parasite Tritrichomonas foetus causes early embryonic death in cattle which results in severe economic loss. In the United States, there are no drugs are approved for treatment of this pathogen. In this study, we evaluated in vitro anti-protozoal effects of compounds from an open access chemical library against T. foetus trophozoites. An initial high-throughput screen identified 16 compounds of interest. Further investigation revealed 12 compounds that inhibited parasite growth and 4 compounds with lethal effects. For lethal compounds, dose-response curves were constructed and the LD₅₀ was calculated for laboratory and field strains of T. foetus. Our experiments revealed chemical scaffolds that were parasiticidal in the micromolar range, and these scaffolds provide a starting point for drug discovery efforts. Further investigation is still needed to investigate suitability of these scaffolds and related compounds in food animals. Importantly, open access chemical libraries can be useful for identifying compounds with activity against protozoan pathogens of veterinary importance.

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No legal treatments are available for bovine trichomoniasis in the United States.

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The open access malaria box was screened for compounds with activity against T. foetus trophozoites.

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Identification of several scaffolds meriting further investigation for suitability in food animals.

Efficacy and safety of ronidazole treatment against Tritrichomonas foetus in a cat colony with multiple disorders

In a group of pedigree cats (n = 17) in poor health condition housed in an animal shelter in Vienna, Austria, with a history of persistent diarrhea, Tritrichomonas foetus infection was detected by PCR. Despite pre-existing clinical conditions all cats were treated with ronidazole (30 mg/kg PO q24h for 14 days) under close observation. After treatment, 11 of 14 initially positive animals remained negative for T. foetus during the observation period (six to eight weeks post treatment) and no diarrhea was observed. During treatment, nine cats showed mild to moderate neurological disorders (incoordination, mild tremor) at least once; six of these had already shown similar signs before treatment. Ronidazole treatment of multimorbid animals is acceptable if the benefit (here: clinical resolution and release from quarantine for adoption) is high. It is hypothesized that a high degree of inbreeding is a significant risk factor for the development of tritrichomonosis in cats.

In Vitro Susceptibility to Metronidazole of Tritrichomonas foetus Bovine Isolates from Argentina

BACKGROUND

Tritrichomonas foetus is the etiologic agent of the sexually transmitted disease Bovine Trichomonosis (BT). In Argentina, BT is endemic and represents a relevant health problem that causes reproductive inefficiency in cattle and large economic losses. Metronidazole is the drug of choice in the treatment of BT. Treatment has been associated with a temporary resolution of the clinical signs but is not able to control the disease. In recent years, the apparition of in vivo and in vitro aerobic and anaerobic resistance leading to ineffective treatments has been reported.

AIMS

Thus, the aim of the present study was to explore the susceptibility of six different isolates of T. foetus under aerobic (AC) and anaerobic (ANC) conditions.

RESULTS AND DISCUSSION

Six isolates of T. foetus were obtained from samples of preputial smegma of bovine origin. Values of minimum lethal concentration and minimum inhibitory concentration were higher than those observed in other works and represent current data in Argentina and provide information to establish new treatment protocols.

Flow cytometry evaluation of in vitro susceptibility of bovine isolates of Tritrichomonas foetus to metronidazole

Bovine Trichomonosis, an endemic sexually transmitted disease in countries with extensive livestock and natural service, represents one of the most common causes of reproductive failure. 5-nitroimidazoles and their derivatives are used for its treatment, mainly metronidazole (Mz). The emergence of resistance mechanisms adopted by the parasites against the drug and failure of the treatments suggest the need to investigate susceptibility and obtain current values. The available information of in vitro susceptibility of these drugs comes from the use of a diversity of methodologies and criteria, especially observation of the mobility of the parasite under the optical microscope to evaluate its viability. These techniques are arduous and time consuming and lead to a subjective assessment dependent on the operator, the methodology used, and the morphology adopted by the protozoan. In this sense, flow cytometry has proven to be a fast and efficient method to evaluate viability in other protozoa. The aim of this study was to evaluate the in vitro susceptibility of six bovine isolates of Tritrichomonas foetus to Mz in aerobic (AC) and anaerobic (ANC) conditions by means of the calculation of the 50% inhibitory concentration (IC₅₀), by flow cytometry, and also to analyze minimum lethal concentration (MLC) by means of recovery tests post-treatment in vitro. IC₅₀ values ranged from 1.06 to 1.25 μM in ANC and from 1.44 to 3.03 μM in AC, these being the only ones reported at 48 h for these protozoa. With respect to MLC at 48 h, the results were from 3.67 to 7.35 μM in ANC, and from 7.35 to 14.7 μM for AC, where two isolates (Tf0 and Tf2) for AC and one (Tf2) for ANC showed higher values than those described in the literature. Flow cytometry has proven to be an effective, rapid and objective methodology and very useful in susceptibility tests. The data obtained through these tests allow us to describe the susceptibility exhibited by these protozoa, this being valuable information when establishing dosages in Mz treatments.

What is known about Tritrichomonas foetus infection in cats?

Tritrichomonas foetus is a parasite that has been definitively identified as an agent of trichomonosis, a disease characterized by chronic diarrhea. T. foetus colonizes portions of the feline large intestine, and manifests as chronic and recurrent diarrhea with mucus and fresh blood, which is often unresponsive to common drugs. Diagnosis of a trichomonad infection is made by either the demonstration of the trophozoite on a direct fecal smear, fecal culture and subsequent microscopic examination of the parasite, or extraction of DNA in feces and amplification by the use of molecular tools. T. foetus is commonly misidentified as other flagellate protozoa such as Giardia duodenalis and Pentatrichomonas hominis. Without proper treatment, the diarrhea may resolve spontaneously in months to years, but cats can remain carriers of the parasite. This paper intends to serve as a source of information for investigators and veterinarians, reviewing the most important aspects of feline trichomonosis, such as trichomonad history, biology, clinical manifestations, pathogenesis, world distribution, risk factors, diagnosis, and treatment.

The conundrum of feline Trichomonosis

Practical relevance: Trichomonosis of the large intestine of the cat was described as a cause of chronic diarrhea over 20 years ago. The trichomonad was identified as Tritrichomonas foetus, with a genotype that is distinct from venereal T foetus of cattle. Clinical challenges: Despite multiple means for diagnosis of the infection, including light microscopy, protozoal culture and PCR amplification using species-specific primers, tests with even greater sensitivity are needed. Feline trichomonosis is resistant to all commonly used antiprotozoal drugs. Ronidazole is currently the only drug demonstrated to be effective in eliminating the infection from cats; however, this drug has a narrow safety margin and clinical resistance is increasingly recognized. The more we learn about trichomonosis in cats, the more complicated and controversial the infection has become, ranging from what we should call the organism to whether we should even bother trying to treat it. Global importance: Feline trichomonosis is recognized to occur worldwide and is regarded as one of the most common infectious causes of colitis in the domestic cat. The infection is widespread in catteries and shelters; and, while remission of diarrhea may occur over time, persistence of the infection is common. Evidence base: This review provides a comprehensive examination of what is currently known about feline trichomonosis and pinpoints areas, based on the authors' opinion, where further research is needed.

Efficacy of guar gum-based ronidazole capsules as a treatment for Tritrichomonas foetus infection in cats

Objectives The aims of the study were to determine the in vitro drug release of guar gum-coated capsules of ronidazole, and to evaluate the pharmacokinetics and efficacy of this formulation for the treatment of cats naturally infected with Tritrichomonas foetus. Methods The pharmacokinetics of ronidazole were evaluated in five healthy cats and five cats infected with T foetus. In a second step, the clinical efficacy of these capsules was evaluated by a controlled, randomised, double-blind clinical trial performed in 47 infected cats from French catteries. In this study, cats were randomly allocated to either the ronidazole treatment group (n = 25) or a placebo group (n = 22). Ronidazole (30 mg/kg) q24h for 14 days was administered to the treated cats. After 14 days of treatment, the presence of T foetus was tested by conventional PCR assay. Results In the pharmacokinetic study, a delayed peak plasma concentration was observed in healthy and infected cats, with no significant difference between these two groups (mean geometric mean of 9 h for time to maximum plasma concentration [Tmax], 21.6 µg/ml for time to maximum plasma concentration [Cmax] and 467.4 μg/h/ml for the area under the curve [AUC] in healthy cats; and 9.4 h for Tmax, 17.1 µg/ml for Cmax and 481 μg/h/ml for AUC in infected cats). In the clinical trial, T foetus was detected in 16% of cats from the treated group and 82% of cats from the placebo group at the end of the study ( P <0.001). No clinical signs of adverse drug reactions were observed. Conclusions and relevance Oral administration of guar gum-coated capsules of ronidazole at a dose of 30 mg/kg once daily for 14 days delays the peak plasma concentration and eradicates infection in most cases.

Mechanisms of Tritrichomonas foetus Pathogenicity in Cats with Insights from Venereal Trichomonosis

Almost 20 years has passed since trichomonosis was first recognized as a potential cause of diarrhea in domestic cats. Despite progress in confirming disease causation, developing means for diagnosis, and identifying approaches to treatment of the infection, we still know very little about how this parasite causes diarrhea. With increasing recognition of resistance of trichomonosis to treatment with 5‐nitroimidazole drugs, new treatment strategies based on an understanding of disease pathogenesis are needed. In this review, lessons learned from the pathogenesis of venereal trichomonosis in people and cattle are applied to clinical observations of trichomonosis in cats in effort to generate insight into areas where further research may be beneficial.

Tritrichomonas foetus infection, a cause of chronic diarrhea in the domestic cat

Tritrichomonas foetus is a very intriguing trichomonad protozoan with respect to its varied choice of residence in the different host species. It is an obligate parasite of the reproductive and the gastrointestinal tract of bovine and feline host respectively, leading to trichomonosis. Bovine trichomonosis is a sexually transmitted disease whereas feline trichomonosis is a disease with a purported fecal-oral route of spread. Further, the trichomonad is a commensal in the nasal passages, stomach, cecum and colon of swine host. Advances have been exponential in understanding the trichomonad biology and specifically feline trichomonosis since late 1990s and early 2000s when T. foetus was soundly determined to be a causative agent of chronic diarrhea in the domestic cat. It is a challenging task, even for a skilled investigator not to mention the busy clinical veterinarian, to keep up with the vast volume of information. Here we comprehensively reviewed the trichomonad biology, clinical manifestations, pathogenesis, host immunity, world map of distribution, risk factors, diagnosis and treatment. Risk factors associated with T. foetus-positive status in the domestic cat include young age, purebred, history of diarrhea, co-infections with other enteral pathogens. In addition, molecular similarity of bovine and feline isolates of T. foetus in DNA sequence was concisely discussed. The data presented serve as an information source for veterinarians, and investigators who are interested in biology of T. foetus and feline trichomonosis.

Cysteine protease activity of feline Tritrichomonas foetus promotes adhesion-dependent cytotoxicity to intestinal epithelial cells

Trichomonads are obligate protozoan parasites most renowned as venereal pathogens of the reproductive tract of humans and cattle. Recently, a trichomonad highly similar to bovine venereal Tritrichomonas foetus but having a unique tropism for the intestinal tract was recognized as a significant cause of colitis in domestic cats. Despite a high prevalence, worldwide distribution, and lack of consistently effective drugs for treatment of the infection, the cellular mechanisms of T. foetus pathogenicity in the intestinal tract have not been examined. The aims of this study were to determine the pathogenic effect of feline T. foetus on porcine intestinal epithelial cells, the dependence of T. foetus pathogenicity on adhesion of T. foetus to the intestinal epithelium, and the identity of mediators responsible for these effects. Using an in vitro coculture approach to model feline T. foetus infection of the intestinal epithelium, these studies demonstrate that T. foetus promotes a direct contact-dependent activation of intestinal epithelial cell apoptosis signaling and progressive monolayer destruction. Moreover, these pathological effects were demonstrated to be largely dependent on T. foetus cell-associated cysteine protease activity. Finally, T. foetus cysteine proteases were identified as enabling cytopathic effects by promoting adhesion of T. foetus to the intestinal epithelium. The present studies are the first to examine the cellular mechanisms of pathogenicity of T. foetus toward the intestinal epithelium and support further investigation of the cysteine proteases as virulence factors in vivo and as potential therapeutic targets for ameliorating the pathological effects of intestinal trichomonosis.

Isolation of Tritrichomonas foetus from cats sampled at a cat clinic, cat shows and a humane society in southern Ontario

Tritrichomonas foetus is a protozoan parasite that has been associated with chronic diarrhea in cats. This study aimed to determine (i) the prevalence of T foetus shedding in cats from three different populations in southern Ontario, and (ii) associations between the presence of T foetus and potential cat management, health and demographic risk factors. A cross-sectional study was conducted involving 140 cats from a cat clinic in Guelph, 46 cats from a humane society in Guelph and 55 cats from two cat shows. Risk factor information was assessed through a questionnaire. The InPouch TF (feline) culture method was used to determine the presence of T foetus in all samples. Polymerase chain reaction was conducted on all samples positive by the InPouch TF, as well as 132 negative samples. The assays were interpreted in series and the prevalence of T foetus shedding and 95% confidence intervals (CI) were estimated at 0.7% (95% CI: 0.0-3.9%; n = 140) from the cat clinic, 0% (95% CI: 0.0-7.7%; n = 46) from the humane society and 23.6% (95% CI: 13.2-37.0%; n = 55) from the cat shows. 'Attendance at cat shows' was the only variable significant in both the univariable and multivariable analyses (P <0.05). No significant association was found between the presence of T foetus and diarrhea at the time of sampling or having a history of diarrhea in the past 6 months. The prevalence of T foetus was highly variable among populations of cats in southern Ontario, with shedding being most common in show cats.

Cattle tick-associated bacteria exert anti-biofilm and anti-Tritrichomonas foetus activities

Research on microbiota in cattle tick and the evaluation of its activity against other microorganisms can contribute to identify new molecules potentially useful to control infections caused by bacteria and protozoa. Biofilms pose increasing problems worldwide, mainly due to their resistance to antimicrobial therapies and host immune response. In this study we investigate the ability Rhipicephalus (Boophilus) microplus-associated bacteria may exhibit to produce anti-biofilm and trichomonicidal compounds. Gut, ovary, salivary glands, and Gené organ were collected from engorged R. microplus female. Homogenates of each tissue were inoculated onto 15 distinct culture media. Anti-biofilm and trichomonicidal activities were analyzed by culturing each bacterium isolated in a liquid medium. Results showed that R. microplus cattle tick microflora varies for different tissues. Bacteria belonging to different genera (Aeromonas, Bacillus, Brevibacillus, Castelaniella, Comamonas, Kocuria, and Microbacterium) were identified. Interestingly, all bacterial species found displayed pronounced activity against Staphylococcus epidermidis and Pseudomonas aeruginosa biofilms, and also against the cattle pathogen Tritrichomonas foetus, confirming the hypothesis that cattle tick could be a source of bacteria active against pathogens. This is the first study showing that bacteria isolated from a tick exert anti-biofilm and trichomonicidal activities.

Development of metronidazole-resistant lines of Blastocystis sp

Metronidazole (MTR) is frequently used for the treatment of Blastocystis infections, but with variable effectiveness, and often with treatment failures as a possible result of drug resistance. We have developed two Blastocystis MTR-resistant (MTR(R)) subtype 4 WR1 lines (WR1-M4 and WR1-M5), with variable susceptibility to a panel of anti-protozoal agents including various 5-nitroimidazoles, nitazoxanide and furazolidone. WR1-M4 and WR1-M5 were developed and assessed over an 18-month period and displayed persistent MTR resistance, being more than 2.5-fold less susceptible to MTR than the parent isolate. The MTR(R) lines grew with a similar g time to WR1, but were morphologically less consistent with a mixture of size. All Blastocystis isolates and the MTR(R) lines were most susceptible to the 5-nitroimidazole drug ronidazole. WR1-M5 was apparently cross-resistant to satranidazole and furazolidone, and WR1-M4 was cross-resistant to nitazoxanide. These MTR(R) lines now provide a valuable tool for the continued assessment of the efficacy and mechanism of action of new and established drugs against a range of Blastocystis sp. subtypes, in order to identify a universally effective drug and to facilitate understanding of the mechanisms of drug action and resistance in Blastocystis.

In vitro susceptibility testing of Dientamoeba fragilis

Dientamoeba fragilis is a commonly encountered trichomonad which has been implicated as a cause of gastrointestinal disease in humans. Despite the frequency of reports recording infections with this parasite, little research has been undertaken in terms of antimicrobial susceptibility. The aim of this study was to evaluate the susceptibility of D. fragilis to several commonly used antiparasitic agents: diloxanide furoate, furazolidone, iodoquinol, metronidazole, nitazoxanide, ornidazole, paromomycin, secnidazole, ronidazole, tetracycline, and tinidazole. Antibiotic susceptibility testing was performed on four clinical strains of D. fragilis, designated A, E, M, and V, respectively. Molecular testing followed, and all strains were determined to be genotype 1. The activities of antiprotozoal compounds at concentrations ranging from 2 μg/ml to 500 μg/ml were determined via cell counts of D. fragilis trophozoites grown in dixenic culture. Minimum lethal concentrations (MLCs) were as follows: ornidazole, 8 to 16 μg/ml; ronidazole, 8 to 16 μg/ml; tinidazole, 31 μg/ml; metronidazole, 31 μg/ml; secnidazole, 31 to 63 μg/ml; nitazoxanide, 63 μg/ml; tetracycline, 250 μg/ml; furazolidone, 250 to 500 μg/ml; iodoquinol, 500 μg/ml; paromomycin, 500 μg/ml; and diloxanide furoate, >500 μg/ml. This is the first study to report the profiles of susceptibility to a wide range of commonly used treatments for clinical isolates of D. fragilis. Our study indicated 5-nitroimidazole derivatives to be the most active compounds in vitro against D. fragilis.

Tritrichomonas foetus infection in purebred cats in Germany: Prevalence of clinical signs and the role of co-infection with other enteroparasites

The aim of this study was to determine the prevalence of Tritrichomonas foetus infection and associated clinical signs in purebred cats in Germany, to investigate the role of co-infection, and identify determinants of infection. Faecal specimens accompanied by epidemiological questionnaires were scored and collected from 230 purebred cats. Faeces were examined for trichomonads and other enteroparasites. The prevalence of T foetus was 15.7% among cats and 18.5% among catteries. An abnormal faecal score and history of diarrhoea were observed in 64% and 61% of T foetus-positive cats, respectively, and correlated significantly with infection. Co-infection, observed in 36% of T foetus-infected cats, was not associated with diarrhoea. Norwegian Forest cats were infected significantly more often than other breeds. No association was found with any environmental factors. This study demonstrated a high prevalence of symptomatic T foetus infections in purebred cats in Germany. Co-infection with other enteroparasites did not worsen clinical signs of trichomonosis.

Ronidazole pharmacokinetics after intravenous and oral immediate-release capsule administration in healthy cats

Ronidazole (RDZ) is an effective treatment for feline Tritrichomonas foetus infection, but has produced neurotoxicity in some cats. An understanding of the disposition of RDZ in cats is needed in order to make precise dosing recommendations. Single-dose pharmacokinetics of intravenous (IV) RDZ and immediate-release RDZ capsules were evaluated. A single dose of IV RDZ (mean 9.2mg/kg) and a 95mg immediate-release RDZ capsule (mean 28.2mg/kg) were administered to six healthy cats in a randomized crossover design. Plasma samples were collected for 48 h and assayed for RDZ using high pressure liquid chromatography (HPLC). Systemic absorption of oral RDZ was rapid and complete, with detection in the plasma of all cats by 10 min after dosing and a bioavailability of 99.64 (±16.54)%. The clearance of RDZ following IV administration was 0.82 (±0.07) ml/kg/min. The terminal half-life was 9.80 (±0.35) and 10.50 (±0.82) h after IV and oral administration, respectively, with drug detectable in all cats 48h after both administrations. The high oral bioavailability of RDZ and slow elimination may predispose cats to neurotoxicity with twice-daily administration. Less frequent administration should be considered for further study of effective treatment of T foetus-infected cats.

Tritrichomonas foetus infection in cats with diarrhoea in a rescue colony in Italy

Faecal samples from 74 cats with chronic large bowel diarrhoea that were living in a rescue colony in Italy, were submitted for assessment of Tritrichomonas foetus by direct microscopy of faecal smears ( n=20) and T foetus-specific culture ( n=74), with confirmation by polymerase chain reaction ( n=1). Twenty-four of the cats (32%) were found to be infected with T foetus. The infected cats were predominantly over a year of age (67%) and were all neutered non-pedigree domestic cats.