Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, New South Wales, 2006, Australia.
Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, New South Wales, 2006, Australia.
Vet Parasitol. 2021 Dec;300:109609. doi: 10.1016/j.vetpar.2021.109609. Epub 2021 Oct 26.
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.
胎儿三毛滴虫可引起猫的慢性大肠腹泻，不仅因其慢性病程，还因其难以治疗，可用的注册药物或有效药物很少，因此常将罗硝唑（ronidazole）超适应证使用。胎儿三毛滴虫对罗硝唑的耐药程度尚不清楚。为了证明猫胎儿三毛滴虫对罗硝唑的体外耐药性及其感染的自行缓解，我们从 2017 年同一家庭的两只猫中分离出新型猫胎儿三毛滴虫“猫”基因型菌株，并在三年内对这些猫进行了监测。使用厌氧和需氧培养测定法，对来自这些猫的胎儿三毛滴虫的体外抗甲硝唑和抗罗硝唑性进行了检测。在有氧条件下孵育 48 小时后，新型菌株的最小致死浓度分别为甲硝唑 50-100 μg/ml 和罗硝唑 6.25-12.50 μg/ml。对于敏感的胎儿三毛滴虫菌株，甲硝唑的最小致死浓度范围为 1.56-12.50 μg/ml，罗硝唑的最小致死浓度范围为 0.39-3.13 μg/ml。通过重复诊断 qPCR 和培养来评估感染的自行缓解情况。虽然在 2018 年呈阳性，但在 2020 年和 2021 年，猫样本不再呈 qPCR 阳性结果，表明在此期间自行缓解。本研究首次证明了澳大利亚猫对罗硝唑的耐药性，并且无需抗菌干预即可自行缓解感染。本研究为临床医生提供了减少使用超适应证罗硝唑的证据，并为单户家庭的猫提供了缓解时间框架的建议。
