Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, VA Tech, 205 Duck Pond Drive, Blacksburg, VA, 24061, USA.
Virginia Tech Animal Laboratory Services, VA-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, 24061, USA.
BMC Vet Res. 2022 Oct 5;18(1):366. doi: 10.1186/s12917-022-03436-9.
Infectious necrotic hepatitis (INH) is typically a disease of ruminants caused by Clostridium novyi type B. Growth of the causative agent is supported by development of an anaerobic environment within the liver. In dogs, C. novyi is rare and has only been previously reported as a post-mortem diagnosis. In one case, infection was secondary to metastatic pancreatic adenocarcinoma and the other was presumptively diagnosed on histopathology of a hepatic lesion in a dog initially presented for acute collapse.
An 8-year-old spayed, female mixed breed dog was presented for acute onset of hyporexia and vomiting. Serum biochemistry revealed elevated hepatocellular injury and cholestatic liver enzymes. Ultrasound revealed peritoneal fluid accumulation and multiple hepatic masses. Cytologic examination of liver aspirates and peritoneal fluid revealed frequent 4 × 1 μm bacilli with a terminal endospore. Anaerobic bacterial growth isolated from the fluid sample could not be identified using typical laboratory identification techniques. Long-read, whole genome sequencing was performed, and the organism was identified as Clostridium novyi type B. Antimicrobial and hepatic support treatment were initiated. The patient re-presented 27 days later, and the follow up liver aspirate with cytology revealed no appreciable bacteria and anaerobic culture was negative. The patient was presented four months later and a large hepatic mass and peritoneal fluid were again identified on abdominal ultrasound. Cytologic examination of the peritoneal fluid revealed bacilli similar to those identified on initial presentation. The patient was euthanized. The most significant finding on necropsy was necrotizing hepatitis with intralesional endospore-forming bacilli compatible with recurrence of Clostridium novyi type B. There was no identifiable cause of an anaerobic insult to the liver.
This case demonstrates the diagnostic utility of using cytology as part of the initial diagnostic work up for infectious hepatitis. The cytologic findings coupled with whole genome sequencing and anaerobic culture were crucial for the identification and classification of the organism identified on fine needle aspirate. Clostridium novyi type B should be considered when bacilli organisms containing a terminal endospore are identified on liver aspirates collected from canine patients.
感染性坏死性肝炎（INH）通常是一种由 B 型诺维梭菌引起的反刍动物疾病。在肝脏内形成厌氧环境支持病原体的生长。在狗中，诺维梭菌很少见，以前只报道过作为死后诊断。在一个病例中，感染继发于转移性胰腺腺癌，另一个病例最初因急性崩溃就诊时，肝病变的组织病理学检查推测为感染。
一只 8 岁已绝育的雌性混种犬因急性食欲不振和呕吐而就诊。血清生化检查显示肝损伤和胆汁淤积性肝酶升高。超声检查显示腹腔积液和多个肝肿块。肝穿刺和腹腔液的细胞学检查显示经常有 4×1μm 的杆菌，末端有内孢子。从液体样本中分离的厌氧细菌不能使用典型的实验室鉴定技术来鉴定。进行了长读、全基因组测序，确定该生物体为 B 型诺维梭菌。开始进行抗菌和肝脏支持治疗。患者 27 天后再次就诊，后续的肝穿刺细胞学检查未见明显细菌，厌氧培养阴性。四个月后，患者再次就诊，腹部超声再次发现大的肝肿块和腹腔积液。腹腔液的细胞学检查显示与初次就诊时相同的杆菌。患者被安乐死。尸检时最显著的发现是坏死性肝炎，伴有腔内形成孢子的梭菌，符合 B 型诺维梭菌的复发。肝脏没有明确的厌氧损伤原因。
本病例证明了细胞学作为感染性肝炎初始诊断检查的一部分的诊断效用。细胞学发现加上全基因组测序和厌氧培养对于从犬患者采集的肝穿刺中鉴定和分类所识别的生物体至关重要。当从狗的肝抽吸物中发现含有末端孢子的杆菌时，应考虑诺维梭菌 B 型。
