Molecular and Pathological Diagnosis of Mixed Rhizopus microsporus and Klebsiella pneumoniae Infections in a Russian shepherd Dog

Abstract

Introduction: Laboratory investigations are essential for diagnosing and managing diseases. The present study aimed to detect Rhizopus microsporus (R. microsporus) and Klebsiella pneumoniae (K. pneumoniae) in a Russian shepherd dog using molecular, gross, and histopathology methods to confirm the disease entity in the clinical setting following treatment failure.
Case report: A 4-month-old female Russian shepherd dog weighing 16 kilograms was presented to the Veterinary Teaching Hospital, University of Jos, Nigeria, with signs of haematuria, melena, ascites, and anorexia. The dog exhibited severe icterus in its mucous membranes with ascites. Blood samples were collected for parasitological and haematological examinations. Haematological evaluations revealed mild leukopenia and a mild babesiosis, which was effectively treated before the dog died. Immediate therapy was started using imidocarb, ceftriaxone, furosemide, lactated Ringer’s solution, B-complex, iron dextran, and piroxicam. Despite initial therapy, the dog died five weeks after treatment. In post-mortem examination, samples from the lung, heart, liver, kidney, and spleen were collected and fixed in neutral buffered formalin 10% and prepared for histological evaluation. The non-formalinized samples of liver and lung were processed for both bacteriology and mycology assessments. To determine the presence of mycotoxins, a urine sample was obtained. Aflatoxin B1 was also detected in the urine at a concentration of 10,000 ng/mL. Generalized icterus, pulmonary congestion, cardiomegaly, splenomegaly, multifocal nodular lesions on the liver, severe intestinal haemorrhages, and ascites were the gross lesions observed. Rhizopus microsporus and K. pneumoniae were detected in microbial cultures of liver and lung samples. The present findings were further supported by PCR and gene sequencing. These strains were genetically related, clustering with Asian strains on the phylogenetic trees.
Conclusion: The present study illustrated challenges in the clinical diagnosis of uncommon mixed microbial infections in veterinary practice, where laboratory diagnosis, after post-mortem examination, was essential in the diagnosis of aflatoxicosis along with systemic R. microsporus and K. pneumoniae infections, which caused nodular hepatopathy, toxic nephropathy, myocardial necrosis, and interstitial pneumonia.