Co-infection of Mycobacterium tuberculosis complex and carbapenem-resistant hypervirulent Klebsiella pneumoniae in captive Asiatic black bears: a case report

Captive Asiatic black bears (Ursus thibetanus) may face increased health risks under conditions of stress or close human contact, including vulnerability to infectious diseases. Bacterial pathogens such as Mycobacterium tuberculosis complex and Klebsiella pneumoniae pose health risks in captive settings. However, co-infections involving these pathogens have not been previously reported in captive Asiatic black bears. Two male Asiatic black bears (Ursus thibetanus), aged 2 and 3 years, developed persistent diarrhea, which improved temporarily after penicillin and cephalosporin treatment but relapsed shortly after. Despite ongoing therapy, both showed progressive weight loss, lethargy, and depression. Five days before death, acute respiratory signs, including fever, tachypnea, and coughing, appeared, followed by rapid decline. Necropsy revealed multisystemic lesions. Histopathological examination, Ziehl–Neelsen and Gram staining revealed acid-fast bacilli and Gram-negative bacilli intralesionally, PCR amplification and sequencing of DNA extracted from lung tissue identified carbapenem-resistant hypervirulent Klebsiella pneumoniae strains carrying multiple virulence and resistance genes, as well as a Mycobacterium spp. agent of the M. tuberculosis complex. This case underscores the risks of fatal co-infections between an agent of the Mycobacterium tuberculosis complex and carbapenem-resistant hypervirulent Klebsiella pneumoniae in captive wildlife. Integrated diagnostics, timely detection, and prudent antibiotic stewardship are essential, but the absence of diagnostic standards could delay recognition. Establishing systematic criteria is urgently needed to improve treatment and long-term health management.