Fatal Toxemic Mastitis and Metritis in a Bitch Caused by a Coinfection of Multidrug-Resistant (MDR) Klebsiella pneumoniae and Staphylococcus aureus

Resumo

Background: Postpartum metritis and mastitis in bitches are life-threatening conditions, particularly when caused by multidrug-resistant (MDR) pathogens. The rising incidence of antimicrobial resistance in veterinary medicine necessitates urgent diagnostic and therapeutic interventions. This report describes a fatal case of toxemic metritis and mastitis due to MDR Klebsiella pneumoniae and Staphylococcus aureus coinfection, highlighting challenges in managing severe postpartum infections with owner compliance limitations.

Case: A 15-month-old bitch mixed-breed, weighing 11.9 kg, was referred to the Veterinary Hospital of Universidade Estadual de Maringá (HV-UEM) with severe postpartum complications. The patient had delivered 8 puppies (6 stillborn, 2 died within 24 h) and exhibited anorexia, intermittent vomiting, fetid vaginal discharge, and locomotor difficulty for 3 days. Physical examination revealed cachexia, 8% dehydration, pale mucous membranes, and painful abdominal palpation. Mammary glands were hyperplastic, with local hyperthermia and necrotic ulcerations. Laboratory findings included severe leukopenia (1,312 cells/μL) with toxic neutrophils, anemia (Hct 20%), thrombocytopenia, metabolic acidosis (pH 7.236), hyperlactatemia (1.26 mmol/L), and hypoglycemia (46 mg/dL). Ultrasonography identified uterine enlargement (right/left horns: 1.05 cm/1.10 cm) with thickened, irregular endometrial echogenicity (acute endometritis/pyometra). Follow-up scans revealed heterogeneous intraluminal uterine content, free abdominal fluid (peritonitis), hepatomegaly, gallbladder sludge, a "reticulated" splenic pattern, and renal medullary sign. Microbiological culture of mammary and vaginal exudates confirmed MDR Klebsiella pneumoniae and Staphylococcus aureus (resistant to β-lactams, fluoroquinolones, and tetracyclines; sensitive only to amikacin and marbofloxacin). Treatment included IV fluids, empirical antibiotics (amoxicillin/clavulanate), surgical debridement, and ectoparasitic treatment. The owner declined ovariohysterectomy and blood transfusion. The patient deteriorated with progressive anemia (Hct 12%), thrombocytopenia, and multiorgan dysfunction, succumbing to sepsis 15 days post-admission.

Discussion: This case exemplifies the devastating consequences of MDR postpartum infections in bitches and highlights several critical aspects of veterinary care. The rapid progression from localized metritis and mastitis to systemic sepsis underscores the importance of early, aggressive intervention, including prompt bacterial culture and susceptibility testing to guide appropriate antimicrobial therapy. The ultrasonographic findings proved invaluable for assessing disease severity and monitoring progression, particularly the characteristic uterine, hepatic, and splenic changes indicative of systemic involvement. The therapeutic challenges encountered in this case reflect broader issues in veterinary practice, including the growing threat of antimicrobial resistance and the ethical dilemmas posed by owner treatment refusals. The report emphasizes the need for: standardized protocols for managing MDR infections in small animals, enhanced client education regarding postpartum risks and antimicrobial stewardship, and continued research into alternative treatment strategies for resistant pathogens. Furthermore, the zoonotic potential of MDR pathogens like K. pneumoniae and S. aureus necessitates increased awareness of cross-species transmission risks between pets and their owners. This case serves as both a clinical warning and a call to action for the veterinary community to address these emerging challenges through improved education, diagnostics, and therapeutic approaches.

Keywords: Klebsiella pneumoniae, Staphylococcus aureus. MDR, mastitis, metritis, sepsis, toxemia.