Case Report of Actinobaculum ureolyticum Cystitis in a Cat with Recurrent Urinary Obstruction

This case report focuses on the diagnosis and treatment process of Actinobaculum ureolyticum cystitis in a domestic cat with recurrent urinary obstruction. Key points include:

• The bacterium is a Gram-positive, highly urease-active, multidrug-resistant pathogen;
• Such rare bacteria should be considered in cats with recurrent refractory urinary tract infections (UTIs);
• Urine culture and drug susceptibility testing are critical for formulating targeted treatment plans;
• Comprehensive management (antibacterial therapy + supportive measures) can effectively cure the condition and prevent recurrence. This article emphasizes the importance of identifying rare multidrug-resistant bacteria and implementing evidence-based treatment in veterinary practice.

Clinical Challenges of Urinary Tract Infections in Small Animals

Urinary system diseases are common health issues in small animals. Feline Lower Urinary Tract Disease (FLUTD) accounts for a high proportion, while urinary tract infections (UTIs) are rare but complex to diagnose and treat. Traditional UTIs are mostly caused by common bacteria such as Escherichia coli, but rare opportunistic pathogens like Actinobaculum ureolyticum have gradually gained attention.

Characteristics of Actinobaculum ureolyticum

• Etiology: Gram-positive, non-spore-forming, facultative anaerobic, with urease activity (decomposes urea to produce ammonia).
• Epidemiology: In humans, it is associated with alkaline encrusted cystitis (in immunocompromised individuals or those with indwelling catheters); it is rare in the veterinary field and mostly found in small animals with structural or functional urinary system abnormalities.
• Drug Resistance: Multidrug-resistant to commonly used antibiotics such as penicillins, cephalosporins, and aminoglycosides; empirical treatment is often ineffective.

History and Clinical Manifestations

An adult domestic shorthair cat with recurrent dysuria, frequent urination, and hematuria. It had previously received catheterization and antibiotic treatment but relapsed. Clinical symptoms: abnormal urination posture, hematuria, sensitivity to bladder distension, and lethargy.

Diagnostic Steps

1. Imaging: Abdominal ultrasound revealed thickened bladder wall and hyperechoic sediment (no stones or structural abnormalities);
2. Urine Analysis: Alkaline urine, large number of white blood cells/bacteria, struvite crystals, and positive urine protein;
3. Culture and Identification: Pure culture of Actinobaculum ureolyticum from urine (confirmed by biochemistry and mass spectrometry);
4. Drug Susceptibility Testing: Sensitive to vancomycin, linezolid, etc., and resistant to multiple commonly used antibiotics.

Treatment Plan

• Targeted Antibacterial Therapy: Select sensitive drugs based on susceptibility test results (e.g., vancomycin, linezolid);
• Obstruction Management: Catheterization + bladder irrigation;
• Supportive Therapy: Fluid therapy (maintain hydration), analgesia, prescription diet (regulate urine pH and minerals);
• Complication Monitoring: Monitor renal function and prevent pyelonephritis.

Treatment Outcomes

Symptoms gradually relieved, follow-up urine culture was negative, urine analysis indicators returned to normal, and no recurrence was observed during follow-up.

Clinical Significance

1. Recognition of Rare Bacteria: Actinobaculum ureolyticum should be considered in recurrent/refractory UTIs (e.g., recurrent obstruction, alkaline urine, treatment failure);
2. Diagnostic Value: Urine culture + bacterial identification are prerequisites for precise diagnosis and treatment;
3. Guidance from Drug Susceptibility Testing: Under multidrug resistance, drug susceptibility testing is key to rational antibiotic use and improving success rates;
4. Comprehensive Management: Antibacterial therapy, obstruction relief, and dietary adjustments need to be combined.

Differential Diagnosis

• Escherichia coli: Common UTI bacterium, acidic urine, sensitive to multiple antibiotics;
• Staphylococcus: Secondary skin infection, coagulase-positive with specific biochemical characteristics;
• Proteus: Urease activity, alkaline urine/stones, but different colony/biochemical features;
• Candida: Fungal UTI, seen in long-term antibiotic use/immunosuppression, yeast cells observed under microscopy. Differentiation relies on microbiological examinations (Gram staining, culture, biochemistry, molecular methods).

Prevention Strategies

1. Dietary Management: Use prescription diets to maintain slightly acidic urine and reduce struvite crystals;
2. Water Intake: Encourage increased water intake to dilute urine;
3. Regular Monitoring: Urine analysis + culture to detect recurrence early;
4. Environmental Management: Reduce stress (a trigger for FLUTD).

Research Limitations and Future Directions

• Limitations: Small sample size (single case), insufficient research on pathogenic mechanisms and host interactions, long-term prognosis requires follow-up;
• Future Directions: Multicenter retrospective studies (epidemiology), molecular resistance gene analysis, exploration of new treatments, and development of rapid diagnostic methods.

This case provides a diagnostic and treatment reference for Actinobaculum ureolyticum cystitis in veterinary practice. Core implications: When facing complex and recurrent urinary tract infections, vigilance for rare pathogens is needed; emphasis should be placed on etiological diagnosis and drug susceptibility testing; evidence-based treatment and comprehensive management should be adhered to. With the advancement of diagnostic technology, reports of such rare cases will increase, enriching the clinical knowledge base and improving diagnostic and treatment capabilities. Clinical veterinarians should maintain an open mind, make good use of modern tools, use antibiotics rationally, and follow evidence-based principles to better serve sick animals.