Helicobacter cinaedi kidney cyst infection and bacteremia in a patient with autosomal dominant polycystic kidney disease

A 48-year-old man with autosomal dominant polycystic kidney disease (ADPKD) was admitted to our hospital with a 5-day history of lower right back pain, high-grade fever, and arthralgia. He was diagnosed with right kidney cyst infection and bacteremia due to Helicobacter cinaedi (H. cinaedi) based on these symptoms, highly elevated CRP (32.25 mg/dL), abdominal magnetic resonance imaging findings, and the identification of H. cinaedi from blood cultures using PCR and sequence analysis of the 16S ribosomal DNA gene. Intravenous cefotaxime 0.5 g twice daily followed by meropenem 0.5 g twice daily and ciprofloxacin 200 mg twice daily were partially effective; oral doxycycline added at 200 mg/day finally eradicated the infection. Total duration of antimicrobial therapy was 9 weeks. H. cinaedi infections typically present as bacteremia with or without cellulitis in immunocompromised patients such as those with AIDS or malignant disease. To our knowledge, this is the first report describing an ADPKD patient with H. cinaedi cyst infection. Although H. cinaedi infections are increasingly recognized, even in immunocompetent subjects, numerous cases may still be overlooked given that this bacterium is slow-growing, and is difficult to culture, be Gram-stained, and identify on phenotypic tests. Consideration of this bacterium as a possible pathogen and sufficient duration of incubation with molecular testing are necessary in treating ADPKD patients with cyst infection.