Ignavigranum ruoffiae, a rare pathogen that caused a skin abscess.

Introduction: Ignavigranum ruoffiae is an extremely rare cause of human infections.

Case presentation: An 83-year-old male with a painless, ten-day-old, erythematous skin abscess on his left flank, which had showed a purulent discharge for 48 h, was admitted to the Emergency service. He was treated with cephalexin, disinfection with Codex water and spray of rifampicin. Five days later, surgical drainage of the abscess was proposed due to the torpid evolution of the patient. Samples were taken for culture, and antibiotic treatment with trimethoprim-sulfamethoxazole was established. The patient returned after 10 days showing healing of the abscess. Microbiological studies showed a few Gram-positive cocci present as single cells and short chains that grew after 72 h of incubation at 35 °C with CO₂ on 5 % sheep blood agar. Colonies presented a strong sauerkraut odour. Initial biochemical test results were negative for catalase, aesculin and bile-aesculin, and positive for pyrrolidonyl arylamidase, leucine aminopeptidase and growth in 6.5 % NaCl broth, which prompted the preliminary identification of Facklamia species or I. ruoffiae. The positive result for arginine deamination and negative result for hippurate hydrolysis, failure to produce acid from mannitol, sucrose, sorbitol or trehalose, plus the distinctive sauerkraut odour identified the organism as I. ruoffiae. The phenotypic identification was confirmed by 16S rRNA gene sequence analysis. The strain seemed to be susceptible to the antimicrobials tested but had decreased susceptibility to carbapenems.

Conclusion: This case provides more insights into the phenotypic characteristics and antimicrobial resistance profile of I. ruoffiae.