SUMMARY:We report the first case of cerebral cyst infection by Helicobacter cinaedi, a fastidious spiral-shaped gram-negative rod bacterium. A 70-year-old man visited Tokyo Medical University Hospital with persisting fever since 2 weeks. He underwent surgery and radiotherapy for parapharyngeal space squamous cell carcinoma 10 years ago. The radiotherapy resulted in a cerebral cyst as a side effect, and an Ommaya reservoir was inserted into the cyst. Blood culture and analysis of the brain cyst fluid revealed the presence of spiral-shaped gram-negative rod bacteria, which were identified as H. cinaedi by polymerase chain reaction. Initially, we administered clarithromycin (400 mg per day). After H. cinaedi infection was confirmed, the treatment was changed to meropenem (MEPM 6 g per day). The patient was treated for 43 days in the hospital with intravenous meropenem, and his clinical course was satisfactory. On the 44th day, he was discharged and prescribed oral minocycline (MINO 200 mg per day). After discharge, the patient's H. cinaedi infection did not recur. Our case illustrated the wide clinical spectrum of H. cinaedi as well as the effectiveness of antibiotic therapy comprising MERM and MINO for treating central nervous system infection by this organism.

Accurate determination of the antimicrobial susceptibilities of clinical isolates is important in establishing adequate treatment with antibiotics, particularly for infections caused by multiple drug-resistant strains of Pseudomonas aeruginosa. However, current laboratory antimicrobial susceptibility testing is affected by various conditions, including cation concentrations. In this study, we analyzed the relevance of the resistance determinants, metallo-lactamase (MBL) and aminoglycoside-modifying enzyme production, and examined the effects of calcium concentration on the in vitro activity of antibiotics. The broth microdilution method using Mueller-Hinton broth supplemented with various concentrations of calcium (5.2, 25, and 50 mg/L) was used to evaluate 58 clinical strains of P. aeruginosa. We observed increases in the minimum inhibitory concentrations (MICs) of aminoglycosides, tetracyclines, quinolones, and somelactam antibiotics with higher concentrations of calcium in the media. Strains that did not produce MBLs would have been affected by calcium concentration. Strains that did not produce aminoglycoside-modifying enzymes tended to lower the MICs of aminoglycosides more substantially than strains that produced aminoglycoside-modifying enzymes. In conclusion, the calcium concentration of the media may affect the results of antimicrobial susceptibilities of P. aeruginosa in relation to each resistance gene.