Correlation between antimicrobial susceptibility data and clinical efficacy for Helicobacter cinaedi bacteraemia

Helicobacter cinaedi is the most common species of enterohepatic Helicobacter reported to cause bloodstream infections in humans. The establishment of effective treatment strategies for H. cinaedi bacteraemia is required, since the association between in vitro susceptibility and clinical response has yet to be demonstrated.

The medical records of all patients diagnosed with H. cinaedi bacteraemia at two Japanese hospitals between March 2009 and December 2016 were retrospectively reviewed. We investigated the antimicrobial susceptibility of H. cinaedi using the broth microdilution method and assessed the clinical efficacy of treatment regimens for H. cinaedi bacteraemia.

We evaluated the data of 131 patients with first-episode H. cinaedi bacteraemia for which MIC data were available for the causative strains. Carbapenems (imipenem and meropenem), aminoglycosides (gentamicin and kanamycin), tetracycline and chloramphenicol exhibited lower MIC values. Fluoroquinolones, especially ciprofloxacin and levofloxacin, demonstrated higher MIC values. Penicillins and cephalosporins showed a wide range of MIC values, from low to high. The MIC₅₀ and MIC₉₀ of amoxicillin were 4 mg/L and 8 mg/L, respectively. Treatment was successful in 42 of 45 patients (93.3%) who received intravenous β-lactam followed by oral amoxicillin switching therapy or amoxicillin monotherapy. Treatment failed in four of eight patients (50%) in the fluoroquinolone monotherapy group.

Based on our MIC and clinical data, intravenous β-lactam-to-oral amoxicillin switching therapy or amoxicillin monotherapy may be a recommended option, whereas levofloxacin therapy is suboptimal and should be avoided.