P2012 Microbiological characteristics of a novel species most closely related to Bergeyella cardium as a pathogen of infective

Li-Na Guo*1, Ying LI1, Po-Ren Hsueh2, Yingchun Xu1

1Peking Union Medical College Hospital, Clinical Microbiology, Beijing, China, 2National Taiwan University Hospital, Departments of Laboratory Medicine and Internal Medicine, Taipei, Taiwan

Background:

The genus Bergeyella, nonfermentative gram-negative bacilli within the family Flavobacteriaceae, is a rare human pathogen. Bergeyella zoohelcum has been known to cause human infections associated with animal bites. Bergeyella cardium was reported as a pathogen of infective endocarditis for the first time in Korea in 2015. In this study, we report the isolation of a bacterial that was genetically most closely related to Bergeyella cardium, from blood culture of a patient with infective endocarditis from

China.

Materials/methods:

A rare case of infective endocarditis caused by a species genetically closely related to Bergeyella cardium is reported. The identification, morphological characteristics and antimicrobial resistance profile of this organism are described.

Results:

A 24-year-old man was admitted to hospital for intermittent fever (Tmax 39.1℃) with chills and fatigue for six months. Antibiotic therapy doesn’t resolve the problem. Echocardiogram revealed congenital disease of patent ductus arteriosus and infective endocarditis was suspected with evidence of aortic regurgitation and multiple vegetations on the and wall. The patient had a sheep contact history. Cardiac surgical operation was performed and antibiotic treatment with ceftriaxone for seven weeks. The patient recovered well. Blood culture was positive for some gram-negative aerobic bacillus with irregularly shaped rods after 68 hours of incubation. This fastidious organism grew slowly on sheep blood agar at 35℃ with 5% CO2 (Fig.1), was identified initially as Brevundimonas spp. by the Vitek 2 compact, but was finally confirmed as a novel species closest to Bergeyella cardium, with similarity of 98.8% to B. cardium strain 13-07T. The BD Phoenix,

Vitek MS and Bruker Biotyper MS failed to identify the isolate. The strain was susceptible to β-lactams and quinolones antibiotics except for Amikacin (24 µg/ml) and Tobramycin (32 µg/ml). Conclusions:

Phylogeny analysis revealed this novel species clustered well with B. cardium and other close species of the genus Bergeyella. Further studies should be performed to ascertain the potential of this bacterium to become an emerging cause of infective endocarditis.

Fig.1. Phenotype. a, b: 2 days; c, d: 5 days; e: gram stain; f: acid fast.