Aortic valve endocarditis due to abiotrophia defectiva: a rare etiology

Infective endocarditis by a rare and fastidious agent: Abiotrophia defectiva

Abiotrophia defectiva is a nutritional variant streptococcus, with affinity for endovascular structures that cannot be cultured on non-supplemented media, leading to a delay in diagnosis. This case describes a 36-year-old woman with a previously known bicuspid aortic valve that presented with asthenia, myalgias and anorexia with 2-month onset. On admission, we documented fever and a systolic murmur. Transthoracic echocardiography revealed an oscillating mass attached to the aortic valve. The patient was admitted with a possible diagnosis of infective endocarditis. Later, blood cultures were positive for A. defectiva Due to severe aortic regurgitation and congestive heart failure, she underwent surgical aortic valve replacement. After 6 weeks of antimicrobial therapy, the patient experienced full recovery. Despite of its rarity, A. defectiva endocarditis is associated with significant morbidity with mortality and physicians must have a high level of suspicion to ensure a prompt diagnosis and provide the appropriate treatment.

A recurrent lung abscess caused by delayed diagnosis of unique co-infection with Abiotrophia defectiva

We report the case of a lung abscess due to Prevotella baroniae with a co-infection by Abiotrophia defective, which is a 'nutritionally variant streptococci' (NVS), in a 48-year-old patient. The delayed diagnosis of this co-infection led to multiple failures of medical treatment and need for surgery. Pathogenicity of these bacteria is well known, particularly in endocarditis, but not in lung infection. In pulmonary abscesses, co-infection with NVS is difficult to detect. It may explain some medical treatment failures. This case highlights the importance to systematically search for and consider NVS in such clinical contexts.

The influence of iron availability on human salivary microbial community composition

It is a well-recognized fact that the composition of human salivary microbial community is greatly affected by its nutritional environment. However, most studies are currently focused on major carbon or nitrogen sources with limited attention to trace elements like essential mineral ions. In this study, we examined the effect of iron availability on the bacterial profiles of an in vitro human salivary microbial community as iron is an essential trace element for the survival and proliferation of virtually all microorganisms. Analysis via a combination of PCR with denaturing gradient gel electrophoresis demonstrated a drastic change in species composition of an in vitro human salivary microbiota when iron was scavenged from the culture medium by addition of the iron chelator 2,2'-bipyridyl. This shift in community profile was prevented by the presence of excessive ferrous iron (Fe(2+)). Most interestingly, under iron deficiency, the in vitro grown salivary microbial community became dominated by several hemolytic bacterial species, including Streptococcus spp., Gemella spp., and Granulicatella spp. all of which have been implicated in infective endocarditis. These data provide evidence that iron availability can modulate host-associated oral microbial communities, resulting in a microbiota with potential clinical impact.

Subarachnoid hemorrhage in a patient with Abiotrophia defectiva endocarditis

Endocarditis caused by Abiotrophia accounts for 5% of all cases of infective endocarditis (Roberts et al, Rev Infect Dis. 1979;1:955-66) and 5% to 6% of all cases of streptococcal endocarditis (Bouvet, Eur Heart J. 1995;16(suppl B):24-7; Brouqui et al, Clin Microbiol Rev. 2001;14:177-207). This endocarditis is associated with a high rate of embolization and treatment failure (Bouvet, Eur Heart J. 1995;16(suppl B):24-7). Neurological complications occur in 20% to 40% of all cases of infective endocarditis (Ossorio et al, Hosp Physician. 2003;39:21-4). Subarachnoid hemorrhage is a rare but devastating neurological complication. The authors presented a case of massive fatal subarachnoid hemorrhage in a patient with Abiotrophia defectiva endocarditis. To our knowledge, there are only 2 reported cases of mycotic aneurysms in Abiotrophia endocarditis, 1 of which was associated with subarachnoid hemorrhage (Leonard et al, N Engl J Med. 2001;344:233-4; Yang et al, Am J Med Sci. 2010;339:190-1).