Abiotrophia

Abiotrophia is a genus of Gram-positive bacteria that are part of the normal flora of the human oral cavity, gastrointestinal tract, and urogenital tract. These bacteria are known for their fastidious growth requirements and have been implicated in various human infections, particularly endocarditis.

Taxonomy

The genus Abiotrophia was previously classified under the genus Streptococcus as nutritionally variant streptococci (NVS). However, due to differences in genetic and phenotypic characteristics, they were reclassified into a separate genus. The genus Abiotrophia currently includes several species, with Abiotrophia defectiva being the most clinically significant.

Morphology and Physiology

Abiotrophia species are small, cocci-shaped bacteria that typically form chains. They are facultative anaerobes, meaning they can grow in both the presence and absence of oxygen. These bacteria are catalase-negative and require specific growth factors, such as pyridoxal or cysteine, which are not present in standard laboratory media.

Pathogenicity

Abiotrophia species are opportunistic pathogens. They are most commonly associated with infective endocarditis, an infection of the inner lining of the heart chambers and valves. This condition is particularly challenging to treat due to the bacteria's fastidious nature and resistance to standard antibiotic therapy.

Infective Endocarditis

Infective endocarditis caused by Abiotrophia is characterized by the formation of vegetations on heart valves. These vegetations can lead to serious complications, including heart failure, stroke, and systemic embolism. Diagnosis is often confirmed through blood cultures and echocardiography.

Other Infections

In addition to endocarditis, Abiotrophia species have been implicated in other infections such as bacteremia, septic arthritis, and osteomyelitis. These infections are less common but can occur in immunocompromised individuals or those with underlying health conditions.

Diagnosis

The diagnosis of infections caused by Abiotrophia is challenging due to their fastidious growth requirements. Blood cultures may be negative or require extended incubation periods. Specialized media supplemented with pyridoxal or cysteine may be necessary to isolate these organisms. Molecular techniques, such as polymerase chain reaction (PCR), can also be used for identification.

Treatment

Treatment of Abiotrophia infections typically involves prolonged courses of antibiotics. Due to their resistance to standard therapies, combination antibiotic regimens are often required. Penicillin or ampicillin combined with an aminoglycoside is commonly used. In cases of endocarditis, surgical intervention may be necessary to repair or replace damaged heart valves.

Prevention

Preventive measures for Abiotrophia infections include maintaining good oral hygiene and regular dental check-ups, as these bacteria are part of the normal oral flora. Prophylactic antibiotics may be recommended for individuals with certain heart conditions undergoing dental procedures.

Research and Future Directions

Research on Abiotrophia is ongoing to better understand their pathogenic mechanisms and to develop more effective treatment strategies. Advances in molecular diagnostics and antibiotic development hold promise for improving outcomes in patients with Abiotrophia infections.

See also

• Endocarditis
• Gram-positive bacteria
• Lactobacillales

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