NVE Due to Anaerobic Bacteria

NVE due to anaerobic bacteria is rare, with studies performed in the 1970s reporting them as the etiologic agent in 2-5% of cases [330]. Most cases of anaerobic NVE are caused by Gramnegative bacilli (predominantly Bacteroides fragilis group, other Bacteroides spp., and Fusobacterium spp.). Anaerobic Gram-positive rods (predominantly Propionibacterium spp.) have also been reported.

Among the 53 cases of endocarditis due to anaerobic Gram-negative bacilli (GNB) reviewed in the English literature [330], the majority (20/53, 38%) are due to B. fragilis group. This group of bacteria includes B. fragilis (sensu stricto), which is the most common isolate, and other species, such as B. distasonis, B. ovatus, B. thetaiotaomicron, and B. vulgatus [331] These bacteria are part of the normal GI flora. As such, the most common sources for B. fragilis group NVE were the gastrointestinal and the genital tracts [330,332]. NVE with this group of bacteria is frequently complicated by systemic embolization, occurring in 60-70% of cases [330]. In case studies published prior to 1974, B. fragilis group endocarditis was associated with a high mortality rate (14/17 cases, 81%) [330]. This dismal prognosis was most likely due to the lack of an effective antimicrobial agent with anaerobic coverage at that time. Of note, members of the B. fragilis group are resistant to penicillins, mostly through the production of P-lactamase [331]. With the introduction of metronidazole in the 1970s, there has been a significant reduction in death rates among patients infected with Bacteroides spp. in general [330]. This decline is related to the high prevalence (>99%) of clinical isolates that are susceptible to metronidazole [331]. Other agents that retain this level of efficacy against clinical isolates include chloram-phenicol and the carbapenems; P-lactam/ P-lactamase inhibitor combinations also demonstrate activity against the majority [95-99%) of isolates [331]. The development of antibiotics with effective anti-Bacteroides activity has facilitated the medical management of this rare endocarditis.

Fusobacterium spp., also members of the Bacteroidaceae family, represent a rare cause of endocarditis. The two major clinical species of this genus are F. necrophorum, the etiologic agent of Lemierre's syndrome (septic internal jugular vein thrombosis) and F. nucleatum. Both organisms have been reported to cause NVE [333]. As with B. fragilis group NVE, arterial embolization was the most common complication [333]. In the pre-antibiotic era, the mortality rate from Fusobacterium bacteremia was approximately 80%; the rates of Fusobacterium NVE per se are unknown [333]. With the advent of antibiotics, the mortality rate has significantly diminished, owing to the general susceptibility of most Fusobacterium spp. to penicillin [330]. All reported cases of Fusobacterium endocarditis have had a favorable clinical course with antimicrobial therapy alone [330,333].

Propionibacterium acnes is an anaerobic, non-spore-forming, Gram-positive bacterium that demonstrates slow growth in vitro. It is part of the normal flora of the skin and mucous membranes [334]. Although frequently considered a contaminant, P. acnes has the capacity to cause serious infections. P. acnes has caused endocarditis involving prosthetic valves as well as native valves [335]. The capacity of this "benign" organism to do so relates to its ability to adhere to tissues with structural abnormality (e.g., rheumatic cardiac valves) or to foreign material (e.g., prosthetic valves) [334]. P. acnes endocarditis can be complicated by abscess formation, congestive heart failure, and arterial embolization [335]. The mortality rate for P. acnes NVE is unknown, but the mortality rate for prosthetic valve endocarditis is 21-46% [336]. Successful treatment of the few cases of NVE have used a combined modality approach [334,335]. P. acnes is usually susceptible to penicillin, ampicillin, vancomycin, and gentamicin [334,335,337].

Bacterial Vaginosis Facts

Bacterial Vaginosis Facts

This fact sheet is designed to provide you with information on Bacterial Vaginosis. Bacterial vaginosis is an abnormal vaginal condition that is characterized by vaginal discharge and results from an overgrowth of atypical bacteria in the vagina.

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