Subacute bacterial endocarditis due to Actinobacillus actinomycetemcomitans

Actinobacillus actinomycetemcomitans endocarditis

Among the bacteria of the HACEK group, Actinobacillus actinomycetemcomitans is the organism involved most commonly in infective endocarditis. However, the epidemiological and clinical features specifically associated with this species have not been evaluated adequately. Three patients with infective endocarditis caused by A. actinomycetemcomitans seen at the Hospital La Timone (Marseille, France) between 1994 and 2001 are reported. Of 99 cases in the literature, 75% of patients had previous heart disease before infective endocarditis, the portal of entry of which was usually the oral cavity. Among the total of 102 cases, 27 had prosthetic valves. Intermittent fever was observed in all cases, and weight loss and peripheral signs of endocarditis were noteworthy in this study. Anaemia and microscopic haematuria were frequently noted. The disease is insidious, with a mean duration of symptoms of 13 weeks before diagnosis, as confirmed by blood cultures incubated for > 5 days. The aortic valve is most commonly involved, and echocardiographic findings were non-specific. Complications occurred in 63% of patients, with emboli being the most common. The surgery rate was 23.5%. The overall mortality rate was 18%. Of the cases, 76.5% were cured with antibiotics alone, including a simple third-generation cephalosporin or a combination of ampicillin and an aminoglycoside. An antibiotic therapy duration of at least 4 weeks is recommended. Surgical therapy is usually required for haemodynamic reasons. Prophylaxis of A. actinomycetemcomitans endocarditis relies on antibiotic therapy for all cardiac patients at risk before dental procedures. Among 17 patients undergoing dental manipulations, only eight received amoxycillin before the procedure, demonstrating that prophylaxis is far from being systematically prescribed. In conclusion, A. actinomycetemcomitans endocarditis should be highly suspected in patients with previous cardiac disease and for whom symptoms have evolved over a number of weeks or even months.

Virulence factors of Actinobacillus actinomycetemcomitans

A. actinomycetemcomitans has clearly adapted well to its environs; its armamentarium of virulence factors (Table 2) ensures its survival in the oral cavity and enables it to promote disease. Factors that promote A. actinomycetemcomitans colonization and persistence in the oral cavity include adhesins, bacteriocins, invasins and antibiotic resistance. It can interact with and adhere to all components of the oral cavity (the tooth surface, other oral bacteria, epithelial cells or the extracellular matrix). The adherence is mediated by a number of distinct adhesins that are elements of the cell surface (outer membrane proteins, vesicles, fimbriae or amorphous material). A. actinomycetemcomitans enhances its chance of colonization by producing actinobacillin, an antibiotic that is active against both streptococci and Actinomyces, primary colonizers of the tooth surface. The fact that A. actinomycetemcomitans resistance to tetracyclines, a drug often used in the treatment of periodontal disease, is on the rise is an added weapon. Periodontal pathogens or their pathogenic products must be able to pass through the epithelial cell barrier in order to reach and cause destruction to underlying tissues (the gingiva, cementum, periodontal ligament and alveolar bone). A. actinomycetemcomitans is able to elicit its own uptake into epithelial cells and its spread to adjacent cells by usurping normal epithelial cell function. A. actinomycetemcomitans may utilize these remarkable mechanisms for host cell infection and migration to deeper tissues. A. actinomycetemcomitans also orchestrates its own survival by elaborating factors that interfere with the host's defense system (such as factors that kill phagocytes and impair lymphocyte activity, inhibit phagocytosis and phagocyte chemotaxis or interfere with antibody production). Once the organisms are firmly established in the gingiva, the host responds to the bacterial onslaught, especially to the bacterial lipopolysaccharide, by a marked and continual inflammatory response, which results in the destruction of the periodontal tissues. A. actinomycetemcomitans has at least three individual factors that cause bone resorption (lipopolysaccharide, proteolysis-sensitive factor and GroEL), as well as a number of activities (collagenase, fibroblast cytotoxin, etc.) that elicit detrimental effects on connective tissue and the extracellular matrix. It is of considerable interest to know that A. actinomycetemcomitans possesses so many virulence factors but unfortunate that only a few have been extensively studied. If we hope to understand and eradicate this pathogen, it is critical that in-depth investigations into the biochemistry, genetic expression, regulation and mechanisms of action of these factors be initiated.

Third-generation cephalosporins in the treatment of rare infections

This article reviews the published clinical experience of the use of the third-generation cephalosporins in the treatment of rare infections. Rare infections are defined as those caused by unusual pathogens or multi-resistant organisms as well as those occurring in unusual or pharmacologically protected body sites. Examples of such infections are uncommon causes of meningitis and ventriculitis, brain abscess, rare causes of bacterial endocarditis, metastatic Salmonella infections, spontaneous bacterial peritonitis and liver abscess, late complications of Lyme borreliosis, uncommon Pseudomonas infections, and post-reconstructive surgery Aeromonas cellulitis. Although these data are largely anecdotal, they form a useful body of information, providing guidance on the management of similar problems encountered by other doctors, while suggesting areas of further investigation for the management of a variety of unusual infections with the third-generation cephalosporins.

The origin of periodontal infections

Periodontal diseases are recognized as bacterial infections, and some forms are associated with specific organisms, such as Actinobacillus actinomycetemcomitans in juvenile periodontitis, and Bacteroides gingivalis and others in adult periodontitis. The source of the periodontal organisms, whether they are part of the indigenous or resident flora and overgrow to become opportunistic oral pathogens, or whether they are exogenous oral pathogens, is important to determine. The chain of periodontal infection, microbial agent(s) and their transmission, and host response are reviewed with respect to the role of A. actinomycetemcomitans in localized juvenile periodontitis and B. gingivalis in adult periodontitis. The present data lead us to hypothesize that some periodontal organisms may be exogenous pathogens.

Prevention of periodontal diseases may be influenced by the knowledge of whether various forms are caused by opportunistic organisms or exogenous pathogens. If exogenous pathogens are responsible, prevention can be directed to intercepting transmission, thereby preventing colonization. On the other hand, if the organisms are opportunistic pathogens, prevention might be directed at interfering with initial acquisition of the flora earlier in life, as well as suppressing them to low levels consistent with health. For those exogenous periodontal infections, attempts at eradication and prevention of re-infection are likely to be effective. If the organisms are part of the indigenous flora, there is little hope of complete elimination of the organism.

Criteria for distinguishing exogenous periodontal pathogens from opportunistic periodontal pathogens include the prediction that exogenous pathogens would be transient members of the oral flora associated with periodontal disease, likely to be comprised of one or a few clonal types, and intrinsically virulent. In contrast, opportunistic periodontal pathogens would likely be members of the indigenous flora and would overgrow. They would likely be comprised of many clonal types, and have an intrinsically low level of virulence.

Septicaemia due to Actinobacillus actinomycetemcomitans with endocarditis and spinal epidural abscess

A case of tricuspid valve endocarditis with spinal epidural abscess caused by Actinobacillus actinomycetemcomitans is reported in a 74-year-old male with an endocardial pacemaker. Despite antibiotic treatment, removal of the endocardial wire was necessary for recovery.

Diagnosis and treatment of localized juvenile periodontitis

An actinomycetemcomitans can cause localized juvenile periodontitis and certain types of adult periodontitis. Optimal treatment of periodontal disease caused by this microorganism requires systemic antibiotic therapy in addition to mechanical debridement of the infected gingival tissues. Laboratory techniques are available to assist the practitioner in identifying this microorganism in dental plaque samples.

Actinobacillus actinomycetemcomitans in human periodontal disease

Recent evidence implicates Actinobacillus actinomycetemcomitans in the etiology of localized juvenile periodontitis. This paper reviews the morphological, biochemical and serological charcteristics of A. actinomycetemcomitans, evidence incriminating it as a periodontopathogen, its importance in human nonoral infections, and virulence factors which may be involved in the pathogenesis of A. actinomycetemcomitans infections. A. actinomycetemcomitans is a non-motile, gram-negative, capnophilic, fermentative coccobacillus which closely resembles several Haemophilus species but which does not require X or V growth factors. The organism has been categorized into 10 biotypes based on the variable fermentation of dextrin, maltose, mannitol, and xylose and into 3 serotypes on the basis of heat stable, cell surface antigens. A. actinomycetemcomitans' primary human ecologic niche is the oral cavity. It is found in dental plaque, in periodontal pockets, and buccal mucosa in up to 36% of the normal population. The organism can apparently seed from these sites to cause severe infections throughout the human body such as brain abscesses and endocarditis. There is a large body of evidence which implicates A. actinomycetemcomitans as an important micro-organism in the etiology of localized juvenile periodontitis including: (1) an increased prevalence of the organism in almost all localized juvenile periodontitis patients and their families compared to other patient groups; (2) the observation that localized juvenile periodontitis patients exhibit elevated antibody levels to A. actinomycetemcomitans in serum, saliva and gingival crevicular fluid; (3) the finding that localized juvenile periodontitis can be successfully treated by eliminating A. actinomycetemcomitans from periodontal pockets; (4) histopathologic investigations showing that A. actinomycetemcomitans invades the gingival connective tissue in localized juvenile periodontitis lesions; (5) the demonstration of several pathogenic products from A. actinomycetemcomitans including factors which may: (a) facilitate its adherence to mucosal surfaces such as capsular polysaccharides; (b) inhibit host defense mechanisms including leukotoxin, a polymorphonuclear leukocyte chemotaxis inhibiting factor, and a lymphocyte suppressing factor (c) cause tissue destruction such as lipopolysaccharide endotoxin, a bone resorption-inducing toxin, acid and alkaline phosphatases, collagenase, a fibroblast inhibiting factor and an epitheliotoxin.(ABSTRACT TRUNCATED AT 400 WORDS)

Endocarditis caused by Actinobacillus actinomycetemcomitans

The first two cases of Actinobacillus actinomycetemcomitans endocarditis in Israel are reported. One involved a 67 year old woman with mitral insufficiency and the other, a 48 year old alcoholic male with bioprosthetic mitral valve. The organism grew in three of seven and seven of fourteen blood culture specimens, taken during the first two or three days of hospitalization respectively. Blood cultures became positive after incubation for seven days. The first patient recovered after therapy with penicillin and an aminoglycoside, and the second one is still being treated. Previously described cases of Actinobacillus actinomycetemcomitans endocarditis are reviewed.