Evolution of Protein Molecules

The etiologic diagnosis of infective endocarditis is easily made in the presence of continuous bacteremia with gram-positive cocci. However, the blood culture may contain a bacterium rarely associated with endocarditis, such as Lactobacillus spp., Klebsiella spp., or nontoxigenic Corynebacterium, Salmonella, Gemella, Campylobacter, Aeromonas, Yersinia, Nocardia, Pasteurella, Listeria, or Erysipelothrix spp., that requires further investigation to establish the relationship with endocarditis, or the blood culture may be uninformative despite a supportive clinical evaluation. In the latter case, the etiologic agents are either fastidious extracellular or intracellular bacteria. Fastidious extracellular bacteria such as Abiotrophia, HACEK group bacteria, Clostridium, Brucella, Legionella, Mycobacterium, and Bartonella spp. need supplemented media, prolonged incubation time, and special culture conditions. Intracellular bacteria such as Coxiella burnetii cannot be isolated routinely. The two most prevalent etiologic agents of culture-negative endocarditis are C. burnetti and Bartonella spp. Their diagnosis is usually carried out serologically. A systemic pathologic examination of excised heart valves including periodic acid-Schiff (PAS) staining and molecular methods has allowed the identification of Whipple9s bacillus endocarditis. Pathologic examination of the valve using special staining, such as Warthin-Starry, Gimenez, and PAS, and broad-spectrum PCR should be performed systematically when no etiologic diagnosis is evident through routine laboratory evaluation.

Endocarditis Due to Rare and Fastidious Bacteria

Infective endocarditis (IE) carries a high risk of morbidity and mortality. Rapid diagnosis, effective treatment, and prompt recognition of complications are essential to good patient outcome. Therapy of IE caused by the more commonly encountered organisms, including streptococci, enterococci, staphylococci, and the HACEK organisms ( Hemophilus parainfluenzae, Hemophilus aphrophilus, Actinobacillus [Hemophilus] actinomycetemcomitans, Cardiobacterium hominis, Eikenella species , and Kingella species), has been addressed previously by this committee.1 Likewise, the antimicrobial prevention of endocarditis has also been previously addressed.2 In this article, we review and update the current literature with respect to diagnostic challenges and strategies, difficult therapeutic situations, and management choices in patients with IE. This article focuses predominantly on adults with IE. A separate article, currently in preparation, will address the issues of IE in childhood.

### Clinical Criteria

The diagnosis of IE is straightforward in those patients with classic oslerian manifestations: bacteremia or fungemia, evidence of active valvulitis, peripheral emboli, and immunologic vascular phenomena. In other patients, however, the classic peripheral stigmata may be few or absent.3 This may occur during acute courses of IE, particularly among intravenous drug abuse (IVDA) patients in whom IE is often due to Staphylococcus aureus infection of right-sided heart valves, or in patients with IE caused by microorganisms such as HACEK. Acute IE evolves too quickly for the development of immunologic vascular phenomena, which are more characteristic of subacute IE. In addition, acute right-sided IE valve lesions do not create the peripheral emboli and immunologic vascular phenomena that can result from left-sided valvular involvement.3 

The variability in the clinical presentation of IE requires a diagnostic strategy that will be both sensitive for disease detection and specific for its exclusion across all the forms of the disease. In 1981, von Reyn et al4 proposed a scheme for strict case definitions of IE …

Diagnosis and Management of Infective Endocarditis and Its Complications

Members of the genus Bartonella (formerly Rochalimaea) were virtually unknown to modern-day clinicians and microbiologists until they were associated with opportunistic infections in AIDS patients about 6 years ago. Since that time, Bartonella species have been associated with cat scratch disease, bacillary angiomatosis, and a variety of other disease syndromes. Clinical presentation of infection with Bartonella ranges from a relatively mild lymphadenopathy with few other symptoms, seen in cat scratch disease, to life-threatening systemic disease in the immunocompromised patient. In some individuals, infection manifests as lesions that exhibit proliferation of endothelial cells and neovascularization, a pathogenic process unique to this genus of bacteria. As the spectrum of disease attributed to Bartonella is further defined, the need for reliable laboratory methods to diagnose infections caused by these unique organisms also increases. A brief summary of the clinical presentations associated with Bartonella infections is presented, and the current status of laboratory diagnosis and identification of these organisms is reviewed.

Bartonella spp. as emerging human pathogens.

Members of the genus Bartonella are facultative intracellular bacteria belonging to the alpha 2 subgroup of the class Proteobacteria and are phylogenetically closely related to Brucella species (15, 73). Until 1993, only three diseases were known to be caused by Bartonella species: Carrion's disease (Bartonella bacilliformis), trench fever (Bartonella quintana), and cat scratch disease (CSD; Bartonella henselae). The genus now comprises B. bacilliformis, species of the former genera Rochalimea and Grahamella (14, 18), and additional, recently described species (Table ​(Table1).1). In mammals, each Bartonella species is highly adapted to its reservoir host; the bacteria can persist in the bloodstream of the host as the result of intraerythrocytic parasitism (49). Intraerythrocytic localization of B. henselae has been demonstrated in cat erythrocytes (88), and B. bacilliformis bacilli have been observed within erythrocytes during the acute phase of Carrion's disease (Oroya fever) (88). Bartonellae also have a tropism for endothelial cells, and intracellular B. henselae can be identified in endothelial cells infected in vitro (28), although intraendothelial cell bacilli have not been identified in vivo.



TABLE 1.

Epidemiological and clinical data for species of the genus Bartonella



Bartonella species cause long-recognized diseases, such as Carrion's disease, trench fever, and CSD, and more recently recognized diseases, such as bacillary angiomatosis (BA), peliosis hepatis (PH), chronic bacteremia, endocarditis, chronic lymphadenopathy, and neurological disorders (Table ​(Table2)2) (73). A remarkable feature of the genus Bartonella is the ability of a single species to cause either acute or chronic infection and either vascular proliferative or suppurative manifestations.



TABLE 2.

Human diseases caused by Bartonella spp.



The pathological response to infection with Bartonella spp. varies substantially with the status of the host immune system. Indeed, infection with the same Bartonella species (e.g., B. henselae) can result in a focal suppurative reaction (CSD in immunocompetent patients), a multifocal angioproliferative response (BA in immunocompromised patients), endovascular multiplication of the bacteria (endocarditis), or an exaggerated inflammatory response without evidence of bacteria in patient tissues (meningoencephalitis) (86).

Some of the diseases due to Bartonella species can resolve spontaneously without treatment, but in other cases, the disease is fatal without antibiotic treatment and/or surgery. The clinical situations are so different that a single treatment for all Bartonella-related diseases has not been identified, and the approach to treatment must be adapted to each species and clinical situation (49). Moreover, the database of clinical studies with a standard case definition, culture confirmation, rigidly defined disease outcomes, and patients with similar host defenses is very limited. Thus, case reports with a very limited number of subjects often serve to dictate therapy. The objective of this minireview is to summarize the antibiotic treatment recommendations for the different infections caused by Bartonella species. We have compiled the in vitro antibiotic susceptibility data and our knowledge of the in vivo efficacies of antibiotics for each clinical manifestation, and finally, we have summarized and ranked our treatment recommendations according to the Infectious Diseases Society of America (IDSA) practice guidelines (see Table ​Table5)5) (51).



TABLE 5.

System for ranking recommendations in clinical guidelines recommended by IDSAa

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Recommendations for Treatment of Human Infections Caused by Bartonella Species

A Rochalimaea-like organism (strain F9251) was isolated from a patient with endocarditis after blood drawn for culture before antimicrobial therapy was subcultured onto blood and chocolate agars and incubated for 2 weeks in 5% CO2. The strain was phenotypically similar to known Rochalimaea species. The cellular fatty acid composition of strain F9251 was close to but distinct from those of the three known Rochalimaea species and was most similar to that of R. vinsonii. Labeled DNA from strain F9251 was 59 to 67% related to DNAs from type strains of the three described Rochalimaea species, and its 16S rRNA gene sequence was 98.9% or more homologous to their 16S rRNA gene sequences. These findings support classification of F9251 as a new Rochalimaea species, for which the name Rochalimaea elizabethae sp. nov. is proposed. The patient infected with the organism had large bacterial vegetations on his aortic valve and was cured with antibiotics and valve-replacement surgery. Recognition of the procedures required to identify this and other Rochalimaea species suggests that clinical laboratories should prolong the incubation times of cultures of blood and tissue from patients with suspected endocarditis, patients with fever of unknown origin, and immunocompromised patients with fever so that the full spectrum of disease caused by these organisms can be recognized.

/pdf/rochalimaea-elizabethae-sp-nov-isolated-from-a-patient-with-34v36ggaa0.pdf

R S Weyant

Papers

Rochalimaea elizabethae sp. nov. isolated from a patient with endocarditis.