Crossed immunoelectrophoresis used for bacteriological diagnosis in patients with endocarditis

Anti-biofilm Approach in Infective Endocarditis Exposes New Treatment Strategies for Improved Outcome

Infective endocarditis (IE) is a life-threatening infective disease with increasing incidence worldwide. From early on, in the antibiotic era, it was recognized that high-dose and long-term antibiotic therapy was correlated to improved outcome. In addition, for several of the common microbial IE etiologies, the use of combination antibiotic therapy further improves outcome. IE vegetations on affected heart valves from patients and experimental animal models resemble biofilm infections. Besides the recalcitrant nature of IE, the microorganisms often present in an aggregated form, and gradients of bacterial activity in the vegetations can be observed. Even after appropriate antibiotic therapy, such microbial formations can often be identified in surgically removed, infected heart valves. Therefore, persistent or recurrent cases of IE, after apparent initial infection control, can be related to biofilm formation in the heart valve vegetations. On this background, the present review will describe potentially novel non-antibiotic, antimicrobial approaches in IE, with special focus on anti-thrombotic strategies and hyperbaric oxygen therapy targeting the biofilm formation of the infected heart valves caused by Staphylococcus aureus. The format is translational from preclinical models to actual clinical treatment strategies.

Biofilms and host response - helpful or harmful

Biofilm infections are one of the modern medical world's greatest challenges. Probably, all non-obligate intracellular bacteria and fungi can establish biofilms. In addition, there are numerous biofilm-related infections, both foreign body-related and non-foreign body-related. Although biofilm infections can present in numerous ways, one common feature is involvement of the host response with significant impact on the course. A special characteristic is the synergy of the innate and the acquired immune responses for the induced pathology. Here, we review the impact of the host response for the course of biofilm infections, with special focus on cystic fibrosis, chronic wounds and infective endocarditis.

Towards diagnostic guidelines for biofilm-associated infections

Biofilms associated with the human body, particularly in typically sterile locations, are difficult to diagnose and treat effectively because of their recalcitrance to conventional antibiotic therapy and host immune responses. The study of biofilms in medicine today requires a translational approach, with examination of clinically relevant biofilms in the context of specific anatomic sites, host tissues, and diseases, focusing on what can be done to mitigate their pathologic consequences. This review, which grew out of a discussion session on clinical biofilms at the 5th ASM Biofilm Conference in Cancun, Mexico, is designed to give an overview of biofilm-associated infections (BAI) and to propose a platform for further discussion that includes clinicians, medical microbiologists, and biofilm researchers who are stakeholders in advancing the scientific pursuit of better diagnosis and treatment of BAI to mitigate their human and healthcare costs. It also highlights the need for better diagnostic markers, which exploit the difference between planktonic and biofilm cells.

Oral infections and systemic diseases

An association between periodontal infection and CVD has been revealed in some epidemiologic studies, whereas other studies were unable to demonstrate such an association. A link between the two diseases may be explained by shared established or nonestablished risk factors. Future studies with extended control of confounding factors and intervention studies may add to the understanding of a possible relationship between the diseases. In some cases, IE is caused by dental plaque bacteria. Several studies are suggestive of oral bacteria causing respiratory infection. The pathogenesis and course of a number of other diseases including DM and rheumatoid arthritis have been associated wish periodontitis, but more research is necessary to elucidate possible pathogenic interactions.

Current status of taxonomic groups of oral streptococci in endocarditis. Can virulence factors discriminate between endocarditis and non-endocarditis strains?

OBJECTIVE: Infective endocarditis is frequently caused by oral streptococci, especially Streptococcus sanguis. In this group, many strains have recently been reclassified on the basis of new taxonomic schemes. The purpose of this study was to classify oral streptococci from patients with infective endocarditis and, further, to assess the importance of specific virulence factors for the development of streptococcal endocarditis. METHODS: Twenty-eight previously identified and 10 new streptococcal isolates from infective endocarditis were classified according to Kilian et al (1989) and compared to 30 streptococcal isolates from the oral cavities of periodontal patients without endocarditis. Subsequently, surface hydrophobicity was assessed by hydrophobic interaction chromatography, production of extracellular dextran was determined by precipitation, and non-specific proteolytic activity was evaluated by determination of hydrolysis of gelatin, and casein-precipitating activity. RESULTS: Eight streptococcal species were represented in the endocarditis isolates. Most strains were highly hydrophobic and none showed non-specific proteolytic activity. Dextran was produced with similar frequency in endocarditis and non-endocarditis isolates. CONCLUSIONS: The present study showed that infective endocarditis may be caused by a variety of oral streptococcal species. The possible virulence factors investigated were found in the same proportions in endocarditis and non-endocarditis isolates, and thus did not seem to be crucial for development of endocarditis.

Immunoblotting in the diagnosis of culture negative endocarditis caused by streptococci and enterococci

AIM

To improve the diagnosis of culture negative endocarditis by diagnosing cases due to streptococci and enterococci.

METHODS

Serum samples were immunoblotted against extracts of the commonest streptococci and enterococci. They were selected from patients with a cardiac murmur, persistent pyrexia and at least three negative blood cultures. The presence of patterns of endocarditis species specific antigenic bands was measured and correlated with clinical outcome.

RESULTS

Negative serology was found in 28 patients where the diagnosis of endocarditis was rejected or, if proved, staphylococcal, yeast, Gram negative, systemic lupus erythematosus, due to Q fever or Chlamydia psittaci or nonbacterial thrombotic. Positive serology was found in 27 of the 34 patients where the response to antibiotics suggested streptococcal or enterococcal infection. In 22 of these there was objective evidence of endocarditis. Positive serology was also found in three of four further patients with vegetations at necropsy.

CONCLUSION

The identification of patterns of antibody response on immunoblotting can be used to make a specific diagnosis of streptococcal or enterococcal endocarditis in the absence of positive blood cultures.

Identity of streptococcal blood isolates and oral isolates from two patients with infective endocarditis

The purpose of this study was to isolate streptococcal strains from the oral cavities of streptococcal endocarditis patients and compare these strains biochemically and genetically with the corresponding streptococcal blood isolates. Total identity was observed between the blood and oral cavity isolates from the two patients studied.

IgG antibody response in bacterial endocarditis using ELISA with multiple antigens

By means of enzyme-linked immunosorbent assays (ELISAs) the antibody responses were detected in sera from normal persons (n = 275), patients with various types of bacteremia (n = 137), and patients with endocarditis (n = 28). Four ELISAs were evaluated. As antigens ultrasonic extracts of Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, and nonhemolytic streptococci were used. The antibody levels against S. aureus increased with age, while antibodies against the other bacteria showed no age variation. The different ELISA systems showed many serological cross-reactions. The ELISA in this limited material was 72% successful in identifying cases of bacterial endocarditis caused by S. aureus (diagnostic sensitivity 84%; diagnostic specificity 89%), while in other cases of bacterial endocarditis it was less successful.