Penicillin-resistant subacute bacterial endocarditis treated by a combination of penicillin and streptomycin

Molecular Targets for Antibody-Based Anti-Biofilm Therapy in Infective Endocarditis

Infective endocarditis (IE) is a heart disease caused by the infection of heart valves, majorly caused by Staphilococcus aureus. IE is initiated by bacteria entering the blood circulation in favouring conditions (e.g., during invasive procedures). So far, the conventional antimicrobial strategies based on the usage of antibiotics remain the major intervention for treating IE. Nevertheless, the therapeutic efficacy of antibiotics in IE is limited not only by the bacterial drug resistance, but also by the formation of biofilms, which resist the penetration of antibiotics into bacterial cells. To overcome these drawbacks, the development of anti-biofilm treatments that can expose bacteria and make them more susceptible to the action of antibiotics, therefore resulting in reduced antimicrobial resistance, is urgently required. A series of anti-biofilm strategies have been developed, and this review will focus in particular on the development of anti-biofilm antibodies. Based on the results previously reported in the literature, several potential anti-biofilm targets are discussed, such as bacterial adhesins, biofilm matrix and bacterial toxins, covering their antigenic properties (with the identification of potential promising epitopes), functional mechanisms, as well as the antibodies already developed against these targets and, where feasible, their clinical translation.

Antagonism between bacteriostatic and bactericidal antibiotics is prevalent

Combination therapy is rarely used to counter the evolution of resistance in bacterial infections. Expansion of the use of combination therapy requires knowledge of how drugs interact at inhibitory concentrations. More than 50 years ago, it was noted that, if bactericidal drugs are most potent with actively dividing cells, then the inhibition of growth induced by a bacteriostatic drug should result in an overall reduction of efficacy when the drug is used in combination with a bactericidal drug. Our goal here was to investigate this hypothesis systematically. We first constructed time-kill curves using five different antibiotics at clinically relevant concentrations, and we observed antagonism between bactericidal and bacteriostatic drugs. We extended our investigation by performing a screen of pairwise combinations of 21 different antibiotics at subinhibitory concentrations, and we found that strong antagonistic interactions were enriched significantly among combinations of bacteriostatic and bactericidal drugs. Finally, since our hypothesis relies on phenotypic effects produced by different drug classes, we recreated these experiments in a microfluidic device and performed time-lapse microscopy to directly observe and quantify the growth and division of individual cells with controlled antibiotic concentrations. While our single-cell observations supported the antagonism between bacteriostatic and bactericidal drugs, they revealed an unexpected variety of cellular responses to antagonistic drug combinations, suggesting that multiple mechanisms underlie the interactions.

Role of transthoracic and transesophageal echocardiography in right-sided endocarditis: one echocardiographic modality does not fit all

The added value of transesophageal echocardiography (TEE) over transthoracic echocardiography in the assessment of left-sided infective endocarditis has been extensively validated in the literature. Little research has dealt with the role of echocardiography in right-sided infective endocarditis (RSE), however. In this review, the differences between RSE and left-sided endocarditis and the different types of RSE according to the types of patients who have the disease are described. Both issues have important implications for echocardiographic workup. Moreover, a systematic echocardiographic protocol to avoid missing right-sided vegetations and several specific morphologic aspects of RSE are reviewed. Normal right-sided structures, which may mimic vegetations, particularly when the clinical picture is compatible, are described. Finally, the value of transthoracic echocardiography and TEE in RSE is reviewed according to the publications available. The diagnostic yield of transthoracic echocardiography is comparable with that of TEE in intravenous drug users. On the contrary, TEE is mandatory in patients with cardiac devices. A Bayesian-based diagnostic approach is proposed for a third poorly characterized group of patients with RSE who are not drug addicts, have no cardiac devices, and have no left-sided endocarditis (the "three no's" endocarditis group).

Management of infective endocarditis: challenges and perspectives

Despite improvements in medical and surgical therapies, infective endocarditis is associated with poor prognosis and remains a therapeutic challenge. Many factors affect the outcome of this serious disease, including virulence of the microorganism, characteristics of the patients, presence of underlying disease, delays in diagnosis and treatment, surgical indications, and timing of surgery. We review the strengths and limitations of present therapeutic strategies and propose future directions for better management of endocarditis according to the most recent research. Novel perspectives on the management of endocarditis are emerging and offer hope for decreasing the rate of residual deaths by accelerating the process of diagnosis and risk stratification, reducing delays in starting antimicrobial therapy, rapid transfer of high-risk patients to specialised medico-surgical centres, development of new surgical methods, and close long-term follow-up.

Methods of testing combined antibiotic bactericidal action and the significance of the results

A DESCRIPTION IS GIVEN OF TWO METHODS OF MEASURING COMBINED ANTIBIOTIC BACTERICIDAL ACTION: a test in liquid medium with subculture and the cellophane transfer method. It is emphasized that information so obtained is necessary in order to predict the effect of combined treatment, particularly in bacterial endocarditis due to organisms not fully sensitive to penicillin. Eight case histories are given, in all of which such a prediction was fulfilled, one of failure and seven of success from the use of five different combinations. The cellophane transfer method was applied to the study of the nature of combined antibiotic action on multiple strains of several bacterial species. The results were rarely uniform for any given combination and species: the necessity for individual tests as a guide to treatment is thus confirmed.Modifications of the theory of combined action formulated by Jawetz are proposed.

Therapy of enterococcal infections

Because enterococci are typically tolerant of the bactericidal effects of cell wall-active antimicrobial agents, bactericidal therapy has required use of these agents in combination with aminoglycosides. For strains which do not demonstrate high-level aminoglycoside resistance, either streptomycin or gentamicin can be used in combination with penicillin, ampicillin or vancomycin. At some centers, as many as 50% of isolates display high-level gentamicin resistance. A minority of such isolates will not be highly streptomycin-resistant, and the latter drug can be used in combination with a cell wall-active drug. Optimal treatment of serious infections due to strains highly resistant to both streptomycin and gentamicin is unknown. While no agent is predictably bactericidal against such isolates, ampicillin, penicillin or vancomycin alone would be expected to cure some patients. Other drugs or drug combinations do not offer any predictable therapeutic advantages.

Antibiotic combinations: should they be tested?

When antibiotic combinations are used to provide a broader spectrum of antimicrobial activity or in an attempt to prevent the emergence of resistant organisms, it is rarely necessary or practical to perform tests of drug interactions in vitro. In vitro testing of combinations may be useful when combinations are used in an attempt to attain synergistic interactions. In some cases, screening methods can be used as substitutes for formal synergy testing. This paper examines the mechanisms of antibiotic interaction leading to synergism or antagonism, surveys attempts to correlate in vitro observations with efficacy in animal models, and reviews clinical data providing evidence for or against a useful role of synergistic antibiotic interactions in the treatment of human infections.

Chemotherapy of experimental streptococcal endocarditis. I. Comparison of commonly recommended prophylactic regimens

The effectiveness of various antibiotics commonly recommended for the prophylaxis of bacterial endocarditis has been evaluated in experimental streptococcal endocarditis in rabbits. High doses of penicillin G did not prevent the development of this infection. The only consistently successful prophylactic regimens using penicillin alone were those which provided for both an early high serum level and more than 9 h of effective antimicrobial action. Vancomycin was the only other drug which proved uniformly successful when given alone, even though the duration of its antimicrobial action in the blood was only 3 h. However, combined therapy using penicillin G or ampicillin with streptomycin was always effective in prophylaxis. Treatment with single injections of ampicillin, cephaloridine, cephalexin, clindamycin, cotrimoxazole, rifampicin, streptomycin, erythromycin, and tetracycline failed to prevent infection. The findings provide information on the effect of antimicrobials in vivo and may be applicable to the chemoprophylaxis of infective endocarditis in clinical practice.

Present position of the chemotherapy of bacterial infections

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Combined agar diffusion and replica plating techniques in the study of antibacterial substances

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Antibiotic therapy of bacterial endocarditis. IV. Successful short-term (two weeks) combined penicillin-dihydrostreptomycin therapy in subacute bacterial endocarditis caused by penicillin-sensitive streptococci

Twenty-three patients with endocarditis caused by penicillin-sensitive streptococci have received short-term treatment with penicillin and dihydrostreptomycin, combined, for two weeks. Five of the patients died from complications of their infection; 18 were living and well, at the time of this study, after an average follow-up period of more than one year. No failures in treatment or relapses have occurred. It is concluded from the study of these patients that 1,000,000 units of aqueous procaine penicillin-G and 1 Gm. of dihydrostreptomycin sulfate given intramuscularly every 12 hours for two weeks is curative for this type of endocarditis.

The treatment of some bacterial infections of the heart and pericardium

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