Efficacy of temafloxacin in experimental Streptococcus adjacens endocarditis and autoradiographic diffusion pattern of [14C]temafloxacin in cardiac vegetations

Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications: A Scientific Statement for Healthcare Professionals From the American Heart Association

BACKGROUND

Infective endocarditis is a potentially lethal disease that has undergone major changes in both host and pathogen. The epidemiology of infective endocarditis has become more complex with today's myriad healthcare-associated factors that predispose to infection. Moreover, changes in pathogen prevalence, in particular a more common staphylococcal origin, have affected outcomes, which have not improved despite medical and surgical advances.

METHODS AND RESULTS

This statement updates the 2005 iteration, both of which were developed by the American Heart Association under the auspices of the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, Council on Cardiovascular Disease of the Young. It includes an evidence-based system for diagnostic and treatment recommendations used by the American College of Cardiology and the American Heart Association for treatment recommendations.

CONCLUSIONS

Infective endocarditis is a complex disease, and patients with this disease generally require management by a team of physicians and allied health providers with a variety of areas of expertise. The recommendations provided in this document are intended to assist in the management of this uncommon but potentially deadly infection. The clinical variability and complexity in infective endocarditis, however, dictate that these recommendations be used to support and not supplant decisions in individual patient management.

Clinafloxacin for the Treatment of Bacterial Endocarditis

We report the results of a prospective, multicenter trial assessing intravenous and oral clinafloxacin treatment for infective endocarditis. Sixty-six patients constituted the final study population. Among the 53 patients with native valve infection, Staphylococcus aureus and Streptococcus viridans were the most common pathogens. Twelve patients with native valve infection required surgery, at which time all valve tissue culture results were negative. The overall success rate for native valve infection was 87%. Single valves were involved in 11 of 13 patients with prosthetic valve endocarditis (PVE), and multiple valves were involved in 2 cases. Enterococcus faecalis was the most common pathogen, causing 4 of the PVE cases. The overall success rate for treatment of PVE was 69%. Patients with PVE who did not respond to treatment presented with complications that predict poor prognosis. Clinafloxacin may be effective for both native and PVE, but further studies are indicated.

Comparative killing kinetics of the novel des-fluoro(6) quinolone BMS-284756, fluoroquinolones, vancomycin and beta-lactams

The primary bactericidal classes used therapeutically as single agents, are the quinolones and the cell-wall active agents. In this study, their rates of killing were compared. The des-fluoro(6) quinolone BMS-284756 (T-3811ME), fluoroquinolones (trovafloxacin, levofloxacin) and cell wall-active agents (beta-lactams, vancomycin) were evaluated against Enterobacteriaceae, Staphylococcus aureus, streptococci, and Enterococcus faecalis. Time-kill analysis was done at 10x the MIC, using Mueller-Hinton broth (supplemented with 7% lysed horse blood for Streptococcus pneumoniae and the viridans streptococci), or Brain Heart Infusion broth for beta-haemolytic streptococci. Using a 3-log(10) decrease in viable count as an index of bactericidal activity, BMS-284756 and the fluoroquinolones killed Enterobacteriaceae rapidly, requiring < 2 h versus > or =6 h for beta-lactams. The staphylococcal cell counts generally decreased more rapidly with quinolone exposure, compared with those treated with vancomycin or the beta-lactams. The antimicrobial agents killed streptococci and enterococci more slowly, requiring > 6 h to decrease the viable count by 99.9%. In summary, BMS-284756 killing rates are similar to those of recent fluoroquinolones and are bacterial group-dependent. Overall, the quinolones are more rapidly bactericidal than vancomycin and the beta-lactam antibiotics.

Comparative killing rates of fluoroquinolones and cell wall-active agents

Killing rates of fluoroquinolones, beta-lactams, and vancomycin were compared against Enterobacteriaceae, Staphylococcus aureus, pneumococci, streptococci, and Enterococcus faecalis. The times required for fluoroquinolones to decrease viability by 3 log(10) were 1.5 h for Enterobacteriaceae, 4 to 6 h for staphylococci, and >/=6 h for streptococci and enterococci. Thus, the rate of killing by fluoroquinolones is organism group dependent; overall, they killed more rapidly than beta-lactams and vancomycin.

Endocardiac infectivity and binding to extracellular matrix proteins of oral Abiotrophia species

Microorganisms of the genus Abiotrophia, formerly known as nutritionally variant streptococci, are members of the oral flora and often isolated from patients with endocarditis, but pathogenicity of oral Abiotrophia species has not been examined yet. In this study, 17 strains isolated from healthy human oral cavities and 7 reference strains (all derived from patients with endocarditis) of Abiotrophia spp. were tested for their abilities to cause infections in damaged heart tissues in catheterized rats and to adhere to extracellular matrix proteins in vitro. The reference strains of A. defectiva and A. adiacens showed high infectivities in the rats. Four oral isolates of these two species showed similarly high infectivities and three had moderate infectivities. Most of 10 oral strains of A. para-adiacens and A. elegans were found to be generally less infective. The highly infective A. adiacens strains showed markedly high fibronectin-binding capacity, suggesting a possible relationship between the fibronectin-binding capacity and damaged heart tissue infectivity of the Abiotrophia species. A. defectiva strains which were also highly infective had moderate levels of binding to fibronectin and other extracellular matrix proteins. Most of A. para-adiacens and A. elegans strains showed low or negligible binding capacities to any extracellular matrix proteins tested.

Efficacy of sparfloxacin and autoradiographic diffusion pattern of [14C]Sparfloxacin in experimental Staphylococcus aureus joint prosthesis infection

Using a new rabbit model of methicillin-susceptible Staphylococcus aureus knee prosthesis infection, we compared the efficacies of sparfloxacin (50 mg/kg of body weight subcutaneously, twice a day) and pefloxacin (50 mg/kg subcutaneously, twice a day). A partial knee replacement was performed with a silicone implant fitted into the intramedullary canal of the tibia, and 5 x 10(7) CFU of methicillin-susceptible S. aureus was injected into the knee. The 7-day treatment regimen was started 15 days later. The MICs and MBCs of sparfloxacin and pefloxacin were, respectively, 0.06 and 0.25 microgram/ml (MIC) and 0.25 and 1 microgram/ml (MBC). The peak levels of sparfloxacin and pefloxacin in serum were 3.6 and 21 micrograms/ml, respectively. Three weeks after the end of treatment, animals were sacrificed and tibias were removed, pulverized, and quantitatively cultured. In contrast to pefloxacin (3.61 +/- 1.64 log10 CFU/g of bone), sparfloxacin significantly reduced the bacterial density (2.12 +/- 1.1 log10 CFU/g of bone) (P = 0.01) in comparison with the level in controls (4.59 +/- 1.21 log10 CFU/g of bone), without selection of resistant variants. Sparfloxacin was significantly more effective than pefloxacin (P = 0.025). The autoradiographic pattern of [14C]sparfloxacin diffusion was studied in noninfected animals with prostheses and in infected animals 15 days after inoculation. Sixty minutes after completion of infusion of 250 microCi of [14C]sparfloxacin, in infected animals the highest levels of radioactivity were detected around the prosthesis, in femoral cartilage, and in articular ligaments. Radioactivity was slightly less intense in bone marrow and muscles and was very weak in compact bone. The distribution of sparfloxacin in uninfected rabbits was similar. Thus, sparfloxacin may represent a valid alternative therapy in these infections provided that it is carefully monitored for potential side effects.

Dextranase enhances antibiotic efficacy in experimental viridans streptococcal endocarditis

In endocarditis, exopolysaccharide production by viridans streptococci has been associated with delayed antimicrobial efficacy in cardiac vegetations. We compared the efficacies of temafloxacin alone and in combination with dextranase, an enzyme capable of hydrolyzing 20 to 90% of the bacterial glycocalyx, in a rabbit model of endocarditis. In in vivo experiments, rabbits were infected intravenously with 10(8) Streptococcus sanguis organisms and were treated 6 days later with temafloxacin (50 mg/kg of body weight intramuscularly twice a day) alone or combined with dextranase (1,000 U per rabbit per day intravenously). After 4 days of treatment (day 11), the animals were sacrificed and vegetations were quantitatively cultured. For ex vivo experiments, rabbits were infected as stated above and, on day 11, vegetations were excised aseptically and incubated in vitro in rabbit serum alone (control) or with temafloxacin or temafloxacin plus dextranase at concentrations similar to peak levels in plasma. In vitro, dextranase alone had no antimicrobial effect. In vivo and ex vivo, temafloxacin combined with dextranase was more effective than temafloxacin alone (P < 0.05). Our results suggest that dextranase is able to increase the effects of temafloxacin by reducing the amount of bacterial glycocalyx in infected vegetations, as confirmed in vitro by electron microscopy showing a markedly reduced amount of glycocalyx and a more clearly visible fibrin matrix.