Efficacy of equine botulism antitoxin in botulism poisoning in a guinea pig model.

BACKGROUND: Botulism is a disease caused by neurogenic toxins that block acetylcholine release, resulting in potentially life threatening neuroparalysis. Seven distinct serotypes of botulinum neurotoxins (BoNTs) have been described and are found in nature world-wide. This, combined with ease of production, make BoNTs a significant bioweapon threat. An essential countermeasure to this threat is an antitoxin to remove circulating toxin. An antitoxin, tradename BAT (Botulism Antitoxin Heptavalent (A, B, C, D, E, F, G)-(Equine)), has been developed and its efficacy evaluated against all seven serotypes in guinea pigs. METHODS AND FINDINGS: Studies were conducted to establish the lethal dose and clinical course of intoxication for all seven toxins, and post-exposure prophylactic efficacy of BAT product. Animals were monitored for signs of intoxication and mortality for 14 days. Guinea pig intramuscular LD50s (GPIMLD50) for all BoNTs ranged from 2.0 (serotype C) to 73.2 (serotype E) of mouse intraperitoneal LD50 units. A dose of 4x GPIMLD50 was identified as the appropriate toxin dose for use in subsequent efficacy and post-exposure prophylaxis studies. The main clinical signs observed included hind limb paralysis, weak limb, change in breathing rate/pattern, and forced abdominal respiration. Mean time to onset of clinical signs ranged from 12 hours (serotype E) to 39 hours (serotype G). Twelve hours post-intoxication was selected as the appropriate time point for intervention for all serotypes apart from E where 6 hours was selected because of the rapid onset and progression of clinical signs. Post-exposure treatment with BAT product resulted in a significantly (p<0.0001) higher survival at >0.008 scaled human dose for serotypes A, B, C, F and G, at >0.2x for serotype D and >0.04x for serotype E. CONCLUSIONS: These studies confirm the efficacy of BAT as a post-exposure prophylactic therapy against all seven known BoNT serotypes.

Therapeutic efficacy of equine botulism antitoxin in Rhesus macaques.

BACKGROUND: There are currently no licensed vaccines available for prevention of botulism in humans. The vaccination is not desirable due to expanding therapeutic indications of botulinum toxins. The only available specific treatment for botulism is antitoxin to remove circulating toxin, thus, preventing further neuronal damage. BAT® (Botulism Antitoxin Heptavalent (A, B, C, D, E, F, G)-(Equine)) has been developed and its therapeutic efficacy evaluated against botulinum neurotoxin serotype A (BoNT/A) in Rhesus macaques. METHODS AND FINDINGS: In a post-exposure prophylaxis (PEP) study, animals were exposed to 4x LD50/kg of BoNT/A and administered intravenously with either BAT (1x or 0.1x scaled human dose), or placebo at 4 hours post-exposure. The animals were monitored for 14 days. For the therapeutic intervention studies, animals were exposed to a 1.7x LD50/kg of BoNT/A and treated intravenously with either placebo or BAT at a 1x scaled human dose at the onset of clinical signs. Animals were monitored on an hourly basis for 14 or 21 days. In the PEP study, all animals tolerated equine based antitoxin without any adverse clinical signs. A 100% survival was observed in groups treated with the BAT compared to 0% survival in those treated with the placebo (p<0.001, Fisher's exact test). BAT antitoxin prevented the development of signs of neurotoxicity of botulinum toxin. In a therapeutic study, treatment with the BAT at scaled 1x human dose after the onset of clinical signs significantly enhanced survival compared to the placebo (46.6% vs. 0%, p<0.0001, Fisher's exact test). Additionally, treatment with the BAT delayed the progression of signs (muscular weakness, respiratory distress, oral/nasal discharge) of toxin intoxication and reduced the severity of the disease. CONCLUSIONS: A single dose of BAT, when administered to symptomatic monkeys, resulted in a statistically significant survival benefit compared to the placebo. Additionally, BAT completely protected monkeys from the clinical signs of intoxication and subsequent death when administered as PEP treatment. These data in part supported the licensure of BAT under the Animal Rule in the United States by the Food and Drug Administration.

Evaluation of therapeutic interventions for vaccinia virus keratitis.

BACKGROUND: Vaccinia virus keratitis (VACVK) is a complication of smallpox vaccination that can result in blindness. There are no Food and Drug Administration-approved treatments for VACVK, and vaccinia immunoglobulin (VIG) is contraindicated in isolated VACVK. We used a rabbit model of infection to compare several therapeutic options for VACVK. METHODS: Rabbit eyes were infected with 10(5) plaque-forming units of the Dryvax strain of vaccinia virus and scored daily for 28 days using a modified MacDonald-Shadduck scoring system. Animals were treated for 10 days after the onset of keratitis with albumin, VIG, prednisolone acetate, trifluridine, or combinations thereof. Ocular viral titers and vaccinia-specific antibody titers were determined by plaque assay and enzyme-linked immunosorbent assay, respectively. RESULTS: Treatment with intravenous VIG neither exacerbated nor ameliorated VACVK. Topical prednisolone acetate interfered with viral clearance, and ocular disease rebounded in prednisolone-treated groups. The most effective treatment was topical trifluridine alone. CONCLUSIONS: We conclude that (1) VIG did not negatively affect the treatment of isolated keratitis, (2) topical corticosteroids should not be used for treating VACVK, and (3) treatment with topical trifluridine, with or without intravenous VIG, is the preferred therapeutic regimen for treating VACVK.

Long-term effect of an ethanol/sodium citrate locking solution on the mechanical properties of hemodialysis catheters.

PURPOSE: To investigate the effect of a 30% ethanol/4% sodium citrate catheter locking solution on the mechanical properties of hemodialysis (HD) catheters over 36 weeks. METHODS: Twenty-one HD catheters were used in this study. Three catheters, not exposed to locking solutions, underwent mechanical testing to determine baseline properties. Nine of the remaining 18 catheters were filled with normal saline and underwent mechanical testing in groups of three at 12, 24 and 36 weeks. Similarly, nine catheters were filled with the 30% ethanol/4% sodium citrate locking solution and tested in a similar manner. RESULTS: The average force required to break the catheter lumens tended to be smaller in the catheters exposed to 30% ethanol/4% sodium citrate compared to saline controls at 12 and 24 weeks; however, there were no statistically significant differences between the groups after 36 weeks of exposure. The forces required to break these HD catheters are magnitudes greater than forces generated during a typical HD session. CONCLUSIONS: We conclude that the 30% ethanol/4% sodium citrate locking solution had an effect on the mechanical properties of the catheters investigated, but not to the degree that would preclude further in vivo investigation. Further studies are necessary to determine the safety and efficacy of this catheter locking solution.

Effectiveness of a 30% ethanol/4% trisodium citrate locking solution in preventing biofilm formation by organisms causing haemodialysis catheter-related infections.

OBJECTIVES: Antibiotic locks may be used to prevent haemodialysis catheter-related infections (CRIs). This in vitro study tested the effectiveness of a novel 30% ethanol/4% trisodium citrate lock solution in preventing biofilm formation by the most common pathogens causing haemodialysis CRIs. METHODS: Ten clinical isolates of Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Escherichia coli were tested. Bacterial suspensions of each isolate were prepared in a control solution of normal saline/Mueller-Hinton broth (MHB) and in a lock solution of 30% ethanol/4% trisodium citrate and MHB. The bacterial suspensions were placed into the wells of a Calgary Biofilm Device (CBD) and incubated with fresh solution every 24 h for 72 h. The biofilm formation was assessed by removing the CBD pegs, placing them in normal saline and sonicating them for 5 min. The resulting solution was sampled and the colony counts were determined after 24 h of incubation. RESULTS: All controls demonstrated biofilm growth of between 6 x 10(6) and 7.4 x 10(7) cfu/mL over 72 h. In the 30% ethanol/4% trisodium citrate lock solution, no biofilm growth was observed after 72 h of incubation. These results were consistent among duplicates of all isolates. CONCLUSIONS: The 30% ethanol/4% trisodium citrate lock solution prevented the biofilm formation of all isolates of S. aureus, S. epidermidis, P. aeruginosa and E. coli in vitro. Further studies are necessary to determine its efficacy and safety in the haemodialysis population.