Sensitivity of mouse bioassay in clinical wound botulism

Outbreak of foodborne botulism in Alexandria, Egypt: modulating indications for administration of heptavalent botulinum antitoxin

In October 2019, ninety-four patients were admitted into Alexandria Poison Center (APC) with a history of ingestion of Feseekh (salted fish). In an attempt to allocate the resources, not all patients were given HBAT (botulism antitoxin heptavalent (A, B, C, D, E, F, G) equine immediately. The current study aimed to portray the clinical characteristics of the cases, explore the possible relation between these characteristics and necessity of HBAT administration, explore the reliability of mouse lethal test, and establish a clinical guide for management including preservation of resources. The current prospective study included 94 patients who were admitted to Alexandria Poison Center (APC) in the period from the 29^th of September to the 27^th of October 2019. The patients' data were recorded using a checklist that includes: personal data, past medical history, clinical assessment, investigations, treatment, and the outcome. The checklist was carried out to assess and follow up each patient. Hospitalized patients were categorized according to symptoms consistent with botulism. The equine HBAT, made by Emergent BioSolutions Canada Inc. (formerly Cangene Corporation), was used in the treatment. HBAT was given to thirty-four patients (36.2%) only out of the total admission. However, eighty-two (87.2%) of patients were completely cured, whereas ten patients (10.6%) were discharged with mild neurological sequels and death occurred only in two cases (2.2%). Sixty cases (63.8%) with suspected foodborne botulism could be managed by supportive treatment only with no need for HBAT, while patients with evident neurological signs received HBAT immediately.

Infections of the Peripheral Nervous System

PURPOSE OF REVIEW

This article describes infections that affect the peripheral nervous system, including their clinical features, differential diagnoses, and treatments.

RECENT FINDINGS

Rates of pyomyositis have increased recently in the United States, possibly because of an increase in risk factors such as IV drug use, obesity, and diabetes. Other peripheral nervous system infections, such as diphtheria, have become more common in older patients secondary to a lack of revaccination or waning immunity. Although recommended treatment regimens for most infections remain unchanged over recent years, debate over the ideal dosing and route of administration continues for some infections such as tetanus and leprosy (Hansen disease).

SUMMARY

Infections of the peripheral nervous system are varied in terms of the type of infection, localization, and potential treatment. Nerve conduction studies and EMG can help determine localization, which is key to determining an initial differential diagnosis. It is important to recognize infections quickly to minimize diagnostic delays that could lead to patient morbidity and mortality.

Safety and Clinical Outcomes of an Equine-derived Heptavalent Botulinum Antitoxin Treatment for Confirmed or Suspected Botulism in the United States

BACKGROUND

Botulism is a rare, life-threatening paralytic illness. Botulism Antitoxin Heptavalent (A,B,C,D,E,F,G)-(Equine) (BAT) manufactured by Emergent BioSolutions Canada Inc is an equine-derived heptavalent botulinum antitoxin product indicated for the treatment of symptomatic botulism following documented or suspected exposure to botulinum neurotoxin serotypes A-G in adults and pediatric patients. BAT product was US-licensed in 2013.

METHODS

In the United States, from October 2014 through July 2017, safety and clinical outcomes data were collected under a registry for patients treated with BAT product.

RESULTS

Registry patients had a median age of 51 years (range, 32 days to 92 years). Among 162 patients, 7 (4.3%) experienced BAT product-related serious adverse events, including 1 (0.6%) report each of pneumonia, pneumonia aspiration, ventricular tachycardia, upper gastrointestinal hemorrhage, anaphylactic reaction, acute kidney injury, and acute myocardial infarction. Thirty-one (19.1%) patients had 41 BAT product-related adverse events. Six (3.7%) deaths were reported in the registry. All deaths were attributed to the underlying illness and were assessed as unlikely related to BAT product. Among 113 (69.8%) patients with a final diagnosis of botulism, those treated early (≤2 days) spent fewer days in the hospital (5 vs 15.5 days), in the intensive care unit (ICU) (4 vs 12 days), and on mechanical ventilation (6 vs 14.5 days) than those treated late (>2 days), respectively.

CONCLUSIONS

BAT product was well tolerated in patients. Treatment with BAT product at ≤2 days of symptom onset was associated with shorter hospital and ICU stays, and shorter duration and need for mechanical ventilation, showing clinical benefit associated with early treatment.

Toxemia in Human Naturally Acquired Botulism

Human botulism is a severe disease characterized by flaccid paralysis and inhibition of certain gland secretions, notably salivary secretions, caused by inhibition of neurotransmitter release. Naturally acquired botulism occurs in three main forms: food-borne botulism by ingestion of preformed botulinum neurotoxin (BoNT) in food, botulism by intestinal colonization (infant botulism and intestinal toxemia botulism in infants above one year and adults), and wound botulism. A rapid laboratory confirmation of botulism is required for the appropriate management of patients. Detection of BoNT in the patient's sera is the most direct way to address the diagnosis of botulism. Based on previous published reports, botulinum toxemia was identified in about 70% of food-borne and wound botulism cases, and only in about 28% of infant botulism cases, in which the diagnosis is mainly confirmed from stool sample investigation. The presence of BoNT in serum depends on the BoNT amount ingested with contaminated food or produced locally in the intestine or wound, and the timeframe between serum sampling and disease onset. BoNT levels in patient's sera are most frequently low, requiring a highly sensitive method of detection. Mouse bioassay is still the most used method of botulism identification from serum samples. However, in vitro methods based on BoNT endopeptidase activity with detection by mass spectrometry or immunoassay have been developed and depending on BoNT type, are more sensitive than the mouse bioassay. These new assays show high specificity for individual BoNT types and allow more accurate differentiation between positive toxin sera from botulism and autoimmune neuropathy patients.

Critical Analysis of Neuronal Cell and the Mouse Bioassay for Detection of Botulinum Neurotoxins

Botulinum Neurotoxins (BoNTs) are a large protein family that includes the most potent neurotoxins known to humankind. BoNTs delivered locally in humans at low doses are widely used pharmaceuticals. Reliable and quantitative detection of BoNTs is of paramount importance for the clinical diagnosis of botulism, basic research, drug development, potency determination, and detection in clinical, environmental, and food samples. Ideally, a definitive assay for BoNT should reflect the activity of each of the four steps in nerve intoxication. The in vivo mouse bioassay (MBA) is the ‘gold standard’ for the detection of BoNTs. The MBA is sensitive, robust, semi-quantitative, and reliable within its sensitivity limits. Potential drawbacks with the MBA include assay-to-assay potency variations, especially between laboratories, and false positives or negatives. These limitations can be largely avoided by careful planning and performance. Another detection method that has gained importance in recent years for research and potency determination of pharmaceutical BoNTs is cell-based assays, as these assays can be highly sensitive, quantitative, human-specific, and detect fully functional holotoxins at physiologically relevant concentrations. A myriad of other in vitro BoNT detection methods exist. This review focuses on critical factors and assay limitations of the mouse bioassay and cell-based assays for BoNT detection.

Safety and Improved Clinical Outcomes in Patients Treated With New Equine-Derived Heptavalent Botulinum Antitoxin

Background

Botulism is a rare, life-threatening paralytic illness. Equine-derived heptavalent botulinum antitoxin (HBAT), the only currently available treatment for noninfant botulism in the United States, was licensed in 2013. No reports have systematically examined safety and clinical benefit of HBAT among botulism patients.

Methods

From March 2010 through March 2013, we collected data prospectively and through medical record reviews of patients with confirmed or suspected botulism who were treated with HBAT under an expanded-access Investigational New Drug program.

Results

Among 249 HBAT-treated patients, 1 (<1%) child experienced an HBAT-related serious adverse event (hemodynamic instability characterized by bradycardia, tachycardia, and asystole); 22 (9%) patients experienced 38 nonserious adverse events reported by physicians to be HBAT related. Twelve (5%) deaths occurred; all were determined to be likely unrelated to HBAT. Among 104 (42%) patients with confirmed botulism, those treated early (≤2 days) spent fewer days in the hospital (median, 15 vs 25 days; P < .01) and intensive care (10 vs 17 days; P = .04) than those treated later. Improvements in any botulism sign/symptom were detected a median of 2.4 days and in muscle strength a median of 4.8 days after HBAT.

Conclusions

HBAT was safe and provided clinical benefit in treated patients. HBAT administration within 2 days of symptom onset was associated with shorter hospital and intensive care stays. These results highlight the importance of maintaining clinical suspicion for botulism among patients presenting with paralytic illness to facilitate early HBAT treatment before laboratory confirmation might be available. Clinical consultation and, if indicated, HBAT release, are available to clinicians 24/7 through their state health department in conjunction with CDC.

Unilateral Botulinum Neurotoxin-A Injection into the Striatum of C57BL/6 Mice Leads to a Different Motor Behavior Compared with Rats

Different morphological changes in the caudate-putamen (CPu) of naïve rats and mice were observed after intrastriatal botulinum neurotoxin-A (BoNT-A) injection. For this purpose we here studied various motor behaviors in mice (n = 46) longitudinally up to 9 months after intrastriatal BoNT-A administration as previously reported for rats, and compared both outcomes. Apomorphine- and amphetamine-induced rotational behavior, spontaneous motor behavior, as well as lateralized neglect were studied in mice after the injection of single doses of BoNT-A into the right CPu, comparing them with sham-injected animals. Unilateral intrastriatal injection of BoNT-A in mice induced significantly increased contralateral apomorphine-induced rotations for 1 to 3 months, as well as significantly increased contralateral amphetamine-induced rotations 1 to 9 months after injection. In rats (n = 28), unilateral BoNT-A injection also induced significantly increased contralateral apomorphine-induced rotations 3 months after injection, but did not provoke amphetamine-induced rotations at all. Lateralized sensorimotor integration, forelimb preference, and forelimb stepping were significantly impaired on the left side. The differences in motor behaviors between rats and mice may be caused by different BoNT-A effects on cholinergic and catecholaminergic fibers in rat and mouse striata, interspecies differences in striatal receptor densities, and different connectomes of the basal ganglia.

Cranial Neuropathies and Neuromuscular Weakness: A Case of Mistaken Identity

We describe a case of wound botulism initially thought to represent Miller-Fisher variant Guillain-Barré syndrome (MFS). Botulism classically presents with the so-called “four D’s” (diplopia, dysarthria, dysphagia, dry mouth) with symmetric, descending weakness. MFS presents with a triad of limb-ataxia, areflexia, and ophthalmoplegia, with variable cranial nerve and extremity involvement. The distinction can be difficult but is important as early initiation of botulinum antitoxin is associated with improved patient outcomes in cases of botulism. Furthermore, it is important to recognize intravenous drug use as a risk factor in the development of botulism, especially given an increase in injection drug use.

A Case of a 34-Year-Old Female with Acute Hypoxemic Respiratory Failure and Proximal Muscle Weakness

Wound associated botulism is an unusual presentation. Early detection of this potentially life-threatening illness can significantly shorten length of hospital stay and improve prognosis. We present a case of a 34-year-old female with a history of heroin abuse who presented to the ED with acute respiratory failure, diplopia, and proximal muscle weakness. There was early concern for wound botulism as the instigating process. After discussion with the CDC, she was given equine serum heptavalent botulism antitoxin. Laboratory analysis later confirmed our suspicion. Symptoms improved and the patient was liberated from mechanical ventilation on day 14 and discharged from the hospital on day 23.

Accuracy of a Mouse Bioassay for the Diagnosis of Botulism in Horses

Background

The laboratory diagnosis of botulism in horses traditionally has relied upon the mouse bioassay (MBA). The accuracy of this test for the diagnosis of botulism in horses is unknown.

Hypothesis/Objectives

Our goal was to determine the sensitivity, specificity, positive predictive value, and negative predictive value of the MBA on laboratory‐processed fecal and gastrointestinal samples for foals and adult horses.

Animals

Cases included all horses with a final clinical diagnosis of botulism that were admitted between 1986 and 2011 and had MBA testing performed. Controls included horses without botulism that were admitted during the same time period and had MBA testing performed.

Methods

Retrospective study. Horses suspected of having botulism had fecal or (less commonly) gastrointestinal content samples tested using MBA. For every hospitalized botulism suspect, control samples were obtained from ≥1 additional hospitalized horses not suspected to have botulism.

Results

One hundred and twenty‐nine adult horses and 253 adult controls were identified. Overall sensitivity of the MBA was only 32% but specificity was 97%. Forty‐three foal cases and 21 foal controls were evaluated; sensitivity of the MBA was 53% and specificity was 100%. Positive predictive value was substantially higher (100% for foals and 89% for adults) than negative predictive value (51% for foals and 67% for adults).

Conclusions and Clinical Importance

Mouse bioassay has low sensitivity but high specificity for the diagnosis of botulism in horses. Positive results are highly suggestive of botulism but negative results do not exclude the diagnosis. Unaffected horses and foals rarely shed C. botulinum in their feces.

View from the front lines: an emergency medicine perspective on clostridial infections in injection drug users

Injection drug use (IDU), specifically non-intravenous "skin-popping" of heroin, seems to provide optimal conditions for Clostridial infection and toxin production. IDU is therefore a major risk factor for wound botulism and Clostridial necrotizing soft tissue infections (NSTI) and continues to be linked to cases of tetanus. Case clusters of all 3 diseases have occurred among IDUs in Western U.S. and Europe. Medical personnel who care for the IDU population must be thoroughly familiar with the clinical presentation and management of these diseases. Wound botulism presents with bulbar symptoms and signs that are easily overlooked; rapid acquisition and administration of antitoxin can prevent neuromuscular respiratory failure. In addition to Clostridium perfringens, IDU-related NSTIs can be caused by Clostridium sordellii and Clostridium novyi, which may share a distinct clinical presentation. Early definitive NSTI management, which decreases mortality, requires a low index of suspicion on the part of emergency physicians and low threshold for surgical exploration and debridement on the part of the surgeon. Tetanus should be preventable in the IDU population through careful attention to vaccination status.

Methods and difficulties in detection of Clostridium botulinum and its toxins

The aim of this work was to present selected data regarding traditional and modern methods for C. botulinum and its toxins detection. In this article, methods based on culturing techniques, mouse bioassay, immunological techniques, chromatography and PCR, PFGE, RFLP, AFLP are described. The mentioned techniques were evaluated considering their usefulness in the samples examination, genotyping of strains and the diagnostics of botulism.

Use of a new functional dual coating (FDC) assay to measure low toxin levels in serum and food samples following an outbreak of human botulism

Clostridium botulinum type A toxin is the most prevalent cause of naturally occurring outbreaks of human botulism in the world. The active dichain neurotoxin molecule is composed of a heavy chain (H-chain) of ~100 kDa with the carboxy-terminal end consisting of a receptor-binding (HC) domain, while the amino-terminal (HN) domain is linked by a critical disulfide bond to a light chain (L-chain) of ~50 kDa. Although the mouse bioassay (MBA) is traditionally used to confirm the presence of toxin in serum or food, its sensitivity is insufficient to detect low toxin levels in approximately 30 to 60 % of botulism patients. A novel FDC (functional dual coating) microtitre plate immuno-biochemical assay, which quantifies botulinum toxicity by measuring the HC domain linked with L-chain endopeptidase activity, was modified to allow human serum (lysed or unlysed) to be tested without interference from the matrix, with toxin detection down to 0.03 mouse LD50 per ml serum or 0.13 pg ml–1 using just 100 µl of clinical samples. The assay was specific for type A toxin and could additionally be applied to whole blood and food samples. Low levels of 1 to 2 mouse LD50 per ml serum of type A toxin were quantified for the first time using the modified FDC assay in two severely intoxicated UK patients who required mechanical ventilation and antitoxin. Toxin levels in recovered food sample extracts were also detected and one MBA-negative sample was found to contain 0.32 LD50 per ml extract. The FDC assay provides a real alternative for public health laboratories to unambiguously confirm all cases of type A botulism and, due to its sensitivity, a promising new tool in toxin pharmacokinetic studies.

Acute neuromuscular weakness in a boy with a facial abscess contaminated with Clostridium botulinum

Wound botulism arising from skin and soft tissue infection is rare in children, most cases being reported in adult intravenous drug users. Cranial nerve palsies are the primary presenting sign, followed by descending neuromuscular weakness. Diagnosis relies on isolation of either toxigenic Clostridium botulinum species or toxin from wound or blood samples. We present an unusual case of wound botulism in a pediatric patient with the intent to inform the reader and improve the time to diagnosis in such cases.

Neurotoxin gene profiling of clostridium botulinum types C and D native to different countries within Europe

Clostridium botulinum types C and D, as well as their mosaic variants C-D and D-C, are associated with avian and mammalian botulism. This study reports on the development of low-density macroarrays based on the GeneDisc cycler platform (Pall-GeneDisc Technologies) applied to the simultaneous detection of the C. botulinum subtypes C, C-D, D, and D-C. The limit of detection of the PCR assays was 38 fg of total DNA, corresponding to 15 genome copies. Artificially contaminated samples of cecum showed a limit of detection below 50 spores/g. The tests were performed with a large variety of bacterial strains, including C. botulinum types C (n = 12), C-D (n = 29), D (n = 5), and D-C (n = 10), other botulinum neurotoxin (BoNT)-producing Clostridium strains (n = 20), non-BoNT-producing clostridia (n = 20), and other bacterial species (n = 23), and showed a high specificity. These PCR assays were compared to previously published real-time PCRs for the detection of C. botulinum in 292 samples collected from cases of botulism events in four European regions. The majority of the samples originated from wild birds (n = 108), poultry (n = 60), and bovines (n = 56). Among the 292 samples, 144 were positive for either the bont/C-D or the bont/D-C gene by using the GeneDisc arrays. The reliability of the results tallied to 97.94%. Interestingly, only BoNT mosaics, types C-D and D-C, were found in naturally contaminated samples whatever their animal origin and their geographical location. Further investigations should now be performed in order to check that mosaic types dominate in Europe and that acquisition of mosaic types helps in survival or adaptation to particular niche.

Recurrent wound botulism among injection drug users in California

BACKGROUND

Botulism is an acute neurologic illness characterized by cranial nerve palsies and descending flaccid paralysis. Botulism is a rare disease and recurrent botulism even more rare. We review cases of recurrent wound botulism (WB) among injection drug users (IDUs) in California from 1993 through 2006 and describe 2 case patients.

METHODS

From botulism surveillance data for 1993-2006, we identified patients with >1 episode of clinical WB, defined as acute descending paralysis with a visible wound or recent history of injection drug use. For each patient, ≥1 of their WB episodes was laboratory confirmed. We extracted demographic, clinical, and laboratory information from case and laboratory reports and compared clinical characteristic frequency of initial and second WB episodes.

RESULTS

During 1993-2006, 17 IDUs had recurrent WB, 14 with 1 recurrence and 3 with 2 recurrences. Of 25 laboratory-confirmed episodes, 22 were confirmed through serum testing and 3 through wound testing. Patients were 32-61 years old, and 94% were male. All patients reported heroin injections; 88% specified black tar heroin use and 76% reported subcutaneous injection. The most common presentations were having a visible wound, speech difficulty, double vision, respiratory difficulty, and trouble swallowing. There were no significant differences in clinical presentation between initial and second episodes.

CONCLUSIONS

As the California epidemic of WB among IDUs continues, WB episodes are recurring. Both clinicians and IDUs should be aware of the potential for WB to recur among IDUs to enable timely diagnosis and early botulinum antitoxin administration and supportive care.