Treatment - Microbial Food Poisoning

Treatment

·      Due to the serious nature of the illness, all cases of botulism must be admitted to hospital and continuous monitoring done with reference to respiratory status (vital capacity, peak expiratory flow rate, negative inspiratory force, pulse oximetry, and gag reflex). The moment signs of bulbar palsy begin to manifest, intubation or tracheostomy may have to be done. Because aspiration pneumonia is a frequent problem in patients with respiratory failure, intubation to protect against aspiration should be considered mandatory. Tracheostomy may be required for long-term ventilatory support. Endotracheal intubation should be performed in all patients with falling inspiratory force (less than 25 cm H₂O) or PO₂ (less than 60 mmHg), rising PCO₂ (greater than 50 mmHg), or vital capacity less than 40% predicted. (Caution: Arterial blood gases may show only minor abnor-malities despite significant ventilatory dysfunction).

·      An attempt should be made to evacuate the GI tract of spores and toxin with the help of activated charcoal, emesis, gastric lavage, or catharsis, if the patient is seen early.

·              Presence of gag reflex must be ascertained. If catharsis is decided upon, sorbitol is the cathartic of choice. Gut decon-tamination is of course not applicable in wound botulism.

·      Botulinum antitoxin: Trivalent botulinum antitoxin (typesA, B, and E) is an equine globulin preparation that is avail-able in the West since the 1960s, but does not appear to be produced in India. The antitoxin is produced by horses immunised against botulinum toxin, and then defibrinated, digested, dialysed, and prepared as a 20% protein antitoxin.

o     Availability: Each 10 ml vial of trivalent botulinumantitoxin contains 7500 IU of type A, 5500 IU of type B, and 8500 IU of type E antitoxins.

o     Dose: 1 vial is administered by slow IV as a 1:10 vol/vol dilution in 0.9% sodium chloride. This dose may be complemented by an IM dose of a single vial given simultaneously. Subsequently, doses are given IV every 2 to 4 hours, depending on the clinical status. In foodborne botulism, additional doses usually are not required. Botulinum antitoxin is not recommended for infant botulism because of its serious side effects and lack of effect on toxin-producing organisms in the gut.

o     Sensitivity testing: Skin or eye tests should be doneprior to administration of the antitoxin or serum, even if the patient has previously received the antitoxin. No testing should be done unless a syringe containing 1 mL of adrenaline solution (1:1000) is immediately available. Death has resulted from some serum/antitoxin skin tests. –– Skin test (in persons with allergic disposition)—0.05 mL of a 1:1000 dilution (in saline), intracutane-ously. Read the reaction in 5 to 30 minutes.

Skin test (in persons with allergic disposition)—0.1 ml of a 1:100 dilution (in saline), intracutaneously.

Read the reaction in 5 to 30 minutes.

Eye test—Except in small children, the eye test is easier to be done, and is more specific. Instil a drop of a 1:10 dilution of antitoxin/serum in physiologic saline in 1 eye; instil a drop of physiologic saline in the other eye as a control. Positive reaction: lacrima-tion and conjunctivitis appears in 10 to 30 minutes in the eye treated with the antitoxin/serum.

Desensitisation is recommended if there is a history of allergy, sensitivity to horse serum, or positive reac-tions in skin/eye tests with antitoxin. The schedule of serial administration of diluted antitoxin/horse serum at 20-minute intervals given subcutaneously {as long as there are no adverse reactions} as recommended by the manufacturer is as follows:

§   0.05 mL of a 1:20 dilution subcutaneous (SC) –– 0.1 ml of a 1:10 dilution SC

§   0.3 ml of a 1:10 dilution SC –– 0.1 ml undiluted serum SC –– 0.2 ml undiluted serum SC –– 0.5 ml undiluted serum SC

§   If a reaction occurs during the desensitisation process, injections should be stopped for one hour, followed by the desensitisation schedule at the last dose which failed to cause a reaction, with 20 minute intervals between each desensitisation dose.

o     Adverse effects: Hypersensitivity reactions, includinganaphylaxis and serum sickness. Since serum sickness reactions are more likely to occur with doses of 40 ml of antitoxin or more, the lowest effective dose is always recommended. Efforts are on in the USA to produce a pentavalent toxoid (types A, B, C, D, E).

·              Guanidine: The use of guanidine is controversial since ithas low efficacy and high incidence of adverse effects. In case it is considered appropriate, the recommended dose is 15 to 40 mg/kg/day orally until EMG improvement occurs at least in the ocular muscles. Respiratory muscles usually do not demonstrate beneficial response. Due to the lack of respiratory improvement, significant nausea and epigastric pain associated with guanidine use, and the lack of a parenteral form, guanidine is considered to be contraindicated by some investigators.

·              Penicillin: It is of no use in foodborne and infant botu- lism, but can be of substantial benefit in wound botulism. Penicillin G is the preferred form.

·              Human-derived botulism immune globulin (BIG) has recently been introduced in the West to treat infant botu- lism. It is a pentavalent (types A, B, C, D, and E) immu- noglobulin harvested by plasmapheresis from donors who have received multiple immunisations with pentavalent botulinum toxoid. The greatest advantage of BIG is that it avoids the use of foreign equine protein, thereby eliminating the risk of hypersensitivity reactions.

·              The neuromuscular blockade antagonist, 4-aminopyridine has been used in addition to regular supportive care and antitoxin therapy. This agent, however, has shown only a transient improvement in reversing peripheral muscle paralysis, and had no effect at all on respiratory muscle. A constant infusion of 4-aminopyridine did allow prolonged reversal of peripheral paralysis in one case, but caused convulsive phenomena following the treatment. Surgical debridement may be necessary for suspected wound botulism. High dose intravenous benzylpenicillin, along with appropriate antitoxin administration, has been used effectively to treat patients with wound botulism.

·              Supportive measures:

o     Nutritional supplementation—oral feeds are contrain-dicated unless there is intact gag reflex.

o      Respiratory support—forms the mainstay of treatment.

o      Antibiotics should only be used to treat complications such as respiratory or urinary tract infections, or wound infections.