A 40-year-old woman is evaluated for neck pain that has gradually worsened over the past several months. The patient reports a pulling sensation in her neck that causes difficulty in keeping her head straight. She has had no trauma and has no other medical conditions. Physical examination shows a spastic and thickened sternocleidomastoid muscle causing head tilt. The patient is diagnosed with idiopathic torticollis. She is treated with injections of a bacterial product into the affected muscle, with significant relief of her symptoms. The substance administered to this patient is derived from bacteria that most likely demonstrate which of the following characteristics?

Question

A 40-year-old woman is evaluated for neck pain that has gradually worsened over the past several months.  The patient reports a pulling sensation in her neck that causes difficulty in keeping her head straight.  She has had no trauma and has no other medical conditions.  Physical examination shows a spastic and thickened sternocleidomastoid muscle causing head tilt.  The patient is diagnosed with idiopathic torticollis.  She is treated with injections of a bacterial product into the affected muscle, with significant relief of her symptoms.  The substance administered to this patient is derived from bacteria that most likely demonstrate which of the following characteristics?

Quizplus · Accepted Answer

11ec160b_387b_5248_9249_e9ae811f15dd_MD0001_00 Clostridium botulinum is a gram-positive, anaerobic bacillus that synthesizes botulinum toxin intracellularly and releases it by autolysis. Botulinum toxin prevents the presynaptic release of acetylcholine from the nerve terminal at the neuromuscular junction. This prevents both nicotinic and muscarinic activation, leading to skeletal muscle weakness and reduced glandular secretions, respectively. Botulism is a result of toxin ingestion and is characterized by cranial nerve deficits and descending symmetric paralysis. Spore formation, which occurs in the subterminal location (between the terminal end and center of the bacteria), allows the bacteria to survive adverse conditions (eg, heat, high-oxygen environment). Focal dystonia is a localized, uncontrollable muscle contraction that can lead to pain and physical deformity. Torticollis is a common manifestation of dystonia and is due to involvement of the sternocleidomastoid muscle. Injection of botulinum toxin type B into the dystonic muscle results in muscular relaxation and relief of symptoms. Botulinum toxin can also be used to treat the muscle spasms of multiple sclerosis and Parkinson disease, to relax the lower esophageal sphincter in achalasia, and to reduce the appearance of facial wrinkles. The localized anticholinergic effect also makes it useful in the treatment of hyperhydrosis. The effects are temporary (approximately 3 months), due to the regeneration of the nerve terminal with time. (Choice A) Hypervariable pili are characteristic of Neisseria meningitidis and Neisseria gonorrhoeae; antigenic heterogeneity aids in immune evasion and allows for repeat infections. (Choice B) The antiphagocytic capsule is a primary virulence factor for Streptococcus pneumoniae, Haemophilus influenzae, Klebsiella pneumonia, and Neisseria meningitidis. (Choice C) Staphylococcus aureus has an IgG-binding outer membrane protein-the protein A virulence factor-which binds the Fc portions of IgG, thereby preventing opsonization, phagocytosis, and complement fixation. (Choice D) Intracellular polyphosphate granules are seen on methylene blue staining and are an identifying characteristic of Corynebacterium diphtheriae. (Choice F) Type III secretion systems allow bacteria to inject proteins directly into host cells to avoid invoking an immune response. They are seen in many gram-negative bacteria, including Shigella, Salmonella, Pseudomonas, Yersinia, and enteropathogenic Escherichia coli. Educational objective: Clostridium botulinum is a spore-forming, gram-positive, anaerobic bacillus that synthesizes botulinum toxin, which prevents the presynaptic release of acetylcholine from the nerve terminal at the neuromuscular junction. Botulinum toxin can be used to treat focal dystonia and other disorders of abnormal muscle contraction.

A 40-Year-Old Woman Is Evaluated for Neck Pain That Has