A 64-year-old man comes to the emergency department due to 2 days of abrupt-onset fever, malaise, and myalgia. He has also had nasal discharge, sore throat, and a nonproductive cough. The patient has a history of hypertension and chronic obstructive pulmonary disease. He is a former smoker but does not use alcohol or illicit drugs. Temperature is 38.3 C (101 F), blood pressure is 130/70 mm Hg, pulse is 96/min, and respirations are 18/min. Physical examination shows watery nasal discharge, pharyngeal erythema, and clear lungs on auscultation. Droplet precautions are immediately instituted to prevent spread of the infection. Hand hygiene with an alcohol-based disinfectant following patient contact is also initiated. This patient's infecting pathogen is likely susceptible to the disinfectant due to the presence of which of the following characteristics?

Question

A 64-year-old man comes to the emergency department due to 2 days of abrupt-onset fever, malaise, and myalgia.  He has also had nasal discharge, sore throat, and a nonproductive cough.  The patient has a history of hypertension and chronic obstructive pulmonary disease.  He is a former smoker but does not use alcohol or illicit drugs.  Temperature is 38.3 C (101 F), blood pressure is 130/70 mm Hg, pulse is 96/min, and respirations are 18/min.  Physical examination shows watery nasal discharge, pharyngeal erythema, and clear lungs on auscultation.  Droplet precautions are immediately instituted to prevent spread of the infection.  Hand hygiene with an alcohol-based disinfectant following patient contact is also initiated.  This patient's infecting pathogen is likely susceptible to the disinfectant due to the presence of which of the following characteristics?

Quizplus · Accepted Answer

Although both influenza and the common cold can be associated with upper respiratory symptoms (eg, rhinorrhea, cough, sore throat), influenza can often be differentiated based on the abrupt onset of symptoms and the presence of nonspecific, systemic manifestations (eg, fever, malaise, myalgias, headache). The influenza virus is an enveloped orthomyxovirus with a segmented, negative-sense, single-stranded RNA genome. Transmission occurs via contaminated, large-particle droplets. Therefore, patients who are hospitalized with influenza generally require droplet precautions (mask and gown for health care providers), and close contacts should be advised to practice appropriate hand hygiene. Alcohol-based disinfectants, which are composed of ethyl or isopropyl alcohol (at concentrations of 60%-90%) in water, are often used for hand hygiene. These solutions kill vegetative bacteria (but not spores), fungus, and enveloped viruses (eg, influenza, HIV, herpes) by dissolving their lipid bilayer membranes and subsequently denaturing their proteins. Nonenveloped viruses such as adenovirus, rhinovirus, enterovirus, and poliovirus are less susceptible to some alcohol-based disinfectants (particularly isopropyl-based solutions) because they do not have a lipid bilayer envelope. (Choice B) Proteins (and spores) are sterilized by moist heat (eg, autoclave), which results in protein denaturation. Although proteins are somewhat susceptible to alcohol-based disinfectants, high concentrations must be used and efficacy is variable. Alcohol has the strongest effect on lipophilic membranes. (Choice C) RNA can be rendered inert by ionizing radiation, which dislodges electrons and results in the formation of reactive ions that break covalent bonds. Alcohol has a minimal effect on RNA molecule integrity. (Choice D) Neuraminidase, 1 of the 2 influenza surface glycoproteins, can be blocked by neuraminidase inhibitors (eg, oseltamivir, zanamivir). These are often used to treat acute influenza (prevent the virus from leaving infected cells). (Choice E) The M2 ion channel mediates fusion of the influenza envelope with the endosome membrane, which liberates the influenza nucleocapsid and enzymes into the cytoplasm of the host cells. Blockade of the M2 ion channel with amantadine can prevent influenza infection. However, because influenza virus has developed widespread resistance to M2 ion channel inhibitors, these drugs are not recommended for use in the United States. Educational objective: Alcohol-based disinfectants kill enveloped viruses (eg, influenza) by dissolving their outer lipid envelope. Nonenveloped viruses are less susceptible to some alcohol-based disinfectants because they have no lipid envelope to target.

A 64-Year-Old Man Comes to the Emergency Department Due to 2