Diphtheria: Nursing

Diphtheria is a toxin-mediated bacterial infection that typically affects the upper respiratory tract, and less commonly, the skin.

Now, let’s quickly review a bit of the anatomy and physiology of the upper respiratory tract, and skin. Starting with the upper respiratory tract, this is made up of the nose, nasal cavity, oral cavity, pharynx, epiglottis, larynx, and the upper part of the trachea.

So, when we breathe in, air enters the respiratory tract through the nose or mouth, respectively into the nasal cavity and oral cavity, and then into the pharynx. At each side of the pharynx, there is a pair of structures called adenoids and tonsils, which are small clumps of lymphoid tissue that act as the body's first line of defense that swallow harmful foreign particles and pathogens that enter through the nose or mouth. The lower part of the pharynx is continuous with the larynx, which is connected through the trachea, or windpipe, with the lungs.

Zooming in, the epithelium lining respiratory tract consists of goblet cells that release mucus, which is sticky and contains enzymes to help trap and destroy harmful foreign particles and pathogens; as well as columnar epithelial cells, that have hair-like projections called cilia, which work to sweep the harmful particles up and out of the airways.

Moving on to the physiology of the skin, this is divided into three main layers: the hypodermis, which is made of fat and connective tissue, the dermis, which contains hair follicles, sweat glands, nerve endings, and blood vessels, and finally, the epidermis. The epidermis itself has multiple layers of squamous or flat epithelial cells.

Alright, now, diphtheria is caused by the gram-positive bacillus bacteria called Corynebacterium diphtheriae. Important risk factors for developing diphtheria include immunodeficiency; being unvaccinated or undervaccinated; coming in contact with an infected client; and finally, living in crowded or unsanitary conditions or traveling to an endemic area.

Moving on to pathology, Corynebacterium diphtheriae is an airborne bacteria, meaning it most often spreads via small bacteria-containing respiratory droplets that get flung in the air when an infected client talks, coughs, or sneezes. If another client breathes in these droplets, or they get in contact with infected surfaces, and then touch their eyes or mouth, they can become infected with what is known as respiratory diphtheria. Less frequently, the bacteria can also enter the body through open lesions on the skin, causing cutaneous diphtheria.

Now, when infected by a beta bacteriophage, C. diphtheriae becomes toxigenic, meaning that it is able to produce diphtheria toxin, or DT for short. So, once the bacteria enters the body, a subunit of the toxin binds to the epithelial cells lining the upper respiratory tract, particularly the pharynx, or tonsils, and less commonly, the skin. In any case, the toxin proceeds to block protein synthesis, effectively causing the cell to die. This causes local inflammation that leads to tissue swelling, and necrosis. Ultimately the necrotic tissue builds up into a gray, leathery pseudomembrane.

The most common complication of diphtheria is obstruction of the airway that can lead to respiratory failure. Additionally, the bacteria may gradually invade deeper into the wall of the respiratory tract or the skin, until they reach the bloodstream, from where they can move to distant organs such as the heart, causing myocarditis, or the kidneys, causing acute tubular necrosis, or destruction to the renal tubules.

C. diphtheriae can also travel to the nerves, causing nerve demyelination, meaning they destroy the myelin sheath covering the nerve axons, leading to polyneuropathy. Diphtheria polyneuropathy usually affects the oculomotor nerve, causing oculomotor nerve palsy.

Now, the clinical manifestations of diphtheria often begin to present 2 to 5 days after infection and include a low-grade fever accompanied by a general malaise and weakness.

In respiratory diphtheria, clients present with a sore throat, a swollen neck that’s commonly called bull neck, and a thick, gray, adherent coating called a pharyngeal pseudomembrane, which ultimately can cause difficulty breathing and stridor. A barking cough and hoarseness are also often present.

In cutaneous diphtheria, there are typically chronic skin ulcers, covered with a dirty gray membrane. With myocarditis, there might be signs of cardiac dysfunction such as arrhythmias, or even heart failure. With acute tubular necrosis, there can be oliguria, or decreased urine production. Finally, clients with oculomotor palsy may experience double vision.

Diagnosis of diphtheria starts with the client’s history and physical assessment, followed by cultures of swabs from the pharynx or the suspected skin lesion to isolate C. diphtheriae. When placed on a gram-stain, gram-positive rods appear in a “Chinese-character” looking distribution. When the culture gets positive, next is to tell if the C. diphtheriae strain in question is toxigenic. This can be done by a polymerase chain reaction or PCR or a rapid enzyme immunoassay.

Treatment for diphtheria includes antibiotic therapy with erythromycin or penicillin. Careful airway management, with early intubation and oxygen supplementation, is also necessary due to the risk of airway obstruction.

Additionally, all close contacts who are not up to date on vaccinations, including members of the client’s household, friends who regularly visit, and exposed medical staff, typically get a culture taken and are given a standard dose of penicillin G benzathine or oral erythromycin.

Finally, clients under 7 are recommended to get the DTaP vaccination and clients over 7 are recommended to get the Tdap. Both prevent diphtheria, tetanus and pertussis, but the difference is that DTaP vaccine works at full capacity against all three diseases, hence the 3 uppercase letters; while the Tdap only contains a full strength dose against tetanus, and sufficient doses for continued immunity against diphtheria and pertussis, hence the uppercase T and the lowercase d and p in the name. Booster shots are recommended every 10 years.