Arcanobacterium Infection: An Overview

Introduction

Arcanobacterium haemolyticum is a non-motile, facultative-anaerobic, and gram-positive bacteria. An organism is facultatively anaerobic if it can switch from aerobic respiration to fermentation without oxygen. This species of bacteria are known to cause head and neck infections, including pharyngitis and sinusitis in humans. Arcanobacterium haemolyticum was first identified as the pathogenic agent causing pharyngitis and skin infections in the United States service men and South Pacific native populations in 1946.

What Is Arcanobacterium Infection?

Infections caused by Arcanobacterium haemolyticum are known as Arcanobacterium infections. Arcanobacterium infectious principally results in pharyngitis and soft-tissue infections, especially in young adults. Despite the rarity of systemic infections like meningitis and bacteremia, A. haemolyticum should be considered a differential diagnosis. Several symptoms of Acanobacterium infections resemble streptococcal infections; therefore, these infections are frequently misdiagnosed.

Are Arcanobacterium Infections Common?

• A. haemolyticum causes 0.5 % to 2.5 % of all bacterial pharyngitis in adults.

• 0.4 % of adult pharyngitis cases in the United States occur due to A.haemolyticum infection.

• Most of the cases present between 15 to 18 years of age in adults.

• Men are more prone to A.haemolyticum infection as compared to women.

• A. haemolyticum is more prone to cause soft-tissue infections in the older population, particularly in people with diabetes mellitus or immunocompromised patients. Most patients with soft tissue infections have diabetes mellitus in about 72 % of cases.

What Causes Arcanobacterium Infection?

• A. haemolyticum is of two types: smooth and rough. Colonies of the smooth type are more frequently linked to infections of soft tissues. Pharyngitis is more frequently linked to colonies of the rough type.

• There is no known reason why A. haemolyticum adheres to the pharyngeal mucosa. However, A. haemolyticum can enter HEp-2 cells (epithelial cells of the upper respiratory tract) and remain there for four days, establishing an internal bacterial reservoir. This eventually leads to the formation of pores in the host cells, which causes the infection.

• The mechanism of development of soft-tissue infections or rash is also not clear. However, the role of bacterial exotoxins (toxins secreted by bacteria) in developing these rashes may be crucial. Phospholipase D, hemolysin, and neuraminidase are the extracellular toxins secreted by A. haemolyticum.

What Are the Symptoms of Arcanobacterium Infection?

The signs and symptoms of Arcanobacterium infection include:

• The infection's severity might range from a minor respiratory infection to a condition that looks like diphtheria, a severe nose and throat infection caused by Corynebacterium diphtheriae.

• Nearly all patients have pharyngitis and pharyngeal erythema.

• About 50 % of the patients also present with fever.

• Erythematous rash.

• The rash manifests as dispersed red blanching bumps that look like "sand-paper." The neck, chest, and back are primarily affected, and the rash starts on the distal extremities and then moves centrally.

• The pharyngitis often appears one to four days before the rash, and the rash lasts for two to five days.

• Tonsil exudates are reported in 70 % of the cases.

• Enlargement of lymph nodes (lymphadenopathy) is reported in 40 % to 48 % of the patients. Patients may experience painful, 1-1.5 cm-sized anterior cervical or submandibular lymphadenopathy.

• A. haemolyticum infections manifest in individuals with soft-tissue infections such as cellulitis, abscesses, or chronic skin ulcers. They are most frequently co-infected with other bacteria, such as streptococci, corynebacterium diphtheria, etc.

• Additionally, A. haemolyticum infections have been linked to osteomyelitis cases. Osteomyelitis is an infection of the bone characterized by pain, fever, chills, and death of the infected part of the bone.

• Rarely, A. haemolyticum infections may get complicated and cause brain abscesses, pneumonia, bacteremia, etc.

How Is Arcanobacterium Infection Diagnosed?

A. haemolyticum can be found in healthy people's normal pharyngeal and skin flora. Since the organism is frequently disregarded as the cause of symptoms during infection, it is difficult to identify the pathogen early on. However, the infection can be diagnosed in the following ways:

• Blood Examinations: The doctor may advise a complete blood count to check for the presence of the infection. A complete blood cell, in the case of Arcanobacterium infection, will show a white blood cell count of 7100 cells/µL to 23000 cells/µL.

• Bacterial Culture: The pharyngeal swab is typically cultured on 5 % blood agar plates at 37 degrees Celcius with a percentage of carbon dioxide for 24 to 48 hours to establish the diagnosis.

• Streptococcal Antigen Test: Additionally, many doctors use pharyngeal rapid Streptococcal antigen testing, which, if they come back negative, can be a sign that A. haemolyticum is the cause of the infection.

• Reverse Christie-Atkins-Munch-Peterson Test: It is a test used to identify group B beta-streptococci. This test is positive in the case of Arcanobacterium infection.

How Is Arcanobacterium Infection Treated?

The treatment of Arcanobaterium infection includes:

• No controlled studies of antibiotic therapy have been carried out to treat pharyngitis caused by A. haemolyticum. Many pharyngitis patients have been treated with Penicillin (intramuscular or oral) and Erythromycin.

• A. haemolyticum is responsive to almost all types of antibiotics used to treat respiratory tract infections except Trimethoprin and Sulfamethazine.

• Antibiotics such as Vancomycin, Fluoroquinolones, Clindamycin, and Doxycycline should be used for patients with beta-lactam allergies.

• Patients with systemic infections may also need surgical treatment, fluid replacement therapy, antihypertensive drugs (vasopressors), and antibiotics therapy.

• However, there have been no clinical studies for the treatment of systemic infections; the antibiotic choice should be based on antibiotic sensitivity testing.

What Are the Complications of Arcanobacterium Infection?

Arcanobacterium can lead to the following complications:

• Lemierre syndrome is a condition characterized by internal jugular vein thrombophlebitis and bacteremia.

• Brain abscess.

• Endocarditis occurs due to the entrance of bacterial infection into the blood and finally reaches the heart.

• Bacteremia is the presence of bacteria in the infected person's blood.

Conclusion

Arcanobacterium infection is a rare infection occurring due to Arcanobacterium haemolyticum. The condition manifests as throat and soft tissue infections. However, when appropriately treated, the condition has an excellent prognosis. A. haemolyticum typically clears up within days. Airway obstruction caused by diphtheria-like membranous pharyngitis may be observed in more severe and chronic cases. Symptoms usually subside when infections are treated with the proper medications.