Arcanobacterium haemolyticum Infections

Arcanobacterium haemolyticum is a bacterium first identified in 1946, known for causing infections like pharyngitis and skin rashes, particularly in US military personnel and indigenous communities in the South Pacific. Initially thought to be a subspecies of Corynebacterium pyogenes, it was later reclassified into the new genus Arcanobacterium, meaning "secretive bacteria," due to its distinct characteristics. Over time, it has been linked to more serious infections, including sepsis and osteomyelitis.

 

Symptoms and Presentation

The most common symptom of A. haemolyticum infection is a sore throat, reported in almost all patients (97-100%). Other symptoms include:

• Itchy skin (33%)
• Nonproductive cough (33%)
• Fever
• Rash

The rash typically starts on the arms and legs, sparing the face, palms, and soles. The rash may last over 48 hours, with mild peeling during recovery. In a review of 191 cases, over 50% of patients experienced tonsillar exudates, fever, and skin rash.

 

Transmission and Risk Factors

Though no confirmed risk factors exist, it's been speculated that contact with animals like cows and buffaloes or consumption of unpasteurized milk may increase the risk of infection. The bacterium has also been found in European bison, although its transmission mechanism remains unclear. Human-to-human transmission is suspected, but proper hygiene, like handwashing, may help prevent its spread.

 

Complications

Complications from A. haemolyticum infection can range from peritonsillar abscesses, sepsis, and various skin and soft tissue infections. In some cases, severe sore throat and fever may lead to hospitalization for drainage of abscesses or intravenous antibiotics.

 

Diagnosis

Diagnosing A. haemolyticum can be tricky, as its colonies are slow-growing and may be missed in routine throat cultures. Specialized blood agar and prolonged incubation (up to 48 hours) are often needed to detect it. In some cases, skin biopsies from rashes show inflammation but do not contain the bacteria itself.

 

Treatment of Arcanobacterium haemolyticum Infection

Arcanobacterium haemolyticum is a significant yet underrecognized bacterium responsible for various infections, ranging from mild pharyngitis to severe invasive diseases such as sepsis or osteomyelitis. Early recognition and proper treatment are critical to minimizing the risk of complications. Below is a comprehensive guide to managing infections caused by A. haemolyticum.

1. Pharyngitis and Mild Infections

Most infections caused by A. haemolyticum manifest as pharyngitis, often presenting with tonsillitis, fever, and sometimes a rash. While mild cases may resolve spontaneously, antibiotic treatment is recommended to shorten symptom duration and avoid complications.

Antibiotic Therapy:

• Penicillin: Although penicillin and related antibiotics like amoxicillin are standard treatments, some cases show resistance due to the bacterium’s ability to survive intracellularly.
• Macrolides (e.g., erythromycin, azithromycin): Preferred for their effectiveness against intracellular bacteria, macrolides are often the first choice for treating A. haemolyticum infections. Azithromycin is especially favored for its convenient dosing schedule.
• Clindamycin: This is a viable alternative for patients allergic to penicillin or those experiencing severe infections. Clindamycin has good tissue penetration and is effective against anaerobic bacteria.

 

Dosage Recommendations:

• Tab. Erythromycin: 250-500 mg every 6-12 hours for 7-10 days.
• Tab. Azithromycin: 500 mg on the first day, followed by 250 mg daily for 4 days.
• Tab. Clindamycin: 150-450 mg every 6-8 hours, depending on severity.

Expected Outcomes: Antibiotic therapy generally resolves pharyngitis within 3 days. Without treatment, symptoms can longer for up to 2 weeks.

2. Severe or Systemic Infections

More severe cases, such as sepsis or deep tissue infections, demand prompt intervention with intravenous antibiotics.

Intravenous Antibiotics:

• Beta-lactams (e.g., penicillin, cefuroxime, cefotaxime): These antibiotics are first-line treatments for severe cases like sepsis or osteomyelitis. They function by interfering with the construction of the bacterial cell wall, weakening the bacteria and preventing it from growing or surviving.
• Vancomycin: Useful for severe infections in patients allergic to beta-lactams or when resistance is suspected. However, resistance to vancomycin has been reported, so sensitivity testing is essential.

Antibiotic Sensitivity: A. haemolyticum is typically sensitive to:

• Minocycline
• Vancomycin
• Beta-lactams

 

Antibiotic Resistance: Resistance has been observed with:

• Gentamicin
• Fluoroquinolones (e.g., levofloxacin, ciprofloxacin)
• Trimethoprim-sulfamethoxazole
• Tetracyclines (30% resistance rate in tested strains)

 

Treatment Duration: For severe infections, intravenous therapy typically lasts 2-6 weeks, depending on the site and severity.

 

3. Management of Complications

In some cases, untreated or severe infections may lead to complications like peritonsillar abscesses or sepsis.

• Peritonsillar Abscess: This condition requires surgical drainage followed by antibiotics (penicillin, clindamycin, or cefuroxime) for 7-14 days.
• Sepsis: Immediate intravenous antibiotics and supportive care are crucial. Blood cultures guide the selection of appropriate antibiotics based on sensitivity results.

 

4. Adjunct Therapies

Supportive treatments can complement antibiotic therapy, particularly in cases of pharyngitis or systemic infections.

• Antipyretics and Analgesics: Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or acetaminophen help manage fever and pain.
• Antiseptic Lozenges: Lozenges with antiseptics such as amylmetacresol can reduce bacterial load and soothe symptoms.

 

5. Hospital Admission and Parenteral Therapy

Hospitalization may be necessary for patients with systemic or severe infections, especially if they cannot swallow or are at risk of complications like sepsis.

Intravenous Antibiotics: These patients will require parenteral antibiotics and close monitoring to ensure the infection resolves.

 

 6. Monitoring and Follow-Up

Patients should be reassessed within 48-72 hours of starting antibiotics to ensure improvement. In severe cases, repeat blood cultures and imaging may be required to confirm recovery.

 

Prevention

While no specific preventive measures are recommended for A. haemolyticum, maintaining good hygiene, avoiding shared utensils, and proper food handling (particularly with dairy products) can help reduce transmission.

In conclusion, early detection and appropriate treatment are critical in managing Arcanobacterium haemolyticum infections and preventing complications.