Diagnostic dilemma: Teenager contracts rare 'welder's anthrax,' marking the ninth known case ever reported

The patient: An 18-year-old in Louisiana

The symptoms: The teenager, who was training to be a welder, developed a cough and was hospitalized with pneumonia and respiratory failure a week later. He was intubated at the hospital, meaning a tube was placed into his airway and attached to a machine to help him breathe.

The teen was six months into his welding apprenticeship, which involved working four hours per day, four days per week. He was otherwise healthy and reported being a nonsmoker with no history of excessive drinking.

What happened next: The doctors ordered a blood test, which revealed an infection with a bacterium in a related group of microbes known as the Bacillus cereus group. At that point, the doctors did not know which specific bacterial species within that group had caused the infection. But most often, B. cereus group bacteria cause intestinal infections, like food poisoning, not lung infections.

Although very rare, the teen's combination of symptoms, occupation and geographic location had previously been documented in cases involving welders in Louisiana and Texas. The knowledge of this rare phenomenon enabled the medical team to quickly identify the likely cause of his symptoms, they wrote in a report of the case.

The diagnosis: The patient was suspected to have welder's anthrax, an anthrax-toxin infection that presents as pneumonia in metalworkers. This severe respiratory disease is exceptionally rare, with only eight documented cases before this patient. All previous cases involved welders or metalworkers. Of those eight patients, only two recovered.

Anthrax is normally contracted following contact with the spores of Bacillus anthracis — a bacterium included within the B. cereus group. In the body, the spores produce anthrax toxin, thanks to anthrax-toxin genes they carry in their DNA.

Exposure to the spores can happen through a cut or scrape or if someone eats infected animal products or breathes contaminated air. The latter, known as inhalation anthrax, is the most lethal form of the condition, according to the Centers for Disease Control and Prevention (CDC).

Welder's anthrax is unusual in that it is caused by a different Bacillus species. Historically, it was thought that only B. antracis could produce anthrax toxin, but in recent years, it's been discovered that some other bacterial species within the B. cereus group share the disease-causing genes normally found in B. anthracis.

The fumes produced through welding are known to increase the risk of developing lung infections. The patient previously conducted shielded metal arc welding, which uses an electric current to join metal plates and produces more fumes than other welding types do.

The treatment: Before waiting for the final diagnosis, the doctors gave the patient four powerful antibiotics — vancomycin, meropenem, ciprofloxacin and doxycycline — that treat some of the most severe bacterial infections, including pneumonia.

Then, in partnership with the CDC, the medical team administered the anthrax antitoxin obiltoxaximab 34 hours after the initial diagnosis. This antitoxin, which in this case was obtained from the U.S. Strategic National Stockpile, targets the protective antigen of B. anthracis, the bacterium that causes the typical form of anthrax.

This case marked the first time obiltoxaximab had been used to treat welder's anthrax; a different antitoxin, raxibacumab, was administered in the one previous case where the patient received an anthrax antitoxin.

The patient recovered quickly after receiving obiltoxaximab, and his breathing tube was removed three days later. The doctors continued to treat him with antibiotics, and they also drained the fluid that had built up around his lungs — a common occurrence in patients with pneumonia.

The Louisiana State Public Health Laboratory tested the patient's blood and found he had been infected with Bacillus tropicus, a bacterium within the B. cereus group.

After 26 days of hospitalization, the patient was discharged with a personalized antibiotic regime. He had fully recovered by his three-month follow-up appointment.

What makes the case unique: There have been only nine known instances of welder's anthrax since the first recognized case in 1994. Only three patients have survived the illness, of which two received an anthrax antitoxin.

This new case is also unique because of the patient's young age; the age range of all previous patients was 34 to 56 years old. Additionally, the patient had been welding for only six months, whereas some individuals who had contracted the disease in the past had been welding for a decade or longer.

In an investigation of the case, the Louisiana Department of Health collected 245 soil and surface samples from the man's workplace and found that 11.4% were positive for anthrax-toxin genes. Limited airflow and ventilation, inconsistent use of personal protective equipment and eating in the work area were risk factors for the patient contracting the disease, the authors wrote in the case report.

However, notably, no one else at the patient's worksite became ill.

"The reason that this previously healthy young man was the only worker to become ill, despite the detection of anthrax toxin genes in multiple environmental samples from his worksite, is unclear," the authors wrote.

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