Diagnostic dilemma: Teen infected with rare ‘welder’s anthrax’, ninth known case ever reported

Patient: 18 years old from Louisiana

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

The teenager was in his sixth month of welding apprenticeship and was working four hours a day, four days a week. He reported being otherwise healthy, with no history of heavy drinking and a non-smoker.

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What happened next: Doctors ordered blood tests, which revealed an infection with bacteria from a related group of microorganisms known as the Bacillus cereus group. At that time, doctors did not know which bacterial species within that group was causing the infection. However, in most cases, bacteria from the B. cereus group cause intestinal infections, such as food poisoning, rather than lung infections.

Although extremely rare, this combination of the teen’s symptoms, occupation, and geographic location was previously documented in cases involving welders in Louisiana and Texas. Knowing this rare phenomenon, the medical team was able to quickly identify the possible cause of his symptoms, he wrote in the case report.

Diagnosis: The patient was suspected of having welder’s anthrax, an anthrax toxin infection that manifests as pneumonia in metal workers. This severe respiratory disease is extremely rare, with only eight cases recorded before this patient. All previous incidents involved welders or metal workers. Only two of these eight patients recovered.

Anthrax is usually contracted after contact with spores of Bacillus anthracis, a bacterium in the Bacillus cereus group. Inside the body, the spores produce anthrax toxin thanks to the anthrax toxin genes they carry in their DNA.

Exposure to spores can occur through cuts or scrapes, or if someone eats infected animal food or breathes contaminated air. The latter is known as inhalation anthrax and is the most deadly form, according to the Centers for Disease Control and Prevention (CDC).

Weld anthrax is unusual in that it is caused by a different Bacillus species. Historically, it was thought that only B. anthracis was capable of producing anthrax toxin, but in recent years it has been discovered that other bacterial species within the Bacillus cereus group share the disease-causing genes normally found in B. cereus.

Fumes produced by welding are known to increase the risk of developing lung infections. The patient previously performed coated metal arc welding, which uses electrical current to join metal plates together, which produces more fumes than other welding types.

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Treatment: Before waiting for a final diagnosis, doctors gave the patient four powerful antibiotics (vancomycin, meropenem, ciprofloxacin and doxycycline) that treat some of the most serious bacterial infections, including pneumonia.

Working with the CDC, the medical team then administered the anthrax antitoxin, obiltokiaximab, 34 hours after the initial diagnosis. The antitoxin, in this case obtained from the U.S. Strategic National Stockpile, targets the protective antigens of anthrax, the bacterium that causes the typical form of anthrax.

This case marked the first use of obiltokiaximab in the treatment of welder’s anthrax. In one previous case in which a patient received anthrax antitoxin, another antitoxin, raxibacumab, was administered.

The patient recovered quickly after administration of obiltoximab, and the breathing tube was removed 3 days later. Doctors continued to treat him with antibiotics and also drained fluid that had built up around his lungs. This is common in patients with pneumonia.

The Louisiana Public Health Laboratory tested the patient’s blood and found it was infected with Bacillus tropicus, a member of the Bacillus cereus group.

After 26 days of hospitalization, the patient was discharged with individual antibiotics. He had fully recovered by the time he was seen again 3 months later.

What’s unique about this case: Only nine cases of welder’s anthrax have been known since the first case was identified in 1994. Only three patients survived the disease, two of whom received anthrax antitoxin.

This new case is also unique in that the patient is young. The age range of all previous patients was 34 to 56 years. Furthermore, although the patient had been welding for only 6 months, some people with the disease had been welding for more than 10 years.

In investigating this incident, the Louisiana Department of Health collected 245 soil and surface samples from the man’s workplace and found that 11.4% were positive for the anthrax toxin gene. Restricted airflow and ventilation, inconsistent use of personal protective equipment, and eating in work areas are risk factors for patients to contract the disease, the authors wrote in a case report.

Remarkably, however, no one else at the patient’s workplace became ill.

“It is unclear why this previously healthy young man became the only worker, even though the anthrax toxin gene was detected in multiple environmental samples at the workplace,” the authors wrote.

For more interesting medical cases, check out our Diagnostic Dilemma archives.