A man contracted the plague while working with bacteria in a lab. (This is a stock photo.) (Photo by poba/Getty Images)
Patient: A 60-year-old man from Chicago who worked in a laboratory.
Symptoms: The patient presented to a medical facility after developing body aches, fever, and cough that lasted for three days. At this point, doctors suspected a respiratory infection similar to the flu and sent him to the emergency room. However, the man refused further examination and left the hospital.
What happened next: Three days later, the man's condition had not improved and he was having trouble breathing. An ambulance was called and when paramedics arrived, they found low oxygen levels in his blood. They provided oxygen via mask and rushed him to the emergency room.
Despite his breathing difficulties, doctors in the emergency room found nothing unusual in his lungs when they x-rayed them. They ran blood tests to see what other factors might have caused his symptoms. After examining a blood sample under a microscope, they counted his white blood cells and found that they were elevated, indicating an infection.
Doctors also found bacteria in a sample of the patient's blood; the exact type of bacteria was not immediately identified, but the presence of bacteria in the blood indicates a serious infection.
Treatment: Medics gave the patient three intravenous antibiotics to fight the infection in his blood. However, his breathing difficulties worsened after about 12 hours, and doctors intubated him. Despite these interventions, he died of cardiac arrest an hour later.
Diagnosis: After the patient died, doctors tried to determine what types of bacteria were in his blood. At that time, it was discovered that the patient had worked in a lab and had been exposed to a weakened strain of Yersinia pestis, the bacteria that causes the plague.
The hospital used laboratory techniques to extract multiple copies of genes from the patient’s bacteria in a petri dish, then sequenced the DNA to identify the species and strain. Although the weakened Y. pestis was thought to be noninfectious, the patient had somehow become infected with it, the researchers confirmed.
What makes the case unique: Before this incident, this weakened strain of plague bacteria had never caused infections in humans. So the Centers for Disease Control and Prevention (CDC) did not consider it a safety hazard, according to the case report.
The weakened bacteria were missing an important gene needed to absorb iron, which they use to produce energy and support processes such as cell growth and division. The CDC independently confirmed that the patient's infection was caused by this weakened strain, not the virulent one.
Concerned that the weakened strain might be more dangerous than anticipated, the CDC and other regulators investigated the lab where the patient worked. The investigation found no evidence of safety protocols being breached, and no cases of infection were reported among the patient’s co-workers, although they were all given antibiotics as a precaution after the man’s infection was reported.
No one could say for sure how the patient had been exposed to the bacteria, but his colleagues noted that he did not always wear lab gloves when handling germs.
To find out whether the weakened strain was a result of evolution or was specifically engineered to cause disease, the CDC experimented with lab mice, exposing them to either the patient strain or the original weakened strain in lab stock. Neither was fatal to the rodents.
This indicated that the man had an unusual susceptibility to bacteria. Although the patient had type 1 diabetes, which can affect immunity, doctors did not consider it significant. Then, a postmortem examination revealed that the patient had abnormally high levels of iron in his liver. In addition, he had three to 13 times more iron in his blood than the average person.
DNA analysis
Sourse: www.livescience.com
