(CNN) - Four people in three states developed sepsis after receiving bacteria-contaminated platelet transfusions between May and October last year, according to a US government report released Thursday. One of the four patients died.
The source of the bacterial contamination of the platelets isn't clear. An analysis by the Centers for Disease Control and Prevention found that the bacteria were closely related, and the contamination might be from a common source. An investigation is underway.
Sepsis, a medical emergency, occurs when an existing infection triggers an extreme response and chain reaction throughout the body, possibly leading to tissue damage, organ failure and death.
Platelets, small cell structures essential to blood clotting, can be collected from donors and transferred to a patient as an intravenous transfusion. When collecting platelets for a transfusion, a donor's blood is drawn into an apheresis cell separator machine, which extracts platelets and returns the rest of the blood into the donor, according to the American Red Cross.
Approximately 1 in every 5,000 platelet collections in the United States is contaminated with bacteria, according to the US Food and Drug Administration.
'Our blood supply is very safe'
The contaminants found in the platelet transfusions that caused sepsis were Acinetobacter calcoaceticus-baumannii complex (ACBC) and Staphylococcus saprophyticus, both typical causes of health care-associated infections, the CDC reported. Taking samples from each patient, the CDC analyzed the bacterial DNA and discovered close relationships, which suggest a common source of contamination.
All of the collection sets used with the apheresis machines came from the same manufacturer, while two of three sets were traced to the same lot, the CDC reported without disclosing the name of the manufacturer. The investigation has not identified the contamination source.
Dr. Amesh Adalja, spokesman for the Infectious Diseases Society of America and senior scholar at the Johns Hopkins Center for Health Security, said that "in general, our blood supply is very safe" and that the fact that this merited a major CDC investigation "underscores the fact that this is a pretty rare occurrence."
Adalja, who was not involved in the CDC investigation, explained that "blood products are a good medium for infectious diseases" because they are added to a patient's bloodstream. And platelets are the most likely blood product to cause an infection; they are stored at room temperature, allowing any potential contaminating pathogens to proliferate.
"There is always going to be a risk of infection with blood products," Adalja said. Still, patients going into a hospital should know that the risk is "the lowest it has been historically. Modern technologies and modern screening procedures have gone a long way to minimizing those risks," he said. "When the investigation is complete, corrective steps will be put into place."
Four cases of sepsis
The California patient, a male with acute lymphoblastic leukemia, began shivering within minutes of completing a platelet transfusion. Two hours later, he was running a fever and had low blood pressure. He recovered fully after being transferred to the intensive care unit for management of septic shock. A culture of what remained in the platelet bag grew both ACBC and Staph. The contamination was traced to a single donation collected five days earlier in California.
The Utah patient, a male with cirrhosis who required a platelet transfusion before a procedure, complained of chills an hour after his transfusion began. Two hours later, he was feverish, his blood pressure low and his breathing quick. Two days later, he had died of septic shock. Samples obtained from platelet agitators at the manufacturing facility and the hospital yielded ACBC isolates. The platelets had been collected in Utah.
The Connecticut patients, two males with acute myeloid leukemia, each received a platelet unit made from the same apheresis donation, collected in Massachusetts. Within two hours of transfusion, both patients became feverish, and their blood pressure dropped. Both recovered after being transferred to intensive care. ACBC and Staph were isolated from the remaining platelets in both bags.
Health care providers should monitor patients for sepsis when transfusing platelets, the CDC advised. Recognizing an unusual patient reaction and reporting it to the platelet supplier and blood supply system administrators is crucial to prevent sepsis associated with contaminated platelets.
Over the past decade, ACBC organisms, which can cause pneumonia acquired from ventilators and infections of the urinary tract, surgical wounds and the bloodstream, have shown an increased resistance to antimicrobials, with some strains now resistant to all commonly used antibiotics.
Staphylococcus saprophyticus bacteria usually do not cause infections outside a health care setting, but in hospitals and other facilities, infections can turn serious or even fatal.
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