(Adds new details on number of potential exposures)
By Julie Steenhuysen
CHICAGO, June 20 (Reuters) - U.S. authorities increased to 84 people their count of government workers potentially exposed to live anthrax at three laboratories in Atlanta as they investigated a breach in safety procedures for handling the deadly pathogen.
The U.S. Centers for Disease Control and Prevention said the number of lab workers who may have been exposed rose from the 75 people first disclosed on Thursday. As of early Friday, 32 staff were taking the powerful antibiotic ciprofloxacin, or Cipro, and 20 were taking another antibiotic called doxycycline, CDC press officer Benjamin Haynes said in a statement.
In addition, as many as 27 people were getting the anthrax vaccine to prevent infection. No illnesses have been reported, but the agency expects the number of possible exposures to rise as more people step forward now that news of the anthrax scare is public.
The safety breach, which originated in the CDC’s bioterror lab, raised new concerns about the way laboratories around the world conduct research into the deadliest known pathogens, from anthrax to Ebola and avian flu. CDC has already been under scrutiny over security lapses and mechanical malfunctions at some of its labs.
Dr. Paul Meechan, director of the CDC’s environmental health and safety compliance office, first disclosed the possible anthrax exposure to Reuters on Thursday. The agency had discovered the lapse on June 13.
According to Meechan, researchers in the CDC’s high-security Bioterror Rapid Response and Advanced Technology laboratory realized they had sent live anthrax bacteria, instead of what they thought were harmless samples, to fellow scientists in two lower-security clearance labs at the agency.
The initial safety lapse occurred as scientists in the bioterror lab were trying out a new protocol for inactivating anthrax, using chemicals instead of radiation.
The scientists in the Bioterror Rapid Response unit had been preparing an especially dangerous strain of the bacteria for use at the two lower-security CDC labs, the Biotechnology Core Facility and the Special Bacteriology Reference Laboratory, Meechan said.
Those teams were experimenting with methods to more quickly identify anthrax in substances and powders sent to the United States.
“If there was a bioterrorism incident, we could more quickly identify yes or no, this sample has anthrax,” Meechan said.
Meechan said the team in the bioterror lab used a new process to purify anthrax samples. To check their work, they took a sample of what they thought was dead bacteria and put it on a nutrient-rich lab dish called an agar plate to see if the bacteria would grow.
“They waited 24 hours,” Meechan said. “They took a look at the plate, and they didn’t see any new growth. At that point, they assumed the material was safe.”
Researchers took the samples to the two lower-security CDC labs, which were developing the new tests. Their experiments did not work, and a week later, one of the labs asked for additional inactivated samples.
At the time, researchers in the bioterror lab discovered that they had left the agar plates in an incubator for an additional week, Meechan said.
As they were about to dispose of them, they noticed growth on one of the agar plates. “The growth turned out to be anthrax,” he said.
That is when the scientists realized the samples they sent to the two lower-security labs might have contained live anthrax bacteria. People working in those labs take fewer safety precautions and were unlikely to be wearing a respirator, putting them at higher risk for infection.
Meechan said the team immediately pulled back the samples and contacted the staff members who had handled them.
Meechan said they reached some of the lab workers that same night. Since then, they have been interviewing managers and using electronic surveillance and keycard data to identify anyone who might have been inside one of the two labs testing the samples.
Meechan said ciprofloxacin was the drug of choice for warding off anthrax infections, but since it has a long list of side effects, the agency is also offering the milder doxycycline antibiotic. CDC employees are expected to take the drugs for at least two months. (Editing by Michele Gershberg, Robert Birsel and Lisa Von Ahn)