ORONO – A 4-year-old boy at a University of Maine child care center died of shock brought on by a rare form of strep and not bacterial meningitis as first suspected, a state health test indicated during the weekend.

Nicholas DeSisto died Wednesday of what was initially thought to be meningitis, an infection of the fluid around the brain and spinal column that in its most virulent form can result in brain damage and death.

But on Saturday, the State Bureau of Health notified university health officials that investigators had determined from a test culture that Nicholas had been infected by a bacterium known as Group A streptococcus. Group A is often found in the throat or on skin. The more common infections by Group A streptococcus are relatively mild illnesses such as strep throat or a skin infection such as impetigo.

And while millions of people are infected with strep throat each year, Nicholas died from an uncommon, invasive form of streptococcus, an infection that can cause kidneys, liver, lungs and other organs to fail in what doctors describe as streptococcus toxic shock syndrome.

So unusual is it that Dr. Robert Holmberg, a specialist in pediatric infectious diseases, likened it to the chances of being struck by lightning.

“It’s exceedingly rare, almost unheard of,” said the Bangor pediatrician.

The U.S. Centers for Disease Control and Prevention reported that there were just 300 cases of STSS in 1999, or 3 percent of the known cases of Group A streptococcus that year. More than half of the people with STSS die, according to the CDC.

That Nicholas died of STSS wasn’t known last week. The boy’s symptoms and rapid decline in health were consistent with bacterial meningococcemia, which Holmberg said can lead to meningitis.

A culture was taken at the request of a medical examiner, but results weren’t available for two days.

In the meantime, health officials wanted to head off the suspected meningitis, which is contagious and potentially fatal. Forty-seven students and staff members associated with UM’s Child Development and Learning Center in Merrill Hall were evaluated, and 25 were given Cipro, an antibiotic.

In light of the test results, health officials have been in contact with all the people who had prolonged contact with Nicholas, including 15 students and seven staff members at the learning center. As of Sunday, a dozen of the students and staff members have come in for throat cultures to be taken in an attempt to determine whether they have Group A streptococcus, said Dr. Mark Jackson, UM’s health services director. Others are expected to be tested today.

Culture tests have also been taken of family members.

While STSS is not contagious, strep can be spread through direct contact with mucus from the mouth or nose or through infected wounds or sores on the skin, according to the CDC.

Health officials said the emphasis has been on reaching people with extensive direct contact with Nicholas, as opposed to people who may have had casual contact, such as at a mall or a school assembly. It was concern about possible infection that prompted officials at the Asa Adams School in Orono on Friday to send home a letter to all parents indicating that Nicholas had been at a school assembly.

Confusion has been part of the problem.

Holmberg said people have confused bacterial streptococcus infections with more common infections such as the common cold, a virus.

“Almost every upper respiratory virus typically goes through a phase with a sore throat,” Holmberg said.

Streptococcus can involve a prolonged sore throat without the runny nose or other cold symptoms or a skin sore that rapidly expands with redness.

The invasive forms of streptococcus occur when the bacteria get past the body’s natural defenses, such as when the body’s immune system is reduced because of illness or when a person has sores or other breaks in the skin that allow the bacteria to get into the tissue. In addition, some strains of streptococcus are more likely to cause severe disease than other strains.

Jackson said that once the bacterium got into Nicholas’ blood stream, it found its way to the fluid of one of his knees, where it grew and produced toxins.

Nicholas was the son of William and Jennifer DeSisto of Orono. A service of remembrance is planned at 11 a.m. today at the Church of the Open Door, 270 Main Road, Hampden.