A former salesman for the New England Compounding Center recalled for a federal jury Friday how he first learned of a fungal meningitis outbreak in September 2012 that would kill more than 60 people and sicken hundreds more — when one of his clients began to complain that patients who had been injected with a steroid produced at the Framingham-based pharmacy were getting sick with a mysterious illness.

The doctor at the St. Thomas Neurological Surgical Center in Tennessee feared his needles were the cause, but he also wanted to know what type of testing was being conducted at the Framingham center, known as NECC.

“I assured them, we had testing results on the medication,” the salesman, Mario Giamei Jr., told jurors, his hands folded in front of him.

Giamei was the first person from the company to testify in a federal trial related to the outbreak, and he expressed a sense of disbelief among workers, if not a sense of denial, that they could be at fault.

“There’s no way it could be us,” he recalled thinking. “I believed our testing was done properly.”

Federal authorities allege that the steroid produced at the compounding center, methylprednisolone acetate, came from one of three batches that were contaminated with mold and distributed nationwide, a case of neglect that became the worst pharmaceutical scandal in the country’s history.

Giamei testified Friday in the trial of Barry J. Cadden, the former president and head pharmacist at NECC, and for more than three hours he described how he was recruited to market NECC as a state-of-the-art compounding center that followed all federal guidelines, employed trained pharmacists, and conducted extensive testing on its products, though he had no history in the industry and never saw the pharmacy laboratory.

“At the time, I thought it was a safe product,” said Giamei, who sold mortgages before he was hired by Medical Sales Management, the sales branch of NECC, in November 2010. He was testifying under an immunity agreement that protected him from prosecution for any of his statements.

Cadden, 50, of Wrentham, faces more than 90 charges, including racketeering and causing the deaths of at least 25 patients. If convicted, he could be sentenced to life in prison.

Prosecutors allege he and other NECC employees ran the pharmacy like a criminal enterprise, skirting industry standards to maximize their profits. They produced drugs in unsanitary conditions that they knew, or should have known, could pose health risks, authorities say.

Several other employees were also charged, though Cadden was one of only two pharmacists accused of directly causing deaths, and he is the first to go to trial.

Lawyers for Cadden say he was an executive who was not directly involved in the actual compounding operations, and so he had no direct involvement in any action that caused a death. If anything, the lawyers argue, Cadden urged staff to follow proper protocol, and he conducted more testing than what was required by standards.

Prosecutors allege that he was responsible as the head pharmacist, and that he knew of the shoddy work environment and the potential risks. In the fifth day of the trial, Giamei was the first witness called to testify regarding the inner workings of NECC.

“We felt very strongly our product we put out there was great,” Giamei told jurors. “That would come from management, from Barry. . . . That we were making world-class products, the safest products.”

Giamei said he was armed with sales pitches and promotional material that stated that NECC followed guidelines set by the United States Pharmacopeia, an industry association, and that it used state-of-the-art compounding methods and conducted extensive testing.

NECC specialized in compounding custom medications, specifically steroids. Giamei was part of a team of close to two dozen salespeople who made pitches to hospitals, surgical centers, and pain clinics.

He acknowledged under cross-examination that he was trained to explain to clients that NECC was only required and typically only conducted end-product testing on certain medications, like stock medications, and not custom medications, an issue that seemed to confuse some clients who believed the center followed the guidelines at all times.

Cadden seemed to get angry when bothered with nuisance questions about testing, or “nit-picking,” Giamei said.

In one situation, Giamei said, Cadden acknowledged that NECC did not conduct testing when guidelines called for it, and he instructed Giamei to tell a client that the pharmacy followed only 99 percent of the guidelines. The client was prepared to test the drug herself.

Giamei did not see a problem with the company’s operations until the outbreak began in September 2012. The clinic in Tennessee was one of the first in the country to see patients sickened by the contaminated steroid. Tennessee health officials contacted the Centers for Disease Control and Prevention.