A Manitoba infant who died last week after being diagnosed with listeriosis was not a victim of the same strain of bacteria involved in a national outbreak that has killed 18 Canadians, health officials said Wednesday.

Six-week-old Alexiss McDonald-Moose died last week. Her mother, Rachel McDonald, says medical officials told her that her daughter contracted listeriosis while still in the womb.

The DNA fingerprint of the Listeria monocytogenes in the infant case is different from the DNA in the bacteria associated with the outbreak that prompted Maple Leaf Foods to recall all products from one Toronto plant, Manitoba Health officials said Wednesday.

Listeria is found in soil, vegetation, sewage, water and the feces of animals and humans, and the bacteria can also be found in unpasteurized dairy products, raw vegetables and meats and processed foods including deli meats and hot dogs.

Earlier on Wednesday before the announcement, McDonald had said she believed she contracted the bacteria through meat eaten during her pregnancy.

During a medical checkup before her daughter was born, McDonald said concerns were raised about her nutrition, and a nurse advised her to eat meat.

Although she had not eaten meat since a previous bout of food poisoning, McDonald said she went out of her way to do so on the nurse's advice.

"She told me that peanut butter wasn't good enough, that I had to side it with meat, so I said OK, and I bought sub mix for subs … because I don't like hamburger or chicken or nothing," she told CBC News.

"I forced myself to eat subs to try to get that meat in me. And I ate that. And my first time ever trusting meat in my life since I got food-poisoned, this is what happens to us."

She now feels betrayed and angry, she said.

5th case of listeriosis in Manitoba

Meanwhile, health officials said Wednesday that a fifth Manitoban has been diagnosed with listeriosis.

A Winnipeg woman in her 50s with an underlying medical condition is being treated in hospital, officials said. Further lab testing is underway to determine if this case is linked to the national outbreak.

One previous case in Manitoba, reported in August in a man in his 60s in western Manitoba, has been linked to the current national outbreak. Two others earlier in the year were not linked.

On average, four cases of listeriosis are reported in Manitoba each year.

Officials with the Public Health Agency of Canada say there may still be more cases related to the outbreak in the future — even though the meat products have been pulled off store shelves — because the listeria strain has an incubation period of up to 70 days.

To date, there have 48 confirmed cases and nine suspected cases of listeriosis connected to the Maple Leaf strain. Listeriosis was the underlying cause of death in 18 of those confirmed cases and is suspected in seven other cases.