Known as the "silent killer", sepsis can lead to organ failure and death without rapid treatment.
A relative of the woman, who lived alone, had raised the alarm after she started slurring on the phone and then was unresponsive.
Paramedics found her slumped semi-conscious in a chair and she was taken to hospital.
At first her symptoms improved, but after four days she developed acute kidney failure and was admitted to intensive care.
Blood tests revealed an infection of Capnocytophaga canimorsus bacteria - a rare but serious cause of sepsis which is often found in the mouths of cats and dogs.
She recovered after two weeks of intensive care and antibiotic treatment and was discharged 30 days after she was first admitted.
The woman's case was particularly unusual because she had not been bitten or scratched by her dog.
Doctors reporting the case said: "This is an interesting case because neither scratch nor bite was established, although close petting including licks was reported."
Only 13 cases of sepsis relating to C. canimorsus have been reported in the UK in the last 26 years.
Of these, just over a quarter of patients died, with 60 per cent of cases occurring following dog bites and 24 per cent relating to other contact with dogs such as scratches.
Elderly people are more at risk because their immune systems may be weaker and because they are more likely to own pets.
Diseases transmitted from pets frequently go undiagnosed and the report authors warned doctors must be alert for pets passing on bacteria which can cause sepsis, particularly in the elderly.
They said: "This report highlights that infection can occur without overt scratch or bite injuries.
"It also reminds us that the elderly are at higher risk of infection, perhaps due to age-related immune dysfunction and increasing pet ownership."
Sepsis is thought to claim over 30,000 lives in the UK a year, although there are no official figures.
Earlier this year it was revealed the number of patients admitted to hospitals nationwide with the condition had surged by 50 per cent in five years to almost 400 a day.
The growing problem is thought to be fuelled by increasing antibiotic resistance, the ageing population and more patients undergoing surgery which puts them at risk of infection.
It can affect patients of any age but is more likely to occur in young children, pregnant women, the elderly and those with underlying conditions.
Experts have claimed the Government and NHS have been 'too slow' to raise public awareness on the issue, despite damning reports revealing how children have died from the illness.
In January, it was revealed that sepsis claimed the life of one-year-old William Mead after 111 helpline staff missed the signs. And in March, a report told how a nine-year-old boy died after being sent home by doctors with a "mild chest infection".
