Playboy founder Hugh Hefner was suffering from a blood infection and a drug-resistant strain of E.coli when he died last week, details of his leaked death certificate show.

Hefner died of cardiac arrest and respiratory failure on September 27 after contracting septicema, according the Los Angeles Department of Public Health documents.

The contents of the death certificate, first reported by The Blast, said Hefner’s E. coli strain was so severe, it was “highly resistant to antibiotics”.

Hefner was surrounded by his four adult children and wife Crystal Harris when he passed away at the Playboy Mansion at the age of 91.

The Chicago native was laid to rest on Sunday in a small ceremony at Westwood Village Memorial Park in Los Angeles in a burial plot next to Marilyn Monroe, Playboy‘s first centrefold.

Hefner’s role in creating the Playboy empire in 1953 has been both praised and condemned since his death as he has been accused of both empowering and exploiting women.

Harris described Hefner as an “American hero”.

Speaking to People magazine, she said her late husband was: “A kind and humble soul who opened up his life and home to the world.”

“I felt how much he loved me. I loved him so much. I am so grateful. He gave me life. He gave me direction. He taught me kindness. I will feel eternally grateful to have been by his side, holding his hand, and telling him how much I love him,” Harris was quoted as saying.

“He was a beacon to the world, a force unlike anything else. There never has and never will be another Hugh M. Hefner.”

Hefner’s former girlfriend Barbi Benton earlier told media the publisher suffered from a long-term back condition that limited his mobility.

Benton said she last saw Hefner six months ago and noticed that his memory was “fading” – he admitted to being “in poor health.”

As Benton told People, “he said he was looking forward to laying next to the gal who kicked off Playboy.”

Despite being married to Hefner for the last five years of his life, Harris is not in line to inherit any of his estimated $US110 million fortune, according to reports.

US media reports claimed an “iron-clad prenuptial agreement” meant the former Playmate of the Year was never added to Hefner’s will.

Us Weekly reported in 2013 that the publisher’s fortune would be divided among his four adult children, the University of Southern California and various charities.

Despite Harris, 31, not having been inked in as a recipient, she will be “looked after,” said the magazine.