The Denver Post also weighs in this morning on the role of third-party food safety auditors in the wake of the listeria-in-cantaloupe outbreak – big thumbs up from the auditor just before the outbreak.

It was only the latest incident when a "third-party" audit — slammed as an inherent conflict of interest by safety experts — failed to note deadly mistakes in a food operation.

• Nine people died and thousands were sickened after a salmonella outbreak at
Peanut Corporation of America in late 2008. Investigators found goods were shipped despite positive pathogen tests, as well as rodents, leaking roofs and extensive mold. An auditor before the outbreak gave the company the "superior" nod.

• FDA inspectors found filthy conditions, from overflowing manure to maggot infestations, at two Iowa farms where hundreds of millions of eggs were recalled last year. Court files show "Record of Achievement" audit certificates before the salmonella outbreaks.

• Earthbound Farm regularly got passing audits before an E. coli outbreak in greens was traced to the farm. The 2006 outbreak sickened hundreds and contributed to three deaths.

• In 2007, after an E. coli outbreak was traced to frozen beef patties from Topps Meat in New Jersey, federal inspectors found multiple problems. The company’s vice president questioned "why and how personnel from his company, outside auditors or consultants failed to find these noncompliances," according to a 2007 USDA document.

• And in a 2007 salmonella outbreak linked to Veggie Booty snacks, a third-party audit swabbed the manufacturing plant for salmonella but found none. Federal inspectors later found the bacteria in snack seasoning.

Grocers are re-examining their supply systems in the wake of 28 deaths and cantaloupe’s ruined reputation as a result of the Jensen Farms listeria.

Costco will require its cantaloupes to pass a "test and hold" program before they make it to the produce department, meaning a few sample cantaloupes per shipment will be swabbed for bacteria. The load won’t ship until lab tests clear.

"That is greatly going to improve the overall food quality in the marketplace," said Craig Wilson, head of safety for the retailer.

Costco uses just nine third-party auditors out of the 120 to 130 available, Wilson said. Every food item in Costco stores comes from a producer inspected by one of those nine auditors.

"The real key to this is audit-company responsibility," he said. "Are they going to step in and help sort out the problem?"

Other grocery store chains were less willing to answer questions about their use of private auditors. Walmart and Safeway officials said they were always looking for ways to improve food safety but wouldn’t elaborate.