Food Safety  ›  Grocery Store Research

You pack your reusable bags, check your list, and head to the store. But the moment you grab a shopping cart, you’re touching a surface that may carry more bacteria than a bathroom doorknob — by a factor of hundreds. Here’s what the data actually shows.

Most shoppers know grocery stores aren’t sterile environments. But few realize just how significant the bacterial load on common surfaces actually is — or how dramatically it varies between store types. To find out, we commissioned EMLab P&K to swab shopping carts, refrigerator door handles, and produce from four store categories: traditional, budget, superstore, and upscale.

The results are measured in colony-forming units per square inch (CFU/sq. in.) — a standard microbiological measure of bacterial density. The numbers are surprising, and the differences between store types are larger than most people would expect.

Carting Around Germs

Traditional grocery stores had the highest bacterial count of any store type tested — by a wide margin. A shopping cart at a conventional grocery store carries over 73,000 CFU per square inch, which is 361 times the bacterial load on a bathroom doorknob. Budget stores aren’t far behind: their carts carry 270 times more CFU than an average toilet handle.

Superstores fall into a middle range at over 1,000 CFU/sq. in. — roughly triple the bacteria found on an average kitchen countertop. Upscale grocery stores were the notable exception: their carts tested at just 28 CFU/sq. in., comparable to a computer keyboard.

Germ Breakdown: What’s Actually on the Handle

Not all bacteria are equal — and the type matters as much as the count. Of all bacteria found on shopping cart handles across the study, nearly 75% were identified as gram-negative rods. This is significant because over 90% of gram-negative rod species are harmful to humans, and most are resistant to common antibiotics, making them particularly difficult to treat if an infection occurs.

Another 24% of surface bacteria were gram-positive rods. While most gram-positive rod species are relatively harmless, certain strains are pathogenic and can contribute to illness — particularly in immunocompromised individuals.

Fewer than 1% of samples contained yeast and bacillus. Despite the small percentage, both carry meaningful risk: bacillus is commonly associated with food poisoning, while yeast can cause skin infections. A small amount of gram-positive cocci — linked to skin infections, pneumonia, and blood poisoning — was also identified.

Germ Type Varies Dramatically by Store

The type of bacteria present differs significantly depending on where you shop. Superstores had the highest proportion of gram-negative rods at over 88% — the most concerning category given their antibiotic resistance. Traditional stores followed closely at more than 80% gram-negative rods.

Budget stores were the outlier in a positive direction — fewer than 20% of cart bacteria were gram-negative rods, with a much higher proportion of the less harmful gram-positive variety. Upscale markets showed no detectable gram-negative rods at all, though their carts contained comparatively higher levels of yeast and bacillus.

According to the Food Marketing Institute, 85% of consumers regularly visit traditional grocery stores — the category with the highest combined bacterial load and the highest proportion of antibiotic-resistant bacteria. Only 11% primarily shop at upscale markets.

The Dirty Truth: How Grocery Stores Compare to Everyday Objects

Shopping cart handles get the most attention, but the refrigerator door handles in the grocery store are significantly worse. Traditional grocery store refrigerator doors tested at nearly 327,000 CFU/sq. in. — more than four times higher than the cart handles in the same stores. These handles are touched by hundreds of shoppers per day, with no cart-wipe station or visible hygiene protocol at most locations.

For context, an average pet toy carries around 18,940 CFU/sq. in. The bottom of a handbag — an item most people would consider relatively dirty — comes in at fewer than 10 CFU/sq. in. A grocery store refrigerator door handle is roughly 32,000 times dirtier than the bottom of your bag.

A Closer Look: What’s on Refrigerator Doors

More than 58% of the bacteria on grocery store refrigerator doors were identified as gram-positive rods. While some research has linked certain strains to health benefits, gram-positive bacteria can also be pathogenic — causing negative side effects and harmful diseases in vulnerable individuals.

Over a third of refrigerator door bacteria were gram-positive cocci — a category that includes strains responsible for skin infections, pneumonia, and blood poisoning. Nearly 4% was yeast, and almost 2% was the more serious gram-negative rod variety.

Produce tested across grocery stores carried a higher proportion of harmful bacteria than the refrigerator doors nearby. Less than half of produce bacteria were gram-positive rods, while nearly 19% were gram-negative rods — a meaningful concentration of antibiotic-resistant bacteria on the food you’re about to bring home and eat.

Washing produce thoroughly before eating remains one of the most effective ways to reduce this bacterial load — regardless of where you shop.

Microbes at the Market: Store-by-Store Refrigerator Data

Budget grocery stores showed the most favorable refrigerator door results — over 96% of bacteria identified on their fridge handles were gram-positive rods, the less harmful category. Traditional stores followed, with less than two-thirds gram-positive rods on fridge surfaces.

Upscale markets and superstores showed the worst refrigerator door results in terms of bacterial type: all germs identified on their fridge handles were gram-positive cocci. This category is responsible for approximately a third of all bacterial infections in humans, including strains associated with staph, strep, and MRSA.

Produce at upscale grocery stores carried over 1,500 times more bacteria than produce at traditional grocery stores. This counterintuitive finding likely reflects the reduced use of synthetic pesticides and chemical treatments on organic and natural produce — methods that, while environmentally preferable, are less effective at eliminating surface bacteria than conventional agricultural chemicals. Thorough washing remains essential regardless of where produce is purchased.

Methodology

We commissioned EMLab P&K to test swabs collected from four store types: traditional grocery, budget grocery, superstore, and upscale market. All values are based on an average of five shopping carts from each store type, as well as three produce items and three refrigerator door handles from each store. Bacterial density is measured in colony-forming units per square inch (CFU/sq. in.).

Bacteria were identified and categorized by type: gram-negative rods, gram-positive rods, gram-positive cocci, yeast, and bacillus. Results represent a snapshot of bacterial presence at the time of testing and are not intended as a comprehensive assessment of any individual store’s hygiene practices.

What You Can Do

The bacterial load in grocery stores is a consistent, documented reality — but simple habits significantly reduce your exposure.

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