ROCKFORD, Ill. (WTVO) — Reusable water bottles might be good for the environment, but they can contain 40,000 times more bacteria than a toilet seat, twice as many germs as a kitchen sink, four times as much as a computer mouse, and 14 times more than a pet’s drinking bowl, according to a new study.

The study, done by WaterFilterGuru, described a reusable water bottle as a “portable Petri dish,” after swabbing parts of different water bottles three times each, finding Gram-negative rods and bacillus present.

Gram-negative bacteria can cause infections that are increasingly resistant to antibiotics – while certain types of bacillus can result in gastrointestinal issues, according to the New York Post.

The Centers for Disease Control and Prevention also said bacillus is a leading cause of Anthrax, which can cause severe illness in both humans and animals.

The study found that squeeze-type bottles were the cleanest of the types of bottles tested, with less bacteria present than screw-top or straw lidded bottles.

Experts said that cleaning once a day and sanitizing once a week was the best way to keep the bacteria at bay.