The bacterium identified in the squid is a "common environmental organism," explains the Post, but in this instance, it had a gene that rendered it resistant to last-resort antibiotics called carbapenems. That organism, Pseudomonas fluorescens, typically wouldn't harm a healthy person. But for someone with a weakened immune system, it could render common bacteria (think E. coli) resistant to carbapenems. That's because, as the Post explains, once the bacteria is in a person's body, it "can share that gene or enzyme with other bacteria. And that makes those other bacteria also resistant." Though properly cooking the squid would have killed the bacteria, it could spread during the food-prep phase. And at Wired, Maryn McKenna notes that seafood is "a type of food that we tend to undercook and sometimes eat raw."