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It’s a beautiful summer day, and you’re strolling around the backyard barefoot. The next thing you know, your heel lands squarely on a nail protruding from the deck stairs—ouch! Luckily, you were able to clean and bandage the wound and the pain quickly stopped. You’re up to date on your tetanus shot, so no big deal, right?
Eh, not so fast.
If something punctures your skin, you could be exposed to a group of bacteria called Pseudomonas aeruginosa, which can cause a serious infection. Here’s what to know, and, importantly, what to do if you do get a puncture injury outdoors.
What is Pseudomonas aeruginosa?
It’s a group of bacteria that lives in soil and water, according to the Centers for Disease Control and Prevention. “Pseudomonas aeruginosa is a really important pathogenic bacteria because it’s everywhere in the environment, and it’s notoriously difficult to treat once it gets past your body’s primary defense mechanisms,” says Mario DeMarco, M.D., M.P.H., associate professor of family medicine and community health at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia.
Pseudomonas aeruginosa can attack tissues in the body, then “move targets”—essentially making it evasive to treatment, according to a 2023 review published in the journal Infectious Medicine. Worst-case scenario, Pseudomonas aeruginosa can be deadly, causing septic shock and/or multiple organ system failure. People with serious underlying conditions are more at risk.
How Pseudomonas aeruginosa enters your body
“Pseudomonas aeruginosa is opportunistic,” says Dr. DeMarco. “It sneaks into your body and loves wet conditions, like the warm, moist, sweat-saturated environment,” such as a sweaty sneaker.
“The inside of a rubber-soled shoe is often an environment where this germ can survive and sometimes grow,” says Gabriela Andujar Vazquez, MD, an infectious diseases physician and hospital epidemiologist at Dartmouth Hitchcock Medical Center in Lebanon, NH. “If a sharp object pierces your shoe, it can push germs that are on your shoe or on the object itself deeper into your foot. The combination of a moist shoe and a deep puncture injury can allow bacteria to be driven into places where infection is more likely to develop.”
Once bacteria is inside, it has free rein. “Many infections stay superficial on your skin, or just below the surface of your skin, but Pseudomonas can take root in deeper tissues, and even in bone,” says Dr. DeMarco.
Who is at highest risk for Pseudomonas aeruginosa infection?
If you’re generally healthy, your chance of developing a serious illness caused by Pseudomonas aeruginosa is small. “While not every exposure will lead to an infection, it’s important to know your risks,” says Dr. DeMarco. “If you’re immunocompromised, your healthcare provider may recommend an antibiotic even before any symptoms develop.”
The following conditions raise your risk for Pseudomonas aeruginosa infection, per the Cleveland Clinic:
Having had an organ transplant
Having suffered severe burns
What are the symptoms of Pseudomonas aeruginosa infection?
Be on the lookout for worsening pain, redness, swelling, drainage from your wound, or fever, says Dr. Andujar.
Infections can present in other, often strange, ways, too. “The greenies,” as social media calls it, is a symptom of a Pseudomonas aeruginosa infection that can cause a secondary infection underneath your fingernails and turn the nails green. When your nails are exposed to water and chemicals, such as when you’re at the nail salon, the dampness on your hands and under your nails can create a breeding ground for the bacteria. Pseudomonas aeruginosa can even merge with other bacteria found on or under your nails, often requiring multiple antibiotics to resolve the infection completely, according to a 2026 case study. If you notice any signs of infection after a nail salon visit or sauna session, too, contact your health care provider right away.
Pseudomonas aeruginosa can also cause a pus-filled skin rash, particularly if the infection initiated from a warm, wet environment, such as a hot tub, says Aishwarya Bhaskar-Shah, D.O., M.P.H., a pediatrician in Aurora, IL Ear and eye infections can also occur, as can blood, GI, and urinary tract infections.
How to treat a Pseudomonas aeruginosa infection
Take action as soon as the injury occurs. The bacteria sometimes causes delayed symptoms, so the infection can progress before you even notice anything is wrong, emphasizing the importance of swift medical attention.
“Wash the wound right away with soap and water, cover it with a clean dressing, and seek medical care the same day, ideally at urgent care or the emergency department,” says Dr. Andujar. “These injuries can appear minor, but carry a higher risk of deeper infection. Your healthcare provider will assess the depth of the wound, check for retained foreign material, and update your tetanus vaccination, if needed.”
“Antibiotics may be prescribed as well, particularly if the puncture is very deep or if you have underlying medical conditions that could put you at higher risk of severe infection complications,” says Dr. Andujar. That said, Pseudomonas aeruginosa can be resistant to antibiotics in some severe cases, according to the National Institutes of Health’s National Center for Biotechnology Information.
How to prevent a Pseudomonas aeruginosa infection
There are two things you can do to lower the odds of developing this bacterial infection:
Limit barefoot or flip-flop time. Touching grass feels great, but going barefoot or wearing shoes with thin soles in any area where sharp objects may be lurking can be problematic.
Check your feet daily. Puncture wounds can be small and hard to see, but that doesn’t mean you shouldn’t give your feet a good once-over after time outdoors. Look for wounds, scratches, and cuts.
The bottom line
Pseudomonas aeruginosa has the potential to make you and your family really sick, so don’t simply shrug off a minor puncture wound, especially if you have underlying medical conditions.
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