Story highlights Clinical samples show that the infection is resistant to common first-line antibiotics

Fifty-five people have fallen ill in 12 states, mostly from contact with infected puppies

(CNN) A multistate outbreak of campylobacter infections initially linked to contact with puppies sold through Petland, a national pet store chain, has spread to 55 people in 12 states and is resistant to common first-line antibiotics, the US Centers for Disease Control and Prevention announced Tuesday.

Campylobacteriosis is a common bacterial infection that can cause diarrhea, abdominal pain and fever. It's usually easily treated with common oral antibiotics, but the CDC said clinical samples taken from puppies and people sickened in the outbreak show signs of antibiotic resistance.

However, the CDC says that most people infected with campylobacter need only supportive care, such as fluids and electrolytes, to recover.

"Talk to your doctor if you think you have a Campylobacter infection and let them know if you recently purchased a puppy at a pet store, visited a pet store, or visited or live in a home with a puppy sold through a pet store before illness began," CDC public affairs specialist Brittany Behm wrote in an email. "If your doctor believes you need to be treated with antibiotics, they should do specialized testing to determine which antibiotic is the best choice for you."

As of Tuesday, 55 people have fallen ill in 12 states: Florida, Kansas, Maryland, Missouri, New Hampshire, New York, Ohio, Pennsylvania, Tennessee, Utah, Wisconsin and Wyoming. There have been 13 hospitalizations and no deaths reported. The first case within this outbreak occurred over a year ago, in September 2016.

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