Sores that look like spider bites on prisoners in Georgia and other states are actually signs of an alarming medical trend: antibiotic-resistant staph infections.

The skin infections, frequently seen in hospitals and nursing homes, have been spotted in recent years among athletes, military recruits and gay men. Increasingly, they're also showing up among prison inmates, federal health officials said Thursday.

Close prison quarters, scant soap supplies and poor laundry facilities contribute to the problem, said officials with the Centers for Disease Control and Prevention in Atlanta.

At least 225 inmates in two prisons and one jail in Georgia have contracted the infections in the last two years, the CDC said. State health officials said the number of incidents is probably much higher and may be impossible to erase.

Texas prisons have reported nearly 11,000 cases in the past seven years, and Los Angeles County's prisons have recorded 1,500 cases since early last year, the CDC said.

The skin infections often appear as lesions that look like boils or spider bites. Left untreated, they can develop into life-threatening blood or bone infections. They are resistant to the antibiotics many doctors initially use, but can be treated with other antibiotics.

Close contact and sharing clothing and equipment can spread staph, making prisons prime incubators, and inmates have additional risk factors, said Dr. Dan Jernigan, a CDC medical epidemiologist.

Liquid soap can be more sanitary than bar soap, but prisons often ban it because it could be squirted into someone's eyes. Alcohol hand-cleaning gels are barred because they are flammable. Inmates often hoard bar soap, leading them to use communal soap in showers or nothing. Laundry is often washed and dried in bulk at temperatures too low to kill bacteria.

Also, prison clinics often require copayments from prisoners, which might be a barrier to seeking treatment for people who think it's a minor problem, Jernigan said.

Dr. Joseph Paris, medical director of the state Department of Corrections, said prisons encourage inmates to take their own soap to showers. They are trying out liquid soap dispensers bolted to walls and making sure laundry is done at higher temperatures. And the $5 copayments don't discourage clinic visits, he said.

Thirteen inmates at Washington State Prison, a women's facility in Davisboro, Ga., recently claimed to have spider bites. One was found to have the staph infection, Paris said. Four had spider bites and the rest had other skin conditions.