LOS ANGELES, Feb. 17 (Xinhua) -- The United States is running out of drugs to treat Acinetobacter baumannii, a drug-resistant bug that prey on the weak in hospitals, it was reported on Tuesday.

    Acinetobacter doesn't garner as many headlines as methicillin-resistant Staphylococcus aureus, the dangerous superbug better known as MRSA, but drug-resistant strains of Acinetobacter baumannii and two other microbes -- Pseudomonas aeruginosa and Klebsiella pneumoniae -- could soon produce a toll to rival MRSA's, the Los Angeles Times warned.

    The three bugs belong to a large category of bacteria called "gram-negative" that are especially hard to fight because they are wrapped in a double membrane and harbor enzymes that chew up many antibiotics, said the paper.

    The drugs once used to treat gram-negative bacteria are becoming ineffective, and finding effective new ones is especially challenging, said the paper.

    "We're literally running out of drugs to treat gram-negatives," Dr. Brad Spellberg, an infectious disease specialist at Harbor-UCLA(University of California in Los Angeles) Medical Center, said in remarks published by the paper. "And there is nothing in the pipeline right now."

    Exact numbers of infections are hard to come by, because infections by these three bacteria are not reportable by law.

    But using 2002 data voluntarily reported to the Centers for Disease Control and Prevention from about 300 large, mostly urban hospitals, the Infectious Diseases Society of America identified about 104,000 gram-negative infections that were resistant to at least some antibiotics, roughly the same as the 102,000 MRSA infections found that year, the paper said.

    A class of broad-spectrum antibiotics known as carbapenems have been the drug of last resort for gram-negative bugs, according to the paper.

    As the drugs fail, doctors find themselves as a last resort turning to older, more toxic ones such as colistin, largely abandoned because of the severe side effects: kidney damage and deafness, said the paper.

    For the most part, gram-negative bacteria are hospital scourges-- harmless to healthy people but ready to infect already-damaged tissue. The bacteria steal into the body via ventilator tubes, catheters, open wounds and burns, causing pneumonia, urinary tractinfections, and bone, joint and bloodstream infections.

    Pseudomonas is widely found in soil and water, and rarely causes problems except in hospitals.

    Klebsiella causes a sudden, severe pneumonia, mostly in people already suffering from ailments such as diabetes or chronic lung disease. It can also cause urinary tract and abdominal infections.

    Acinetobacter generally causes wound and bloodstream infections. It has become notorious among veterans of the wars in Iraq and Afghanistan. They are believed to have contracted it in field hospitals and carried it to veterans hospitals in the U.S.