Bloomberg News

BERLIN — Greek doctors are fighting a new invisible foe every day at their hospitals: a pneumonia-causing superbug that most existing antibiotics can’t kill.

The culprit is spreading through health centers already weighed down by a shortage of nurses. The hospital-acquired germ killed as many as half of people with blood cancers infected at Laiko General Hospital, a 500-bed facility in Athens.

The drug-resistant K. pneumoniae bacteria have a genetic mutation that allows them to evade such powerful drugs as AstraZeneca’s Merrem and Johnson&Johnson’s Doribax. A 2010 survey found 49 percent of K. pneumoniae samples in Greece aren’t killed by the antibiotics of last resort, known as carbapenems, according to the European Antimicrobial Resistance Surveillance Network. Many doctors have even tried colistin, a 50-year-old drug so potent that it can damage kidneys.

“We’re not used to seeing people die of an untreatable infection,” said John Rex, vice president for clinical infection at AstraZeneca, which is developing a new generation of antibiotics. “That’s like something in a novel of 200 years ago.”

The superbug is one among many challenges facing the home of the Hippocratic oath, “first do no harm.” The government, confronting a 14.5 billion-euro ($19.3 billion) bond payment on March 20, is trying to arrange financing to avert a collapse of the economy. Partly as a result, the health system is in crisis, with some life-saving drugs in short supply and hospitals struggling to pay their bills.

Greece has the lowest nurse-to-patient ratio in Europe and one of the highest rates of antibiotic use — and abuse — on the continent, hindering the attack on the infection.

The superbug, dubbed KPC, first appeared in Greece in 2007 after spreading through the United States and then Israel. By 2010, Austria, Cyprus, Hungary and Italy were also experiencing an increase in cases, the European Centre for Disease Prevention and Control said in a surveillance report in December.

In the worst outbreaks, as many as half of the people who develop a blood infection due to KPC are killed, doctors in Toronto said in an article in the journal of the Canadian Medical Association last year.

Greece has a bigger problem than do other countries because its doctors over-prescribed antibiotics, said George Dimopoulos, an associate professor of intensive care medicine at Attikon University Hospital in Athens. Greeks used more antibiotics than residents of any other European country, according to a 2009 survey.