An organic farm in the state of Lower Saxony came under the suspicion of health authorities as a probable source of the outbreak after they discovered that it had directly or indirectly supplied bean sprouts to a number of restaurants and canteens in several cities in northern Germany where many cases of Escherichia coli infection were reported.
A restaurant in the Baltic Sea port city of Luebeck suspected of being a source of the infection also had received supplies of bean sprouts from the farm.
However, laboratory tests of bean sprouts from the farm in Uelzen showed no traces of the killer bacteria, Lower Saxony health ministry officials confirmed. More than half of 40 samples taken from the farm tested since yesterday were negative, a spokesman for the ministry said in Hannover.
Tests of bean sprouts from the farm left in a refrigerator by an E coli patient who was treated in a hospital in northern Germany also showed no evidences of the enterohaemorrhagic bacteria, health officials in Hamburg said.
Nevertheless, investigators are continuing their examination of bean sprouts as a potential source of infection because the conditions in which they are grown are ideal for the breeding of the bacteria, the officials said. They also pointed out that a much larger E coli epidemic in Japan in 1969 was caused mainly by bean sprouts tainted with the bacteria.
This was the second time since the E coli outbreak in northern Germany nearly a month ago that suspicions about a potential source of infection turned out to be negative and it underlined the difficulties facing the authorities in tracing its origin.
Hamburgs health authorities had ordered ten days ago an investigation of cucumbers imported from Spain and banned their imports following suspicion that they may be carrying the deadly bacteria.
However, laboratory tests showed that even though some Spanish cucumbers carried the E coli bacteria, they were not the highly virulent strain, which causes the life-threatening haemolytic uraemic syndrome (HUS). It can lead to acute kidney failures, seizures, strokes and coma.
The Robert Koch Institute (RKI), Germanys national disease prevention and control centre, confirmed yesterday that the death toll in Germany rose to 25.
The institute said 15 of them died as a result of complications caused by HUS. It estimates that around 2,700 people have been infected nation-wide with the lethal bacteria and more than 600 of them have been diagnosed with HUS symptoms.
The health authorities continue to advise the public against consuming raw tomatoes, cucumbers, lettuce and bean sprouts even though suspicions about them as possible carriers of the E coli bacteria so far have not been confirmed.
President of the Robert Koch Institute Reinhard Burger said it was very worrying for the health authorities and the scientific community that the origin of the E coli outbreak could not be traced so far. In a television interview, he expressed fears that the number of new infections will continue to rise.
Meanwhile, public criticism of government's handling of the crisis is growing and some newspapers described the situation as "chaotic" and asked why the government did not act more swiftly to stem the outbreak.
