As the reliability of epidemiologic surveillance largely depends on the reliability of its case definitions, it is essential to create and revise case definitions based on systematic evaluations [9] . Most of the basic principles for the revision of the German case definition edition deducted from this analysis may also be applicable for case definitions in other countries (such as the United States, Ireland, Sweden, Mexico) or international networks (EU, WHO) as they share the same structural and editorial characteristics that we identified to be problematic in the first edition of the German case definitions [4, 7, 8, 26, 27] . We therefore believe that our findings are highly relevant for many national and international surveillance systems. Ventilator associated pneumonia and infection control Ventilator associated pneumonia (VAP) is the leading cause of morbidity and mortality in intensive care units. The incidence of VAP varies from 7% to 70% in different studies and the mortality rates are 20–75% according to the study population. Aspiration of colonized pathogenic microorganisms on the oropharynx and gastrointestinal tract is the main route for the development of VAP. On the other hand, the major risk factor for VAP is intubation and the duration of mechanical ventilation. Diagnosis remains difficult, and studies showed the importance of early initiation of appropriate antibiotic for prognosis. VAP causes extra length of stay in hospital and intensive care units and increases hospital cost. Consequently, infection control policies are more rational and will save money. Nosocomial pneumonia (NP) is defined as parenchymal lung infection, occurring after the first 48 hours of hospital admission [1] . It accounts for 13-18% of all hospitalacquired infections, but leading cause of death from nosocomial infections [2] . It is a major threat to patients admitted intensive care units (ICU) and receiving mechanical ventilation (MV). In the recent studies, it was shown that ventilator associated pneumonia (VAP) was the most common infectious complication among patients admitted ICU [3, 4] . It results in high mortality and morbidity, prolonged lengths of hospitalisation, and also increased cost of hospitalisation. The mortality rates for VAP range from 20% to 75% according to the study population [5] [6] [7] [8] [9] [10] [11] [12] [13] . The average excess cost of pneumonia was estimated to be U.S.$1255 per patient in 1982 (14) , U.S.$2863 per patient in 1985 [15] , and in a recent study in 1999, it was >U.S.$40 000 per patient [16] .