Antibiotic resistance of pathogenic bacteria is a worldwide cause for concern. Investigations into the use of antibiotics and their effects use an international unit of measurement, called the defined daily dose (DDD). The DDD represents the assumed average dose for a drug per day being used to treat a specific disease in adults. A study investigated the antibiotic resistance of Streptococcus pneumoniae. The study was carried out in some European countries and the percentage of S. pneumoniae resistant to the antibiotics penicillin and macrolide was determined. The results are shown in Table 2.1. [Table 2.1] DDD per 1000 people per day country | penicillin | macrolide | penicillin | macrolide Netherlands | 9 | 1 | 1 | 5 Denmark | 11 | 2 | 2 | 2 Sweden | 13 | 1 | 4 | 3 Germany | 14 | 2 | 7 | 9 UK | 14 | 3 | 11 | 19 Austria | 18 | 4 | 12 | 11 Italy | 24 | 5 | 13 | 29 Portugal | 29 | 4 | 29 | 9 France | 37 | 6 | 43 | 53 Spain | 33 | 6 | 50 | 36