An overview of the 17 veterinary clinics that participated in the study (hereafter referred to as clinics A to Q) is provided in Table 1. Two clinics (L and P) did not return a questionnaire of general data about their centre (see Section 2) and in two other cases (clinics H and K) the returned questionnaire was incomplete. Participating clinics were scattered within the Madrid region (14 were located in the capital city, two in other municipalities within the metropolitan area and one in a rural location) and varied widely in their year of opening (from 1981 to 2014), number of cases attended per week (x±S.D.=37.6±18.7 and 16.5±11 for dogs and cats, respectively), number of fecal cultures requested per week (1.6±2.4 and 0.9±1.8), and other parameters (Table 1). These clinics also differed in the antibiotics used for the treatment of diarrhea, but 12 of them (80% for which pharmacological data were available) reported the use of metronidazole for the treatment of these conditions. Only three clinics (20%; F, J and O) acknowledged frequent request of microbiological culturing for anaerobes, and five clinics (33.3%; D, F, H, N and O) reported occasional suspicion of C. difficile and/or C. perfringens involvement in severe cases of diarrhea.Table 1Overview of the characteristics of the veterinary clinics that participated in the study.aTable 1ClinicOpening yearNo. cases per weekbNo. diarrea cases per weekbNo. fecal samples per weekbNo. fecal cultures per weekbA201461 (55 D, 6 C)2.5 (2 D, 0.5 C)1 (1 D)0.5 (0.5 D)B199482 (50 D, 32 C)2.5 (2 D, 0.5 C)3.5 (3 D, 0.5 C)0C200911 (10 D, 1 C)5.5 (5 D, 0.5 C)1 (1 D)0D201440 (22 D, 18 C)8 (7 D, 1 C)7 (5 D, 2 C)0E199340 (20 D, 20 C)2 (2 D)4 (2 D, 2 C)4 (2 D, 2 C)F1981100 (70 D, 30 C)14 (10 D, 4 C)2.3 (2 D, 0.3 C)0.31 (0.3 D, 0.01 C)G198427.5 (16 D, 11.5 C)11.5 (8 D, 3.5 C)1.5 (1 D, 0.5 C)1.5 (1 D, 0.5 C)H200255 (35 D, 20 C)5 (4 D, 1 C)NANAI199270 (60 D, 10 C)8 (7 D, 1 C)1.5 (1 D, 0.5 C)0J200490 (48 D, 42 C)12 (8 D, 4 C)16 (10 D, 6 C)14 (8 D, 6 C)K1985NANA10 (6 D, 4 C)10 (6 D, 4 C)LNANANANANAM200147.5 (35 D, 12.5 C)4.5 (4 D, 0.5 C)4.5 (4 D, 0.5 C)3 (2.5 D, 0.5 C)N199935 (25 D, 10 C)4 (3 D, 1 C)4 (3 D, 1 C)1 (1 D)O201026 (20 D, 6 C)3 (2.5 D, 0.5 C)0.5 (0.5 D)0.5 (0.5 D)PNANANANANAQ200572 (60 D, 12 C)20 (20 D)2 (2 D)0Totalc54.1±25.3 (37.6±18.7 D, 16.5±11 C)7.3±5.1 (6±4.6 D, 1.3±1.4 C)4.2±4.1 (3±2.5 D, 1.2±1.7 C)2.5±4.1 (1.6±2.4 D, 0.9±1.8 C)aSee also Fig. 1.bD, dogs; C, cats. All figures refer to the last 12-month period.cx±S.D.