1 Table S1. The documentation rate of reasons for antimicrobial drug use. Reasonsa Total Site A Site B Any reasons 232/327 (70.9%) 53/79 (67.1%) 179/248 (72.2%) Treatment of infection 138/163 (84.7%) 37/43 (86.0%) 101/120 (84.2%) Prophylaxis Surgical 76/101 (75.2%) 14/28 (50.0%) 62/73 (84.9%) Medical 18/46 (39.1%) 2/5 (40.0%) 16/41 (39.0%) Non-infectious reasons 0/3 (0.0%) 0/1 (0.0%) 0/2 (0.0%) Unknown reasons 0/14 (0.0%) 0/2 (0.0%) 0/12 (0.0%) aInvestigators speculated the reasons for antimicrobial drug use by reviewing the medical electronic records when the reasons were not documented in medical records. 2 Table S2. Clinical and demographic characteristics of surveyed patients according to the different sitesa. Total Site A Site B Characteristics N = 820 N = 256 N = 564 Age, yr, median (IQR) 70 (55 – 80) 76 (67 – 84) 68 (48 – 77) Age category < 1 year 34 (4.2) 2 (0.8) 32 (5.7) 1 – 17 year 30 (3.7) 11 (4.3) 19 (3.4) 18 – 24 year 10 (1.2) 1 (0.4) 9 (1.6) 25 – 44 year 74 (9.0) 12 (4.7) 62 (11.0) 45 – 64 year 160 (19.5) 33 (12.9) 127 (22.5) 65 – 84 year 415 (50.6) 142 (55.5) 273 (48.4) > 84 year 97 (11.8) 55 (21.5) 42 (7.5) Women 380 (46.3) 131 (51.2) 249 (44.2) Residence before the index admissionb Home 747 (91.1) 230 (89.8) 517 (91.7) Nursing care facility 27 (3.3) 14 (5.5) 13 (2.3) Other hospitals 23 (2.8) 12 (4.7) 11 (2.0) Past medical history Ischaemic heart disease 57 (7.0) 16 (6.3) 41 (7.3) Stroke 89 (10.9) 34 (13.3) 55 (9.8) Dementia 39 (4.8) 21 (8.2) 18 (3.2) Liver cirrhosis 19 (2.3) 8 (3.1) 11 (2.0) Diabetes mellitus 150 (18.3) 47 (18.4) 103 (18.3) Dialysis 26 (3.2) 0 (0.0) 26 (4.6) Immunosuppression drug use 107 (13.1) 23 (9.0) 84 (14.9) Location in hospitals Ward 777 (94.8) 247 (96.5) 530 (94.0) Critical care unit 43 (5.2) 9 (3.5) 34 (6.0) Central line in place on survey date Any 54 (6.6) 17 (6.6) 37 (6.6) Peripherally inserted 4 (0.5) 0 (0.0) 4 (0.7) Peripheral line in place on survey date 284 (34.6) 88 (34.4) 196 (34.8) Urinary catheter in place on survey date 121 (14.8) 33 (12.9) 88 (15.6) Intubated or tracheal tube in place on survey date 25 (3.1) 2 (0.8) 23 (4.1) Drainage tube in place on survey date 49 (6.0) 6 (2.3) 43 (7.6) 3 Median days to survey date from admission (IQR) 9 (3 – 23) 9 (3 – 22) 8 (3 – 23) aValues are the number of patients, with percentage of the total patients in parenthesis according to the survey site. bTwenty-three patients who were born in site B were excluded. 4 Table S3. Prevalence of antimicrobial drug use according to different specialties. Specialty Number of patients Prevalence, % (95% CI)a Total 820 33.5 (30.3 – 36.8) Site A 256 28.5 (23.0 – 34.1) Site B 564 35.8 (31.9 – 39.8) General surgery 144 34.0 (26.2 – 41.8) Site A 53 30.2 (17.4 – 43.0) Site B 91 36.4 (26.2 – 46.3) Orthopaedic surgery 91 24.2 (15.2 – 33.1) Site A 46 17.4 (6.0 – 28.8) Site B 45 31.1 (17.0 – 45.2) Neurosurgery 39 28.2 (13.4 – 43.0) Site A 23 30.4 (10.1 – 50.8) Site B 16 25.0 Cardiac surgery 20 45.0 (21.1 – 68.9) Site A 0 NA Site B 20 45.0 (21.1 – 68.9) Gynaecology 63 36.5 (24.2 – 48.7) Site A 4 25.0 Site B 59 37.3 (24.6 – 50.0) Oral and maxillofacial surgery 13 76.9 Site A 13 76.9 Site B 0 NA Otorhinolaryngology 22 36.4 (14.5 – 58.2) Site A 5 60.0 Site B 17 29.4 Ophthalmology 15 86.7 Site A 0 NA Site B 15 86.7 Urology 43 41.9 (26.5 – 57.2) Site A 13 23.1 Site B 30 50.0 (31.0 – 69.0) Dermatology 4 25.0 Site A 4 25.0 Site B 0 NA Internal medicine 301 26.9 (21.9 – 31.9) 5 Site A 90 23.3 (14.4 – 32.2) Site B 211 28.4 (22.3 – 34.6) Haematology 19 78.9 Site A 0 NA Site B 19 78.9 Paediatrics 43 30.3 (15.9 – 44.5) Site A 5 60.0 Site B 38 26.3 (11.6 – 41.0) aThe 95% confidence intervals were not calculated if the number of patients was less than 20. CI, confidence interval; NA, not available. 6 Table S4. Groups of antimicrobial drugsa representing more than one percent of antimicrobial drugs given to surveyed patientsb. Type Total Site A Site B All antimicrobial drugs 327 (100.0) 79 (100.0) 248 (100.0) First-generation cephalosporins 71 (21.7) 20 (25.3) 51 (20.6) Cefazolin 70 (21.4) 19 (24.1) 51 (20.6) Cefalexin 1 (0.3) 1 (1.3) 0 (0.0) Third-generation cephalosporins 44 (13.5) 15 (19.0) 29 (11.7) Ceftriaxone 30 (9.2) 11 (13.9) 19 (7.7) Cefoperazone-sulbactam 4 (1.2) 0 (0.0) 4 (1.6) Cefcapene 4 (1.2) 1 (1.3) 3 (1.2) Ceftazidime 3 (0.9) 2 (2.5) 1 (0.4) Cefditoren 3 (0.9) 1 (1.3) 2 (0.8) Penicillin combinations 43 (13.1) 16 (20.3) 27 (10.9) Piperacillin-tazobactam 22 (6.7) 3 (3.8) 19 (7.7) Ampicillin-sulbactam 19 (5.8) 12 (15.2) 7 (2.8) Amoxicillin-clavulanate 2 (0.6) 1 (1.3) 1 (0.4) Sulfonamide and trimethoprim combinations 27 (8.3) 4 (5.1) 23 (9.3) Trimethoprim-sulfamethoxazole 27 (8.3) 4 (5.1) 23 (9.3) Extended-spectrum penicillins 26 (8.0) 5 (6.3) 21 (8.5) Piperacillin 18 (5.5) 1 (1.3) 17 (6.9) Ampicillin 5 (1.5) 1 (1.3) 4 (1.6) Amoxicillin 3 (0.9) 3 (3.8) 0 (0.0) Second-generation cephalosporins 26 (8.0) 12 (15.2) 14 (5.6) Cefmetazole 21 (6.4) 9 (11.4) 12 (4.8) Cefotiam 4 (1.2) 3 (3.8) 1 (0.4) Cefaclor 1 (0.3) 0 (0.0) 1 (0.4) Fluoroquinolones 20 (6.1) 0 (0.0) 20 (8.1) Levofloxacin 18 (5.5) 0 (0.0) 18 (7.3) Ciprofloxacin 1 (0.3) 0 (0.0) 1 (0.4) Tosufloxacin 1 (0.3) 0 (0.0) 1 (0.4) Triazole antifungals 12 (3.7) 0 (0.0) 12 (4.8) Fluconazole 11 (3.4) 0 (0.0) 11 (4.4) Itraconazole 1 (0.3) 0 (0.0) 1 (0.4) Carbapenems 9 (2.8) 0 (0.0) 9 (3.6) Meropenem 9 (2.8) 0 (0.0) 9 (3.6) 7 Glycopeptide (parenteral) 8 (2.4) 1 (1.3) 7 (2.8) Vancomycin 8 (2.4) 1 (1.3) 7 (2.8) Macrolides 8 (2.4) 3 (3.8) 5 (2.0) Erythromycin 4 (1.2) 1 (1.3) 3 (1.2) Clarithromycin 3 (0.9) 1 (1.3) 2 (0.8) Azithromycin 1 (0.3) 1 (1.3) 0 (0.0) Fourth-generation cephalosporins 7 (2.1) 0 (0.0) 7 (2.8) Cefozopran 6 (1.8) 0 (0.0) 6 (2.4) Cefepime 1 (0.3) 0 (0.0) 1 (0.4) Nucleoside and nucleotide antivirals 4 (1.2) 0 (0.0) 4 (1.6) Valaciclovir 2 (0.6) 0 (0.0) 2 (0.8) Ganciclovir 1 (0.3) 0 (0.0) 1 (0.4) Famciclovir 1 (0.3) 0 (0.0) 1 (0.4) Tetracyclines 4 (1.2) 2 (2.5) 2 (0.8) Minocyclin 4 (1.2) 2 (2.5) 2 (0.8) aAntimicrobial drugs were classified and reported based on the World Health Organization Anatomical Therapeutic Chemical fifth-level classification. bValues are the number of antimicrobial drugs, with the percentage of the total number of antimicrobial drugs in parenthesis according to the site. 8 Table S5. Number and type of antimicrobial drugs given to treat infections according to the survey sitea. Type Total Site A Site B Total antimicrobial drugs 163 (100.0) 43 (100.0) 120 (100.0) Ceftriaxone 25 (15.3) 9 (20.9) 16 (13.3) Piperacillin-tazobactam 22 (13.5) 3 (7.0) 19 (15.8) Cefmetazole 13 (8.0) 7 (16.3) 6 (5.0) Cefazolin 12 (7.4) 6 (14.0) 6 (5.0) Ampicillin-sulbactam 12 (7.4) 5 (11.6) 7 (5.8) Meropenem 9 (5.5) 0 (0.0) 9 (7.5) Vancomycin (parenteral)b 8 (4.9) 1 (2.3) 7 (5.8) Levofloxacin 6 (3.7) 0 (0.0) 6 (5.0) Cefozopran 6 (3.7) 0 (0.0) 6 (5.0) Ampicillin 5 (3.1) 1 (2.3) 4 (3.3) Cefoperazone-sulbactam 4 (2.5) 0 (0.0) 4 (3.3) Ceftazidime 3 (1.8) 2 (4.7) 1 (0.8) Trimethoprim-sulfamethoxazole 3 (1.8) 1 (2.3) 2 (1.7) Amoxicillin 2 (1.2) 2 (4.7) 0 (0.0) Amoxicillin-clavulanate 2 (1.2) 1 (2.3) 1 (0.8) Piperacillin 2 (1.2) 1 (2.3) 1 (0.8) Cefcapene 2 (1.2) 0 (0.0) 2 (1.7) Minocycline 2 (1.2) 1 (2.3) 1 (0.8) Rifampicine 2 (1.2) 0 (0.0) 2 (1.7) Micafungin 2 (1.2) 0 (0.0) 2 (1.7) Cefalexin 1 (0.6) 1 (2.3) 0 (0.0) Cefaclor 1 (0.6) 0 (0.0) 1 (0.8) Cefotiam 1 (0.6) 0 (0.0) 1 (0.8) Cefditoren 1 (0.6) 1 (2.3) 0 (0.0) Cefepime 1 (0.6) 0 (0.0) 1 (0.8) Ciprofloxacin 1 (0.6) 0 (0.0) 1 (0.8) Tosufloxacin 1 (0.6) 0 (0.0) 1 (0.8) Clindamycin 1 (0.6) 0 (0.0) 1 (0.8) Clarithromycin 1 (0.6) 0 (0.0) 1 (0.8) Azithromycin 1 (0.6) 1 (2.3) 0 (0.0) Fosfomycin 1 (0.6) 0 (0.0) 1 (0.8) Vancomycin (enteral)c 1 (0.6) 0 (0.0) 1 (0.8) 9 Metronidazole (parenteral)b 1 (0.6) 0 (0.0) 1 (0.8) Metronidazole (enteral)c 1 (0.6) 0 (0.0) 1 (0.8) Daptomycin 1 (0.6) 0 (0.0) 1 (0.8) Linezolid 1 (0.6) 0 (0.0) 1 (0.8) Fluconazole 1 (0.6) 0 (0.0) 1 (0.8) Itraconazole 1 (0.6) 0 (0.0) 1 (0.8) Amphotericin B (parenteral)b 1 (0.6) 0 (0.0) 1 (0.8) Famciclovir 1 (0.6) 0 (0.0) 1 (0.8) Ganciclovir 1 (0.6) 0 (0.0) 1 (0.8) aValues are the number of antimicrobial drugs, with the percentage of the total number of antimicrobial drugs in parenthesis according to the site.