Number of S, I and R to six antibiotics Poster at the 15th ECCMID, April 2-5 2005, Copenhagen Antibiotic Resistance among invasive pneumococcal Isolates from Southwest Sweden 1998-2001 Erik Backhaus1, Birger Trollfors2, Stefan Berg2, Berndt EB Claesson1, Rune Andersson. 1. 1Department of Infectious Diseases and Clinical Microbiology, Kärnsjukhuset, Skövde, 2Department of Paediatrics, The Queen Silvia Children's Hospital, Göteborg,SwedenCorrespondence: erik.backhaus@vgregion.se The abstract has been slightly revised with addition of new data. Objectives Streptococcus pneumoniae is a major human pathogen. In Southwest Sweden, with a population of 1.8 million, 200 patients are diagnosed each year with invasive pneumococcal disease. The rapid emergence of isolates with decreased susceptibility to several antibiotics is an increasing problem in many parts of the world. The aim of the present study was to investigate the pattern of susceptibility among invasive isolates, in order to see if the current treatment policies are appropriate, and to see if there seems to be a trend of increasing antibiotic resistance. Methods All clinical isolates of S. pneumoniae from blood, cerebrospinal and joint fluid were collected at the laboratories in Göteborg, Skövde, Borås, Uddevalla and Halmstad during 1998-2001. The MIC-values for seven commonly used antibiotics (penicillin G, erythromycin, clindamycin, tetracycline, moxifloxacin, cotrimoxazole and cefotaxime) were determined with E-test (AB Biodisk) according to standard methods. E-test Distribution of MIC’s Serotype distribution Results 827 invasive strains were tested. Of these, 766 were fully susceptible and 61 (7.4%) were classified as Indeterminate (I) or Resistant (R) for any of the tested antibiotics, according to the Swedish Reference Group for Antibiotics system of species related breakpoints. No isolate had a MIC>1.0 mg/L against penicillin (R). 22 isolates (2.7%) were classified as I to penicillin (MIC >0.06, 1.0 mg/L). 13 of them had MIC’s  0.5 mg/L. Among the 22 isolates classified as I to penicillin 12 isolates were also I against cefotaxime (MIC >0.12, 1.0 mg/L) (1.5%).   The other tested antibiotics showed the following results: Erythromycin R (MIC >0.5 mg/L) 30 isolates (3.6%), clindamycin R (MIC>2 mg/L) 6 isolates (0.7%), tetracycline R (MIC>2mg/L) 16 isolates (1,9%), and moxifloxacin R (MIC>0,5 mg/L) 1 isolate (0.1%). There were no isolates classified as I for those antibiotics. There were 21 isolates (2,5%) classified as I against cotrimoxazole (MIC >16, 32 mg/L), but no R (MIC>32 mg/L). Conclusion The proportion of invasive isolates of pneumococci with decreased sensitivity to commonly used antibiotics is very low. Our results indicate that there might be a clonal spread of isolates of serotype 9V and 14 with reduced susceptibility to antibiotics. 61 isolates with elevated MIC All isolates (827 patients) Antibiotic agent MIC 50 MIC 90 median 90 percentile mg/L Penicillin G 0.016 0.023 Erythromycin 0.190 0.250 Clindamycin Tetracycline 0.125 Moxifloxacin Trim /Sulfa 1/19*** 0.5 1 12,5% 15,6% 7,8% 43,8% Other 9V 6B 19F 19A 14 1 17,8% 8,6% 8,5% 14,3% Other 9V 9N 8 7F 6B 6A 4 3 23F 19A 14 12F 1 Number of S, I and R to six antibiotics Sensitivity pattern and serotypes Antibiotic agent Total Sensitive Indeterminate Resistant number breakpoint** Penicillin G 827 805 < 0.06 mg/L 22(2.7%) >1.0 mg/L Erythromycin 797 0.5 mg/L n.r.* 30 (3.6%) >0.5 mg/L Clindamycin 821 2 mg/L 6 (0.7%) >2 mg/L Tetracycline 811 16 (1.9%) Moxifloxacin 826 1 (0.1%) Trim/Sulfa 1/19*** 815 16 mg/L 21(2.5%) >32 mg/L ** Species related breakpoints according to the Swedish Reference Group for Antibiotics system. *** Values on the MIC scale refer to the first component of the combination. *not relevant Distribution of MIC values for 827 invasive strains of Streptococcus pneumoniae Penicillin G Erythromycin Clindamycin Tetracycline Moxifloxacin Trimethoprim/sulphamethoxazole MIC (mg/L) 1 ,75 ,50 ,380 ,250 ,190 ,125 ,094 ,064 ,047 ,032 ,023 ,016 ,012 ,008 ,006 Number 400 300 200 100 S I R 1,5 2 MIC (mg/L) ,500 ,380 ,250 ,190 ,125 ,094 ,064 Number 400 300 200 100 256 128 64 48 32 24 16 12 S R MIC (mg/L) 256 ,500 ,380 ,250 ,190 ,125 ,094 ,064 Number 400 300 200 100 S R MIC (mg/L) ,750 ,500 ,380 ,250 ,190 ,125 ,094 ,064 Number 500 400 300 200 100 48 32 24 16 8 4 2 6 3 1,5 S R 1 12 64 MIC (mg/L) 8 ,380 ,250 ,190 ,125 ,094 ,064 ,047 Number 500 400 300 200 100 S R MIC (mg/L) 32 8 6 4 3 2 1,500 1,0 ,75 ,50 ,380 ,250 ,190 ,125 ,064 Number 400 300 200 100 S I R 48 64