Antibiotic Resistance among invasive pneumococcal Isolates from Southwest Sweden 1998-2001

All isolates (827 patients)

17,8%

8,6%8,5%

14,3%

Other

9V

9N

8

7F

6B

6A

4

3

23F

19A

14

12F

1

61 isolates with elevated MIC

12,5%

15,6%

7,8%

7,8%

43,8%

Other

9V

6B

19F

19A

14

1

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

Poster at the 15th ECCMID, April 2-5 2005, Copenhagen

The abstract has been slightly revised with addition of new data.

ObjectivesStreptococcus 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.

MethodsAll 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.

Results827 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).

ConclusionThe 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.

Antibiotic agent Total Sensitive Indeterminate Resistant

number breakpoint** number number breakpoint**

Penicillin G 827 805 <0.06 mg/L 22(2.7%) 0 >1.0 mg/L Erythromycin 827 797 <0.5 mg/L n.r.* 30 (3.6%) >0.5 mg/LClindamycin 827 821 <2 mg/L n.r.* 6 (0.7%) >2 mg/LTetracycline 827 811 <2 mg/L n.r.* 16 (1.9%) >2 mg/LMoxifloxacin 827 826 <0.5 mg/L n.r.* 1 (0.1%) >0.5 mg/LTrim/Sulfa 1/19*** 827 815 <16 mg/L 21(2.5%) 0 >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

Number of S, I and R to six antibiotics

Distribution of MIC values for 827 invasive strains of Streptococcus pneumoniae

Distribution of MIC’s Serotype distribution

Sensitivity pattern and serotypes

E-test

Penicillin G Erythromycin Clindamycin Moxifloxacin Trimethoprim/sulphamethoxazole

MIC (mg/L)

,500

,380

,250

,190

,125

,094

,064

Num

ber

400

300

200

100

0256

128

64

48

32

24

16

12

S R

MIC (mg/L)

256,500,380,250,190,125,094,064

Num

ber

400

300

200

100

0

S R

Sensitivity pattern number serotypes (no of isolates)

Sensitive to all tested substances 766

I or R to any substance 61

- I or R to only one substance 40 Penicillin G (I) 3 19A(1), 19F(2) Erythromycin (R) 24 14(24) Tetracycline (R) 6 several Trim/Sulfa (I) 6 several Moxifloxacin (R) 1 1

- I or R to more than one substance 21 PcG (I)+T/S (I) 11 9V(8), 14(2), 6B(1) PcG (I)+Tet (R) 2 14(1), 19F(1) PcG (I)+Tet (R)+T/S (I) 2 6A(1), 19A(1) PcG (I)+Ery (R)+Clin(R)+Tet (R) 2 6B(1), 14(1) PcG (I)+Ery (R)+Clin(R)+Tet (R)+T/S (I) 2 19F(2) Ery (R)+Clin(R)+Tet (R) 2 6B(1), 14(1)

Total 827 61

Tetracycline

MIC (mg/L)

,750

,500

,380

,250

,190

,125

,094

,064

Num

ber

500

400

300

200

100

0

48

32

24

16842

631,5

S R

1

12

64

MIC (mg/L)

1

,75

,50

,380

,250

,190

,125

,094

,064

,047

,032

,023

,016

,012

,008

,006

Num

ber

400

300

200

100

0

S I R

1,5

2

MIC (mg/L)

8,380,250,190,125,094,064,047

Num

ber

500

400

300

200

100

0

S R

MIC (mg/L)

32

8

6

4

3

2

1,500

1,0

,75

,50

,380

,250

,190

,125

,064

Num

ber

400

300

200

100

0

S I R

4864

Antibiotic agent MIC 50 MIC 90median 90 percentilemg/L mg/L

Penicillin G 0.016 0.023Erythromycin 0.190 0.250Clindamycin 0.190 0.250Tetracycline 0.125 0.190Moxifloxacin 0.125 0.190Trim /Sulfa 1/19*** 0.5 1