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

1
Antibiotic Resistance among invasive pneumococcal
Isolates from Southwest Sweden 1998-2001
Poster at the 15th ECCMID, April 2-5 2005,
Copenhagen
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_at_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
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 MICgt1.0 mg/L against penicillin (R). 22
isolates (2.7) were classified as I to
penicillin (MIC gt0.06, ?1.0 mg/L). 13 of them had
MICs ? 0.5 mg/L. Among the 22 isolates
classified as I to penicillin 12 isolates were
also I against cefotaxime (MIC gt0.12, ?1.0 mg/L)
(1.5).   The other tested antibiotics showed
the following results Erythromycin R (MIC gt0.5
mg/L) 30 isolates (3.6), clindamycin R (MICgt2
mg/L) 6 isolates (0.7), tetracycline R
(MICgt2mg/L) 16 isolates (1,9), and moxifloxacin
R (MICgt0,5 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 gt16, ?32 mg/L), but no
R (MICgt32 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.
Distribution of MICs
Serotype distribution
61 isolates with elevated MIC
All isolates (827 patients)
Sensitivity pattern and serotypes
Number of S, I and R to six antibiotics
Distribution of MIC values for 827 invasive
strains of Streptococcus pneumoniae
Erythromycin
Penicillin G
Clindamycin
Trimethoprim/sulphamethoxazole
Tetracycline
Moxifloxacin