Objectives. Epidemiology of AB resistance in S. pneumoniae. Pasteur Institute (R. Vanhoof) AB resistance evaluation (MIC) & mechanisms

Transcription

1 Epidemiological survey of susceptibility to β-lactams, macrolides, and fluoroquinolones in a Belgian collection of Streptococcus pneumoniae isolated from patients with CAP A. Lismond, S. Carbonnelle, F. Jacobs, M. Struelens, J. Gigi, 3 A. Simon, 3 Y. Van Laethem, A. Dediste, D. Pierard, 5 A. De Bel, 5 F. Van Bambeke, P.M. Tulkens Unité de Pharmacologie cellulaire et moléculaire, Université catholique de Louvain ; Hôpital Erasme, Université Libre de Bruxelles ; 3 Cliniques Universitaires Saint-Luc, Université catholique de Louvain ; Hôpital Saint-Pierre, Université Libre de Bruxelles ; 5 Universitaire Ziekenhuis, Vrije Universiteit Brussel ; Bruxelles.

2 Objectives Epidemiology of AB resistance in S. pneumoniae Belgian Centers for S. pneumoniae Pasteur Institute (R. Vanhoof) AB resistance evaluation (MIC) & mechanisms Reference Lab. (J. Verhaegen) AB resistance evaluation (antibiograms) & serotyping CAP only (from selected centers) AB used in Belgium resistance evaluation (MIC) & efflux mechanism link with the clinic!

3 General protocol Patient with suspicion of pneumonia Sampling for microbiology Isolation of SP Clinical examination, X-ray CAP diagnostic signal Microbiology (A. Lismond) Analysis of the SP MIC, efflux confirmation Clinic : clinical file (Dr. Carbonnelle) Analysis of the case - Symptoms, severity - X-ray - AB: previous, current - Contact of GP - Reason(s) of referral to hospital Microbiological & clinical data are assembled (anonymous) Population analysis for microbiology, PK/PD assessment, pharmacoeconomics 3

4 Efflux pumps: role in antibiotic resistance * AB resistance mechanism Intrabacterial targets: - ribosomes (macrolides) - enzymes (fluoroquinolones) AB activity depends on its capacity to reach its target Efflux pumps intrabacterial concentration AB activity Low level usually NOT detected in the clin. microbiol. lab. May affect more than one antibiotic Favors emergence of high level resistance (Avrain et al., JAC 007; 60:965-97) Equivalent to sub-optimal treatment Therapeutic consequences??? * Van Bambeke et al., JAC 003; 5:

5 Collection: Methods 0/00 /007 today isolates analyzed UZ VUB St-Luc St-Pierre Erasme N = 33 Erasme: St-Luc: 39 St-Pierre: 6 UZ VUB: 5

6 Methods MIC testing according to CLSI: UUUUUUUUUU MIC Geometric microdilutions

7 Methods MIC testing according to CLSI: UUUUUUUUUU MIC Geometric microdilutions UUUU Semi-geometric microdilutions around breakpoint value ( mg/l in this example): efflux detection 7

8 Results: Amoxicillin cumulative percentage AMX Wt S I R MIC values 8 6 Susceptibility according to EUCAST breakpoints: S 0.5: 88% I: % R > : 0% MIC 50 = mg/l MIC 90 =.5 mg/l 8 3

9 β-lactams cumulative percentage AMX CFX CRO MIC values 9

10 β-lactams cumulative percentage AMX CFX CRO MIC values 0

11 Macrolides & Ketolides cumulative percentage MIC values CLR TEL

12 Fluoroquinolones cumulative percentage MXF LVX MIC values

13 Fluoroquinolones cumulative percentage MXF LVX MIC values 3

14 Results: efflux observation Efflux percentage? Macrolides: MIC to ERY (36%R) >< CLI (8%R) 8% of strains get M phenotype ~0% of R strains by efflux only!

15 Results: efflux observation Efflux percentage? Macrolides: MIC to ERY (36%R) >< CLI (8%R) Which strains get efflux? % of strains % of strains get M phenotype ~0% of R strains by efflux only! S I R ERY < dil dil dil 3 dil dil MIC 50 MIC 90 MIC values MLS

16 Efflux percentage? Results: efflux observation Fluoroquinolones: MIC to CIP, MXF & LVX ± reserpine Which strains get efflux? CIP 7.% CIP MIC distribution I R <dil dil dil % of strains MIC 50 MIC 90 MIC values 6 8 6

17 Efflux percentage? Results: efflux observation Fluoroquinolones: MIC to CIP, MXF & LVX ± reserpine Which strains get efflux? MXF 6.3% MXF MIC distribution S R <dil dil % of strains MIC 50 = MIC MIC values.5 3

18 Efflux percentage? Results: efflux observation Fluoroquinolones: MIC to CIP, MXF & LVX ± reserpine Which strains get efflux? LVX 6.8% LVX MIC distribution S R <dil dil % of strains MIC 50 MIC 90 MIC values

19 Conclusions From this evaluation of SP from CAP: β-lactams Significant proportion (~ %) of "intermediates" for AMX high doses are needed!! Significant proportion (~3%) of "resistants" for CFX Can we still use it safely? Macrolides/ketolides Conventional ML are no longer usable with efflux being responsible for 0 % of resistance Resistance to TEL becomes detectable follow-up is needed Fluoroquinolones MXF and LVX MIC's are still below breakpoints (high dose for LVX) Efflux is important for CIP and marginal for LVX and MXF 9

20 0