Activity of cefditoren versus seven other antimicrobials against amoxicillin non-susceptible Streptococcus pneumoniae

Abstract number: 1733_1524

Perez-Trallero E., Marimon J., Erzibengoa M., Gimenez M., Coronel P., Aguilar L.

Objective: Amoxicillin has the highest intrinsic activity against S. pneumoniae but amoxicillin non-susceptibility is not rarely found among penicillin-resistant isolates. Antibiotic susceptibility testing against these isolates can be considered the workhorse to test new and old compounds.

Methods: Susceptibility to penicillin (PEN), amoxicillin/clavulanic acid (2:1) (AMC), cefuroxime (CXM), cefpodoxime (CPD), cefotaxime (CTX), cefditoren (CDN), erythromycin (ERY), and levofloxacin (LVX) was determined by microdilution with Mueller-Hinton broth supplemented with 3% lysed horse blood according to CLSI guidelines, against 244 isolates exhibiting non-susceptibility to amoxicillin (MIC ≥4mg/mL) and higher amoxicillin vs. penicillin MIC. CLSI susceptibility breakpoints (mg/mL) were considered.

Results: MIC distribution of the antimicrobials tested: no. of isolates inhibited (cumulative percentage) at concentration (mg/mL) are shown in the Table.

 MICa (mg/mL)
PEN  51 (20.9)162 (87.3)31 (100)  0
AMC    124 (50.8)117 (98.8)3 (100)0
CXM    64 (26.2)138 (82.8)42 (100)0
CPD1 (0.4) 29 (12.3)141 (70.1)40 (86.5)29 (98.4)4 (100)0
CTX 36 (14.8)146 (74.6)52 (95.9)9 (99.6)1 (100) 74.6
CDN58 (23.8)126 (75.4)51 (96.3)7 (99.2)2(100)  
ERY67 (27.5)  1 (27.9)3 (29.1) 173 (100)27.5
LVX7 (2.9)99 (43.4)102 (85.2)5 (87.3)1 (87.7)19 (95.5)11 (100)87.3
aMIC90 and MIC50 values are in bold.

Conclusions: On a MIC90 basis, CDN (1mg/mL) exhibited the highest intrinsic activity followed by CTX (2mg/mL), AMC, CPD and LVX (8mg/mL), with a clear inadequacy of CXM and ERY (≥16mg/mL). CDN activity (twice that of CTX) may be useful against amoxicillin non-susceptible strains where only CTX and LVX offer significant activity (70–90% susceptibility rates).

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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