Evaluation of the EUCAST recommendations for antimicrobial susceptibility of Campylobacters on the 3 main Campylobacter species isolated in humans in France. Lehours Philippe, Sifré Elodie, Ben Amor Salha, Ducournau Astrid, Chardon Hubert, Mégraud Francis. CNR des Campylobacters et Hélicobacters, Laboratoire de Bactériologie, Université de Bordeaux et Hôpital Pellegrin, Bordeaux, France. Centre Hospitalier du Pays d'Aix, Service de diagnostic biologique des maladies infectieuses, Aix en Provence.
Introduction and aim Material and Methods
- Disk diffusion (DD) method was used for erythromycin (15 IU); ciprofloxacin (5 µg); tetracycline (30 IU); ampicillin (10 µg); The EUCAST recently proposed epidemiological cut-offs for Campylobacters and especially for amoxicillin+clavulanic acid (20/10 µg); ertapenem and gentamicin (10 µg). Campylobacter jejuni (CJ) and Campylobacter coli (CC). The aim of the present study was 1) to - MICs with E-test strips for ampicillin, amoxicillin+clavulanic acid and ertapenem, were also determined. test the recommendations for erythromycin, ciprofloxacin and tetracycline on a large number of - The EUCAST method was used on 326 CJ, 114 CC and 100 CF isolates. Mueller-Hinton agar + 5% defibrinated horse blood strains, 2) to test if they could also be used for Campylobacter fetus (CF) and finally 3) to define and 20 mg/L β-NAD (MH-F) was used and plates were flooded with a 0.5 McFarland bacterial suspension and incubated at epidemiological cut-offs for other antibiotics important for treatment of systemic infections. 37°C (instead of 42°C), 24h. Read zone edges as the point showing no growth viewed from the front of the plate with the lid removed and with reflected light. Quality control: Campylobacter jejuni ATCC 33560
EUCAST C. jejuni C. coli C. fetus this study Results
ERY ERY: The cut-offs defined by the EUCAST are different for CJ (R<20 mm) and CC (R<24 mm). There were no resistant CJ isolates and 17 macrolide resistant CC (14.91%) including 8 strains with inhibitory diameters between 20 and 24 mm. These strains were all susceptible C. fetus -Ciprofloxacin No. isolates 30 according to their MIC (S<4 mg/L). Therefore the same cut-off for both CJ and CC (R<20 mm) appears justified. For CF there was no 20 real separation in the inhibitory diameter distribution.
10 CIP CIP: The EUCAST cut-off (R<26 mm) was found to be appropriate for CJ and CC but not for CF: 174 out of 326 CJ (53.37%) and 87 out of 114 0 mm 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 CC (76.31%) strains were resistant. TET: Considering the EUCAST cut-off (R<30 mm), 199 out of 326 CJ (61.04%), 89 out of 114 CC (78.07%) and 31 out of 101 CF (30.69%) TET strains were resistant. AM, AMC and ETP: The following cut-offs for ampicillin and amoxicillin+clavulanic acid could be used for the three species: S>19 mm and R<14 mm. For MICs S<4 and R>16mg/L: 123 out of 326 CJ (37.73%) and 25 out of 114 CC (21.92%) strains were resistant to ampicillin by DD method and 121 out of 326 CJ (37.1%) and 24 out of 114 CC (21.92%) using Etest. For CF, no resistance was detected. For ertapenem the AM cut-off >1 mg/L can be used even if 2 CJ, 9 CC and 1 CF had higher MICs (up to 4-16 mg/L). GM: Only one CC isolate was resistant (confirmed by Etest, MIC> 256 mg/L). Correlation DD/MIC for ampicillin MIC (mg/L) DD (mm) AMC Antibiotic SR SR CIP <0,5 >0,5 >26 <26 non valuable for CF ERY* <4>4>20 <20 valuable for CJ and CC but not for CF GM TET <2>2>30 <30 valuable for CJ, CC and CF AM <4>16>19 <14 AMC <4/2 >16/2 >19 <14 valuable for CJ, CC ETP <1>1 and CF GM <2>2>17 <17 * this study Conclusions There was a perfect correlation between diameters and MIC categorization for CJ and only 3 CC isolates defined as susceptible by disk diffusion were in the intermediate category according to their MICs
The EUCAST recommendations are adapted for CJ and CC testing but only include cut-offs for 3 antibiotics. The present study proposes some minor modifications and provides data for other antimicrobial compounds and CF which were not Perspectives included initially. AST for CF should be interpreted with caution based on the DD method, and MICs should be preferred. MICs for C. fetus should be determined.