Escherichia coli resistance to amoxicillin and co-amoxiclav in a community with high aminopenicillin consumption rate

A. Torres1, F. de la Torre1, M. Díez-Alonso2, J. Romanyck2, A. Torrellas3 and L. Aguilar3
1Surgery and Microbiology Departments, Hospital San Carlos, Madrid; 2Surgery and Microbiology Departments, Hospital "Príncipe de Asturias", Alcalá de Henares; 3Medical Department SmithKline Beecham Pharmaceuticals, Madrid, Spain.

Sir,
In a recent publication (1), the authors report a percent- age of 4.3% resistance to co-amoxiclav of 185 Escherichia coli strains collected in a study conducted in two centers from each of the followmg countries Spain, France and Germany.
If antibiotic resistance is accepted to be related with antibiotic consumption (2), the expected resistance rate to penicillins in Spain should be very high, as a recent survey showed that 88% of the Spanish population take antibiotics at least once a year (50% of the total consumption are aminopenicillins or their combinations with beta-lactamase inhibitors) (3). This fact may explain the high amoxicillin resistance rate (56.2%) obtained in the E. coli strains provided by the two Spanish centers participating in the referenced study (1), as compared to a resistance rate of 47% obtained in the German and French centers. When clavulanate is added to the susceptibility test (2:1), this high amoxicillin resistance rate is significantly reduced. Co-amoxiclav resistance rate (4.2%) is similar to the one obtained in the German and French centers (4.4%), even though Spain has one of the highest E. coli aminopenicillin resistance rates within the European Union countries (3).
The sample (n = 97) of E. coli strains from the Spanish centers was prospectively collected from patients admitted to hospital surgical wards between March to November 1994, from the following sources: 58.1% from peritoneal fluid, 22.6% abscess material, 16.1% urine and 3.2% other sources. The resistance rates shown in this letter were obtained following NCCLS guidelines (4).
The high ampicillin/amoxicillin E. coli resistance rate of our strains is similar to the one described by other authors in our country from urinary tract isolates (5-8). However, despite the high aminopenicillin consumption when compared to other European countries (3), the incidence of E. coli co-amoxiclav resistance in our community remains in a similar range to that of the German and French centers participating in the study.

REFERENCES
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2. Moellering, R.C. Interaction between antimicrobial consumption and selection of resistant bacterial strains. Scan J Infect Dis 1990; 70 (Suppl.): 18-24.
3. Baquero, F. and the Task Force of the General Direction for Health Planning of the Spanish Ministry of Health. Antibiotic resistance in Spain: What can be done? Clin Infect Dis 1996; 23: 819-823.
4. National Committee for Clinical Laboratory Standards. Antimicrobial Susceptibility Testing SC-3B. NCCLS, Villanova, PA 1993.
5. Grupo de Estudio Multicéntrico, Román Pumar, J.L. Estudio de ámbito nacional para valorar la actividad in vitro de la norfloxacina y otros seis antibacterianos frente a patógenos urinarios. Med Clin (Barc.) 1986; 86: 741.
6. Cercenado, E., Aguiar, J.M., González-Palacios, R., Delgado Iribarren, A., Baquero, F. Situación actual de la resistencia de bacterias aisladas de bacteriurias intra y extrahospitalarias. Med Clin (Barc.) 1987; 88: 93-96.
7. Alós, J.I., Chacón, J. Bacteriología de las infecciones urinarias extra hospitalarias. Med Clin (Barc.) 1988; 90: 395-398.
8. Alós, J.I., Gómez-Garcés, J.L., García-Bermejo, I., García-Gómez, J.J., González-Palacios, R., Padilla, B. Prevalencia de susceptibilidad de Escherichia coli a quinolonas y otros antibióticos en bacteriurias extrahospitalarias de Madrid. Med Clin (Barc.) 1993; 101: 87-90.

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