Phenotypic and genotypic characterisation of antimicrobial resistance in faecal enterococci of healthy humans and animals

Abstract number: P1193

Torres C., López M., Ruiz E., Sáenz Y., Domínguez E., Guerra E., Tenorio C., Lozano C., Ruiz-Larrea F., Zarazaga M.

Objective: To characterise the phenotypes and genes implicated in antimicrobial resistance in faecal enterococci of healthy humans and animals.

Methods: 171 faecal samples of healthy animals (66 pigs, 22 pets and 15 bulls) and humans (50 children under two years old and 18 adults) were seeded onto mEnterococcus agar plates. Two colonies per sample were selected and identified. Susceptibility testing to 10 antimicrobials were carried out by agar dilution method and aminoglycoside, glycopeptide, macrolide and tetracycline resistance genes were studied by PCR and sequencing.

Results: A total of 133 E. faecalis, 63 E. faecium, 55 E. hirae, 4 E. casseliflavus, 4 E. gallinarum, 4 E. avium, 3 E. durans and 7 Enterococcus spp. were recovered. E. faecalis was found in 72% of the isolates from human origin, and this species in addition to E. hirae were the most prevalent ones among pig samples (43 and 37%, respectively). E. faecium was found in 57% of isolates from pets and bulls. The percentages of antibiotic resistance (found in isolates from pigs/pets and bulls/human samples) were as follows: tetracycline (93/66/54%), erythromycin (81/23/29%), ciprofloxacin (18/23/14%), penicillin (5/6/0%), vancomycin MIC > 8 mg/L (0.9/2/4%) and high-level resistance (HLR) to streptomycin (44/9/12%), gentamicin (6/6/5%) and kanamycin (37/9/14%). None of the 273 enterococci showed ampicillin- or teicoplanin-resistance, whereas the highest resistance were found to tetracycline (72%) and erythromycin (49%). One E. faecalis isolate of porcine origin showed a VanB phenotype characterised by acquired inducible resistance to vancomycin and susceptibility to teicoplanin (MICs of 8 mg/L and leqslant R: less-than-or-eq, slant0.5 mg/L, respectively). The vanC gene was found in the six E. gallinarum and E. casseliflavus isolates recovered from human and bulls. The ant(6)-Ia, aac(6')-aph(2") and aph(3')-III genes were demonstrated in most of the isolates with HLR to streptomycin, gentamicin and kanamycin, respectively. The ermB and tet(M) genes were detected in 95% and 92% of erythromycin- and tetracycline-resistant isolates, respectively.

Conclusions: Differences in antimicrobial resistance percentages were observed among faecal enterococci of different origins, being those recovered from pigs the most resistant to tetracycline, erythromycin and streptomycin. The normal microbiota of healthy humans and animals represents a considerable reservoir of antimicrobial resistance genes.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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