Characterisation of an outbreak of nosocomial infection caused by a multiresistant Acinetobacter baumannii producing OXA-30 type-b-lactamase

Abstract number: P1215

Biendo M., Canarelli B., Adjide C., Thomas D., Castelain S., Rousseau F., Hamdad F., Eb F.

Objectives: 1. Analysis of the molecular mechanisms involved in the b-lactam resistance of multidrug-resistant A. baumannii isolates; 2. the phenotypically and genotypically comparison of clinical and environmental outbreak strains to those obtained before the outbreak.

Methods and Results: Forty multiresistant-drug A. baumannii (MDRAB) isolates were consisted of: 8 preoutbreak isolates, 27 clinical and 5 environmental outbreak isolates. Thirty-five clinical isolates were recovered from twenty-six patients admitted to different wards belonging to Amiens University Hospital (AUH), France. MDRAB outbreak strains were observed in the orthopaedic and plastic surgery wards.

The A. baumannii isolates were resistant to all of b-lactams tested (MICs, 48–>256 ug/mL) except imipenem (MIC < 4 ug/mL), to aminoglycosides (MICs, 24–>256 ug/mL), and to ciprofloxacin (MIC > 256 ug/mL). All isolates remained susceptible to colistin (MIC < 2 ug/mL).

The frequency of intl1 gene carriage was 96.8% and 37.8% in the outbreak and preoutbreak isolates respectively.

By using isoelectric focusing, three b-lactamases were detected: one produced a band with a pI > 8.0, probably corresponding to a chromosomal AmpC cephalosporinase, the second focused at pI 5.4 and was consistent to TEM-1, the third focused at pI 7.3 and corresponded to OXA-30 type.

blaOXA-30 analysis revealed 3 gene cassettes: intl1 gene with 459-bp coding for an integrase; aacA4 gene with 759-bp encoding a 6'-N-aminoglycoside acetyl transferase and blaOXA-30 gene with 852-bp coding for OXA-30 b-lactamase, with ATG as initiation codon and TAA as termination codon. The deduced amino acid sequence showed an enzyme of 276 amino acids long with Ser-Thr-Phe-Lys at positions 71 to 74, Tyr-Gly-Asn at positions 144 to 146, and Lys-Thr-Gly at positions 215 to 217. blaOXA-30 differed from blaOXA-1 by one base at codon (AGA 131-GGA) resulting in amino acid substitution Arg128-Gly. Pulsed Field Gel Electrophoresis with ApaI showed a single pattern (A) in outbreak and environmental isolates, and 6 unrelated genotypes (B-G) in preoutbreak isolates.

Conclusion: The present work is the first report of A. baumannii clinical isolates in France that produce an OXA-30 b-lactamase.

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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