First identification in Italy of contemporary presence of qnrB9 element and blaTEM-116 ESBL-gene in Citrobacter freundii environmental strain

Abstract number: P1203

Forcella C., Perilli M., Pellegrini C., Tavìo-Perez M.M., Rainaldi S., Bellio P., Di Lisio C., Segatore B., Amicosante G., Celenza G.

Objectives: Bacteria resistant to antibiotics and disinfectants have been detected in environmental compartments such as waste water, surface water, ground water, sediments and soils; resistant bacteria may be released directly into waste water systems from hospitalised and non-hospitalised patients. The aim of this study was to monitor the antibiotic resistance in the municipal sewage of a small city, in an Italian region.

Methods: 0.1 mL of the samples, collected during the period January-May 2008 from waste water of a urban sewage plant of the L'Aquila city (Italy), were diluted in sterile saline solution and plated on Nutrient Agar or MacConkey plates supplemented with nalidixic acid (6 mg/L) in order to select for potential resistance to quinolones. Genomic DNA was extracted from the strain according to the standard procedure. The blaTEM-like and qnr gene were sequenced on both strands according to the dideoxy-chain termination method by using an ABI-PRISM 310 (Applied Biosystem, Monza, Italy) automatic sequencer. MICs were determined by the conventional macrodilution broth procedure, according to the CLSI guidelines.

Results:Citrobacter freundii AQ/1, selected for resistance to nalidixic acid, showed a large plasmid named plCHIGR sized more than 100 Kb and carrying both qnrB9 and blaTEM-116 gene. The plasmid was inserted by transformation into E. coli HB101 and resistance to nalidixic acid and ceftazidime was co-transferred.

MIC values were evaluated for C. freundii AQ/1 in comparison with E. coli HB101(plCHIGR) and E. coli recipient cells. Both C. freundii AQ/1 and E. coli HB101(plCHIGR) were resistant to penicillin, cephalosporins (i.e. ceftazidime, MIC > 64 mg/L; cefotaxime MIC > 128 mg/L) and aztreonam (MIC > 64 mg/L), nalidixic acid (MIC > 64 mg/L). Clavulanic acid is unable to restore the susceptibility of amoxicillin while tazobactam lowered the MIC value of piperacillin from 256 mg/L to 8 mg/L. Concerning levofloxacin and ciprofloxacin molecules we observed the MIC values for C. freundii AQ/1 and E. coli HB101(plCHIGR) of 0.25 and 0.5 mg/L, respectively.

Conclusion: Our finding suggests how qnr elements and blaESBLs genes are easily co-transferred among Enterobacteriaceae in different environments.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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