Dissemination of acquired metallo-beta-lactamases in Gram-negative pathogens: first Italian countrywide survey

Abstract number: p1418

Pagani  L., Luzzaro  F., Mugnaioli  C., Spalla  M., De Luca  F., Perilli  M., Babini  G., Gesu  G., Amicosante  G., Toniolo  A., Rossolini  G.M.

Objectives: 

The emergence of acquired metallo-beta-lactamases (MBLs) in gram-negative pathogens (Pseudomonas aeruginosa, Acinetobacter spp. and Enterobaceriaceae) is a worrisome phenomenon since MBLs can confer resistance to carbapenems and most other beta-lactams. MBL producers have now been reported worldwide. In Italy, both IMP- and VIM-type enzymes have been detected, mostly in P. aeruginosa but also in other gram-negatives. In this work we report the results of the first Italian nationwide survey on the prevalence of acquired MBLs in P. aeruginosa and other gram-negative nonfermenters (GNNFs), and in Enterobacteriaceae.

Methods: 

During a 4 month period (Sept.–Dec. 2004), consecutive nonreplicate isolates showing reduced susceptibility to imipenem (using ad hoc breakpoints, depending on species) were selected from 14 clinical microbiology laboratories distributed across Italy. Identification and susceptibility testing were carried out with the Phoenix ID/AST System (Becton Dickinson). MBL genes were screened by colony-blot hybridization and identified by sequencing.

Results: 

Of 2721 GNNFs and 12 245 Enterobacteriaceae nonreplicates isolated at the participating laboratories during the study period, 319 and 117, respectively, were selected for further investigation. Overall, 30 isolates were positive for acquired MBL genes including 27 P. aeruginosa (1.3% of total and 10% of carbapenem-resistant P. aeruginosa isolates, respectively), 1 Pseudomonas putida, 1 Acinetobacter baumannii, and 1 Enterobacter cloacae. MBL producers were detected in 10 of 14 sites. In 24 isolates the enzyme was of the VIM type, while in the remaining 6 it was of the IMP type.

Conclusions: 

P. aeruginosa producing acquired MBLs are broadly distributed in Italy, although their overall prevalence remains relatively low. In other gram-negative species acquired MBLs remain quite uncommon. Enzymes of the VIM type appear to be more common than those of the IMP type. A financial contribution from Becton Dickinson Europe is acknowledged.