[Comparison of phenotypic methods for the detection of beta-lactamases MBL in strains from the Enterobacteriaceae family and non-fermentative bacilli isolated from clinical specimens].

Abstract

Introduction: Bacterial resistance is growing because of treatment a broad spectrum antibio- tics. Gram-negative pathogens which producing carbapenemase are a one of major problem in many hospitals. Rapid detection those strains provide an early inhibition of infection and control the expansion of microorganisms. The aim of work was to characterize the frequency of appearance MBLs in specific groups of Gram-negative bacilli which are resistant or intermediate to at least one of carbapenems.

Methods: Bacterial isolates were collected from Baby Jesus Clinical Hospital from 2003 to 2009. Pathogens were isolated from urine, blood, fluids, swab of the wound, pharyngeal swab. They were identified by the ID 32 E (bioMérieux, France) and Vitek2. Antimicrobial resistance was marked by the ATB G-5 and ATB UR (bioMérieux, France). Detection of metalo-beta-lactamases was tested by disk diffusion test recommended by the EUCAST. The DDS test using imipenem, ceftazidime, ethylenediaminetetraacetic acid (EDTA) and 2-mercaptopropionic acid (2-MPA). Positive test was reading as enlargement of inhibition zone about imipenem- or ceftazidime-impregnated disk.

Results: Of the 88 isolates, 32 come fromEnterobacteriaceae and 56 from non-fermentative bacilli. All strains were tested of production of MBL by disk diffusion test. This method used two inhibitors: ethylenediaminetetraacetic acid and 2-mercaptopropionic acid. As a result of EDTA there was 45 MBL positive strains. In apply 2-MPA there was 55 MBL positive strains. Both the EDTA and 2-MPA disk test showing the highest percentage of positive result in Enterobacter cloacae, Serratia marcescens, Pseudomonas aeruginosa and Pseudomonas putida.

Conclusions: Resistance to carbapenems in the non-fermentative bacilli occurs more often than in the Enterobacteriaceae. Method with 2-mercaptopropionic acid was more effective to detect metallo-beta-lactamases than EDTA. Concerns especially bacilli from Enterobacteriaceae.