Detection of VIM- and IMP-type metallo-beta-lactamase genes in acinetobacter baumannii isolates from patients in two hospitals in Tehran

Background: acinetobacter baumannii, is an opportunistic pathogen and is responsible for numerous nosocomial infections. In recent years, this microorganism has been resistant to a wide range of antibiotics. One of the most important mechanisms of resistance in this microorganism is production of metallo-beta-lactamases [MBLs]

Objectives: The aim of this study was to detect VIM- and IMP-type metallo-beta-lactamase genes in Acinetobacter baumanniiisolates from patients in two Hospitals in Tehran

Materials and Methods: 104 isolates were tested using the PCR method for the identification of VIM- and IMP-type Genes

Results: vim1, vim2, imp1and imp2 genes were detected in 6.7%, 41.7%, 50% and 1.7% of the isolates from Tehran Heart Center, and in 29.5%, 38.6%, 4.5% and 4.5% of the isolates from Shahid Mutahhari Hospital respectively

Discussion: our analysis revealed that the majority of the isolates had at least one of these genes, indicating that MBLs production is an important resistance mechanism in Acinetobacter baumannii

[Synthesis of silver nanoparticles through chemical reduction and biosynthesis methods and evaluation of their antibacterial effects]

Silver nanoparticles have wide applications in medicine and treatment of bacterial infections due to their disinfection properties. Chemical synthesis, biosynthesis and antibacterial properties of silver nanoparticles have been studied previously, but regarding the high costs of chemical synthesis and the increase of antibiotic-resistance phenomenon among bacteria, assessment of the biosynthesis of silver nanoparticles and their effects on different clinical and standard bacterial strains is of great importance. Silver nanoparticles were synthesized through chemical and biosynthesis methods and their size and size distribution was assessed Transmission Electron Microscope. Chemically synthesized nanoparticles were added to tubes containing TSB medium and different bacterial strains for their antibacterial effects and their minimum inhibitory concentration was calculated Chemically synthesized silver nanoparticles had high monodispersity, but biosynthesized nanoparticles had higher polydispersity. Smaller silver nanoparticles had better antibacterial effects on Gram-negative and Gram-positive bacteria, in such a manner that they inhibited the bacterial growth at 0.2 mM concentration, but larger nanoparticles had lesser effects. Biosynthesis through bacterial supernatant is cost effective, but it produces polydisperse nanoparticles. Silver nanoparticles can replace antibiotics due to their suitable antibacterial effects, but it should be mentioned that clinical strains are more resistant than standard strains and bacterial resistance to these nanoparticles should be checked before their prescription

Detection of vim- and ipm-type metallo-beta-lactamases in Pseu-domonas aeruginosa clinical isolates

Pseudomonas aeruginosa is the most important bacterium isolated from burn wounds, and its resistance to imipenem due to metallo-beta-lactamases is increasing. This study was designed to detect vim1, vim2, Ipm1 and ipm2 metallo-beta-lactamases genes between Pseudomonas aeruginosa isolates isolated from Shahid Motahari Burns Hospital, Iran. To that end, we isolated 483 nonduplicate consecutive isolates of P aeruginosa from burn infections; and after biochemical confirmation, we examined the imipenem susceptibility via the Kirby-Bauer method. All the imipenem-resistant and imipenem-intermediate isolates were screened for vim1, vim2, ipm1 and ipm2 genes through the FOR method. From the 483 isolates, 272 [56%] and 63 [13%] isolates had resistant and intermediate zones in their imipenem antibiogram pattern, respectively. Fifty-four [16.1%], 7[2.1%], 22[6.6%], and 11[3.3%] of the resistant and intermediate isolates had vim1, vim2, ipm1 and ipm2 genes in their PCR results, respectively. MBL-mediated imipenem resistance in P aeruginosa is a cause for concern in the treatment of infective burn patients. The rate of imipenem resistance due to MBL was increased dramatically and newer versions of MBL families were detected for the first time. These results suggest that an effective method should be provided to fight MBL production in clinical isolates