Isolation and genetic characterization of metallo-β-lactamase and carbapenamase producing strains of Acinetobacter baumannii from patients at Tehran hospitals

International audienceBACKGROUND AND OBJECTIVE: Carbapenems are therapeutic choice against infections caused by gram-negative bacilli including strains of Acinetobacter baumannii. Resistance to these antibiotics is mediated by efflux pumps, porins, PBPs and ß-lactamases. The aim of this study was to determine the possibility of existence of MBLs, OXAs and GES-1 betalactamase genes among clinical isolates of Acinetobacter collected from Tehran hospitals. MATERIAL AND METHODS: Two hundred and three Acinetobacter isolates were collected from patient at Tehran hospitals. The isolates were identified using biochemical tests. The susceptibility to different antibiotics was evaluated by disk diffusion method and MICs of imipenem were determined using Micro broth dilution method (CLSI). PCR was performed for detection of bla(VIM-2), bla(SPM-1), bla(IMP-2), bla(GES-1), bla(OXA-51), bla(OXA-23) betalactamase genes. Clonal relatedness was estimated by PFGE with the restriction enzyme SmaI. RESULTS AND CONCLUSION: Of 100 isolates of imipenem resistant Acinetobacter spp. collected from Tehran hospitals in 2009 and 2010, 6 isolates produced metallo-beta-lactamases and 94 isolates produced OXA-type carbapenemase. The bla(SPM-1), bla(GES-1), bla(OXA-51), bla(OXA-23) genes were detected by PCR among 6, 2, 94 and 84 isolates of A. baumannii, respectively. The MICs of isolates to imipenem were 8-128 µg/mL. PFGE analysis of 29 bla(OXA-51) and bla(OXA-23)-positive A. baumannii isolates gave 6 different patterns. This is the first report of SPM-1 and GES-1 beta-lactamase producing A. baumannii. Production of the OXA-23, OXA-51, GES-1 and SPM-1 enzyme presents an emerging threat of carbapenem resistance among A. baumannii in Iran

Molecular identification and detection of virulence genes among Pseudomonas aeruginosa isolated from different infectious origins.

International audienceBACKGROUND AND OBJECTIVES: Pseudomonas aeruginosa possesses a variety of virulence factors that may contribute to its pathogenicity. The aim of this study was to evaluate oprI, oprL and toxA genes for PCR identification of clinical P. aeruginosa. In order to find out any relation between special virulence factors and special manifestation of P. aeruginosa infections, we detected virulence factors among these isolates by PCR. Ribotyping was used to evaluate the clonal relationship between strains with the same genetic patterns of the genes studied. MATERIALS AND METHODS: In this study, 268 isolates of P. aeruginosa were recovered from burn, wound and pulmonary tract infections. The prevalence of oprI, oprL, toxA, lasB, exoS and nan1 genes was determined by PCR. One hundred and four isolates were selected randomly to investigate clonal diversity of the isolates with ribotyping using SmaI. RESULTS AND CONCLUSIONS: All P. aeruginosa isolates in this study carried oprI, oprL and lasB genes. Difference between exoS prevalence in isolates from pulmonary tract and burn isolates was statistically significant. Prevalence of nan1 and toxA gene was significantly higher in pulmonary tract and burn isolates, respectively. Ribotyping showed that most of the isolates (87%) belonged to clone A and B. Detection of oprI, oprL and toxA genes by PCR is recommended for molecular identification of P. aeruginosa. Determination of different virulence genes of P. aeruginosa isolates suggests that they are associated with different levels of intrinsic virulence and pathogenicity. Ribotyping showed that strains with the same genetic patterns of the genes do not necessarily have similar ribotype patterns