Assistant Lecturer of Microbiology and Immunology at Modern University for Technology and Information, Egypt., Modern University for Technology and Information(MTI) , Egypt.
Multilocus sequence typing on Klebsiella pneumoniae harboring carbapenemases genes : KPC, NDM ,VIM,
Microbial typing is often employed for determination of infections sources, confirmation of pathogens outbreaks and recognition of virulent strains. In addition, typing plays an important role in evaluation of the effectiveness of surveillance systems and assessment of the relationship between microbial isolates. Typing can be employed by phenotypic or genotypic methods. Phenotyping results in grouping of organisms according to their similarity in characters resulting from the expression of their genotypes. Although there is a fact of having no genome of 100% identical counterpart- due to copying mistakes of DNA polymerases during replication - but these mutations are neutral and in line with existing structure- function relationship among corresponding gene products. So, there will be a great challenge to study useful epidemiological markers of the pathogens. DNA based typing methods can determine the genetic relatedness and show similarity degree between isolates. One of the most popular genotyping methods for characterizing bacterial strains is Multilocus sequence typing (MLST). It is an unambiguous procedure for characterizing isolates of bacterial species using the sequences of internal fragments of (usually) seven house-keeping genes. (Approximately 450-500 bp internal fragments of each gene are used). These fragments can be accurately sequenced on both strands using an automated DNA sequencer. DNA sequences are easily stored in online databases, which allow convenient exchange of strain typing data both within and between laboratories. These databases also facilitate the global epidemiological survey of bacterial infections. So far, MLST has been applied to more than 23 bacterial species and is regarded as a reference genotyping method for many bacteria. The Klebsiella pneumoniae MLST scheme uses internal fragments of the following seven housekeeping genes namely: rpoB (beta-subunit of RNA polymerase) , gapA (glyceraldehyde 3-phosphate dehydrogenase), mdh (malate dehydrogenase), pgi (phosphoglucose isomerase), phoE (phosphorine E), infB (translation initiation factor 2), tonB (periplasmic energy transducer).. The significance of the study is attributed to the global distribution of antimicrobial resistance which leads to limited therapeutic choices, long hospitalization, and increased mortality rates. The identification of different allelic variants can give an indication about certain gene whether it is reported, epidemic or endemic.
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