الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 108 |  |  |
| | | from | 108 | | |
Abstract
P. aeruginosa presents a serious therapeutic challenge for treatment of both community-acquired and hospital associated infections, and selection of the appropriate antibiotic to initiate therapy is essential to optimize the clinical outcome.
Selection of the most appropriate antibiotic is complicated by the ability of P. aeruginosa to develop resistance to multiple classes of antibacterial agents, even during the course of treating an infection.
Among these antibiotics, carbapenems have been regarded as the most potent beta lactams against MDR Gram-negative bacilli including P. aeruginosa. Resistance to carbapenems is particularly challenging in clinical settings because they are the mainstays for treatment of multidrug resistant P. aeruginosa.
Among the various antimicrobial resistance mechanisms, the production of carbapenemases is one of the most important mechanisms by which P. aeruginosa acquires carbapenem resistance. The most common carbapenamases in P. aeruginosa are MBLs. MBLs are broad spectrum enzymes that hydrolyze most beta lactam antibiotics, except monobactams, and are not inhibited by conventional beta lactamase inhibitors. Among the MBLs, VIM and IMP are the most common MBL types identified worldwide.
The aim of this work was to detect MBL production among imipenem resistant P. aeruginosa clinical isolates and to detect MBL encoding genes and class 1 integron among these isolates. Also to detect the genetic relatedness of these isolates, in order to understand the distribution of resistant P. aeruginosa in hospital settings.
Imipenem resistant P. aeruginosa represented 61.3% of all P. aeruginosa isolates recovered from clinical specimens of patients in Alexandria Main University Hospital (AMUH) delivered to the Medical Microbiology department laboratory throughout a period between May 2015 and August 2016.
Fifty randomly selected imipenem resistant P. aeruginosa isolates were tested for MBL production by DDST, followed by detection of MBL genes (blaVIM, blaIMP and blaNDM-1) and class 1 integron by conventional PCR. Genetic relatedness of the isolates was determined by ERIC PCR.
In the current study, according to the results of antimicrobial susceptibility testing by the disc diffusion method, all of the isolates were resistant to the following antibiotics; meropenem, ceftazidime, gentamicin, tobramycin, piperacillin, ciprofloxacin and levofloxacin. While, 34%, 30%, 6% and 4% were intermediately susceptible to aztreonam, piperacillin/tazobactam, amikacin and cefepime, respectively. The remaining isolates were resistant to these antibiotics. No resistance was detected among our isolates to colistin.
Phenotypic detection of MBLs by DDST, Revealed 38 out of 50 isolates were MBL producers (76%), out of which 36 carried the VIM gene, the remaining 2 isolates were negative for the studied MBL genes. On the other hand, twelve of the isolates were non-MBL producers (24%), out of which 8 were negative for VIM gene, while the remaining 4 isolates carried the VIM gene.
Most of the isolates (80%) carried the VIM gene, while none of the isolates carried the blaIMP or the blaNDM-1 genes. On the other hand all the isolates carried the class 1 integron gene.
For determining the genetic relatedness among our isolates, ERIC PCR was performed. Fifty isolates yielded thirty ERIC PCR genotypes and were analyzed using the Phoretix TotalLab TL120 software to draw a dendrogram. Five ERIC-PCR groups were identified designated I to V. The 50 isolates were classified in 24 clusters, from closely related isolates sharing an average ~80% of genotype similarity. The Simpson’s Diversity Index was calculated for ERIC PCR clusters and the result was 0.947 revealing low level of similarity among the studied isolates.
Although our studied isolates showed high genetic diversity, nevertheless, there is constellation of isolates towards ERIC PCR groups IV and V, including 16 and 15 isolates respectively, (62%). Also there is constellation towards certain clusters, Q, R, V and W representing 44% of the total isolates, demonstrating that most of the isolates probably originated from the patients themselves; however, cross-infection of P. aeruginosa between patients is possible to occur, suggesting nosocomial infection control problem