الفهرس 
Introduction And RationaleOnly 14 pages are availabe for public view
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Abstract
Colistin is considered the “last resort” antibiotic for treatment of infections with carbapenem resistant Enterobacteriaceae (CRE). In 2012 colistin was reclassified by the World Health Organization as critically important for human medicine (WHO, 2012). Colistin is a polycationic molecule which interacts with the bacterial outer membrane by displacing divalent cations from the negatively-charged phosphate groups of the Lipid A of the lipopolysaccharide membrane, resulting in cell lysis (Olaitan et al., 2014).
Recently, transferable polymyxin resistance mediated by the mcr-1 gene has been described in Enterobacteriaceae. The continuous spread of plasmid-borne mcr genes will compromise the clinical utility of last-resort polymyxins, which may lead to more frequent treatment failures and substantial additional morbidity and mortality. The distribution of these resistance determinants amongst carbapenem resistant organisms, especially in the hospital setting, may catalyze a return of the “pre-antibiotic era” (Caniaux et al., 2017).
The purpose of the present study is to evaluate the frequency of colistin resistance among carbapenem- resistant E.coli and K.pneumoniae isolates obtained from patients in SCUH in Ismailia and to detect the presence of mcr-1 and mcr-2 genes among the colistin-resistant isolates.
The study included 116 carbapenem resistant E.coli and K.pnemoniae isolates collected from 536 specimens. Isolates were mostly collected from endotracheal aspirates (46.6%). Other carbapenem- resistant strains were isolated from blood (21.6%), urine (9.4%), sputum (8.6%) and pus (13.8%) specimens. Antibiotic susceptibility test was done to the carbapenem resistant K.pneumoniae and E.coli isolates by disk diffusion method (Kirby Bauer method). It showed 100% extended spectrum beta-lactamase as all isolates were resistant to both amoxicillin -clavulanic and ceftazidime antibiotics. While gentamycin, amikacin, levofloxacin and cefipime showed 51.3%, 63%, 79.5% and 87.7% resistance respectively. Modified carbapenem inactivation method was done to assess carbapenemases activity, 82 isolates were carbapenemases positive (70.7%). Fourty three isolates (37.1%) were colistin resistant (Non-wild type) as shown by MIC by broth microdiluton method. The 43 colistin resistant E.coli and K.pneumoniae isolates were tested by conventional PCR to detect plasmid