الفهرس 
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Abstract
Escherichia coli is an important member in family Enterobacteriaceae. Although E. coli is predominant commensal in the human gut, it is a leading cause of community and hospital acquired human infections. It is involved in considerable morbidity and death worldwide. E. coli is responsible for both intestinal and extra intestinal infections as diarrhea, urinary tract infections, septicemia, neonatal meningitis, respiratory tract infections or Skin and soft tissues infections. Treatment of such infections has become challenging due to the increased resistance of E. coli to variable antimicrobial agents.
The current study has identified, 200 E. coli isolated from 425 patients suffering from different infections. Specimens were collected from attendants to different hospitals including: Minia general hospital, Minia university hospitals and Minia chest hospital. Escherichia coli was most frequent in urine samples (62%), while least isolated from eye infections (10%). Intestinal E. coli were serotyped to confirm its pathogenicity, 75% of the isolates were found to be diarrheagenic.
Antibiotic susceptibility testing was carried out using different antimicrobial agents. The present work has reported high level of resistance rate to the tested antibiotics. For example, amoxicillin/clavulanic, cefotaxime and ampicillin/sulbactam resistance frequencies were 97.5%, 92%, 86.5% respectively. Imipenem and Azithromycin showed the lowest resistance frequency of 20% and 26% respectively.
Out of the all isolates 100 MDR isolates were selected for further investigations. The production of ESBLs was detected phenotypically by combined disc test. MHT was used for carbapenemase detection while combined disc synergy test was used to Metallo-beta-lactamase detection. The ESBL producing E. coli was found to be 89.4% and MβL producers were 64.8% of the 74 carbapenem resistant isolates.
PCR was used to determine the presence of blaNDM and some ESBL and carbapenemase genes as blaCTX-M, blaTEM, blaSHV, blaIMP, blaKPC and blaOXA-48 like. The study reported high phenotypic tests sensitivity as, 98.8% of ESBL producers and 79% of MBL producers were confirmed genotypically. The incidences of ESBL genes: blaCTX-M, blaTEM, blaSHV were 42%, 80% and 54.7% respectively. The carbapenemase blaKPC and blaOXA-48 like have not been detected among the isolates.
Carbapenem-hydrolyzing metallo-beta-lactamase blaNDM and blaIMP were detected. In this study, blaNDM and blaIMP genes were found in 43% and 36.8% of the isolates in that order. Also, the fluoroquinolone modifying enzyme gene aac-(6′)-Ib-cr that confer resistance to fluoroquinolones beside the aminoglycosides was detected within 25.2% of the isolates.
The present study showed that 81% of the isolates had more than one resistance gene. Over all there was a positive correlation between the detected genes. Significant association was found between blaCTX-M + blaSHV and aac(6′)-Ib-cr + blaCTX-M genes at 0.01 level. The most frequent co-existence was found between blaNDM, blaIM, blaTEM, blaCTX-M and blaSHV accounted for 8.5% of the isolates. None of the isolates harbored blaNDM alone indicating that blaNDM often co harbored with other resistance determinants.
Finally, MAR index was calculated to express the overall resistance of the isolates. It was significantly increased in ESBL and MBL producers. The most effective antibiotics on ESBL and MBL producers were Azithromycin and Chloramphenicol.