الفهرس 
History and discovery of colistinOnly 14 pages are availabe for public view
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Abstract
Summary
The emergence of MDR (and increasingly pan-resistant) Gramnegative
bacilli has affected practice in every field of medicine. The most
serious Gram-negative infections occur in health care settings and are most
commonly caused by Enterobacteriaceae, P.aeruginosa, and Acinetobacter.
MDR Gram-negative pathogens are also becoming increasingly prevalent in
the community.
Polymyxins, recently reintroduced in human medicine practice,
constitute one of the last resorts for the treatment of MDR Gram-negative
bacteria. Colistin (polymyxin E), with pronounced antimicrobial activity
against Gram-negative bacteria, is a cyclic polycationic peptide that interacts
with anionic LPS molecules. Even though LPS is the initial target, the exact
mechanism underpinning the effect of polymyxins on Gram-negative
bacteria remains unclear.
Unfortunately the re-use of colistin especially to treat carbapenem
resistant bacteria, has led to the appearance of colistin resistance. Acquired
resistance to colistin mostly results from chromosomal mutations, however, a
new transferable plasmid-mediated colistin resistance gene, mcr-1, encoding
a phosphoethanolamine transferase, has recently been described in China in
2015.
So, the aim of this study was to isolate the causative Gram-negative
bacteria from different HA- and CA-infections, determine the antibiotic
susceptibility pattern of the isolated bacteria including ESBL and MBL
detection, determine colistin resistance by 2 phenotypic methods and investigate the existence of mcr-1 gene in colistin resistant isolates using
conventional PCR.
The present study was carried out in Medical Microbiology and
Immunology Department, Faculty of Medicine, Tanta University, on 400
patients admitted during the period of research from March 2017 to February
2018 to Medical and Surgical intensive care units, Burn unit, Surgical unit,
Nephrology unit and Outpatient clinics of Tanta University hospitals. The
subjects were divided into 2 groups:
-group 1 (300 patients): patients with HA-infections.
-group 2 (100 patients): patients with CA- infections.
The samples were taken from sputum, endotracheal aspirates, BAL,
wound, burn, stool and blood. All samples were subjected to bacteriological
examination including, isolation and identification of different Gramnegative
bacteria using routine standard methods, antimicrobial susceptibility
tests using the disc diffusion method according to CLSI guidelines, ESBL
detection by MDDST and MBL detection by (IMP)-EDTA combined disc
test.
Resistance to colistin was tested by 2 phenotypic methods, all isolates
were tested by disc diffusion method then the isolates that fell in the resistant
and intermediate categories according to Gale’s criteria, were confirmed by
tube macrodilution method. Existence of mcr-1 gene was tested by
conventional PCR in colistin resistant isolates detected by tube
macrodilution method.
The current study showed that Gram-negative bacteria were the
commonest isolates in both HA- and CA-infections, responsible for 67.6%
and 79.4% of HA- and CA-infections, respectively. The most common.