الفهرس 
Aim of the workOnly 14 pages are availabe for public view
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Abstract
Antibiotic resistance in bacteria has emerged as a medical catastrophe. This results from the speed at which bacteria multiply and are spread, and the ease with which they can change their genetic material or acquire new genes.
Amp C type -lactamases are commonly isolated from extended-spectrum cephalosporin- resistant Gram- negative bacteria. Amp C -lactamases (also termed class C or group 1) are typically encoded on the chromosome of many Gram- negative bacteria. In the late 1980s, these inducible chromosomal genes were also detected on plasmids.
Differentiation of organisms expressing ESBLs from organisms expressing plasmid-mediated Amp C -lactamases is necessary in order to address surveillance and epidemiology, as well as hospital infection control issues associated with these resistance mechanisms. Several phenotypic tests can distinguish these two resistance mechanisms but are unable to differentiate the different types or families of plasmid-mediated Amp C - lactamases.
In our study the isolates were cultured on blood, Macconkey, Chocolate agar media and identified by conventional methods & screened for Amp C production by using Cefoxitin disc. Diagnosis of Amp C - Lactamases is phenotypic and genotypic.
phenotypic detection is done by modified three dimensioned test. Genotypic detection of plasmid mediated AmpC beta lactamase was done using multiplex PCR . AmpC multiplex PCR could differentiate the six plasmid mediated AmpC specific families in microorganisms.The six plasmid mediated AmpC specific famililes are MOX,CIT,DHA,EBC,FOX ACC-1.The family ACC-1 was excluded from our study as it is cefoxitin sensitive.
In this study, we collected 100 gram negative bacilli , from the 100 clinical samples, 62 isolates showed cefoxitin resistance, of them 33 isolates were positive for modified three dimensional test, of them 30 isolates were confirmed by PCR genotyping of plasmid mediated AmpC β lactamases.
The genotype patterns among the 30 plasmid mediated AmpC producing strains, were as follows: 10 isolates were positive for only FOX gene, one isolate was positive for only MOX gene, two isolates were positive for only EBC. On the other hand, we detected relatively large number of isolates expressing more than one gene. 11 isolates were positive for both MOX and FOX genes, two isolates were positive for both FOX and CIT genes, 3 isolates were positive for FOX, MOX and CIT genes, one isolate was positive for FOX, MOX and EBC. These combinations of different genes expresses the severity of the horizontal transfer of these genes by plasmids among different nosocomial pathogens and lack of infection control surveillance.