الفهرس 
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Abstract
This Study Was Conducted On A Total Of 310 Non Duplicated Gram Negative Bacilli Collected from Different Hospitals Wards In A Period Between April 2014 And January 2015. Samples Were Recovered from Inpatients That Developed Their Infections After Hospital Admission By At Least 48 Hours. Major Infections Were Due To Klebsiella Spp 94 (30.25%), Followed By E.Coli 75 (24.2%), A.Baumannii 57 (18.4%), Pseudomonas Aeruginosa 52 (16.8%), Proteus Spp 20 (6.5%), Provedenca Spp 7 (2.25%) And Enterobacter Spp 5 (1.6%). In The Following Study, Hospital Acquired Infections Associated With A.Baumannii Were As Follows Skin And Soft Tissue Infection 28%, Respiratory Tract Infections And Bacteraemia 24.6%, Urinary Tract Infections 10.5%, Meningitis 7.1%, Wound Infections 3.5% And Bacterial Peritonitis 1.7%. Different Types Of Infections Were Caused By Pseudomonas Aeruginosa Including Skin And Soft Tissue Infections 42.3% Followed By Urinary Tract Infections 28.8%, Respiratory Tract Infections 21.1% And Wound Infections 7.8%. Screening The Antimicrobial Activity Of The Isolates Showed That Most Isolates Were Multidrug Resistant. A.Baumannii Isolates Showed High Levels Of Resistance To Clindamycin 100% Followed By Ceftazidime 98%, Sulbactam/Ampicillin 94%, Meropenem And Clarithromycin Both Were 89%, Trimethoprim /Sulphamethoxazole And Ciprofloxacin 86%. Moderate Levels Of Resistance Were Recorded Against Imipenem 79% And Rifampicin 72%.Lower Rates To Colistin 65% And Doxycycline 58%. High Resistance Rates Were Observed In P. Aeruginosa Isolates Against Clindamycin, Trimethoprim/Sulphamethoxazole, Rifampicin, Clarithromycin 100%, Doxycycline 98%, Sulbactam/Ampicillin 96% And Lower Rates Were Found Against Ciprofloxacin 64%, Imipenem 56%, Meropenem 46% And Colistin 35%
Evaluation Of The Sensitivity Patterns Of Different Isolated A.Baumannii And P. Aeruginosa Strains Against Most Frequently Used Aminoglycosides In Our Hospitals Was Necessary To Get A Better Understanding Of Their Behavior. The Highest Resistance Levels In A.Baumannii Were Recorded Against Streptomycin 95% Followed By Kanamycin 87%, Amikacin 86%, Tobramycin 81%, Neomycin 70%, Netilmicin 63% And Gentamicin 51%. While P. Aeruginosa Showed 94% Streptomycin, Kanamycin 94%, Tobramycin 85%, Gentamicin 67%, Neomycin 65% And The Least Values Were Recorded Against Netilmicin And Amikacin Both Were 46%.
In Our Study, The Antimicrobial Activity Of Aminoglycosides With The Efflux Pump Inhibitor Carbonyl Cyanide 3-Chlorophenylhydrazone (CCCP) Was Tested Against A.Baumannii And P. Aeruginosa. Our Results Indicated That 19.4 % Of The A .Baumannii Isolates Became Less Resistant To Kanamycin, 44% To Tobramycin, 46% Amikacin But Lower Rates Were Recorded Against Gentamicin And Neomycin 12.2% And 9.4 % Respectively. This Indicates That The Efflux Mechanism Plays A Main Role In The High Resistance Level Of To Such Antimicrobial Agents In A.Baumannii Strains Under Investigation In This Study. In Contrast P. Aeruginosa Showed No Reduction In The Resistance Levels Of Kanamycin And Minor Changes In The Resistance Rates Of Amikacin 15.5%, Gentamicin 4.7%, Neomycin 4.1% And Tobramycin 3.8% Which Indicates That Efflux Mechanism Does Not Play An Important Role In The High Level Of Resistance To Aminoglycosides In P. Aeruginosa. This Ensures That High Levels Of Resistance In P. Aeruginosa Are Reached When Associated With Other Mechanisms.
In Our Study, The Occurrence Of Different Plasmid Mediated AME Genes And 16s Rrna Methylases And Their Correlation With Aminoglycoside Resistance In A. Baumannii And P. Aeruginosa Isolates Were Investigated. Distribution Of Arma In Our Hospitals Showed That It Was Harbored By 51% Of The A.Baumannii Stains. They Also Possessed Aph(3’)-VI 100% And Aac(6’)-Ib 94.7%. Those Genes Alone Or In Combination With Other AME Genes Showed High Levels Of Resistance To Amikacin. The Presence Of Ant(3″)-Ia In A. Baumannii Was 66.6% And P. Aeruginosa Was 56%. The Prevalence Of Aac(6’)-Ib Was Significantly Low In Pseudomonas 43% But It Was Found In 73.6% Of The A. Baumannii. The Occurrence Of The Aac(6’)-Iia In Acinetobacter Isolates Was 49.1% While The Aac(3’)-Iia Was 31.6%. Our Results Reveled That Aac(3’)-Iia Was Detected In 34% Of The Pseudomonas Isolates And The Aac(6’)-Iia Was Identified In 1.5%. None Of The Isolates Were Positive For16s Rrna Methyltransferase Rmta Or Rmtb.
In The Present Study Blaoxa-51 Like Gene Was Found In All A. Baumannii Isolates As This Was To Be Expected. As The Blaoxa-51 Gene Is An Intrinsic, chromosomal Carbapenemase Naturally Present In All A. Baumannii Strains Regardless Of The Drug Susceptibility. Sequence Analysis Of The 16S Rrna Region Was Also Used For Identification Of A. Baumannii. In The Present Study Plasmid Extraction And PCR Revealed That Most Isolates Carry At Least One Plasmid. We Found That AME Encoding Genes Aac(3)-Iia, Aac(6’)-Ib, Aac(6’)-Iia, Ant(3″)-Ia And Aph(3’)-VI Were Mostly Located On Plasmids And 100% Of The Isolates Harbouring The Arma Were Found To Be Mainly Located On Plasmids. Plasmid Curing Using Ethidium Bromide Was Carried Out For Some A. Baumannii And P. Aeruginosa Strains Had Contributed To Increase Their Susceptibility To The Tested Aminoglycosides. Determination Of The Genomic Diversity Through Analysis Of A. Baumannii Isolates from Both Hospitals Using ERIC-PCR Analysis Showed That 28 Distinct Patterns Were Recognized Among The 57 Isolates. P. Aeruginosa Isolates Were Typed Using REP–PCR Which Showed 20 Different Patterns. Analysis Of The Genomic Diversity Using ERIC-PCR And REP–PCR Indicated The Presence Of Clonal Expansion And Microbial Colonization.
We Observed The Change In The Activity Of Aminoglycosides When Combined With Other Most Commonly Used Antibiotics In The Treatment Of A.Baumannii And P. Aeruginosa Infections. In A.Baumannii The Best Synergistic Effect Was Obtained When Combining Aminoglycosides With Tigecycline And Rifampicin 71% And 64.2% Respectively. While, In P.Aeruginosa Combinations Of Amikacin With Piperacillin 92% Followed By Amikacin With Meropenem 85% And Colistin With Amikacin And Tobramycin 77% Showed High Synergetic Activity.
Finally, It Was Concluded That The Emergence Of MDR A.Baumannii And P. Aeruginosa In Egyptian Hospitals Resembles A Great Concern, Which Necessitates The Implementation Of Strict Infection Control Measures. Rational Uses Of Antimicrobial Agents And Appropriate Antibiotic Policy Have To Be Applied Within Our Health Care Settings. In Addition The Use Of Double And Triple Antibiotic Combinations Has Been Effective Against Multidrug-Resistant Organisms.