الفهرس 
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Abstract
Klebsiella pneumoniae is a member of the Enterobacteriaceae family that widely spread in the environment. It is also considered as an opportunistic pathogen which can cause a wide range of diseases in human and animals including poultry. Knowledge of the mechanism by which this bacterium causes different diseases is still unclear and most studies have limits because of the narrow ranges of virulence factors investigated.
The goals of this study was to identify and characterize genetic relationship among K. pneumoniae that isolated from clinically different samples from different hosts (broilers, human and cows), expression of virulence factors (phenotypic and genotypic), antimicrobial resistance in multi-drug resistant, ESBLs production confirmation and determination, semi-quantitation of biofilm formation.
A total of 390 clinically different samples were collected during 2019 -2020 in El -Behira governorate which include :175 broiler chickens samples comprising clinically diseased (nasal and tracheal swabs) and freshly dead (lung and liver) showed signs of loss of appetite, coughing and sneezing , 120 human clinical subjects (sputum, urine, pus and blood) from patients with chest infections, urinary tract infections, wound, and blood stream infections and 95 cows samples (clinically mastitis milk and nostrils swabs) of sick cows suffering from respiratory signs . The collected swabs were separately plated onto MacConkey’s agar. Large, mucoid, and pink colonies were picked up and identified morphologically and biochemically.
The results are outlined in the following points:
Out of 390 samples were examined, a total of 88 positive klebsiella pneumoniae isolates were isolated (22 from broiler chickens, 48 human and 18 cows) with a percentage of 22.6%.
The antimicrobial susceptibility testing revealed that klebsiella pneumoniae isolates were highly sensitive to Enrofloxacin followed by Gentamicin. While these isolates showed the highest resistant to Ampicillin and Amoxicillin/clavulanic acid followed by Ceftriaxone.
The multidrug resistance rates in high percent were found among the K. pneumoniae isolates from human (83.3%), followed by the broilers (77.3%) and cows isolates (72.2%)
ESBLs producing K. pneumoniae isolates were 43 out of 88 isolates (48.8%) by using confirmatory tests for ESBLs production. The highest percentage of ESBLs production was detected in human isolates (56.3%).The isolation of ESBLs producing K. pneumoniae from cows samples implies its public health significance; as such pathogens may enter the human food chain causing severe health hazards.
Phenotypic detection of virulence factors of K. pneumoniae isolates revealed that the capsule found in all isolates (100%). The highest hypermucoviscosity phenotype was observed in human isolates (37.5%).While the highest hemolytic activity was detected in broilers isolates (36.4%).
The biofilm producer isolates of K. pneumoniae were (77.3%). The highest percent of biofilm model was mod¬erately-adherent (38.6 %).
In this study only , fifteen ESBL producing and MDRs K. pneumoniae isolates (5 from broilers , 5 from human and 5 from cows) were further confirmed using ERIC-PCR which resulted from it a low level of genetic diversity among isolates .
The fifteen K .pneumoniae isolates that were used in ERIC-PCR were also, tested for two virulence genes: uge and kfu gene using PCR assay, all tested isolates (100%) were positive for the uge gene. While kfu gene was detected in broilers and human isolates by percentage of 40% and 60% respectively and not detected on cows isolates (0%).
The results indicated the probability of occurrence of transverse infections between the three hosts. This possibility from fact to be confirmed it needs more investigation of hundreds of isolates from many different hosts.