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Abstract In this study, a total of 200 chickens of different ages (51 apparently healthy broiler chickens, 84 diseased broiler chickens and 65 freshly dead broiler chickens) were collected from different broilers farms in Suez Canal area. The present study revealed that P. aeruginosa was recovered in 28 out of 200 samples (28⁄200) with an incidence of 14%. P. aeruginosa was isolated from apparently healthy chickens with a rat e of 2 (3.9%), diseased 20 (23.8%) and freshly dead 6 (9.2%). The total number of P. aeruginosa isolated from broiler chicks (1-7 days) were 19 with an incidence of 22.6% and from broiler chickens (1-6 weeks) were 9 with an incidence of 7.8%. The yolk sac and cloacal swabs samples gave the highest recovery rates with percentages of 15.5% and 12.6%, respectively. Moreover, the recovery rate of P. aeruginosa from internal organs was higher from liver followed by intestine, heart blood and lung with incidence rates of 4.5%, 2.5%, 1.5% and 0.5%, respectively, but it was not isolated from neither gall bladder nor kidney samples. P. aeruginosa isolates were tested for antimicrobial susceptibility. The results revealed that all P. aeruginosa isolates were resistant to ampicillin, lincomycin, nalidixic acid, streptomycin and tetracycline (100%). In contrast, the isolates were highly sensitive to colistin sulphate (78.6%), ciprofloxacin (67.9%), gentamicin (64.3%) and norfloxacin (57.1%). While the isolates exhibited less sensitivity to levofloxacin, trimethoprim-sulfamethoxazole, amikacin, doxycycline and chloramphenicol with percentages of 46.4%, 42.9%, 39.3%, 14.3% and 3.6%, respectively. Summary 162 Conventional polymerase chain reaction inveterated the existence of P. aeruginosa DNA in ten isolates by using 16S rRNA gene. Also, PCR was done for detection of virulence genes as oprL, toxA and aprA as well as quorum sensing genes (lasI, lasR, rhlI, rhlR) using specific primer for each gene. The findings from the present study showed that the oprL gene was expressed in all ten examined P. aeruginosa isolates (100%), also, toxA, lasI, lasR, rhlI and rhlR were present with an incidence rate 80% for each of them, and aprA gene was expressed in 40% of P. aeruginosa isolates. Moreover, PCR detected the presence of higBA, pprA and pprB genes in P. aeruginosa isolates with percentages of 100%, 90% and 100%, respectively. Plasmid profiling of 10 multidrug resistant P. aeruginosa isolates revealed one common plasmid profile with characteristic bands at 13000 bp in eight isolates (8 out of 10) with a percentage of 80%. The detection of antibiotic resistance genes (some efflux pumps system genes as ” mexA, mexR, oprJ, oprM and nfxB ” as well as ampC) in the isolated plasmid DNA of multidrug resistant P. aeruginosa isolates using specific primer for each gene was carried out by PCR with percentages of 62.5%, 75%, 87.5%, 75%, 62.5% and 75%, respectively. Sequencing of 16S rRNA gene of P. aeruginosa was applied and had accession number MW051028 at GenBank which was 100% identical to the corresponding GenBank sequences. Also, Sequencing of oprL gene of P. aeruginosa was applied and had accession number MW056321 at GenBank which was (98.7. |