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Abstract Brucellosis is a highly contagious disease affecting almost all domestic species, leading to sever economic losses due to abortion, infertility and reduced milk production. It is considered one of the most economically important zoonoses globally. The causative agent belongs to genus Brucella. An alarming prevelance of human brucellosis has been lately reported among high-risk population in Egypt. Brucellosis in humans is strongly linked to contact with infected animals. The bacteriological methods has a limited sensitivity and has the added difficulty of being unpractical to apply on large scale in control campaigns. Therefore, the present work focused to evaluate the diagnostic performance of eight serological tests as relative sensitivity / specificity, area under the recover operating characteristics curve (AUC), diagnostic odds ratio and kappa agreement (K) with complement fixation test (gold standard). The serological tests were BAPAT, RBPT, mRBT, MAT, EDTA-m MAT, Riv.T, CFT & iELISA. The study included isolation and identification of because from different samples of large and small ruminants in five governorates of Egypt. The antimicrobial susceptibility of isolated Brucella strains for commonly antibiotc used for human brucellosis treatment were tested and compared with the sensitivity of standard strains. 1- A total of 596 blood samples was collected from 212 cows, 135 buffaloes, 120 ewes and 129 goats as individual animals, small and large herds, and small flocks with age ranged from 1-5 years in large ruminants and 1-4 years in small ruminants. Blood samples were collected from animals sent to abattoir for slaughter because of evidence of brucellosis aiming to evaluate the diagnostic performance characteristics of serological tests used in this investigation. All animals were from the vicinity of the Nile delta governorates; viz. Kafr ElSheikh, Gharbia, Beheira, Sharkia and Giza. There was no history of vaccination against brucellosis. Some animals were reported to have lateterm abortions. Milk and tissue samples were collected from live and slaughtered serologically positive animals in some governorates for the isolation and typing of Brucella microorganisms. Samples included milk, supramammary and retropharyngeal lymph nodes, liver, and fetal stomach contents and fetal livers. 2- Bacteriological trials for the isolation of Brucella from animal species in the five governorates under investigation resulted in the recovery of 11 field isolates including 6 from cows, 1 from a buffalo, 2 from ewes, 1 from a goat. Phenotypic bacteriological identification at the genus and biovar levels in addition to genotypic characterization at the species level resulted in the identification of 4 isolates as Brucella abortus biovar 1 from cow and the rest (7 isolates) were identified as Brucella melitensis biovar 3 from cow, buffaloes, sheep and goats. 3- The zones of inhibition recorded by the antibiotics used against B. melitensis bv. 3 (field) were arranged in descending order: Doxycycline (4.6 mm), Sulphamethoxazole & trimethoprim (2.8 mm), Ciprofloxacin (2.8 mm), Ceftriaxone (2 mm), Tobramycin ( 1.8 mm), Rifampicin (1.6 mm) and Streptomycin (1.4 mm). The corresponding profile of antimicrobial susceptibility arranged in descending order for the B. melitensis bv. 3 Ether strain (reference strain) was as follows: Doxycycline (4.8 mm), Ceftriaxone (2.8 mm), Sulphamethoxazole & trimethoprim (2.4 mm), Rifampicin (2.4 mm), Ciprofloxacin (2.2 mm), Streptomycin (2.2 mm) and Tobramycin (1.8 mm). The zones of inhibition recorded of the antimicrobial susceptibility of B. abortus bv. 1 (field strain) arranged in descending order were as follows: Doxycycline (3.2 mm), Ciprofloxacin (3.2 mm), Streptomycin (3.2 mm), Tobramycin (2.4 mm), Ceftriaxone (1.8 mm) and Rifampicin (1.6 mm). The corresponding profile of antimicrobial susceptibility arranged in descending order for the B. abortus bv. 1 strain 544 (reference strain) was as follows: Streptomycin (4.4 mm), Ciprofloxacin (4 mm), Doxycycline (3.6 mm), Ceftriaxone (2.8 mm), Tobramycin (2.6 mm) and Rifampicin (2 mm). All Brucellae whether field or reference strains were resistant to Azithromycin (AZM). B. abortus bv. 1 field strain and reference strains were resistant also to Sulphamethoxazole & trimethoprim (SXT). 4- The highest relative sensitivities were recorded for both BAPAT, RBPT and iELISA in cow (96%, 93% and 94%) and buffaloes (95%, 92% and 91%) respectively on the expense of the relative specificities (76%, 78% and 81%) in cow and buffaloes (70%, 75% and 80%) correspondingly. Low relative sensitivities of EDTA-mMAT and MAT of 77%, 77%, 81% and 78% and moderate relative specificities of 86%, 82%, 85% and 80% were recorded in cow and buffaloes respectively. EDTA-mMAT recorded better specificity in all animal species. High relative specificities of Riv.T were recorded in both cow (92%) and buffaloes (90%). The relative sensitivities were lower in cow (82%) than in buffaloes (88%). 5-All the serological tests used to diagnose brucellosis in large ruminants agreed significantly with CFT at p < 0.05. The estimated κ agreement values in cow and buffaloes indicated substantial agreement in case of the BAPA, RBPT, iELISA and Riv. T, where the values ranged from 0.682 to 0.762 in cow, and from 0.620 to 0.648 in buffaloes. The estimated κ agreement values indicated moderate agreement in case of EDTA-mMAT and MAT, where the κ values ranged from 0.564 to 0.596 in cow and from 0.406 to 0.473 in buffaloes.*AUCs in cow arranged in descending order were as follows: BAPAT (0.956), Riv.T (0.948), RBPT (0.922), iELISA (0.92), EDTA-mMAT (0.826) and MAT (0.811) respectively. The equivalent picture in buffaloes was as follows: Riv.T (0.987), RBPT (0.945), BAPAT (0.908), iELISA (0.886), EDTA-mMAT (0.821) and MAT (0.789) respectively. *The DOR results of serological tests in cow arranged in descending order were as follows: BAPAT (66.25), iELISA (66.15), Riv.T (55), RBPT (44.5), EDTA-mMAT (20.25) and MAT (15.2) respectively. The corresponding image in buffaloes was Riv.T (65), RBPT (53), BAPAT (42.4), iELISA (42), EDTA-mMAT (24) and MAT (14) respectively. *Good diagnostic results were obtained in small ruminants with BAPA, mRBT and iELISA in the form of high sensitivities (96%, 96% and 95%) in sheep and goats (94%, 93% and 94%) on the expense of specificities (73%, 82% and 82%) in sheep and goats (70%, 75% and 80%). Those tests offered a substantial agreement with CFT (gold standard), high DORs and better performance based on ROCs and AUCs. *Debatable diagnostic results were obtained by MAT in both sheep and goats based on the overall low relative sensitivities of 74% each and specificities of 73% and 70% respectively, in addition to fair agreement with CFT (0.308 and 0.339), very low DORs (7.7 and 6.7) and low AUCs (0.703 and 0.723) in that order if compared with other tests. *The Riv. T recorded the lowest relative sensitivity and specificity in ewes of 73% and fair agreement of 0.224 with the CFT test, in addition to the lowest DOR (7.35), AUC of 0.8 ranking before the last (MAT). The corresponding picture of Riv.T in goats appeared better than that of sheep, where the test recorded better sensitivity of 83% and better specificity of 80%, in addition to moderate agreement (0.479) with CFT, DOR of 18.9 and AUC. |