الفهرس 
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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.