Tpp chi Khoa hpc Trudng Dpi hpc Can Tha Phan B: Nong nghiip, Thiiy sdn vd Cdng nghi Sinh hpc: 34 (2014) • 70- 76
Tap chl Khoa hoc Trirdng Dai hoc Can Thd website: sj.ctu.edu.vn
XAC DJNH KHA NANG SINH KHANG THE
CUA CA TRA {PANGASIANODON HYPOPHTHALMUS)
CAM NHlfiM VI KHUAN EDWARDSIELLA ICTALURI fmJXOC DOC Dang Thi Hoang Oanh', Nguyin Hoang Nhat Uyen\ Huynh Kim Nguyen' va Jung Tae Sung^
' Khoa Thuy sdn, Trudng Dgi hgc Cdn Tha
^ Lap Binh hgc Thdy sdn khda 36, Khoa Thuy sdn. Trudng Dgi hoc Cdn Tha
•' Khoa Thii y, Dai hgc Qudc gia Gyeongsang, Hdn Qudc Thong tin chung:
Ngdy nhgn: 10/05/2014 Ngdy chdp nhgn: 30/10/2014 Title:
Determination of the possibility to produce antibody of stripped catfish (Pangasianodon hypophthalmus) infected by anttenuated Edwardsiella ictaluri bacteria Tirkhda:
Cd tra (Pangasianodon hypophthalmus), ddp ung mien dich, Edwardsiella ictaluri, vaccine nhugc dgc Keywords:
Pangasianodon hypophthalmus, immune response, Edwardsiella ictaluri. attenuated vaccine
ABSTRACT
This study was conducted to evaluate the immune response of striped catfish (Pangasianodon hypophthalmus) to attenuated Edwardsiella ictaluri bacteria.
Agglutination test was used to quantify the level of specific antibody from striped catfish weekly after soaking with different concentrations of the attenuated bacteria (2 x 10*^ CFU/mL) and control group. The challenge test by injecting virulent Eictaluri (1.5'>^1(^ CFU/fish) were done al 2 weeks post exposure. The results showed that specific antibody against E.iclaluri of all experimented fishes were detected at 2"^ week after soaking. Antibody liters increased quickly al the 3"' week following by a gi-adual rise. In &'' week the highest titer from treatments was found in treatment 1 xJO* with level 9.0 which was significant difference (p<0.05) from the control ^oup (2.0). In addition, group soaking with l^ltf CFU/mL of the attenuated bacteria showed significant lower mortality (25%) (p<0.05) compared lo control group (70%).
These results demonstrated that using attenuated Eictaluri at concentration of 1 xyO* CFU/mL can stimulate striped catfish generate specific antibody against E.ictaluri infection in experimental condition.
TOM TAT
fNgKiirrcteu diegc thiec hiin nhdm xdc djnh khd ndng sinh khdng thi dgc hiiu cda cd tra (Pangasianodon hypophthalmus) cdm nhiim vi khudn Edwardsiella ictaluri nhugc dgc. Phuongphdp ngung kit dugc su dung di xdc dfnh hiiu gid(?) khdng thi dac hiiu cua cd tra sau mdi tudn ngdm cd vdi vi khudn E.ictaluri nhugc ddc a cdc ndng do 2x10*. 1,5x10^. 2^1^.
2x10^ I^IO^ CFU/mL vd ddi chiing. Sau 2 tudn, cd tra dugc cam nhiem vdi chung E.ictaluri cd dgc luc vdi ndng dg 1,5 xlO^ CFU/mL. Kit qud cho thdy muc khdng thi cua cd d tdt cd cdc nghiem thuc tdng ddn tir tudn thu 2.
tang nhanh din tudn thu 3 sau khi ngdm vi khudn nhugc dgc vd cao nhdt din cudi giai dogn khdo sdt. Trong do, cd a nghiem thuc ngdm vi khudn nhugc dgc I ^1(^ CFU/mL cd hiiu gid khdng the trung binh tdng cao nhdt (gdn 9,0). khdc biit cd y nghia so vdi nhdm ddi chung (chi 2,0) (p<0.05).
Ngodi ra, cd tra d nghiem thuc ngdm vi khudn nhugc ddc 1 ^10^ CFU/mL cd ti li chit thdp nhdt (25%) trong khi do a nhdm ddi chung ti le cd chet Id 70% (p<0.05). Qua nhieng kit qud trin cho thdy cd tra trong diiu kien thi nghi?m khi ngdm Kiclaluri nhugc dgc ndng dg I ^10^ CFU/mL cd khd ndng tao khdng thi dgc hiiu chdng lgi vi khudn Kiclaluri.
Tap chi Khoa hpc Truong Dpi hpc Cdn Tha Phan B: Nong nghiep, Thiy sdn vd Cdng n^ Sinh hpc: 34(2014): 70-76 1 GIOI THIEU
Cd ua (Pangasianodon hypopthalmus) la lorn cd nudi va chi biin xuit khau dat the manh kinh te thii hai cda nin kinh ti thuy san Ddng bdng sing Cuu Long (DBSCL) nin diin tich nudi khdng ngiing dupe md rdng va mdt dp nudi ciing duac lang cao. Tuy nhiin, nhiing nam gin day do vi?c siJr dung hda chit va khang sinh khdng diing qui djnh, klidng kiim soat ldm lac ddng den mdi trudng, he sinh thai cua khu vyc hodc de Iai du luong trong san pham ihuy sdn vd din den hiin tupng khdng khdng sinh Uong cac loai vi khuin gay binh trin ca (Aoki, 1988; Sarter vd ctv., 2007; Dung vd ctv., 2009) lam binh ngdy cang xuat hiin nhiiu la nguy CO dii vdi ngudi nudi dan den tinh trang giam ndng suit gidm chit lupng vd keo theo la dien tich nudi gidm. Theo Nguyin Trpng Binh (2008) benh mu gan xudt hiin cao nhdt dnh hudng nghiem trgng din cd tra. Tac nhdn gay binh mu gan dupe da sd cdc nghiin ciiu khoa hpc cdng bd Id do vi khuan Edwardsiella ictaluri (Cnimlish vd ctv., 2002;
Yuasa vd ctv., 2003; Tir Thanh Dung vd ctv., 2004;
Ddng Thi Hoang Oanh vd Nguyin Tnic Phuong, 2009). Di khdc phuc tinh Uang Uen ciing nhu khdc phyc cac nhupc diem cda phuong phdp dung khang sinli, d nude ta dd cd mdt sd nghien ciiu ve vaccine budc ddu thu nghi?m trin cac ddi tuong nudi thuy sdn nhung vin chua dupe iing dyng rpng rai.
Vaccine tir vi khuan Eictaluri nhupc dgc cd nhiiu uu diim Id kich tiu'ch sinh khang the mien dich dac hiiu nhanh va kio dai, de san xudt, chi phi thdp, ...
dupe nhiiu nha n ^ i i n ciiu quan tam. Do do, di tai dupe thyc hiin tiong dieu ki^n phdng thi nhiira nhdm cung cip thim thdng tin vi mien dich ciing nhu vaccuie trin ca Idm co sd cho viic sdn xudt vaccine nhupc ddc phdng binh d ca Ua sau nay.
2 PHUONG PHAP NGHlfeN CUtJ 2.1 Vat liiu nghieu cuu
Ca thi nghiim: Ca tra gidng (Pangasianodon hypophthalmus) cd kich ca khoang 20-25 g/con, cd Idide. Thudn dudng ca khodng 1-2 tuin trudc khi tiin hanh thi nghiem de cho ca on dinh vd quen vdi diiu kiin sing trong be.
Vi khuin EActaluri: Chung vi khudn E.ictaluri dupe phan lap va dinh danh tii mdu cd binh thu tai ao. Chiing vi kliudn E.ictaluri nhupc ddc DeIlaE3 dupe tao bdng phuong phdp biin doi gen do phdng thi ng^em Binh Thdy san, Khoa Thu y, Dai hpc Qudc gia Gyeongsang, Han Qudc cung cip. Hai chung nay dupe tiii trong tu -80°C tgi Bd mon Binh hgc Thiiy san, Khoa Thdy san, Trudng Dai hpc Can Tho.
Vi khuin gdy cam nhilm dupe phuc hdi trin mdi trudng tryptic soy agar (TSA. Merck) va git trong tii im 48 gid d 28''C, sau dd chgn mpt khuin lgc nudi tdng sinh Uong mdi trudng tryptic soy brotii (TSB. Merck) tir 24-30 gid, Iy tam 4000 vdng/phut trong 3 phiit, rira 2 lin bdng dung dich 0,85% NaCI va xac djnb mdt dp vi khuin bdng mdy so mau quang phi d budc sdng 590 nm kit hap vdi phuong phdp dim sd khuin lac phdt triin tren mdi trudng TSA (CFU/mL).
2.2 B 6 tri thi nghifm
Thi nghiim ngam vaccine vi khuin EActaluri nhinrc dpc: bd tri hodn loan ngau nhien vdi 5 nghiera thiic (NT) i^am vi khuan (VK) E.ictaliui nhupc ddc DeItaE3 d ndng dg 10\ 10^ 10^ 10', 10^ CFU/mL, ddi chiing ngam nude muoi sinh \</
(0,85% NaCI) (DC NaCI 0,85%) va doi chimg dm khdng ngam vi khudn hay nude muoi sinh Iy ^ C (-)). Mdi NT gdm 40 con, ldp Iai 2 Idn, thi nghi?m dupe bd tri nhu d Bang 1 (Hinh IB). Sau khi ngdm trong vdng 3 ^id cd sue khi, ca d moi NT dupe chuyin sang bi 250 L (Moi bi cdp nude khoang 2/3 bi) (Hinh 1 A) dh theo ddi h-ong 2 min.
Bang 1: Bo tri thi nghiim ngdm vi khudn EActaluri nhup'c dpc Nghifm
thuc
2x10^
CFU/mL 1,5x10^
CFU/mL 2x10' CFU/mL
2x10' CFU/mL
1x10*
CFU/mL Doi chung 96i chung Socd
Chit ngam Cam nhiim Lieu tiem cam nhiem
40 E.ictaluri nhupc ddc E.ictaluri 1,5x10^
CFU/mL 40 E.ictaluri nhupc ddc E.ictaluri
1,5x10^
CFU/mL 40 Eictaluri nhuac ddc E.ictaluri 1,5x10^
CFU/mL
40 40 E. ictaluri E. ictaluri nhupc ddc nhupc ddc
E.ictaluri E.ictaluri E.ictaluri 1,5x10^ 1,5x10^ 1,5x10*
CFU/raL CFU/mL CFU/mL 40 40 NaCl 0.85% khdng
khdng khdng Thi nghiim xdc dinh kha nang bao hp cua
vaccine: Sau 2 tudn ngam vdi vi khuin nhupc dpc, cd tia duoc tiem cam nhiim vdi chiing vi khudn E.
ictaluri cd dgc luc HL3 vai ndng dO 1,5x10^
CFU/mL (tiim d gdc vi nguc 0,i mL/cd) (Hinh IC). Cd dupe tiiu miu mdu trudc khi ngdm vd dinh
Tt^ chi Khoa hgc Truong Dgi hgc Cdn Tha Phan B: Ndng nghiip. Thiiy sdn vd Cong nghi Sinh hpc: 34(2014): 70-76 ky moi tuan sau ngam vi khuan nhupc ddc va thu
trong 4 tuin. Mil Idn thu 3 con/nghiem thiic I ^ Iai 2 Idn. Cd chit sau khi tiem cdm nhiem vdi vi khuin
E. ictaluri cd ddc Iuc dupe ghi nhdn vd thu Idy than trii Uong ethanol (Merck) di kiim tra su hiin dien cua vi khuan bang phuong phdp PCR.
Hinh 1: A) H$ thong be tbi nghifm; B) Cd tra dupe ngam vi khuin EActaluri nhupc ddc; (C) Ca tra
&M(fc giy nhiim bdng phuong phSp tiem Sd cd chit trong dgt cam nhilm dupe ghi nhan
va tfnh ti Ii bdo hd (TLBH) cua vaccine theo cdng thdc cua Amend (1981):
TLBH RPS =[1 - (% ca chit c6 vaccine/% ca chit nhdm ddi chlhigl x 100%
2.3 Phan u'ng ngung kit khang nguyen- khdng thl
Phucmg phdp ly trich huyit thanh: Sii dyng benzocain (Merck) ndng dp 100 ppm di gdy rai ca 1-2 phdt. Vi sinh vimg gan cudng dudi, diing kira tiira I mL cham nhe vao phdn cuing dudi de lay mdu tir dOng mgch chu d cOt sdng (Houston, 1990).
Cho mdu vao ong eppendorf 1,5 mL va di yin 2-3
^ d trong ngan mdt tii lanh, tiip tiieo, ly tdm 6000 vdng/phdt trong 5 phiit. Lay phan huyit thanh phia tien cho vao ing eppendorf khdc vd dem xdc dinh ham lupng khdng thi hodc tiii lanh (Hmh 2).
Phutmg phap bit ho^t vi kbuSn bdng formaline: Chiing vi khuin E.ictaluri cd ddc lyc HL3 sau khi nudi tdng sinh duac bat hogt bdng formalin (37%). Xac vi khudn dupe nia sgch formaline bing nude mudi sinh Iy va bdo qudn Uong ngan mdt tii lanh hoac d -20*'C.
Phan ung ngung kit khang nguyen-khdng thi: Phdn ting duoc thyc hi^n tren cac dia nhya (microplate) 96 giing tiieo phuang phdp vi ngung kit khdng nguyin-khang thi ciia Roberson (1990).
Cho 25 pL huyet thanh vao giing sd 1 yd 2. Tii giing sd 2 trd di pha loang huyet thanh bing nuoc rauii sinh I^f vdi ndng dp pha lodng bdng Vi. Cudi ciing cho 25 pL huyin dich xac vi khudn vdo giing rdi trpn diu. Di yin 4-5 gid d nhiit dp phdng rdi dpc kit qud. Mdi dia 96 giing cd su- dyng 1 ddi chiing duang (radu huyit thanh cbo dupe cd hiiu qud khang tilii cao nhat) vd 1 ddi chiing dm (nude
muoi smh \^).^ ~"
1^
s)^tec)
Hinh 2: A) Phurong phdp lay mSu ca tra, B) Mau ca da ly tam, C) Huyit thanh da duoc ly trich, D) Dpc kit qua phan ihig ngung kit mien djch
Sau 4-5 gid, khao sat hiiu gid khdng thi trung binh d cdc nghidm tiiirc tir IO"* din 10* Ah xdc dinh kba ndng ddp ihig khang tiii ciia ca Ua. Niu day
giing tao tiidnh mpt Idp i^ung kit ti-ai rpng Id duong tinh (+), niu day giing chi cd mdt chim udn nhd mdu trdng la am tinh (-) (Hinh 2D).
Tpp chiKhoa hgc Trudng Dai hpc Cdn Tha Phdn B: Ndng nghiip. ThOy sdn vd Cdng nghi Sinh hpc: 34 (2014): 70-76 2.4 Kiim tra su hiin diin ciia vi khuin E.
ictaluri bSng phuffng phap PCR
Chiit tach DNA: DNA tir md tiian dupe chiit tach theo phuang phdp cua Dang Thi Hoang Oanh vd ctv. (2009). DNA tir vi khuin dupe chiit tach theo phuang phdp ciia Bartie va ddng tac gia (2006). Vi khuin duac nudi tdng sinb tir 16-18 gid ti-ong 5 mL mdi truong NB d nhiet dp 28°C, sau dd dupe sii dung di Iy trich DNA bing each cho cho 1,5 mL dung dich vi khuin vao dng Iy tdm cung vdi 100 ^L 10 mM Tris-HCL, 1 mM EDTA, pH 8,0 (TE). Hdn hop dupe dun ndng d 95°C trong 15 phiit, rdi dupe lam lanh trong nude da va Iy tdm 2 phiit d vdn tdc 14.000 vdng/phiit 6k tach dung dich DNA va tru d -20''C cho din khi sii dyng.
Khuyich d^i DNA: Thanh phin hda chit phdn ling PCR dupe thuc hiin dya theo qui Uinh cua Panangala va ddng tac gid (2007, cd chinh siia) gdm I X dung dich dim 10 X; 1,5 mM MgCh; 200
^M dNTPs; 5 U Taq DNA polymerase; 0,4 p.M moi xuoi (EiFd-l); 0,4 ]xM mdi ngupc (EiRs) va 20 ng mdu DNA. Chu kj' nhiit thuc hiin phdn iing Id 95°C uong 4 phut; sau dd 95°C trong 30 giay, 53''C Uong 45 giay, 72°C trong 30 giay; ldp lgi chu ki Irin 35 ldn; 72X trong 10 phiit; giu d 20°C.
Diin di: 10 pL san pham PCR dupe chay di^n di Irin gel 1,5% agarose (ABgene, UK) tiong dung djch dim xl TAE (10 mM Tris, 5 mM acetate, 0,1 mM EDTA). Kit qua diin di dupe ghi nh|n bdng may dpc gel Vilber Loiumat (Phdp). Thang DNA 1 kb plus (Invitrogen) dupe chay chung vdi mau di xdc dinh kich thudc ciia cdc vach DNA. Trpng lupng phdn tii doan DNA ciia vi khuan Eictaluri can phat hien ta 407bp.
Bang 2: Hifu gid IXSiTg the.trung binh'ciia cd tra trong giai doan khao sdt
3 KET QUA VA THAO L U . ^ 3.1 Kit qua kiim tra ham lugng khdng the dac biiu ciia cJ tra
Mdu mau ciia ca trudc khi ngdm vi khudn E.ictaluri nhupc ddc deu cd hiiu gia khdng thi bing 0. Gidng nhu Thune et al. (1997) nhihig cd thi khde sdng trong mdi trudng sach benh se cd hieu gia khang the bdng 0. Sau khi ngdm vi khuin E.ictaluri nhupc ddc ham lupng khdng the xuit hien va khdc nhau d mSi nghiera tiuic, d§c biet tdng nhanh ki tir tuin thd 2 (Bdng 2). Tuy nhiin, d nhdm ddi chiing vdn chua cd su dap irng miin dich, cho din tuin thii 4 sau khi ngam vi khuan E.ictaluri nhupc dOc, cd d nhdm ddi chumg (NaCl 0,85%) xuit hien khdng thi Uong mdu vdi hi^u gid khdng thi ti-ung binh (HGKTTB) la 1,67. Vi nhom ndy cd ti le chit cao nhit (71,43%) nin khdng co mlu man d i tiip tuc quan sat ham lupng khdng the.
Theo Vinitiiantiiarat va Plumb (1993) cho tiiiy nhiing ca sdng sdt sau khi tiip xuc vdi mam binh cd ham lupng khdng tiii cao va bdo vi dupe co tiii kliang Igi vi khuin E. ictaluri.
Su khdc biit vi ham lupng khdng thi giiia nhdm ddi chiing va cac nghidm thiic cam nhilm vi khuin duac thi biin ro tur tudn thii 3: tiong khi nhdm ddi chiing vin d miic 0,00 tiii HGKTTB d cac nghiem thiic cdn Iai diu tdng vgt cd y nghia (p<0,05), va dgt miic cao nhit la 6,33 d nghifm thiic 10* vd khdng khac biit nhieu vdi mdc 5,83 ciia nghiem thiic 10'. Ngupc Igi, nghiem thdc 10^
cd sy dap iing miln dich thdp nhit (miic 3,50) trong sd cdc nghiem thiic dupe cam nhilm vi khuan.
Nghiim thirc/ tuan I II HI IV VI
4.5 ± 0,7"
6,4 ±1,1"
6,0 ± 2,0" 7,0 ± 0,0"
6.6 ±0,9" 8,0 ±0,0"^
10' 0,5±0,6' 3,5±0,8''= 6,3 ± 2,6" 6,7± 1,2-^ 7,3± 1,2'' 8,7±2,1''
w
10' 10' 10'0,0"
0,0"
0,2 ±0,4- 0,3 ± 0,8"
0,3±0,5^ 3,5±1,P 3,7±1,0'' 1,7 ±0,8" 4,2 ± I,S*" 5,8 ±1,3^
2,0 ± 1,4'' 4,2 ± 1,8**" 6,2 ± 1 ,&"
2,3 ±2,3'' 5,8 ±1,5*=" 6,2 ±1,2' Dii chiing 0,0' 0,0" 0,0" 1,7 ±0,6''
Cdc gid Iri Irong bdng Ihi hiin gid ni Irung binh vd dp lich chudn, Cdc gid trj trong cung cgl mang chir cdi mS khdc nhau thi khdc nhau coy nghia ihdng ki (p<0,05)
Theo nghiin curu tham dd dgc tinh gdy dap iing mien djch cua ldc nhdn gdy benh ddm trdng mu Uin cd tra cua Nguyin Thi Mdng Hodng vd ctv.
(2009) dd chi ra ring viic tiim nhic vao ngay thii 14 kich thich ddp iing mien dich thii phat nen khang thi hinh tiianh sdm, cao hon vd duy tii Idu
ban so khang thi nguyin phdt. Bin canh dd, nh&ng till nghiim ciia Phgm Cdng Thanh (2010) cung cho thiy trin cd tra kbi tiim nhdc vdi vi khudn E.
ictaluri bit hogt thl nhan thiy lupng khdng thi tdng Iin ddng ki so vdi khi tiem ldn diu. Bdi vay, khang till ddc hieu tdng nhanh la do cd sau khi ngam (tiip
^gp chi Khoa hpc Truomg Dai hpc Cdn Tha Phdn B: Ndng nghiip. Thuy si a Cong nghi Sinh hoc: 34 (2014): 70-76 XUC vdi E.ictaluri lin tiui nhit) dd hmh tiidnh
khang tiii ngiwin phdt; sau 2 tuin Iai duge gay cam nhilm (tiep xiic lin 2) hmh tiidnh khang tiii thii phat.
Do dd HGKTTB cua ca d cdc nghiim tiuic tiep tuc_ tdng cao d cdc tuin tiip theo va dgt miic cao nhdt vao cudi giai doan khdo sdt (hidn tiiu 6).
Nghiim thdc 10* Id nghiim thiic cd dap iing miin djch cao nhdt, HGKTTB la 8,67 va vin khdng khac biet nhiiu so vdi nghiim thuc 10' (miic 8,00) nhung khac biit cd y nghia so vdi nghiim thiic 10^
(miic 7,00). Ddi vdi nghiem tiuic 10^ 10^ va ddi chiing (NaCI 0,85%) cd ti Ie chit cao nin khdng cdn mau thu. Cho nen, cd thi thdy rd ring su dap
iing khdng tiie cda ca tia d tit ca nghiem thiic diiu diin ra din cuii giai doan khao sdt.
3.2 Kit qua cam nhiim
Cd tra benh mu gan bin ngoai binh thudng, mgt sd cd bi xuat huyit d da vd vdy, mang tai nhat Giai phdu bin trong, ngi quan cd man nhat mdt sd ca cd dich trong xoang byng. Gan, than vd ty tang xuit hien nhiiu ddm Uang cd dudng kinh tCr 1-2 mm (Hinh 3A). Mdt vdi ca benh cd hien hrong thgn sung to vd bi nhOn. Dau hiiu binh ly cua ca Ua sau khi cdm nhiim vi khuan E. ictaluri tuong tu nhu md td cua Ferguson et al. (2001), Tir Thanh Dung va ctv. (2004). Ca benh Uong nhung ngay ddu va chit vdo ngay thii 4 din ngdy tiui 9 sau khi tiim vi khuin E. ictaluri ddc luc.
Hinh 3: (A) Ca tra sau khi cam nhilm vi khuin E. ictaluri. (B) Kit qua diin di sdn phim PCR Kit qud dinh danh vi khuan bang phuang phap
PCR cho thay cdc mlu than thu dupe tii cd chit diu duong tinh (+) vdi Eictaluri (Hinh 3B). Nhu vdy cd the ndi ca chit Uong dpt gay nhiem nay nguyen nhdn chinh Id do vi khudn E. ictaluri gay ra.
Ben cgnh dd, cd su khac biel ddng ki vi ti li chit va ti Ii bao hd vaccine d cac nghiem thiic dupe trinh bay d Bang 3, Hinh 5, nghifm thiic ddi chiing NaCI 0,85% cd ti Id chit cao nhit (71,43%), ti If bdo hd vaccine thap nhdt (30%) vd ciing Id nghiem thiic cd HGKTTB t h ^ nhat. Trong sd cac n^iem tiuic dupe ngdm vi khudn E.ictaluri nhupc
ddc cd sd cd chet giam khi liiu ngdm tdng, tuong ling vdi ti li bdo hd tdng ddn va vdi ndng dg ngdm 10* CFU/mL dat ti li bdo hd cao nhit (65%) (Bdng 3).
Hdu hit cac thu nghiem ve ngam vaccine, kit qua cho thdy, khdng the sinh ra khdng dupe phdt hiin trong huyet thanli, ngay khi cd sir xuat hien thi ciing khdng cd lien quan tdi viic bao hd (Nakanishi vd Ototake, 1997). Nhung sau khi tiem si kich thich ddp img mien dich hodc tgo ra mien dich bdo hd trong mdi trudng tdi uu (Muiswinkel va Wiegertjes, 1997).
Bang 3: Ti le chet v^ ti If bao I19 ciia c^ tra «r cac nghieir Nghifm thii-c DC (-) BC (NaCI 0,85%)
Tile chat (%) 0,00 71,43 Tile bao h9(%)
1 thi>c NTl 10' 50,00 30,00
NT2 10' 39,29 45,00
NT3 10' 39,29 45,00
NT4 10' 28,57 60,00
NTS 10" 25,00 65,00 Nhu vay, cd sy lien quan giiia ham lupng
khang tiii trong mau vd ti Ii chit cda ca tra tiii nghifm. Lupng khdng thi cang cao thi ti Ii chit cang tfiip, ngupc Igi, lupng khdng tiii cdng tiiip thi ti li chit cang cao. Dii vdi cac nghidm tiuic thi nghifm cd sir cam nhiem ciia vaccine nhupc ddc: ti le chit cdng thap ihi ti If bdo hd ciia vaccine cang
cao, nguac lai, ti li chit cang cao thi ti Ii bdo hd vaccine cdng thap.
4 KET LUAN VA DE XUAT
Cd tra cd dap iing miin djch ddc hiiu ddi vdi vi khudn E.ictaluri nhupc ddc Ddp iing miin dich manh nhdt khi duac ngam vi khuan E.ictaluri
Tap chi Khoa hpc Trudng Dai hgc Cdn Tha Phdn B: Nong nghiip. Thiiy sdn vd Cong nghi Sinh hpc: 34 (2014): 70-76 nhupc ddc d ndng dp 1x10* CFU/mL vd gay nhiim
d liiu 1,5x10^ CFU/mL (HGKTTB la 8,7, ti Ii bao hp 65%). Viic tiem cam nhiem d tudn thii 2 cdn co vai Ud nhu miii tiim nhdc giiip kich thich qua trinh smh khdng the dien ra nhanh, manh hon va miic HGKTTB d tit ca cac nghiem thiic van tiep tuc tdng nhanh tir tuin thii 3 den cudi giai dogn khao sat.
Cdn thur nghiera vaccine E.ictaluri nhupc ddc vdi sd luang ca tra Idn hmi, thai gian khao sat dai hon nham tim ra quy luat bien ddng cua lupng khang thi trong mdu ca. Ddng thdi tiin hanh thii nghiera vaccine trong mdi irudng ao nudi thyc nghiera.
TAI LIEU THAM KHAO
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