Detection of bovine trichomoniasis with a specific DNA probe and PCR amplification system

Copyright© 1994, American SocietyforMicrobiology

Detection of

Bovine Trichomoniasis with

a

Specific

DNA

Probe and

PCR

Amplification

System

MICHAEL S. Y.HO,1 PATRICIA A.

CONRAD,`*

PHILLIPJ. CONRAD,1 RANCE B.

LEFEBVRE,'

ENRIQUE PEREZ,2ANDROBERT H.BONDURANT3

DepartmentofVeterinary Microbiology and

Immunology'

and DepartmentofReproduction,3 Schoolof VeterinaryMedicine, Universityof

Califoria,

Davis, Califomia 95616, and Herd Health Section,

DutchInteruniversityCooperation Program, School ofVeterinary Medicine, UniversidadNacional, Heredia, Costa

Rica2

Received 6July1993/Returnedfor modification1 September1993/Accepted 1 October 1993

Trichomoniasis is a widespread,

economically

important venereal disease of cattle which causes

infertility

and abortion.Effective control oftrichomoniasis has been impeded by theinsensitivityof traditionaldiagnostic procedures, which require the isolation and cultivation of the parasite,

7Titrichomonasfoetus,

from infected cattle. Wedeveloped a0.85-kbT.foetusDNAprobe by

identifying

conserved sequences in DNAs from T.foetus that wereisolated from cattle inCalifornia, Idaho, Nevada, and CostaRica. The probe hybridized

specifically

to DNAs of T.foetus isolates from different geographic areas but not to DNA preparations ofTrichomonas vaginalis,bovine cells, or a

variety

of bacteria from cattle. The probedetected DNA from aminimumofi05 T.foetusorganisms. To improve

sensitivity,

a partial sequence of theprobe was used to

identify

oligonucleotide primers (TF1 and TF2) which could beused to amplify a 162-bp product from T. foetus DNAs by PCR. A chemiluminescent internal T.foetus sequence probe was hybridized to Southern blots of the amplification product. This system detected as few as one T.foetusorganism in culture media or 10 parasites in samples containing bovinepreputialsmegma.

Analysis

of 52 clinical samples showed that 47(90.4%)of the 52 samples were

correctly

identified, with no false-positivereactions. Incomparison, the traditional cultivation method detected 44(84.6%) of the 52 samples from T. foetus-infected and uninfected bulls. These results indicate that the PCR-based amplification system could be a useful alternative method for the diagnosis of bovine trichomoniasis.

Trichomoniasis has a worldwide distribution and is a major cause of infertility in naturally bred cattle in many countries (1, 11, 21). The causative agent, Titrichomonas foetus,is aflagellatedprotozoan

parasite

thatis transmitted frominfected, asymptomatic bullstoheifers orcows atthe time ofcoitus.Theparasitetheninvadesthevagina,uterus, and oviduct,causing embryonic death andinfertility which may last for 2 to 6months(4, 10, 14).InthewesternUnited States, the

prevalence

of trichomoniasis among bulls is estimated to be at least 5 to 8% (14,

22).

A recent U.S. DepartmentofAgricultureNationalAnimal Health Monitor-ing System survey of California beef herds showed that 15.8% ofrandomly sampledherdshad T.

foetus

infections, with a 27% meanwithin-herd prevalence of infected bulls

(5).

A major limitation to more accurately determining the prevalence and economic impactofbovine

trichomoniasis,

as well as

controlling

the

disease,

is the

insensitivity

of current

diagnostic procedures.

Atpresent, the

diagnosis

of trichomoniasis is based primarily on the identification of flagellated T.foetus parasites, bymicroscopic examination, inpreputial scrapingsorwashingsfrom bullsor cervicovag-inal secretions from female cattle. Often, the number of trichomonads in these samplesfrom infected cattle is rela-tively low and the parasites generally must be grown in

*

Corresponding

author.Mailingaddress:Departmentof

Pathol-ogy, Microbiology and Immunology, School ofVeterinary Medi-cine,University of California, Davis,CA95616-8738.Phone:(916) 752-7210. Fax:(916)752-3349.Electronicmail address:paconrad@

ucdavis.edu.

culture before they reach detectable numbers (7, 22, 46). Diagnostic sensitivity can be improved 10 to 48% if the samples are placed in special medium and cultured in the laboratory for 2 to 5 days(15,27, 41,42). However, despite the additional time and expense,this methodofcultivation detectsonly81 to90% of naturally infectedbulls andonly58 to 78%ofinfectedfemale cattle(15,40, 42).

Theobjectiveof theprojectdescribed here was toobviate the need for cultivation and to increase the accuracy of diagnosis bydeveloping a highly sensitive diagnosticDNA probe that specifically detects T. foetus in samples from infected cattle.Inthis report, we describethe evaluation of a 0.85-kb T.

foetus

DNA probe which was developed by identifyingconserved sequences in DNAs fromdifferent T. foetusisolates and clonedintoaplasmidvector.Inaddition, amore sensitivemethod of

parasite

detection with

specific

primers selected from the probe sequence to amplify T. foetusDNAbyPCRis described.

MATERIALSANDMETHODS

Parasite cultivation. T. foetus isolates from California (isolates

Dl,

RE2, and NA4) (6), Idaho (isolates RE20, RE23, andRE24), Nevada(isolates RE19), andCosta Rica (isolates CR1, CR2, CR3, CR4, CR5, and CR6) (31) were cultivated inDiamond's medium(12) supplementedwith5% heat-inactivated bovine serum at 37°C. Trichomonas vagi-nalis isolates TO15 and T048

(kindly

provided by John Alderete, Health Science Center, UniversityofTexas, San Antonio)were grown in Diamond's mediumwith 8% heat-inactivated horse serum at 37°C. Testsamples were taken duringthelogarithmic phase ofgrowth, and the number of

98

on May 15, 2020 by guest

http://jcm.asm.org/

parasites

was determined by

diluting aliquots

with

phos-phate-buffered

saline

(PBS; pH 7)

and

counting

ina hemo-cytometer

(x

100

magnification) by using

a

light microscope.

Specimen

collection.

Smegma samples

from 10infected and 2 uninfected bulls were collected by insertion of a sterile 24-in.

(61-cm)

uterine infusion

pipette through

the

preputial

orificetothefornix of theprepuce. The prepucewas

scraped

while

applying

vacuumwith a

disposable syringe. Smegma

samples

weremixedwith PBS

(pH 7)

to atotal volume of1.5 ml. Onemilliliterofthe dilutedsmegma

sample

was inocu-lated into culture

medium,

andthemixturewasincubatedat

37°C.

Parasite

growth

was determined

by observing

the culturewith aninverted

microscope

every 24 h for7

days.

Another

200-,ul aliquot

of each

sample

was used for DNA isolation and slot blot

analyses.

Bulls were classified as

infected ifany

samples

were culture

positive,

because T.

foetus

causes

persistent

infections in bulls

(4). Smegma

samples

collected from

healthy

bulls thatweredeterminedto be uninfected on the basis of at least three consecutive

negative

culture

samples

were usedasdiluent in

sensitivity

testsandas

negative

controls.

Preparationof DNA forSouthernand slot blot

analyses.

T.

foetus

and T.

vaginalis

DNAswere

prepared

as described

previously (36),

with

slight

modifications.

Briefly,

1 x 108 cells in the

logarithmic phase

of

growth (1

x 106 to 2 x

106/ml)

wereharvested

by centrifugation

at

4,000

xg for 10 min. Cells were washed twice with PBS

(4°C)

and were

resuspended

in5 ml of NETbuffer

(100

mM

NaCl,

10 mM

EDTA,

10 mM Tris

[pH 8]).

Sodium

dodecyl

sulfate

(SDS)

wasaddedto afinal concentration of0.2%

(wt/vol),

and the solution was mixed

gently

before the DNAwas extracted once each with an

equal

volume of

phenol,

a mixture of

phenol-chloroform

(1:1;

vol/vol),

and then chloroform. Two volumes of ice-cold95%

(vol/vol)

ethanol and0.1volumeof 3 Msodiumacetate wereaddedto

precipitate

the DNA. The DNA

pellet

obtained after

centrifugation (12,000

xgfor 20 minat

4°C)

wasrinsed with70%

(vol/vol)

ethanol,

air

dried,

and dissolved in 200 pl ofTE

(pH 8)

buffer. DNase-free RNase

(GIBCO

BRL,

Gaithersburg, Md.)

was added to a final concentration of 50

,ug/ml,

and the mixture was incu-bated at

37°C

for 30 min. Proteinase K

(GIBCO BRL)

was then added to a final concentration of 100

p,g/ml,

and the mixture was incubated at

37°C

for 45 min. DNA was extractedwith

phenol, phenol-chloroform (1:1;

vol/vol),

and chloroform as described

above,

andthe DNAwas

precipi-tated with 2 volumes of95%

(vol/vol)

ethanol and0.1volume of3Msodiumacetate.The DNA

pellet

wasrinsed with70%

(vol/vol)

ethanol,

air

dried,

and dissolved in 200

pLI

ofTE buffer. An average

yield

of100 pg of DNAwasobtained

by

this

procedure.

DNAwas

prepared

from bovine

thymocytes

(kindly provided

by Jeffery Stott, University

of

California,

Davis)

asdescribed

previously (8).

Acinetobacter

calcoaceticus, Campylobacter fetus

var.

veneralis, Corynebacterium

pyogenes, Enterobacter aero-genes, Escherichia coli,

Haemophilus

somnus, Moraxella

bovis, Staphylococcus

epidermidis, Staphylococcus

sapro-phyticus,

Streptococcus

lactis,

and

Streptococcus

viridans

(kindly provided by Veterinary

MedicineTeaching Hospital

Diagnostic

Laboratory, University

of

California,

Davis)

were cultivated

by

standard methods

(9, 49).

Cells were harvested in the

logarithmic growth phase,

and

genomic

DNAwas

prepared

asdescribed

previously (13).

Restriction enzyme digestion and doning. The genomic DNAs of T.

foetus

isolates from various geographic loca-tionswere

digested

witheitherHindIII, EcoRI, HaeIII, or Sau3Arestriction endonuclease

according

to the

manufac-turer's instructions (GIBCO BRL). Digested DNA frag-ments wereseparatedon a1.4% (wt/vol) agarosegel(FMC Bioproducts, Rockland, Maine) inTBE(45mMTris-borate, 1 mM EDTA) at 40 V for 17 h. Gels were stained with ethidium bromide(0.5 ,g/ml) and photographed under UV illumination. Aprominentband of 0.85 kbpresentin HindIII digests of the genomic DNAs of all T. foetus isolateswas excised fromagarosegelsandpurified by usingaGeneclean kit (Bio 101, Inc., La Jolla, Calif.). The purified sequence wasligated into the HindIII site of the plasmidvectorpUC19 by established methods (37). The ligated recombinant plas-midswereintroduced intocompetentE. coli JM83cells,and individual transformants were selected after growth ofthe cells onLuriabroth (LB)agar plates containing ampicillin and

5-bromo-4-chloro-3-indolyl-13-D-galactopyranoside

(37). Southern blot hybridization. Restriction fragments sepa-ratedon 1.4% agarosegelsweredenatured and transferred ontonylon membranes (Hybond-N; Amersham Corp., Ar-lington Heights, Ill.) by Southern blotting as described previously(43).DNAwascross-linkedto anylon membrane byusingaStratalinker UV crosslinker(Stratagene,LaJolla, Calif.). Small-scale preparations of plasmid DNAwere ob-tainedby the alkaline miniprep method (37). The recombi-nant plasmid pUC19 was digested with HindIII, and the 0.85-kb fragmentwas recovered by usingan NA45 DEAE membrane following the manufacturer's recommendation (Scheicher&Schuell, Keene, N.H.).The0.85-kb fragment was labeled with

[a-32P]dCTP

(3,000

Ci/mmol)

by using a RandomPrimers DNALabeling System (GIBCO BRL) and was hybridized to nylon membranes (Amersham Corp.) containing restriction

endonuclease-digested

T. foetus DNAs (37). Southern hybridization was carried out over-nightin a Sx Denhardt's solution containingSx SSC(20x SSC is 0.3 M sodium citrate

[pH

7.0] and 3 M sodium chloride), 50% formamide, salmon testis DNA (100 ,ug/ml), 0.5%

(wt/vol)

nonfat dry milk, and 0.1% (wt/vol) SDS at 42°C. Membraneswerewashedtwice in4x SSC-0.1%SDS for 15min at room temperatureandwerethen washedtwice inlx SSC with0.1% SDS for 30min at50°C. The autorad-iographswere exposedtoX-Omatfilm(Kodak, Rochester, N.Y.)with intensifying screens(DuPont Lighting Plus) for 24 to 72 h at -70°C.

Slotblot

analyses.

The

specificity

of theprobewas tested by hybridizationtoslot blots of DNAsfrom variousbacteria (5 ,ug),bovinethymocytes (5

p,g),

T. vaginalis

(5

pg),

andT. foetus (1

pg).

DNAs werepermanently boundedontoBA-S 85 nitrocellulose membranes by heatingat80°C for30 min under vacuum according to the manufacturer's specifica-tions (Scheicher & Schuell) and were hybridized with the

[a-32P]dCTP-labeled

probeasdescribed above.

Probe sensitivity was evaluated by hybridization of the

[a-32P]dCTP-labeled

probe to DNAprepared from known numbers of invitro-cultivated T.foetus mixed withsmegma samples from healthy, uninfected bulls. Spiked smegma samples(200 ,ul) containing various numbersof T.foetus

(103

to107)weremixedwith 2x NETbuffer(200 ,ul),proteinase K(200

p,g/ml),

and0.2%(wt/vol) SDS; incubatedat65°C for 15 min; and then extracted once with phenol, phenol-chloroform (1:1; vol/vol), andchloroform. DNAs were pre-cipitatedwith95%(vol/vol)ethanol and dissolved in 10

p1

of TEbuffer.Clinicalspecimens, negativesmegma controls(no parasite DNA),andnegativebuffercontrols(no DNA)were processed bythe sameprocedure (36).

Selection and synthesisofprimers.Plasmid DNA contain-ingtheprobewaspurifiedon a CsCl gradientas described previously (37) and was sequenced bythe double-stranded

on May 15, 2020 by guest

http://jcm.asm.org/

DNA

dideoxynucleotide

chain-termination sequencing method

(38)

withaSequenasekit

(Version

2.0; UnitedStates

Biochemicals, Cleveland, Ohio). Aliquots

of 3 to 5 ,g of

plasmid

DNAwereused for each reaction. The autoradio-graphs were developed at -70°Cfor 2 to 4 days. Oligonu-cleotide

primers

TF1

(5'-CATTATCCCAAATGGTATAAC-3')

and TF2

(5'-GTCATTAAGTACATAAATTC-3')

andan

internal

probe

sequence

(5'-CATCATITAATGCCTIl7TG

ATGGATCAGGCAACCATTI'ATA-3')

were synthesized

by

using

a

Cyclone

Plus DNA

Synthesizer

(MilliGen/Milli-pore,

Bedford, Mass.). Oligonucleotide

productswere puri-fied with

Oligo-Pak synthetic oligonucleotide

purification columns as recommended by the manufacturer

(MilliGen/

Millipore).

Preparation of DNAsamples forPCR. (i) Spiked smegma and culture samples. To test the

sensitivity

of the PCR detection system,various numbers ofinvitro-cultivated T.

foetus (1, 5,

and 10

parasites)

were mixed with 100-plI smegma

samples

from uninfected bulls. DNAwas isolated

by

the

rapid

DNAextraction

protocol by using

anIsoQuick Nucleic Acid Extraction kit

(MicroProbe

Corp., Garden

Grove,

Calif.).

Nucleic acid

pellets

weredissolvedin RNase-freewaterforPCR.

Negative

smegmacontrols(noT.foetus)

were includedineach

experiment.

To

investigate

theeffect ofsmegma

samples

on the

sensitivity

ofthe system, culti-vated T.

foetus

cellsweremixed with100pIoffreshculture

medium,

and DNAwas isolatedasdescribed above.

(ii)Freshclinical smegmasamples. Smegma samplesfrom infected and uninfected bulls were collected as described above. About 500 pIofeachsmegma

sample

wasinoculated into Diamond's medium and observed

daily

in a separate

laboratory

(that

of

R.H.B.)

for

parasite growth.

Another500 ,u of the

sample

was

centrifuged

at

4,000

x gfor 5 minat room temperature. The supernatant was

removed, leaving

100pl of

sample

forDNAextraction

by using

the

IsoQuick

NucleicAcid Extraction kit

(MicroProbe Corp.). Briefly,

the cell

pellet

was

resuspended

andmixed with 100 plof

lysis

solution-700 ,u of extraction matrix-400 ,u of extraction buffer. Each

sample

was vortexed for 10s andwas

centri-fuged

at

12,000

x g for 5 min. The aqueous

phase

was removed and mixed with

equal

volume of ice-cold

isopro-panol

and0.1 volume of sodiumacetate to

precipitate

DNA at

-20°C

for 2 h or

overnight

for convenience. The DNA

pellet

obtained

by centrifugation

(12,000

xgfor 10 minat

4°C)

was rinsed with 70%

(vol/vol)

ethanol,

air

dried,

and dissolved inRNase-freewaterfor PCR

(MicroProbe Corp.).

(iii)

Bacteria samples. Borrelia

burgdorferi

DNA

samples

(isolates

from Texas and

Denmark)

were obtained from R.B.L. Escherichia coli

(isolates

DH5a and

T9100889),

Pasteurella multocida

(isolate

P1059),

andSalmonella

typh-imurium

(isolates

845 and

1033)

DNA

samples

were a

gift

kindly provided by Dwight

Hirsh

(University

of

California,

Davis).

Amplification

byPCR andproductdetection. DNA

ampli-fication wascarried outina totalvolume of 50 ,u

by

using

either the DNA

sample

obtained from clinical or

spiked

smegma

samples,

250to300 ng ofbacterial

DNA,

or100 ng ofbovine cell DNA. The reaction mixture contained 10 mM Tris-HCl

(pH 9.0),

50 mM

potassium chloride,

0.1% Triton

X-100,

1.25 mM

magnesium chloride,

200

,uM

(each)

deox-ynucleoside triphosphates,

0.384

p,M

primer TF1,

and 0.365

p,M

primer

TF2. After

precycle

denaturation at

94°C

for 4 mintoreduce

nonspecific amplification (29),

1.25 U ofTaq DNA

polymerase (Promega Corp., Madison, Wis.)

was added and the mixturewasoverlaidwith 50

RI

ofmineraloil.

Amplification

was

performed

in a DNA Thermal

Cycler

(Perkin-Elmer CetusCorp., Norwalk, Conn.) for 41 cycles, asfollows: denaturation at94°C for 1 min, annealing at 45°C for 1min,and extensionat72°C for 2 min. The last cycle was givenaprolonged extension period of 7 min. Positive (100 ng of the 0.85-kb probe) and negative reagent controls were included with each batch oftestsamples. To avoid carryover of contaminating nucleic acids which may result in false-positivereactions(25, 32), the pre-PCRsample preparation, mixingofPCR reagents withthe samples,and thefinalPCR thermalcyclereactionswereperformed in separate labora-tories(24, 30).

After amplification, 5 ,ul of each sampleor a BioMarker Low

(BioVentures,

Inc., Murfreeboro, Tenn.) DNA size standard was mixed with 1

pl

of 6x loading dye and the mixturewas electrophoresedon a 3%Nusieve 3:1 agarose gel (FMC Bioproducts). Thegelwas stained ina

0.5-p,g/ml

ethidium bromide solution for 30 min and was observed for the presence ofamplification products under UV illumina-tion. Amplification productswere denatured in thegel and weretransferredtonylon membranes (Amersham Corp.)by Southern blotting as described previously (37). DNA was cross-linked to a nylon membrane by using a Stratalinker UV crosslinker (Stratagene, LaJolla, Calif.).

Prehybridiza-tion, preparation

ofthe labeled internalprobe, and hybrid-ization were performed as recommended by the manufac-turerofthe Enhanced Chemiluminescence 3'-Oligolabeling andDetectionSystems(Amersham).Labeledinternalprobe wasaddedto afinalconcentrationof 10ng/mlof hybridiza-tion solution, and the mixture was incubated overnight at

50°C

with gentle agitation. After hybridization, the mem-branes were washed twice for 5 min each time at room temperature in Sx SSC-0.1% (wt/vol) SDS and were then washed twice for 15 min eachtimeat60°Cin0.1xSSC-0.1%

(wt/vol)

SDS. Membrane blocking, antibody incubations, and

signal generation

and detection were performed as described

by

themanufacturer. Membraneswereexposedto Kodak X-Omat film for 3to10 min.

RESULTS

Restriction enzyme digestion and Southern hybridization. Restriction

endonuclease-digested

DNAs from different T.

foetus

isolateswere

analyzed,

and bands thatwere

promi-nentand conserved among all of theisolateswereidentified

as candidate T.

foetus probes.

Restriction fragment length

polymorphisms

were discerniblewhen DNAs of T. foetus isolates from California

(Dl,

RE2, and

NA4),

Idaho

(RE20,

RE23,

and

RE24),

Nevada

(RE19),

and Costa Rica (CR1,

CR2,

and

CR3)

were

digested

with

HindIII,

EcoRI, HaeIII,

orSau3A and the

fragments

wereseparatedon1.4%agarose

gels (data

not

shown).

A

prominent

band of 0.85 kb from

HindIII-digested genomic

DNAswhichwaspresentinall T.

foetus

isolateswas

purified

and cloned intoplasmidvector

pUC

19.

Figure

1illustrates the

typical

Southernblot

hybrid-ization

patterns

observed when

EcoRI-digested (lane 1)

and

HindIII-digested

(lane 2)

T.

foetus

DNAwashybridizedwith the radiolabeled0.85-kb T.

foetus

sequence. The

autoradio-graph

showed that the probe

hybridized

to a0.85-kb

frag-mentin

HindIII-digested

DNA

(lane 2)

aswellas to

multiple

fragments

at

higher

molecularmassesin both

digests.

These

hybridization

patternsindicated that this may bea

repetitive

sequence

in the T.

foetus

genome.

Specificity

test of the

probe by

slotblot

hybridization.

To evaluate the

specificity

of the

probe,

the radiolabeled0.85-kb DNA

probe

was

hybridized

toslotblots of DNAs

prepared

on May 15, 2020 by guest

http://jcm.asm.org/

1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

I I

I I

FIG. 3. Sensitivity test ofT. foetus probe by hybridization to slot-blotted DNAs of spikedand clinicalsmegmasamples. Al and Bi, 103 T. foetus; A2andB2,104T.foetus;A3 andB3,

10'

T.foetus; A4 andB4, 106 T. foetus; A5 andB5, 107T. foetus; A6, negative

smegmacontrol;A7,1agof T.foetusDNA; A8,0.85-kbprobe; A9 to A14 and B9to B12, smegma samples from T. foetus-infected bulls;B13 andB14,smegmasamplesfromhealthy,uninfectedbulls; B6 andB8, negativebuffer control(noDNA); B7, bovine thymo-cytes.

FIG. 1. Southern blot of EcoRI or HindIII-digested T. foetus DNAhybridizedwitharadiolabeled0.85-kb T.foetus probe.Lanes:

1, T.foetusDl DNAdigestedwithEcoRI; 2, T.foetusDl DNA digested with HindIII. Molecular sizes are indicated on left (in kilobases).

from T. foetus (isolates Dl, RE19, CR1, CR2, CR3, CR4, CR5, CR6), T. vaginalis (isolates T015 and T048), bacteria (Acinetobacter calcoaceticus, Campylobacter fetus var.

veneralis, Corynebacteriumpyogenes, Enterobacter

aero-genes, Escherichia coli, Haemophilus somnus, Moraxella bovis, Staphylococcus epidermidis, Staphylococcus

sapro-phyticus, Streptococcus lactis, Streptococcus viridans), bo-vinethymocytes, negative buffer controls (no DNA), anda

positive control (0.85-kb probe). Figure 2 shows that the probehybridizedtoDNAs of T.foetus isolates from various geographicareas(AltoA8)butnot toDNAsof T.vaginalis (A9 andA10),bovinethymocytes (All),ordifferent bacteria (BltoBll).

1 2 3 4 5 6 7 8 9 10 11 12 13

A

B

FIG. 2. Specificity test of T. foetus probe hybridized to slot-blottedDNAs oftrichomonads, bacteria, and bovinecells.Al, T. foetus Dl; A2, T.foetus REl9;A3, T.foetus CR1; A4, T.foetus CR2; AS,T.foetus CR3;A6,T.foetus CR4; A7,T.foetusCR5; A8, T.foetus CR6; A9, T. vagmafis T048; AlO,T.vaginalisTOlS;All,

bovinethymocytes; Bl,Acinetobacter calcoaceticus; B2, Campy-lobacter fetusvar.veneralis; B3,Corynebacteriumpyogenes; B4,

Enterobacter aerogenes; B5, Escherichia coli; B6, Haemophilus

somnus;B7,Moraxellabovis; B8, Staphylococcus epidermidis; B9, Staphylococcus saprophyticus; B10, Streptococcus lactis; Bll, Streptococcus viridans; A12, A13,andB12,negativebuffercontrols (no DNA); B13, positivecontrol(0.85-kbprobe).

Sensitivity

test of the probe by slot blot hybridization. Repeated experiments were conductedto determine probe sensitivity by hybridization of the radiolabeled 0.85-kb probe tosmegmasamples spiked with various numbers of T. foetus parasites. Figure 3 shows that the

probe

reliably detected DNAfrom 107 (A5 and B5) and

10'

(A4 and B4) T.foetus organisms. The minimumnumberofparasitesdetectableby this methodwas

105

(A3andB3) organisms. The DNA probe

wasfurther usedtoanalyzeclinicalsmegmaspecimensfrom 10 infected (Fig. 3, A9 to A14 and B9 to B12) and 2 uninfected(Fig.3, B13 and B14) bulls. The probeshowedno

reactivity with the clinical specimens under these experi-mental conditions.

PCR amplification of T. foetus DNA. To improve the sensitivity of the detectionsystem, theprobesequencewas

usedtoidentifytwooligonucleotide primers(TF1andTF2) anda162-bptargetsequenceforaPCR-basedamplification system. By using theseprimers, PCR products of

approxi-mately 162 bpwere amplified from the DNAs ofall nineT.

foetus isolates from California, Nevada, Idaho, and Costa Rica (Fig. 4A, lanes 2 to 10). No PCR products were

produced with DNAs from the different bacteria tested(Fig. 4B, lanes 2 to 8). Bovine cell DNA had an amplification

product of approximately 400 bp (Fig. 4B, lane 9). Multiple amplification productswereobtained with T. vaginalis DNA

(Fig. 4B, lane 10), and thesewere easily distinguished from thePCRproducts produced with T. foetus DNA (162 bp)or

the 0.85-kb probe controls (Fig. 4A and B, lanes 11). In repeatedexperiments, amplification productswerenot

pro-duced withanyofthenegativereagentcontrols(Fig. 4Aand B, lanes 12to14). Only the amplification products produced with T.foetus DNAs (Fig. 4C, lanes 2to10) and the 0.85-kb probe controls(Fig. 4C and D, lanes 11) showed hybridiza-tionsignals with the chemiluminescent internal probe.

Totest thesensitivity of the PCR detection system, 1:10 serial dilutionsofcultivated T.foetus parasiteswere added tosmegmasamples from uninfected bulls. All sampleswere

tested intriplicate in repeated experiments. PCR amplifica-tionproductswereobserved inanethidiumbromide-stained

gel from all three samples containing 10 T. foetus, one of three samples containing 5 T. foetus, and one of three samples containing 1 T.foetus (Fig. 5A, lanes2 to 10). No amplification product was produced from smegma sample controls(Fig. 5A,lanes 11to13).To determine the effect of smegmaonthesensitivity of the PCR detectionsystem,1:10 serial dilutions ofT.foetus parasites wereadded toculture

12

I'

23.1- 9.4-

6.6-4.4-

- 2.3-

on May 15, 2020 by guest

http://jcm.asm.org/

1 2 3 4 5 6 7 8 9 1011121314 1 2 3 4 5 6 7 8 9 1011121314

A

1000-

700-

500- 400-

300- 200-

100-

50-FIG. 4. Specificityof T.foetusdetectionby PCR amplification of T.foetus,T. vaginalis, bacteria, and bovine cell DNAs. Amplifica-tionproductswereelectrophoresedon a3%Nusieve 3:1agarosegel

stained with ethidium bromide (A and B) and hybridized to a

chemiluminescentinternalprobe (CandD). (A)Lanes: 2to10,T. foetus Dl, NA4, RE19, RE20, RE23, RE24, CR1, CR2, and CR3, respectively; 11,0.85-kbprobe control; 12to14, negativereagent

controls. Molecularsizesareindicatedonthe left(inbasepairs). (B) Lanes: 2 and 3, Borrelia burgdorferi isolates from Texas and Denmark, respectively; 4 and 5, Eschenichia coli DH5a and T9100889, respectively; 6, Pasteurella multocida P1059; 7 and8, Salmonellatyphimurium845 and1033,respectively;9,bovinecells; 10,T.vaginalis; 11,0.85-kbprobe control;12to14, negativereagent

controls. Molecular sizesareindicatedontheleft(inbasepairs).

medium. The resultshowed that in the absence ofsmegma,

amplification products could be produced fromoneT.foetus

organism (Fig. 5B, lanes 8 to 10). Thus, substances in the

smegma maybe responsible for the inhibitionofTaqDNA polymerase orthethick, mucus-like smegma mayinterfere with DNA isolation and thereby reduces the sensitivity of thetest.

1 2 3 4 56 7 8 91011121314 1 2 3 4 5 6 7 8 91011121314

C

D

FIG. 5. Sensitivity of T. foetus detection by PCR of spiked

smegmaand culturedsamples. Amplification productswere electro-phoresedon a3% Nusieve 3:1agarosegel stained with ethidium bromide(AandB)andhybridizedtoachemiluminescent internal probe (CandD).(A)Lanes: 2to4,10 T.foetusaddedtosmegma

samples;5to7,5T.foetusaddedtosmegmasamples;8 to10,1T. foetusaddedtosmegmasamples;11 to13,smegmasample-negative controls; 14,0.85-kbprobecontrol. Molecular sizesareindicatedon

the left(in basepairs). (B)Lanes: 2 to 4, 10 T.foetusinculture medium;5to7,5 T.foetusinculturemedium;8to10,1 T.foetusin culture medium; 11 to 13, culture medium-negative controls; 14, negativereagentcontrols. Molecular sizesareindicatedonthe left

(inbasepairs).

B

700-

500- 400-

300-

200-1 2 3 4 5 6 7 8 91011121314

100-FIG. 6. Detection of T. foetus in clinicalsmegma samples by

PCR amplification. Amplification productswereelectrophoresedon a3% Nusieve 3:1agarosegelstainedwithethidium bromide (A) and hybridizedtoachemiluminescentinternal probe (B). (A)Lanes:2,

3, 5, 6, 8, and 10, smegma samples from infectedbulls showing amplificationof T.foetusDNAby PCR;4 and7,smegmasamples from uninfectedbulls; 9,smegmasample from infected bull withno

detectable PCR amplification product; 11, bovinecell DNA; 12, 0.85-kbprobe control;13and14, negativereagentcontrols. Molec-ular sizesareindicatedonthe left(in base pairs).

Detection of T.foetus in clinical smegma samples byPCR

amplification. Smegmasamples from 10 infected bulls and 2 healthy uninfected bulls were collected weekly and

evalu-atedby PCR andby in vitro cultivation for the presenceof

parasites. The PCR detectionsystemidentified 39 of the 44 samples from infected bullsaspositive, whereasnoparasite

DNA was amplified from the other 5 samples from the

infected bullsor anyof the 8samples from uninfected bulls (Fig. 6). Nofalse-positive sampleswerereported by the PCR

detection system. In vitro cultivation andmicroscopic

ex-amination of aliquots from the same samples revealed T. foetus parasitesin36 of the44samplesfrom infected bulls. Parasites were not detected in eight of the samples from infected bulls orin theeight samples from uninfectedbulls. Thesamples from infected bulls thatwerenegative by PCR were different from those thatwereparasite negative after

cultivation andmicroscopic examination.

DISCUSSION

Accurate diagnosis is essential for the prevention and control of bovinetrichomoniasis,particularlyinthe absence ofanapprovedtreatmentmethod(4)or acompletely effica-cious vaccine(6, 19, 23, 39). Currently,adependable immu-nologicaltestfor bovinetrichomoniasis isnotavailable (50). Cultivation and microscopic examination are the standard

methods used for the diagnosis of T. foetus infection in cattle. Thetechniqueisspecific;however,it is time-consum-ing and lackssensitivity (15, 41, 42). Developmentofhighly sensitive and specific DNA probes was undertaken as a means ofimproving the diagnosis of T.foetus. The 0.85-kb A

1000-

700-:9=

300-

200-

1w-

50-B

1000-

700-48=

300- 200- 100-

50-C

D

on May 15, 2020 by guest

http://jcm.asm.org/

sequence was selected as the best candidate probe on the basis of its specificity for the parasite and no cross-reactivity with bovine cell DNA or DNAs from pathogenic and non-pathogenic bacteria which inhabit the bovine reproductive tract (9, 49).

Although the 0.85-kb probe was highly specific for T. foetus, the sensitivity of the system was limited to the

detection of 105 T. foetus organisms. To overcome this problem, we used PCR technology, similar to that which has been used for the improved diagnosis of other pathogenic protozoa (3, 18, 33, 35). The application of this technology allowed for the reliable detection of a single T. foetus organism in culture medium or 10 T. foetus organisms in spiked smegma samples. The PCR system amplified the DNAs of T.foetus isolates from different geographic areas. In addition, the system amplified T. vaginalis DNA to produce a unique amplification product pattern which was easilydistinguishedfrom that produced with T. foetus DNA. Riley et al. (35) reported that notable genomic differences exist among T. vaginalis isolates, and not all PCR primer pairs in their study amplified products with the same inten-sity. Therefore, the TF1 and TF2 primers should be further evaluated to determine their usefulness in the detection of different T. vaginalisisolates.

In the initial development of the PCR-based detection system for T.foetus,weattempted to use an easy method of sample preparation by heating samples at 97°C for 15 min during the precycle denaturation step (20). Unfortunately, noPCRamplification productswereobtainedbythis method with known infected bull samples or culture-derived para-sites (data not shown). This may be because trichomonads, such as T.foetus and T. vaginalis, contain relatively large amounts ofendogenous nucleases which digest their DNAs completely in a short period oftime after cell lysis occurs (26, 28, 47, 48). Therefore, afast, easy, and reliable method for samplepreparationwas needed to isolate intact genomic DNAfromtrichomonads. Previously described methods for theisolationoftrichomonad DNA are effective (34, 36, 48), but time-consuming. With the rapid procedure (IsoQuick Nucleic Acid Extraction kit) used in our study, large num-bers ofsamples can behandledsimultaneously. DNA isola-tion is reliable and easy to perform by using guandinium thiocyanate in the lysis solution to inhibit nuclease activity and anorganic extractionmatrix to remove protein and cell debriswithoutusing phenol orchloroform.

This is the first report of aPCR-basedamplification system for the detectionof T.foetus infectionsin cattle. Speer and colleagues (44, 45) previously reportedthedevelopment of a T. foetus-specific DNA probe. However, a recent compari-son of different diagnostic methods showed that this DNA probelacks thesensitivityneeded for theeffective diagnosis of bovinetrichomoniasis (2).

In a comparison ofthe PCR-based system with in vitro cultivation, neither system showed 100% sensitivity in de-tecting T. foetus in clinical samples from infected bulls. Although a single T. foetus trophozoite was detected with the PCR-basedamplification system,testsensitivitymay be lower because of inhibition of Taq DNA polymerase by inhibitors (16, 17, 20) in the bovine smegma that are not removed in theprocess of DNAisolation. Thesensitivityof the cultivation method may be restricted by a lack of sufficient numbers of viable parasites in some smegma samples that are able to adapt to culture and grow to detectable numbers. Overall, the PCR-based T. foetus de-tection system appearsto be highly specific and at least as sensitive as thecultivation method,with theadvantage that

this molecular method can accommodate a large number of samples, is easy to perform, and can be performed relatively quickly. The total time required for sample collection, DNA isolation, and visualization of an amplification product on an ethidium bromide-stained gel was 1 working day. Confirma-tion of T. foetus-specific amplification products by hybrid-ization with the chemiluminescent

internal

probe could be completed onthe next day. Therefore, bystandardizing the method of smegma collection and processing, the PCR detection system described here may provide a

powerful,

efficient, and reliable alternative method for detecting T. foetus infections in cattle.

ACKNOWLEDGMENTS

This work was supported by grants from America Veterinary Medical Association Foundation, California Cattlemen's Associa-tion, LivestockDisease Research Laboratory at the University of California at Davis, and U.S. Department of Agriculture Formula Funds.

We are grateful for the excellent technical support of William Innes, Marcello Schonmann, Wendy Baltzer, Cassandra Kachulis, John Thomford, Robin Houston, and David Ferrick. We also thank Ana Ortuno, John Alderete, Jeffery Stott, and Dwight Hirsh for various parasite and DNA samples. M.S.Y.H. thanks T. Y. Lai for superb support and help in manuscript preparation.

REFERENCES

1. Abbitt, B., and G. W. Meyerholz. 1979. Trichomonas fetus infectionof rangebulls in South Florida. Vet. Med./SmallAnim. Clin. 74:1339-1342.

2. Appell, L. H., W. D. Mickelsen, M. W. Thomas, and W. M. Harmon. 1993. A comparison of techniques used forthe diag-nosis of Tritrichomonasfoetus infections in beef bulls. Agri-Practice 14:30-34.

3. Avila,H.A.,D. S.Sigman, L. M. Cohen,R.C. Millikan, and L Simpson. 1991. Polymerase chain reaction amplification of Trypanosoma crui kinetoplast minicircle DNA isolated from wholebloodlysates: diagnosis of chronic Chagas' disease. Mol. Biochem.Parasitol. 48:211-221.

4. BonDurant, R. H. 1985. Diagnosis, treatment and control of bovine trichomoniasis. Compend. Contin. Educ. Pract. Vet. 7:S179-188.

5. BonDurant, R.H., M. L. Anderson, P. Blanchard, D. Hird, C. Danaye-Elmi, C. Palmer, W. M. Sischo, D. Suther, W. Utter-back, and B. J. Weigler. 1990. Prevalence of trichomoniasis among California beef herds. J. Am. Vet. Med. Assoc. 196: 1590-1593.

6. BonDurant, R. H., R. R. Corbell, and L. B. Corbeil. 1993. Immunization ofvirgin cows with surface antigen TF1.17 of Tnt,ichomonas foetus. Infect. Immun. 61:1385-1394.

7. Clark,B.L.1971.Venerealdiseases of cattle. Vet. Rev. 1:5-26. 8. Conrad, P.A., L Iams,W.C.Brown, B. Sohanpal, and0.KL ole-MoiYoi. 1987. DNA probes detect genomic diversity in Theilena parva stocks. Mol. Biochem. Parasitol. 25:213-226.

9. Corbeil,L.B.,W.Woodward,A.C. S. Ward, W. D. Mickelsen, and L.Paisley. 1985. Bacterial interactions in bovine respiratory andreproductiveinfections. J.

Clin.

Microbiol. 21:803-807. 10. Dawson, L. J. 1986. Diagnosis, prevention, and control of

campylobacteriosis and trichomoniasis. Bovine Pract.

21:180-183.

11. Dennett, D. P., R. L.Reece, J.0.Barasa, and R. H. Johnson. 1974. Observations on the incidenceand distribution of sero-types ofTritichomonasfoetus inbeefcattle in north-eastern Australia.Aust.Vet.J. 50:427-431.

12. Diamond, L. S. 1957. The establishment of various trichomo-nads of animals and man in axenic cultures. J. Parasitol. 43:488-490.

13. Ferrari,F.A., E.Ferrari,andJ.A.Hoch.1982. Chromosomal location of a Bacillus subtilis DNA fragment uniquely tran-scribed bysigma-28-containing RNApolymerase. J. Bacteriol. 152:780-785.

on May 15, 2020 by guest

http://jcm.asm.org/

14. Fitzgerald, P. R. 1986. Bovine trichonomiasis. Vet. Clin. N. Am.Food Anim. Pract. 2:277-282.

15. Fitzgerald, P. R., D. M. Hammond,andJ.L.Shupe. 1954.The role of cultures in immediate and delayed examinations of preputial samples for Tnichomonas foetus. Vet. Med. 49:409-413.

16. Gelfand, D. H. 1989. TaqDNApolymerase, p. 17-22. In H. Erlich (ed.), PCR technology: principles and applications for DNAamplification. M. Stockton Press, New York.

17. Gelfand, D. H., and J. W. Thomas. 1990. Thermostable DNA polymerase, p. 129-141. In M.A. Innis, D. H. Gelfand, J. J. Sninsky, and T. J. White (ed.), PCR protocols: a guide to methods and applications. Academic Press, Inc., San Diego, Calif.

18. Grover, C. M., P. Thulliez, J. S. Remington, and J. C. Booth-royd. 1990.Rapid prenataldiagnosis of congenital Toooplasma infection by usingpolymerasechain reaction and amniotic fluid. J. Clin. Microbiol. 28:2297-2301.

19. Hall, M. R., W. G. Kvasnicka, D. Hanks, L. Chavez, and D. Sandblom. 1993. Improved control of trichomoniasis with Tnchomonasfoetus vaccine. Agri-Practice 14:29-34.

20. Higuchi, R 1989. Simple and rapid preparation of samples for PCR, p. 31-38. In H. Erlich(ed.), PCRtechnology: principles and applications for DNA amplification. M. Stockton Press, NewYork.

21. Johnson, A. E. 1964. Incidence anddiagnosis of trichomoniasis inwesternbeefbulls. J. Am. Vet. Med. Assoc. 145:1007-1010. 22. Johnson,A.E.1965.The diagnosis oftrichomoniasis in the bull.

Proc. U.S.LivestockSanit. Assoc. 69:183-189.

23. Kvasnicka, W. G., D. Hanks, J. C. Huang, M. R Hall, D. Sandblom, H. J. Chu, L. Chavez, and W. M. Acree. 1992. Clinical evaluation of theefficacy ofinoculating cattle with a vaccine containing Tritrichomonas foetus. Am. J. Vet. Res. 53:2023-2027.

24. Kwok, S. 1990.Procedures tominimize PCR-product carryover, p.142-158. In M. A. Innis, D. H. Gelfand, J. J. Sninsky, and T. J. White (ed.), PCR protocols: a guide to methods and applications.AcademicPress, Inc., SanDiego,Calif.

25. Kwok,S., andR.Higuchi. 1989. Avoidingfalsepositives with PCR. Nature(London)339:237-238.

26. Mandel, M., and B. M.Honigberg. 1964. Isolation and charac-terization of deoxyribonucleic acid of two species of

TichomonasDonne. J. Protozool. 11:114-116.

27. Marquez, N. A., G. W. Benz,D. F.Walker, andR. S. Hudson. 1972. Anevaluation oftechniques for the diagnosis of tricho-moniasis in bulls. AuburnVet.29:22-23.

28. Muller, M. 1973. Biochemicalcytology of trichomonad flagel-lates. J. Cell Biol.57:453-474.

29. Nuovo, G. J., F. Gallery, P. MacConnell, J. Becker, and W. Bloch. 1991. Animproved techniquefor thein situdetection of DNA after polymerase chain reaction amplification. Am. J. Pathol. 139:1239-1244.

30. Orrege, C. 1990. Organizing a laboratory for PCR work, p. 447-454. In M. A.Innis,D. H.Gelfand,J. J.Sninsky,and T. J. White(ed.), PCRprotocols: aguide tomethods and applica-tions. AcademicPress, Inc.,SanDiego,Calif.

31. Perez, E., P. A. Conrad,D. Hird, A.Ortuno, J. Chacon, R BonDurant, and J. Noordhulzen. 1992. Prevalence and risk factorsforTrichomonas foetusinfection incattle in northeast-ern Costa Rica. Prevent. Vet. Med. 14:155-165.

32. Persing, D. H. 1991. Polymerase chain reaction: trenches to

benches. J. Clin. Microbiol. 29:1281-1285.

33. Persing,D.H.,D.Mathiesen,W. F.Marshall, S. R. Telford, A. Spielman,J.W.Thomford, and P. A. Conrad. 1992. Detection of Babesia microti by polymerase chain reaction. J. Clin. Microbiol. 30:2097-2103.

34. Riley,D.E., andJ.N.Krieger.1992. Rapid and practical DNA isolation from Tnichomonas vaginalis and other nuclease-rich protozoa.Mol. Biochem.Parasitol. 51:161-163.

35. Riley, D. E., M. C. Roberts,T.Takayama,andJ. N. Krieger. 1992. Development ofapolymerase chain reaction-based diag-nosis ofTrchomonas vaginalis. J. Clin. Microbiol. 30:465-472. 36. Rubino, S., R. Muresu, P.Rappelli, P. L. Fiori, P. Rizzu, G. Erre,andP.Cappuccineili. 1991. Molecular probe for identifi-cation of Trichomonas vaginalis DNA. J. Clin. Microbiol. 29:702-706.

37. Sambrook, J.,E. F.Fritsch,and T.Maniatis. 1989. Molecular cloning: a laboratory manual, 2nd ed. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.

38. Sanger, F., S. Nicklen,andA.R.Coulson. 1977. DNA sequenc-ing with chain-terminatsequenc-ing inhibitors. Proc. Natl. Acad. Sci. USA 74:5463-5467.

39. Schnackel, J. A., B. L. Wallace, W. G. Kvasnicka, D. R.Hanks, and M. R. Hall. 1989. Tnichomonas foetus vaccine immunoge-nicity trial.Agri-Practice10:11-14.

40. Skirrow,S.1987.Identification oftrichomonad-carriercows.J. Am. Vet. Med. Assoc. 191:553-554.

41. Skirrow, S., R. BonDurant, J. Farley, and J. Correa. 1985. Efficacy of ipronidazole againsttrichomoniasis in beef bulls. J. Am. Vet. Med. Assoc. 187:405-407.

42. Sklrrow, S. Z., and R. H. BonDurant. 1990. Induced Tnitni-chomonasfoetus infection in beef heifers. J. Am. Vet. Med. Assoc. 196:885-889.

43. Southern, E. M. 1975. Detection ofspecific sequences among DNA fragments separated by gelelectrophoresis. J. Mol. Biol. 98:503-517.

44. Speer, C. A., W.E.Severson,H.J.Cranston, D.Scollard, J. R. Thompson, and M. W.White.1992. Adiagnostic DNA assay for trichomoniasis incattle, p. 128-137. Ann. Meet. Proc. Live-stock Conserv. Inst.

45. Speer, C. A., and M. W. White. 1991. Bovine trichomoniasis. LargeAnim.Vet.46:18-20.

46. Tedesco,L.F., F. Errico, and L. P.DelBaglivi. 1979.Diagnosis ofTnitnichomonasfoetus infection in bulls usingtwosampling methods andatransport medium. Aust. Vet. J. 55:322-324. 47. Turner,G., and M. Muller. 1983. Failuretodetect extranuclear

DNA in Tnichomonas vaginalisand Tntnichomonas foetus.J. Parasitol. 69:234-236.

48. Wang, A. L., and C. C.Wang. 1985. Isolation and character-ization of DNA from Tnitnichomonasfoetusand Tnichomonas vaginalis.Mol. Biochem. Parasitol. 14:323-335.

49. Ward, A. C. S., L. R. Stephens, B. J. Winslow, R. P. Gogo-lewski, D. C.Schaefer, S. K. Wasson, and B. L. Williams. 1986. Isolation of Haemophilus somnus: a comparative study of selective media, p. 479-486. 29th Ann. Proc. Am. Assoc. Vet. Lab.Diagn.

50. Yule, A., S. Z.Skirrow, J. Stants,andR.H. Bondurant.1989. Development andpreliminaryassessmentofapolyclonal anti-body-based enzyme immunoassay for the detection of Tnitni-chomonasfoetus antigen in breeding cattle. Vet. Parasitol. 31:115-123.

on May 15, 2020 by guest

http://jcm.asm.org/