8/13/2019 D8967

1/5

8/13/2019 D8967

2/5

7 6the tes t ing of so-ca l led pre ven t ive d is infec t ion - which is pe rfo rm ed dur in g the in te r va lbe tw e e n re m ova l f rom the p re m ise s of one g roup o f a n ima l s a nd in t roduc t ion o f t he ne x tgroup - wi th spec ia l regard to day-old chicks and newborn animals .

W H E R E A N D W H E N S H O U L D T H E E F FIC A C Y O FDISINFECTION BE TESTED?Af te r th e rem ov al of anim als and b i rds f rom a bui ld ing and c leanin g of the p rem ises ,

t h e s u r f a c e s w il l s ti ll b e c o n t a m i n a t e d w i t h m i c r o b e s . T h e e x t e n t o f m i c r o b i a lc o n t a m i n a t i o n d if fe rs b e t w e e n t h e v a r i o u s s u r f a c e s . T h e f lo o r c a n b e r e g a r d e d a s t h em o s t c o n t a m i n a t e d a r e a o f t h e a n i m a l h o u s e ; t h e n a t u r e a n d i r r e g u l a r i t y of t h e f l o o rusua l ly make th i s more d i f f icul t to d i s infec t than o ther surfaces . There fore , i f a te s t ingme thod show s tha t d i s in fe c t ion ha s be e n e f fe c t i ve on the f l oo r , t he o the r su r fa c e s a rel ikely to have been sat isfactori ly disinfected.

The t iming o f s a mple c o l l e c t i on i s a no the r impor t a n t a spe c t o f t e s t i ng . Sa mple s fo rmic rob io log ic a l t e s t i ng shou ld no t be t a ke n f rom a w e t su r fa c e . O n the one ha n d , t h edis infec tant might s t i l l be ac t ing on a wet surface , and the end-point of the d is infec t ionh a s t h e r e f o r e n o t y e t b e e n r e a c h e d . O n t h e o t h e r h a n d , d i s i n f e c t a n t r e s i d u e s i n s u c hsa m ple s migh t p re ve n t t he g row th of mic ro orga n i sm s in c u l tu re me d ia . N e u t ra l i s i ng thed i s i n f e c t a n t w i t h a n a n t a g o n i s t b e f o r e t a k i n g s a m p l e s fr o m s u r f a c e s u n d e r f ie l dc ond i t i ons w ou ld be nonse ns i c a l . The f l oo r shou ld t he re fo re be a l l ow e d to d ry be fo resa m ple s a re t a k e n for c u l tu re .

C U LTU R E S ELEC TI O N A N D I N TER P R ETA TI O N O F R ES U LTSBe fore d iscuss ing the pr inc ip les invo lved in the se lec t ion of a tes t mic ro org anis m , it i suse fu l t o re c a l l t he func t ion o f d i s in fe c t ion : t o k i l l c on ta mina t ing mic roorga n i sms a ndthus p re ve n t t he i nc ide nc e o f a d i se a se . D i s in fe c t a n t s a re ra re ly re qu i re d t o a c t i n a na b s o l u t e c a p a c it y , a n d t h e r e f o r e t h e p r i n c i p l e of al l s u c h t e s t i n g i s t o d e t e r m i n e t h e

degree of surviva l of microorganisms.A n u b i q u i t o u s m i c r o b e ( i .e . f o u n d i n s t a b l e s , e q u i p m e n t , f a e c e s , e t c .) m i g h t b econs idered sui table for te s t ing d is infec t ion under f ie ld condi t ions . In prac t ice , two such

s t ra ins of t e s t m ic r oo rg a n i sm s a re use d : a s t r a in o f c o l i fo rm ba c t e r i a a n d a s t r a in o fs t a phy loc oc c i , bo th c u l tu re d us ing a s e l ec t ive me d ium (3 , 4 ) . T he use o f t he se o rga n i sm sc a n u n d o u b t e d l y b e of c o n s i d e r a b l e v a l u e , b u t t h e r e s u l t s o b t a i n e d m u s t n o t b ei n t e r p r e t e d t o o b r o a d l y , a s t h e s e s t r a i n s d o n o t e x h i b i t a h i g h d e g r e e o f r e s i s t a n c e t od i s i n f e c t a n t s ( 6 ) . D e t e r m i n a t i o n o f t h e t o t a l a e r o b i c b a c t e r i a l c o u n t p r o v i d e s a m o r er e l i a b l e t e s t m e t h o d . S a m p l e s a r e t a k e n f r o m s u r f a c e s i n a n i m a l h o u s i n g , u s i n g asu i t a b l e me tho d , t o ob t a in a c oun t of t he nu m be r o f v i a b le mic ro orga n i sms p re se n t .

T h e e x t e n t o f t h e s u r v i v a l o f t h e t o t a l a e r o b i c m i c r o o r g a n i s m s c a n b e u s e d a s ameasure of the e ff icacy of d i s infec t ion . This i s one of the most c r i t i ca l e lements in thein te rpre ta t ion of resul t s , and i s of grea t s igni f icance . Many exper iments in th i s f ie ld (7)h a v e l e d t o t h e f o l l o w i n g c o n c l u s i o n : the count of viable bacteria on the f loor after adisinfect ion m ust not excee d the value of one viable bacterium per cm 2 or 100 bacteriaper 100 cm 2 ) .

8/13/2019 D8967

3/5

77A n e n v i r o n m e n t a l m i c r o b i o l o g i s t w i ll b e a w a r e t h a t t h i s c a n n o t s e r v e a s a s tr i c t

de f in it i on . H ow eve r , it shou ld be no t e d t ha t two sepa ra t e , conse cu t ive d i s in fec t ions a reusua l l y neces sa ry t o r each such a l ow l eve l o f con t amina t i on on t he f l oo r o f an an imalh o u s e .

M E T H O D S O F T E S T I N GDirect swabbing techniques

S e v e r a l t e c h n i q u e s h a v e b e e n u s e d f o r t h e a s s e s s m e n t o f d i s i n f e c t i o n e f fi ca c y ,involv ing the co l lec t ion of samples . f rom a g iven area (e .g . 100 cm 2 ) by swabbing , and asub seq uen t qua n t i t a t i ve (o r s em i -qua n t i t a t i ve ) a s ses sm en t o f su rv iv ing o rgan i sms . Ev enaf ter a good d is infect ion , one or two of t en swabs may be pos i t ive in e i ther co l i form ors t aphy lococc i t e s t s ( e . g . i n speed t e s t s ) (1 , 3 , 4 , 5 ) .Agar cyl inder techniques

A s ta in less s tee l cy l inder (e .g . 20 x 8 cm ) is f il led w i th an aga r me diu m . Th e cyl ind eris f i t t e d w i t h a p i s t o n , e n a b l i n g a 3 -4 m m l a y e r of t h e m e d i u m t o b e p u s h e d o u t t ocon t ac t t he su r face t o be i nve s t i ga t ed . Th i s laye r is t he n cu t and p l ac ed i n a P e t r i d i sh .I n c u b a t i n g t h e a g a r s l ic e p r o v i d e s a q u a n t i t a t i v e a s s e s s m e n t o f s u r v i v i n gmicroo rgan i sms wi th in a g iven a rea (2 ) .Agar sausage m etho d

O n e end of a t ef lon tub e is seale d , an d the tub e is f il led wi th agar m ed iu m to pr od uc ean aga r s aus age , wh ich is t he n rem ov ed f rom the t ube . On e end of t he aga r s au sag e iscut , and the cu t surface i s touched onto the surface to be inves t igated . A s l ice i s then cuta n d p l a c e d i n a P e t r i d is h , p r o v i d i n g a q u a n t i t a t i v e a s s e s s m e n t of s u r v i v i n gmicroo rgan i sms (9 ) .Agar-carrying l inen

Thi s t echn ique has p roved t o be more p rac t i ca l t han t he o the r t e s t s desc r ibed above .A circle of l inen is cu t to th e dim en sio ns of a Pe tri dish, with a sm all f lap wh ich ex te nd sbeyond the d i sh when the l inen i s pos i t ioned ins ide the base of the d i sh . The l inen c i rc leand the d i sh are s ter i l i sed . The Pet r i d i sh i s then f i l l ed wi th agar medium. The cover ofthe Pet r i d i sh is re m ov ed , and th e flap of l inen can be used to l if t the ag ar me di um ou t ofthe d i sh and p lace th i s on the surface to be inves t igated . The f lap should again be usedto re tu rn t he agar t o t he P e t r i d i sh (A . F o r ray , pe r sona l communica t i on ; 8 ) .Ready-to-use tes t

Al though a l l o f t he above t echn iques a re more o r l e s s f eas ib l e and can p rov ide ve ryusefu l informat ion , they cannot be eas i ly in tegrated in to the d i s infect ion pract ice of thep rem ises , as t hey a ll r eq u i re a l abo ra to ry ba ck gro un d a nd sk il l i n p rac t i ca l m ic rob io logy .S o m e r e a d y - t o - u s e s e t s h a v e t h e r e f o r e b e e n d e v e l o p e d , w h i c h d o n o t r e q u i r e s u c hski ll s. T he us of on e of these se t s is des cr ib ed below.

A p i ec e of l i nen (2 c m 2 ) i s i m p r e g n a t e d w i t h a g a r m e d i u m , m i x e d i n d i c a t o r s a n dc a t a l y s e r s ; t h i s is p l a c e d i n a s m a l l p l a s t i c b a g . T h e s e t a l s o c o n t a i n s w e t t i n g a g e n t ,tw eez er s , an i nc ub a t i o n bag (a l l a re s t e r i l i s ed ) and a s t r i p o f g lue . T h e bag con t a in in gthe med ium shou ld be cu t open , and t he p i eces o f l i nen (wi th med ium) shou ld be p l acedon t he f l oo r u s ing t he twe ez er s . T he p i ec es o f l i nen shou ld be w e t t ed a nd t he n l i gh t l y

8/13/2019 D8967

4/5

78r ubbed on the f l oor . T he sample s shou ld be p l aced in t he incuba t ion bag , which shou ldthen be c losed wi th the s t r ip of g lue and s tored a t room tempera ture in a dark place . Thesamples should be inves t iga ted a f te r 4-16 h . I f the viole t colour of the medium has notcha ng ed, or has chang ed in only on e of f ive pieces , th i s de m on st ra tes t he e f ficacy of thed i s in f ec t ion ( r epr e sen t ing a coun t o f l e s s t han 100 v i ab le bac t e r i a pe r 100 cm 2 ) . If theco lour o f t he media ha s changed f r om v io l e t t o ye l low/br own in 4 - 6 h , o r i f mor e thano n e of f iv e p i e c e s h a s b e c o m e y e l l o w / b r o w n i n 1 6 h , t h i s d e m o n s t r a t e s t h a t t h edisinfect ion has not been effect ive (8) .

* *TESTER L EFFICACIT DES DSINFECTANTS. - G. Tamsi .

sum : Les preuves de laboratoire sont indubitablemen t utiles pour valuerl'action des dsinfectants. Cepen dant, elles ne doivent tre considres quecomm e p rliminaires des essais sur le terrain. Cela mon tre non seulement leslimites de fiabilit des tests en laboratoire, mais pose galemen t un problmeplus vaste, savoir com ment tendre une valuation faite en laboratoire auxconditions du terrain.C estpourqu oi de nom breuses tentatives ont t faites en vue de mettre aupoint des t stspermettant d'valuer les besoins concrets du terrain en matire dedsinfection (par exemple dans l sfermes). L'objectif de ces techniques est defixer le seuil d'efficacit d'une mthode de dsinfection des surfaces dans lesbtiments destins aux animaux-Prena nt en considration la ncessit de norma liser les conditions d'tudessur le terrain, l'auteur donn e des dtails sur le mom ent et le lieu optimum s poureffectuer des prlvements sur le terrain. Les prlvements qui devront tre misen culture seront prlevs lorsque le sol est sec.Les diverses techniques (couvillonnage, cylindre et conteneur de glose,trousse ad hoc) devraient fournir des informations sur le seuil d'efficacit de lamthod e d e dsinfection. Le seuil souhait est approxim ativement d'unebactrie viable par centimtre carr.La technique utilise devrait permettre de vrifier si la dsinfection a tefficace.

M O T S - C L S Dsin fection - Efficacit - E ssais en labora toire - Essais sur leterrain - Logement des animaux - Mthodes d 'essais .

EVA LUA CIN D E LA E FICACIA D E LOS DESINFECTAN TES. - G . Tamsi.esumen Las pruebas de laboratorio son ciertamente tiles para evalua r laaccin de los desinfectantes; pero no debe considerrselas sino comopreliminares a las pruebas que se realizarn en el terreno. Lo cual no solamentemuestra los lmites de fiabilidad de las pruebas realizadas en laboratorio, sinoque plantea a la vez el problem a ms vasto de cmo hacer la correlacin entreuna evaluacin realizada en laboratorio y las condiciones del terreno.

8/13/2019 D8967

5/5

79Esto ha llevado arealizar varios intentos de desarrollar pruebas capacesdeevaluar las necesidades concretas del terreno en materia de desinfeccin (porejemplo enlas granjas). Suobjetivo es establecer el umbra l de eficacia de unmtodo de desinfeccin de las su perficies en los locales destinados a losanimales.Tom ando en consideracin la necesidad de estandarizar las condiciones deevaluacin en el terreno, el autor ofrece d etalles precisos acerca del mom ento yel lugar ptimos p ara o btener muestras de campo . Las muestras que se pondrnen cultivo sern tomadas del suelo cuando ste est seco.Las distintas tcnicas (escobillones, cilindro ycontenedor de gelosa, kita dhoc) deberan proporcionar informaciones sobre elumbra l de eficacia delmtodo de desinfeccin. Elumbra l deseable es aproximadamente de unabacteria viable por centmetro cuadrad o.La tcnica utilizada tendra que permitir verificar si la desinfeccin ha sido

eficaz.P A L A B R A S C L A V E : D e s i n f e c c i n- Eficac i a- L o c a l e s p a r a a n i m a l e s -M todos de p ruebas- Pru ebas en e l t e r re no- Pruebas en laborator io .

R E F E R E N C E S1. A C K E R M A N NH.H., H R T U N G J. H I L L I G E R H.G. (1982). - Vergleich eines neuenVerfahrens mi t zweibekannten Verfahren zur Bes t immung der Keimzahl an Oberf lchenim Stahl.Berl. M nch, tierrtzl Wschr.,95,5-10.2. KOVCSF. (1980).- llathiginia, 2nd Ed. Agric ul tural Publ ishing Co . , Bu dap est , 601 pp .3 . M E H L H O R N G., M E T H L I N G W., B E E R K., E R W E R T H W. N E U P A R T H V. (1980). -M i k r o b i o l o g i s c h e S c h n e l l m e t h o d e n zur D e s i n f e k t i o n s k o n t r o l l e . In P r o c . 3rdIn terna t ional Congress for An ima l Hyg iene, Vienna (H. Wi l linger G. Thie ma nn, eds) ,188-189.4. POLYAKOV A.A. (1979).-V eterina rnay a san i tariya. Ko los, Moscow , 618 pp .5. STEIGER A. (1981) . - M g l i c h k e i t e n und G r n z e n der fr i s chen D es in fek t i on .Mh. VetMed., 36 ,725-728.6. SYKESG. (1967).- Disinfect ion andS ter i l i sa tion, 2nd Ed. Spon Ltd. , London, 486 pp.7. TAMSI G. (1983).- U j k s z t m n y ' D I S I N T E S T 'afer t t lemts e l l en rzs re . MagyarAllatorvosok Lapja, 38,88-90.8. T A M S I G. N A G Y A. (1971) . - A p r e v e n t i v f e r t t l e m t s s z e r e p e az i p a r s z e r ser ts tar tsban . Ma gyar Allatorvosok Lapja, 26,605-614.9. T E NCATE L. (1965).- Anote ona simple and rap id methodof bacteriological samplingby mea nsofagar sa usages.J . appl. Bacterio , 28 ,221-223.