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Lysogeny and other characteristics of Staphylococcus hyicus isolated from chickens
Veterinary Microbiology, 8 (1983) 411--415 Elsevier Science Publishers B.V., Amsterdam --Printed in The Netherlands
411
Short Communication LYSOGENY AND OTHER CHARACTERISTICS OF STAPHYLOCOCCUS
HYICUS ISOLATED FROM CHICKENS
F.S.B. KIBENGE, J.I. ROOD and G.E. WILCOX
Division of Veterinary Biology, School of Veterinary Studies, Murdoch University, Murdoch, W.A. (Australia) (Accepted 31 January 1983}
ABSTRACT Kibenge, F.S.B., Rood, J.I. and Wilcox, G.E., 1983. Lysogeny and other characteristics of Staphylococcus hyicus isolated from chickens. Vet. Microbiol., 8: 411--415. Lysogeny was readily demonstrated among strains of Staphylococcus hyicus that were isolated from chickens. Susceptibility to phage lysis was affected by prophage immunity, but lipase activity and erythromycin resistance were not affected by the presence of temperate phage. In contrast to previously published results, lipase-negative strains of S. hyicus were relatively common and the use of selective media based on lipase activity would have been unsuitable for detection of the S. hyicus strains examined.
INTRODUCTION
Staphylococcus hyicus (subsp. hyicus) o c c u r s f r e q u e n t l y o n the skin and nares o f h e a l t h y p o u l t r y (Devriese, 1 9 8 0 ) , pigs (Devriese, 1 9 7 7 ) , cattle (Devriese and D e r y c k e , 1 9 7 9 ) and in animal p r o d u c t s and slaughter h o u s e effluents (Devriese and Hajek, 1 9 8 0 ) . In p o u l t r y , S. hyicus is c o n s i d e r e d t o be o f low virulence (Devriese, 1 9 8 0 ) as t h e organism has been isolated o n l y f r o m n o r m a l c h i c k e n s or t h o s e with m i x e d i n f e c t i o n s o f the skin (Sato et al., 1972). Previous results s h o w e d t h a t several b i o c h e m i c a l characteristics o f S. hyicus varied b e t w e e n d i f f e r e n t g r o u p s o f isolates (Devriese et al., 1978). In this c o m m u n i c a t i o n , we r e p o r t the results o f e x p e r i m e n t s a i m e d at the e x a m i n a t i o n o f the p r o p e r t i e s o f S. hyicus strains isolated f r o m chickens a f f e c t e d with t e n o s y n o v i t i s in Australia (Kibenge et al., 1982a, b). MATERIALS AND METHODS Twelve strains were isolated f r o m chickens and were identified using t h e criteria p r o p o s e d b y Devriese et al. ( 1 9 7 8 ) as previously described (Kibenge et al., 1 9 8 2 b ) . Eleven strains were isolated f r o m various tissues o f c h i c k e n s with t e n o s y n o v i t i s f r o m seven farms as s h o w n in Table I. Isolates 1 8 6 6 a n d
0378-1135/83/$03.00
© 1983 Elsevier Science Publishers B.V.
412 TABLE I Characteristics of Staphylococcus hyicus from chickens
Strain
Source Farm Tissue
Characteristic Lysogenya Lysis by phage CHll jc
1609 (A) 1777 (B) 1389 (C) 1865 (D) 1866 (E) 1867 (F) 1874 (G) 1997 (H) 1999 (I) 2000 (J) 2005 (K) 2006 (L) P/S CHI1 d
1 2 3 4 4 4 4 5 6 7 8 8
---+ + + + -+ + ---
Tendon Trachea Tendon Tendon Liver Heart Footpad Footpad Liver Liver Tendon Heart
Lipase activity
Antibiotic resistance b T C PB E S
4-
--
4-
+
--
+
4-
4-
4-
4-
--
4-
--
4-
4-
4-
44-
--
4-
4-
4-
4-
--
W e
4-
--
4-
4-
4-
--
W
4-
4-
4-
4-
4-
4-
--
4-
4-
-I-
--
4-
4-
--
4-
÷
--
--
4-
44-
4-
4-
--
4-
4-
m
4-
4-
m
44-
aReleased temperate phage active on strains 1777 and 1389 following treatment with mitomycin C. bT = tetracycline; C = chloramphenicol; PB = polymyxin-B; E = erythromycin; S = sulphafurazole. Cphage released from strain 2000 (J). dp/s C H l l -- propagating strain of avian group IV phage C H l l (Shimizu, 1979). eW denotes weak positive test.
1 8 6 7 , and also 2 0 0 5 and 2 0 0 6 , were f r o m d i f f e r e n t tissues o f the same chickens. One isolate, designated 1777, was isolated f r o m a tracheal swab o f a c h i c k e n with r e s p i r a t o r y disease. As the p r o p a g a t i n g strain o f the avian g r o u p IV phage ( C H l l (Shimizu, 1 9 7 9 ) a p p e a r e d t o be a strain o f S. hyicus (Kibenge et al., 1 9 8 2 b ) , it was also e x a m i n e d . Bacteriological m e t h o d s , b i o c h e m i c a l tests and phage t y p i n g p r o c e d u r e s were as previously described (Kibenge et al., 1 9 8 2 b ) . L y s o g e n y was d e t e c t e d using the m i t o m y c i n C i n d u c t i o n t e c h n i q u e o f V e r h o e f et al., (1971). E a c h strain t e s t e d for l y s o g e n y was in t u r n used as an i n d i c a t o r strain, and released phages were purified and p r o p a g a t e d on susceptible strains as previo u s l y described (Kibenge et al., 1 9 8 2 b ) . Resistance to t e t r a c y c l i n e (50 ug), c h l o r a m p h e n i c o l (50 pg), p o l y m y x i n B ( 3 0 0 units), e r y t h r o m y c i n (10 pg) and s u l p h a f u r a z o l e ( 5 0 0 pg) was d e t e r m i n e d o n diagnostic sensitivity agar ( O x o i d ) with a n t i b i o t i c discs ( O x o i d Ltd., Basingstoke, H a m p s h i r e , Gt. Britain) using the m e t h o d s and the interpretative criteria p r o p o s e d by the m a n u f a c t u r e r s . Results were analysed ztatistically using Fisher's e x a c t test (Maxwell, 1 9 6 1 ) .
413
All 13 strains of S. hyicus were non-pigmented and non-haemolytic on sheep blood agar. They were all slide coagulase-negative, were strongly fibrinolytic on rabbit and sheep plasma, produced a crystal violet type E reaction and did not ferment mannitol. RESULTS AND DISCUSSION
The results of lysogenicity, antibiotic resistance, bacteriophage typing and lipase activity of the individual strains are shown in Table I. Six of the 13 S. hyicus strains (46%) released phage active on two of the strains (1777 and 1389). Although the remaining strains were n o t lysogenic under these conditions we cannot rule out the possibility that they may have been lysogenic had suitable indicator strains been available. The majority of strains were resistant to tetracycline and polymyxin-B, but sensitive to chloramphenicol. Resistance to e r y t h r o m y c i n and sulphafurazole, susceptibility to phage lysis and lipase activity were variable characteristics. Variability in sensitivity of S. hyicus to c o m m o n antibiotics has previously been reported by Hunter et al. (1970), Devriese et al. (1978) and Holland and Hodges (1981). Similar variability was encountered in the present study, but it is of interest t h a t the number of strains sensitive to erythromycin was apparently significantly higher (P ~ 0.001) in non-lysogenic than in lysogenic strains. Lipase-negative strains of S. hyicus are considered rare and the lipase reaction is c o m m o n l y used as an elective marker in the selective medium for the isolation of S. hyicus (Devriese, 1977; Devriese and Derycke, 1979; Holland and Hodges, 1981). However, six of the 13 isolates in the present study were lipase-negative and would n o t have been detected using this selective medium. Although no significant association was demonstrated between lysogeny and lipase activity, five of the seven lipase-positive strains were non-lysogenic and the two lysogenic strains (1866 and 1867, Table I ) w h i c h produced lipase only had narrow zones of precipitation on Tween 80 agar. These zones were only visible after incubation for an additional 24 h at room temperature. Similar weak reactions have also been described in S. aureus strains (Devriese, 1977) in which the lipase activity is known to be altered by lysogenic conversion (Lacey, 1973). As the results of the present study suggested that erythromycin resistance and possibly lipase production may be influenced by temperate phages, the effect of lysogenic conversion on these parameters was investigated. Lysogenic derivatives were isolated from strains 1777 and 1389 by picking colonies from the centre of plaques derived from lysis by bacteriophage J. These colonies were purified and tested for lysogeny, phage susceptibility, lipase production and e r y t h r o m y c i n resistance. The results (Table II) show that the derivatives were lysogenic for bacteriophage J as they lysed the appropriate indicator strains and were immune to phage J infection. However the lysogenic strains were sensitive to erythromycin and produced lipase activity. It
414 TABLE II The effect of lysogeny on various characteristics of S. hyicus Strain
Phage carried
Lysis of indicator strains c 1777
1777 1389 2000 1777 (j)a 1389 (j)b
. . J j j
. .
. . + + +
1389 . . . + +
Lysis by phage J
Lipase activity
Erythromycin resistance
+ + . _ _
+ +
--+ __ __
2000
.
. __ __
+ +
aDerivatives (10) of strain 1777 that were lysogenic for phage J. bDerivatives (10) of strain 1389 that were lysogenic for phage J. c+ indicates lysis of indicator strain by supernatant of culture of test strain; -- indicates no lysis of indicator strain by supernatant of test strain.
is c o n c l u d e d t h e r e f o r e t h a t p h a g e J d o e s n o t c a r r y a n e r y t h r o m y c i n resist a n c e d e t e r m i n a n t o r a r e p r e s s o r o f lipase p r o d u c t i o n . T h e a p p a r e n t s t a t i s t i cally significant relationship between these properties and prophage immunity was p r o b a b l y d u e to small sample n u m b e r s . In these e x p e r i m e n t s we have e x a m i n e d the p r o p e r t i e s of 13 avian strains o f S. hyicus a n d h a v e o b s e r v e d s i g n i f i c a n t h e t e r o g e n e i t y . A s e i g h t s t r a i n s t h a t p r o d u c e little or n o lipase activity were isolated it m a y be necessary to r e - e x a m i n e t h e u s e o f t h i s r e a c t i o n i n m e d i a s e l e c t i v e f o r S. hyicus.
ACKNOWLEDGEMENT T h e p r e s e n t s t u d y was s u p p o r t e d b y a g r a n t f r o m t h e A u s t r a l i a n C h i c k e n Meat Research Committee.
REFERENCES Devriese, L.A., 1977. Isolation and identification of Staphylococcus hyicus. Am. J. Vet. Res., 38: 787--792. Devriese, L.A., 1980. Pathogenic staphylococci in poultry. World's Poult. Sci. J., 36: 227--236. Devriese, L.A. and Derycke, J., 1979. Staphyloccus hyicus in cattle. Res. Vet. Sci., 26: 356--358. Devriese L.A. and Hajek, V., 1980. A review: identification of pathogenic staphylococci isolated from animals and foods derived from animals. J. Appl. Bacteriol., 49: 1--11. Devriese L.A., Hajek, V., Oeding, P., Mayer, S.A. and Schleifer, K.H., 1978. Staphylococcus hyucus (Sompolinsky, 1953) comb. nov. and Staphylococcus hyucis subsp. chromogenes subsp, nov. Int. J. Syst. Bacteriol., 28: 482--490. Holland, J.T.S. and Hodges, R.T., 1981. Bacteriological observations on exudative epidermitis of pigs in New Zeland. N.Z. Vet. J., 29: 57--59.
415 Hunter, D., Todd, J.N. and Larkin, M., 1970. Exudative epidermitis of pigs. The serological identification and distribution of the associated staphylococcus. Br. Vet. J., 126: 225--229. Kibenge, F.S.B., Robertson, M.D., Wilcox, G.E. and Pass, D.A., 1982a. Bacterial and viral agents associated with tenosynovitis in broiler-breeders in Western Australia. Avian Pathol., 11 : 351--359. Kibenge, F.S.B., Wilcox, G.E. and Perret, D., 1982b. S t a p h y l o c o c c u s aureus isolated from poultry in Australia. I. Phage typing and cultural characteristics. Vet. Microbiol., 7: 471--483. Lacey, R.W., 1973. Genetic basis, epidemiology and future significance of antibiotic resistance in S t a p h y l o c o c c u s aureus: a review. J. Clin. Pathol., 26: 899--913. Maxwell, A.E., 1961. Analysing Qualitative Data. Chapman and Hall, London. Sato, G., Miura, S. and Terakado, N., 1972. Classification of chicken coagulase-positive staphylococci into 4 biological types and relation of the types to additional characteristics including coagulase antigenic type. Jpn. J. Vet. Res., 20: 90--110. Shimizu, A., 1979. Phage typing results of S t a p h y l o c o c c u s aureus isolated from poultry in Japan and Europe. Avian Dis., 23: 39--46. Verhoef, J., Van Boven, C.P.A. and Winkler, K.C., 1971. Lysogeny in coagulase-negative staphylococci. J. Med. Microbiol., 4: 405--412.
411
Short Communication LYSOGENY AND OTHER CHARACTERISTICS OF STAPHYLOCOCCUS
HYICUS ISOLATED FROM CHICKENS
F.S.B. KIBENGE, J.I. ROOD and G.E. WILCOX
Division of Veterinary Biology, School of Veterinary Studies, Murdoch University, Murdoch, W.A. (Australia) (Accepted 31 January 1983}
ABSTRACT Kibenge, F.S.B., Rood, J.I. and Wilcox, G.E., 1983. Lysogeny and other characteristics of Staphylococcus hyicus isolated from chickens. Vet. Microbiol., 8: 411--415. Lysogeny was readily demonstrated among strains of Staphylococcus hyicus that were isolated from chickens. Susceptibility to phage lysis was affected by prophage immunity, but lipase activity and erythromycin resistance were not affected by the presence of temperate phage. In contrast to previously published results, lipase-negative strains of S. hyicus were relatively common and the use of selective media based on lipase activity would have been unsuitable for detection of the S. hyicus strains examined.
INTRODUCTION
Staphylococcus hyicus (subsp. hyicus) o c c u r s f r e q u e n t l y o n the skin and nares o f h e a l t h y p o u l t r y (Devriese, 1 9 8 0 ) , pigs (Devriese, 1 9 7 7 ) , cattle (Devriese and D e r y c k e , 1 9 7 9 ) and in animal p r o d u c t s and slaughter h o u s e effluents (Devriese and Hajek, 1 9 8 0 ) . In p o u l t r y , S. hyicus is c o n s i d e r e d t o be o f low virulence (Devriese, 1 9 8 0 ) as t h e organism has been isolated o n l y f r o m n o r m a l c h i c k e n s or t h o s e with m i x e d i n f e c t i o n s o f the skin (Sato et al., 1972). Previous results s h o w e d t h a t several b i o c h e m i c a l characteristics o f S. hyicus varied b e t w e e n d i f f e r e n t g r o u p s o f isolates (Devriese et al., 1978). In this c o m m u n i c a t i o n , we r e p o r t the results o f e x p e r i m e n t s a i m e d at the e x a m i n a t i o n o f the p r o p e r t i e s o f S. hyicus strains isolated f r o m chickens a f f e c t e d with t e n o s y n o v i t i s in Australia (Kibenge et al., 1982a, b). MATERIALS AND METHODS Twelve strains were isolated f r o m chickens and were identified using t h e criteria p r o p o s e d b y Devriese et al. ( 1 9 7 8 ) as previously described (Kibenge et al., 1 9 8 2 b ) . Eleven strains were isolated f r o m various tissues o f c h i c k e n s with t e n o s y n o v i t i s f r o m seven farms as s h o w n in Table I. Isolates 1 8 6 6 a n d
0378-1135/83/$03.00
© 1983 Elsevier Science Publishers B.V.
412 TABLE I Characteristics of Staphylococcus hyicus from chickens
Strain
Source Farm Tissue
Characteristic Lysogenya Lysis by phage CHll jc
1609 (A) 1777 (B) 1389 (C) 1865 (D) 1866 (E) 1867 (F) 1874 (G) 1997 (H) 1999 (I) 2000 (J) 2005 (K) 2006 (L) P/S CHI1 d
1 2 3 4 4 4 4 5 6 7 8 8
---+ + + + -+ + ---
Tendon Trachea Tendon Tendon Liver Heart Footpad Footpad Liver Liver Tendon Heart
Lipase activity
Antibiotic resistance b T C PB E S
4-
--
4-
+
--
+
4-
4-
4-
4-
--
4-
--
4-
4-
4-
44-
--
4-
4-
4-
4-
--
W e
4-
--
4-
4-
4-
--
W
4-
4-
4-
4-
4-
4-
--
4-
4-
-I-
--
4-
4-
--
4-
÷
--
--
4-
44-
4-
4-
--
4-
4-
m
4-
4-
m
44-
aReleased temperate phage active on strains 1777 and 1389 following treatment with mitomycin C. bT = tetracycline; C = chloramphenicol; PB = polymyxin-B; E = erythromycin; S = sulphafurazole. Cphage released from strain 2000 (J). dp/s C H l l -- propagating strain of avian group IV phage C H l l (Shimizu, 1979). eW denotes weak positive test.
1 8 6 7 , and also 2 0 0 5 and 2 0 0 6 , were f r o m d i f f e r e n t tissues o f the same chickens. One isolate, designated 1777, was isolated f r o m a tracheal swab o f a c h i c k e n with r e s p i r a t o r y disease. As the p r o p a g a t i n g strain o f the avian g r o u p IV phage ( C H l l (Shimizu, 1 9 7 9 ) a p p e a r e d t o be a strain o f S. hyicus (Kibenge et al., 1 9 8 2 b ) , it was also e x a m i n e d . Bacteriological m e t h o d s , b i o c h e m i c a l tests and phage t y p i n g p r o c e d u r e s were as previously described (Kibenge et al., 1 9 8 2 b ) . L y s o g e n y was d e t e c t e d using the m i t o m y c i n C i n d u c t i o n t e c h n i q u e o f V e r h o e f et al., (1971). E a c h strain t e s t e d for l y s o g e n y was in t u r n used as an i n d i c a t o r strain, and released phages were purified and p r o p a g a t e d on susceptible strains as previo u s l y described (Kibenge et al., 1 9 8 2 b ) . Resistance to t e t r a c y c l i n e (50 ug), c h l o r a m p h e n i c o l (50 pg), p o l y m y x i n B ( 3 0 0 units), e r y t h r o m y c i n (10 pg) and s u l p h a f u r a z o l e ( 5 0 0 pg) was d e t e r m i n e d o n diagnostic sensitivity agar ( O x o i d ) with a n t i b i o t i c discs ( O x o i d Ltd., Basingstoke, H a m p s h i r e , Gt. Britain) using the m e t h o d s and the interpretative criteria p r o p o s e d by the m a n u f a c t u r e r s . Results were analysed ztatistically using Fisher's e x a c t test (Maxwell, 1 9 6 1 ) .
413
All 13 strains of S. hyicus were non-pigmented and non-haemolytic on sheep blood agar. They were all slide coagulase-negative, were strongly fibrinolytic on rabbit and sheep plasma, produced a crystal violet type E reaction and did not ferment mannitol. RESULTS AND DISCUSSION
The results of lysogenicity, antibiotic resistance, bacteriophage typing and lipase activity of the individual strains are shown in Table I. Six of the 13 S. hyicus strains (46%) released phage active on two of the strains (1777 and 1389). Although the remaining strains were n o t lysogenic under these conditions we cannot rule out the possibility that they may have been lysogenic had suitable indicator strains been available. The majority of strains were resistant to tetracycline and polymyxin-B, but sensitive to chloramphenicol. Resistance to e r y t h r o m y c i n and sulphafurazole, susceptibility to phage lysis and lipase activity were variable characteristics. Variability in sensitivity of S. hyicus to c o m m o n antibiotics has previously been reported by Hunter et al. (1970), Devriese et al. (1978) and Holland and Hodges (1981). Similar variability was encountered in the present study, but it is of interest t h a t the number of strains sensitive to erythromycin was apparently significantly higher (P ~ 0.001) in non-lysogenic than in lysogenic strains. Lipase-negative strains of S. hyicus are considered rare and the lipase reaction is c o m m o n l y used as an elective marker in the selective medium for the isolation of S. hyicus (Devriese, 1977; Devriese and Derycke, 1979; Holland and Hodges, 1981). However, six of the 13 isolates in the present study were lipase-negative and would n o t have been detected using this selective medium. Although no significant association was demonstrated between lysogeny and lipase activity, five of the seven lipase-positive strains were non-lysogenic and the two lysogenic strains (1866 and 1867, Table I ) w h i c h produced lipase only had narrow zones of precipitation on Tween 80 agar. These zones were only visible after incubation for an additional 24 h at room temperature. Similar weak reactions have also been described in S. aureus strains (Devriese, 1977) in which the lipase activity is known to be altered by lysogenic conversion (Lacey, 1973). As the results of the present study suggested that erythromycin resistance and possibly lipase production may be influenced by temperate phages, the effect of lysogenic conversion on these parameters was investigated. Lysogenic derivatives were isolated from strains 1777 and 1389 by picking colonies from the centre of plaques derived from lysis by bacteriophage J. These colonies were purified and tested for lysogeny, phage susceptibility, lipase production and e r y t h r o m y c i n resistance. The results (Table II) show that the derivatives were lysogenic for bacteriophage J as they lysed the appropriate indicator strains and were immune to phage J infection. However the lysogenic strains were sensitive to erythromycin and produced lipase activity. It
414 TABLE II The effect of lysogeny on various characteristics of S. hyicus Strain
Phage carried
Lysis of indicator strains c 1777
1777 1389 2000 1777 (j)a 1389 (j)b
. . J j j
. .
. . + + +
1389 . . . + +
Lysis by phage J
Lipase activity
Erythromycin resistance
+ + . _ _
+ +
--+ __ __
2000
.
. __ __
+ +
aDerivatives (10) of strain 1777 that were lysogenic for phage J. bDerivatives (10) of strain 1389 that were lysogenic for phage J. c+ indicates lysis of indicator strain by supernatant of culture of test strain; -- indicates no lysis of indicator strain by supernatant of test strain.
is c o n c l u d e d t h e r e f o r e t h a t p h a g e J d o e s n o t c a r r y a n e r y t h r o m y c i n resist a n c e d e t e r m i n a n t o r a r e p r e s s o r o f lipase p r o d u c t i o n . T h e a p p a r e n t s t a t i s t i cally significant relationship between these properties and prophage immunity was p r o b a b l y d u e to small sample n u m b e r s . In these e x p e r i m e n t s we have e x a m i n e d the p r o p e r t i e s of 13 avian strains o f S. hyicus a n d h a v e o b s e r v e d s i g n i f i c a n t h e t e r o g e n e i t y . A s e i g h t s t r a i n s t h a t p r o d u c e little or n o lipase activity were isolated it m a y be necessary to r e - e x a m i n e t h e u s e o f t h i s r e a c t i o n i n m e d i a s e l e c t i v e f o r S. hyicus.
ACKNOWLEDGEMENT T h e p r e s e n t s t u d y was s u p p o r t e d b y a g r a n t f r o m t h e A u s t r a l i a n C h i c k e n Meat Research Committee.
REFERENCES Devriese, L.A., 1977. Isolation and identification of Staphylococcus hyicus. Am. J. Vet. Res., 38: 787--792. Devriese, L.A., 1980. Pathogenic staphylococci in poultry. World's Poult. Sci. J., 36: 227--236. Devriese, L.A. and Derycke, J., 1979. Staphyloccus hyicus in cattle. Res. Vet. Sci., 26: 356--358. Devriese L.A. and Hajek, V., 1980. A review: identification of pathogenic staphylococci isolated from animals and foods derived from animals. J. Appl. Bacteriol., 49: 1--11. Devriese L.A., Hajek, V., Oeding, P., Mayer, S.A. and Schleifer, K.H., 1978. Staphylococcus hyucus (Sompolinsky, 1953) comb. nov. and Staphylococcus hyucis subsp. chromogenes subsp, nov. Int. J. Syst. Bacteriol., 28: 482--490. Holland, J.T.S. and Hodges, R.T., 1981. Bacteriological observations on exudative epidermitis of pigs in New Zeland. N.Z. Vet. J., 29: 57--59.
415 Hunter, D., Todd, J.N. and Larkin, M., 1970. Exudative epidermitis of pigs. The serological identification and distribution of the associated staphylococcus. Br. Vet. J., 126: 225--229. Kibenge, F.S.B., Robertson, M.D., Wilcox, G.E. and Pass, D.A., 1982a. Bacterial and viral agents associated with tenosynovitis in broiler-breeders in Western Australia. Avian Pathol., 11 : 351--359. Kibenge, F.S.B., Wilcox, G.E. and Perret, D., 1982b. S t a p h y l o c o c c u s aureus isolated from poultry in Australia. I. Phage typing and cultural characteristics. Vet. Microbiol., 7: 471--483. Lacey, R.W., 1973. Genetic basis, epidemiology and future significance of antibiotic resistance in S t a p h y l o c o c c u s aureus: a review. J. Clin. Pathol., 26: 899--913. Maxwell, A.E., 1961. Analysing Qualitative Data. Chapman and Hall, London. Sato, G., Miura, S. and Terakado, N., 1972. Classification of chicken coagulase-positive staphylococci into 4 biological types and relation of the types to additional characteristics including coagulase antigenic type. Jpn. J. Vet. Res., 20: 90--110. Shimizu, A., 1979. Phage typing results of S t a p h y l o c o c c u s aureus isolated from poultry in Japan and Europe. Avian Dis., 23: 39--46. Verhoef, J., Van Boven, C.P.A. and Winkler, K.C., 1971. Lysogeny in coagulase-negative staphylococci. J. Med. Microbiol., 4: 405--412.