INFECTION AND IMMUNITY, May 1975, P. 904-907 Copyright @,1975 American Society for Microbiology
Vol. 11, No. 5 Printed in U.S.A.
Serotyping of Chlamydia: Isolates of Bovine Origin JULIUS SCHACHTER,* JOYCE BANKS, NANCY SUGG, MINNIE SUNG, J. STORZ, AND KARL F. MEYER' World Health Organization Collaborating Centre for Reference and Research on Trachoma and Other Chlamydial Infections, and the George Williams Hooper Foundation for Medical Research,* University of California, San Francisco, California 94143; and the Department of Microbiology, Colorado State University, Fort Collins, Colorado 80521 Received for publication 26 December 1974
Chlamydial isolates of bovine origin were serotyped by a plaque reduction method. Of the two major serotypes observed, type 1 included isolates from bovine abortion and enteric infections, whereas type 2 isolates were associated with polyarthritis or encephalomyelitis. These two serotypes were identical to those with a similar disease distribution previously observed in isolates of ovine origin. The two groups did not cross-react and they were serologically unrelated to chlamydiae of avian origin. Thus, it appears that many chlamydial isolates causing intestinal infections or abortion in sheep or cattle are closely related antigenically, as are those producing polyarthritis, encephalomyelitis, and conjunctivitis, and that the two groups are distinct. The plaque reduction test has been used in efforts to serotype Chlamydia of avian and mammalian origin (3, 6). Previous studies showed that avian isolates appear to be host specific, whereas those derived from sheep appear to fall into antigenic groups correlating with specific disease syndromes. Thus, two major serotypes were observed among ovine isolates; type 1 included strains associated with sheep abortion and intestinal infections, and type 2 strains were associated with polyarthritis and conjunctivitis. These studies have been extended to include isolates recovered from cattle. The results are presented in this paper. MATERIALS AND METHODS The techniques used have been described previously. Briefly, they included a plaque reduction test using hyperimmune rooster antiserum prepared against yolk sac suspensions of chlamydiae (3). The plaque assay is performed in monolayers of L-929 cells (2). Titers of antisera are presented as the dilution resulting in reduction of plaque count by 50% from controls. Isolates tested and their origin. Antisera were prepared against eight chlamydial field isolates from cattle. Isolates 66-P-130 and Cow H were cultured from fecal samples of, respectively, an apparently normal calf and an apparently normal cow; LX-206 was isolated from abomasal mucosal scrapings of a calf with gastroenteritis; EBA-Colo was cultured from the placenta of an aborting cow; SVS-136 was isolated from semen of a bull with seminal vesiculitis syndrome (9); LW-613 was isolated from a tarsal joint of a calf with polyarthritis; LW-508 was recovered from 'Deceased. 904
the jejunum of a calf with polyarthritis; and LW-623 was recovered from the mucosal scrapings of a bull with sporadic encephalomyelitis. These antisera were then tested against a number of chlamydial isolates from the Colorado State University (CSU) collection that represented chlamydial infections of cattle, rabbits, mice, and guinea pigs. All were tested on a coded basis with clinical diagnoses and anatomic sites made available after tests were completed. Other antisera tested were those to avian and ovine isolates, described previously (2, 3).
RESULTS The plaque reduction testing of bovine isolates demonstrated two major serotypes (Table 1), which did not cross-react. There was some evidence of antigenic heterogeneity within the types. The type 1 isolates included agents associated with abortion and intestinal infections in cattle; type 2 isolates were associated with polyarthritis and sporadic encephalomyelitis. The type 1 antisera prepared against chlamydial isolates of bovine origin were tested against chlamydiae recovered from sheep, and reactions of identity were seen with the previously described ovine type 1 isolates. Likewise, the type 2 antiserum against bovine chlamydiae reacted only with the type 2 ovine isolates (Table 2). The same pattern of results was obtained with antisera to the ovine chlamydiae. There was no cross-reaction between these two groups. A number of other isolates recovered from diverse host species, as well as those recovered from cattle, were also tested against representa-
905
SEROTYPING OF CHLAMYDIA
VOL. 11, 1975
TABLE 1. Plaque reduction by antisera to bovine chlamydiae Antisera
66-P-130
66-P-130 EBA Colo LX 206 Cow H SVS-136 LW-508 LW-613 LW-623 a
Type 2
Type 1
Agents
26a 15 13
EBA Colo
LX 206
Cow H
SVS-136
LW-508
LW-613
LW-623
_
_ 19 32
-
-
-
-
-
30
-
-
-
65 40
36 26 48 35 44
-
19 30 25
12 16 22 22 22
-
-
-
-
-
-
-
-
-
-
63 29
26 19
-
20 13 29
-
-
-
_
-
-
--
-
-
-
-
Reciprocal of serum dilution reducing plaque count by 50%. No reduction at 1:10 serum dilution. TABLE 2. Plaque reduction by antisera to bovine and ovine chlamydiae Antisera
Type 2
Type 1
Agents SVS-136
LW-5OS
Sheep
Sheep abortion enteritis Fitz-65
Sheep poiypoly- arthritis/ arthritis conjunc-
Sheep
LW-623
LW-613
MO-907
LW-646
tivitis
FC-Strach
SVS-136 LW-508 Sheep abortion Fitz-65 Sheep enteritis MO-907
22a 22 17 40
35 44 29 43
29 38 55 49
15 20 49 45
LW-623
-
-
-
-
LW-613 Sheep polyarthritis LW-646
-
-
-
-
-
-
-
-
Sheep polyarthritis/conjunc-
-
-
-
-
__
-
_ _
_
19 26 31 25
29 63 29 33
-
-
_ -
30 32 75 64
44 30 31 26
tivitis FC-Strach
Reciprocal of serum dilution reducing plaque count by 50%. h No reduction at 1:10 serum dilution. a
tive type 1 and type 2 antisera (Table 3). Many of these isolates could be typed as 1 or 2. The disease distribution was generally consistent, with abortion strains falling into type 1 and arthritis and sporadic encephalomyelitis strains falling into type 2. Chlamydiae recovered from rabbits (5), mice (1), and guinea pigs (7) were identified as type 1. One chlamydial isolate (CSU-15) recovered from the spleen of a lamb with polyarthritis was identified as type 1. A number of other bovine chlamydial isolates did not fall into either of the two types in these one-way tests. One field isolate (CSU-20) was the only isolate tested that reacted with both types of antisera, predominantly with type 2. Antisera against the bovine isolates were tested against chlamydiae recovered from three avian species (Texas turkey, Meyer parrot, and pigeon AU-46), and antisera against the avian
species (homologous titers of 1:520, 1:20, and 1:18, respectively) were tested against the cattle isolates. No cross-reactions were observed.
DISCUSSION The finding that bovine chlamydiae could be classified into two serotypes identical to those observed among ovine chlamydiae suggests that these strains are not host specific. Rather it would appear that they have specific pathogenic potential or tissue tropism (8). Type 2 isolates were usually associated with polyarthritis, encephalomyelitis (including the original Wenner strain [11 ]), or conjunctivitis in either sheep or cattle. Type 1 chlamydiae were generally associated with abortions and genital and enteric infections in sheep and cattle. The intestinal tract is a natural habitat for both
906
INFECT. IMMUN.
SCHACHTER ET AL. TABLE 3. Other chlamydiae related to the ovine-bovine schema Antisera
Type 2
Type 1 Isolates
Sheep
Rabbit abortion (PHT-6) Mouse lung (S-mouse-4) Mouse lung (K-mouse-4) Guinea pig (Davis) CSU-4, bull semen CSU-5, bovine abortion (Utah) CSU-7, lamb feces CSU-9, ewe (aborting) feces CSU-12, lamb (polyarthritis) spleen CSU-15, sheep blood CSU-17, lamb (still born) gut CSU-18, lamb (still born) brain (Utah) CSU-3, calf feces CSU-6, bovine-sporadic encephalomyelitis (Wenner) CSU-8, lamb feces (Utah) CSU-13, lamb (polyarthritis) feces CSU-20, lamb (polyarthritis) conjunctiva CSU-21, lamb (polyarthritis) conjunctiva
chlamydial types, and such infections are very common in some herds. For experimental studies, researchers must often treat the animals before challenges are initiated to assure that observed effects are produced by inoculated, not resident, chlamydiae. In our typing study, isolates from the intestinal tract have not always been the type expected on the basis of observed disease. However, in experimental studies, the type 2 isolates have been more invasive and produced arthritis and conjunctivitis, whereas the type 1 isolates have produced abortions. Numerous experimental studies with sheep and cattle have shown that chlamydial isolates recovered from diseased animals of one species can produce similar disease in the other. Thus, chlamydiae recovered from aborting cattle have produced abortions in sheep (10). Fraser and Berman (4), among others, have noted an antigenic similarity between abortion isolates from different hosts. Our study demonstrates that chlamydial strains from abortions of sheep and cattle are either antigenically identical or very closely related. Expansion of these studies could enable us to devise a rational system for typing chlamydial isolates, based upon antigenic structure. It should be emphasized that some chlamydiae apparently associated with naturally occurring abortions and capable of producing abortion under experimental circumstances
Sheep polyLW-613
abortion Fitz-65
LW-508
21 24 20 48 15 21 19 20 25 17 20 25
54 55 56 25 11 11 28 32 51 47 59 54
-
-
-
-
-
-
-
-
-
-
80 34
12 29
-
-
24 60 41
25 50 36 54
13 -
arthritis LW-646
126
-
could not be typed in this system, indicating either a lack of sensitivity or the more likely possibility that other serotypes exist and simply were not represented among those strains used to produce antisera. The two serotypes were very sharply divided, although there was some variation within serotypes. It was possible with only a few sera to type isolates as belonging to type 1 or type 2: a single broadly reactive serum gave positive results with all type 2 strains tested, whereas at least two antisera were required for type 1 strains. The demonstration that some isolates recovered from rabbits, mice, and guinea pigs were type 1 isolates, coupled with the knowledge of interspecies transfer of these agents, suggests that some of these isolates merely reflect introduced rather than naturally occurring infections. It is known that chlamydiae of type 1 or type 2 are found in the bovine (or ovine) intestinal tract and may be excreted in the feces. The peak titers reached in feces are high, on the order of 105 to 107 mean lethal doses/g of feces; therefore, considering that an average bovine produces up to 50 pounds (ca. 22.7 kg) of feces a day, the environmental contamination could be quite extensive. In addition, the conditions associated with these chlamydial infections in guinea pigs have not been suggestive of naturally occurring infec-
VOL. 11, 1975
SEROTYPING OF CHLAMYDIA
tions; the cataclysmic die-off observed in young guinea pigs is more indicative of a recently introduced infection than of a successful, welladapted host-parasite relationship (7). For many years, the guinea pig has been considered the host of choice in isolation attempts for chlamydiae of bovine or ovine origin. The fact that the isolates associated with the epizootic in guinea pigs are antigenically identical to some of the chlamydiae recovered from the larger mammals suggests the possibility that proximity of the animals in a vivarium setting may have resulted in the introduction of the parasite. The same reasoning may hold true for the rabbit and mouse isolates, although these rodents are naturally much more resistant to the chlamydiae. However, the possibility that the strains were introduced through environmental contamination should be considered. More chlamydiae recovered from these species will have to be studied before this point can be settled. The effect of passage on the antigenic structures measured in the plaque reduction test is not known. However, the results of this and previous studies (3) suggest antigenic stability during prolonged passage in yolk sac or mice. Recent isolates from parakeets, turkeys, or cattle with sporadic encephalomyelitis have been antigenically indistinguishable from isolates from the same sources, but with 20- to 34-year histories of laboratory passage. Our observations suggest a very real possibility of developing a rational and useful method of typing plaque-forming chlamydiae. This system is independent of host species, a significant advance because chlamydiae have been recovered from virtually every species where they have been sought.
907
ACKNOWLEDGMENTS This investigation was supported in part by Public Health Service grants CC-00553 (from the National Communicable Disease Center) and AI-11881 (from the National Institute of Allergy and Infectious Diseases), and by the World Health Organization. LITERATURE CITED 1. Ata, F. A., E. H. Stephenson, and J. Storz. 1971. Inapparent respiratory infection of inbred Swiss mice with sulfadiazine resistant, iodine-negative chlamydiae. Infect. Immun. 4:506-507. 2. Banks, J., B. Eddie, J. Schachter, and K. F. Meyer. 1970. Plaque formation by Chlamydia in L cells. Infect. Immun. 1:259-262. 3. Banks, J., B. Eddie, M. Sung, N. Sugg, J. Schachter, and K. F. Meyer. 1970. Plaque reduction technique for demonstrating neutralizing antibodies for Chlamydia. Infect. Immun. 2:443-447. 4. Fraser, C. E. O., and D. T. Berman. 1965. Type-specific antigens in the psittacosis-lymphogranuloma venereum group of organisms. J. Bacteriol. 89:943-948. 5. Parker, H. D., W. W. Hawkins, and E. Brenner. 1966. Epizootiologic studies of ovine virus abortion. Am. J. Vet. Res. 27:869-877. 6. Schachter, J., J. Banks, N. Sugg, M. Sung, J. Storz, and K. F. Meyer. 1974. Serotyping of Chiamydia. I. Isolates of ovine origin. Infect. Immun. 9:92-94. 7. Storz, J. 1964. Uber eine natiirliche Infektion eines Meerschweinchenbestandes mit einem Erreger aus der psittakose-lymphogranuloma Gruppe. Zentralbl. Bakteriol. Parisitenkd. Infektionskr. Hyg. Abt. 1 Orig. 193: 432-446. 8. Storz, J. 1966. Psittacosis-lymphogranuloma infection of sheep. J. Comp. Pathol. 76:351-362. 9. Storz, J., E. J. Carroll, L. Ball, and L. C. Faulkner. 1968. Isolation of a psittacosis agent (Chlamydia) from semen and epididymis of bulls with seminal vesiculitis syndrome. Am J. Vet. Res. 29:549-555. 10. Studdert, M. J., and D. G. McKercher. 1968. Bedsonia abortion of sheep. I. Aetiological studies. Res. Vet. Sci. 9:48-56. 11. Wenner, H. A., G. S. Harshfield, T. W. Chang, and R. W. Menges. 1953. Sporadic bovine encephalomyelitis. II. Studies on the etiology of the disease, isolation of nine strains of an infectious agent from naturally infected cattle. Am. J. Hyg. 57:15-29.
Vol. 11, No. 5 Printed in U.S.A.
Serotyping of Chlamydia: Isolates of Bovine Origin JULIUS SCHACHTER,* JOYCE BANKS, NANCY SUGG, MINNIE SUNG, J. STORZ, AND KARL F. MEYER' World Health Organization Collaborating Centre for Reference and Research on Trachoma and Other Chlamydial Infections, and the George Williams Hooper Foundation for Medical Research,* University of California, San Francisco, California 94143; and the Department of Microbiology, Colorado State University, Fort Collins, Colorado 80521 Received for publication 26 December 1974
Chlamydial isolates of bovine origin were serotyped by a plaque reduction method. Of the two major serotypes observed, type 1 included isolates from bovine abortion and enteric infections, whereas type 2 isolates were associated with polyarthritis or encephalomyelitis. These two serotypes were identical to those with a similar disease distribution previously observed in isolates of ovine origin. The two groups did not cross-react and they were serologically unrelated to chlamydiae of avian origin. Thus, it appears that many chlamydial isolates causing intestinal infections or abortion in sheep or cattle are closely related antigenically, as are those producing polyarthritis, encephalomyelitis, and conjunctivitis, and that the two groups are distinct. The plaque reduction test has been used in efforts to serotype Chlamydia of avian and mammalian origin (3, 6). Previous studies showed that avian isolates appear to be host specific, whereas those derived from sheep appear to fall into antigenic groups correlating with specific disease syndromes. Thus, two major serotypes were observed among ovine isolates; type 1 included strains associated with sheep abortion and intestinal infections, and type 2 strains were associated with polyarthritis and conjunctivitis. These studies have been extended to include isolates recovered from cattle. The results are presented in this paper. MATERIALS AND METHODS The techniques used have been described previously. Briefly, they included a plaque reduction test using hyperimmune rooster antiserum prepared against yolk sac suspensions of chlamydiae (3). The plaque assay is performed in monolayers of L-929 cells (2). Titers of antisera are presented as the dilution resulting in reduction of plaque count by 50% from controls. Isolates tested and their origin. Antisera were prepared against eight chlamydial field isolates from cattle. Isolates 66-P-130 and Cow H were cultured from fecal samples of, respectively, an apparently normal calf and an apparently normal cow; LX-206 was isolated from abomasal mucosal scrapings of a calf with gastroenteritis; EBA-Colo was cultured from the placenta of an aborting cow; SVS-136 was isolated from semen of a bull with seminal vesiculitis syndrome (9); LW-613 was isolated from a tarsal joint of a calf with polyarthritis; LW-508 was recovered from 'Deceased. 904
the jejunum of a calf with polyarthritis; and LW-623 was recovered from the mucosal scrapings of a bull with sporadic encephalomyelitis. These antisera were then tested against a number of chlamydial isolates from the Colorado State University (CSU) collection that represented chlamydial infections of cattle, rabbits, mice, and guinea pigs. All were tested on a coded basis with clinical diagnoses and anatomic sites made available after tests were completed. Other antisera tested were those to avian and ovine isolates, described previously (2, 3).
RESULTS The plaque reduction testing of bovine isolates demonstrated two major serotypes (Table 1), which did not cross-react. There was some evidence of antigenic heterogeneity within the types. The type 1 isolates included agents associated with abortion and intestinal infections in cattle; type 2 isolates were associated with polyarthritis and sporadic encephalomyelitis. The type 1 antisera prepared against chlamydial isolates of bovine origin were tested against chlamydiae recovered from sheep, and reactions of identity were seen with the previously described ovine type 1 isolates. Likewise, the type 2 antiserum against bovine chlamydiae reacted only with the type 2 ovine isolates (Table 2). The same pattern of results was obtained with antisera to the ovine chlamydiae. There was no cross-reaction between these two groups. A number of other isolates recovered from diverse host species, as well as those recovered from cattle, were also tested against representa-
905
SEROTYPING OF CHLAMYDIA
VOL. 11, 1975
TABLE 1. Plaque reduction by antisera to bovine chlamydiae Antisera
66-P-130
66-P-130 EBA Colo LX 206 Cow H SVS-136 LW-508 LW-613 LW-623 a
Type 2
Type 1
Agents
26a 15 13
EBA Colo
LX 206
Cow H
SVS-136
LW-508
LW-613
LW-623
_
_ 19 32
-
-
-
-
-
30
-
-
-
65 40
36 26 48 35 44
-
19 30 25
12 16 22 22 22
-
-
-
-
-
-
-
-
-
-
63 29
26 19
-
20 13 29
-
-
-
_
-
-
--
-
-
-
-
Reciprocal of serum dilution reducing plaque count by 50%. No reduction at 1:10 serum dilution. TABLE 2. Plaque reduction by antisera to bovine and ovine chlamydiae Antisera
Type 2
Type 1
Agents SVS-136
LW-5OS
Sheep
Sheep abortion enteritis Fitz-65
Sheep poiypoly- arthritis/ arthritis conjunc-
Sheep
LW-623
LW-613
MO-907
LW-646
tivitis
FC-Strach
SVS-136 LW-508 Sheep abortion Fitz-65 Sheep enteritis MO-907
22a 22 17 40
35 44 29 43
29 38 55 49
15 20 49 45
LW-623
-
-
-
-
LW-613 Sheep polyarthritis LW-646
-
-
-
-
-
-
-
-
Sheep polyarthritis/conjunc-
-
-
-
-
__
-
_ _
_
19 26 31 25
29 63 29 33
-
-
_ -
30 32 75 64
44 30 31 26
tivitis FC-Strach
Reciprocal of serum dilution reducing plaque count by 50%. h No reduction at 1:10 serum dilution. a
tive type 1 and type 2 antisera (Table 3). Many of these isolates could be typed as 1 or 2. The disease distribution was generally consistent, with abortion strains falling into type 1 and arthritis and sporadic encephalomyelitis strains falling into type 2. Chlamydiae recovered from rabbits (5), mice (1), and guinea pigs (7) were identified as type 1. One chlamydial isolate (CSU-15) recovered from the spleen of a lamb with polyarthritis was identified as type 1. A number of other bovine chlamydial isolates did not fall into either of the two types in these one-way tests. One field isolate (CSU-20) was the only isolate tested that reacted with both types of antisera, predominantly with type 2. Antisera against the bovine isolates were tested against chlamydiae recovered from three avian species (Texas turkey, Meyer parrot, and pigeon AU-46), and antisera against the avian
species (homologous titers of 1:520, 1:20, and 1:18, respectively) were tested against the cattle isolates. No cross-reactions were observed.
DISCUSSION The finding that bovine chlamydiae could be classified into two serotypes identical to those observed among ovine chlamydiae suggests that these strains are not host specific. Rather it would appear that they have specific pathogenic potential or tissue tropism (8). Type 2 isolates were usually associated with polyarthritis, encephalomyelitis (including the original Wenner strain [11 ]), or conjunctivitis in either sheep or cattle. Type 1 chlamydiae were generally associated with abortions and genital and enteric infections in sheep and cattle. The intestinal tract is a natural habitat for both
906
INFECT. IMMUN.
SCHACHTER ET AL. TABLE 3. Other chlamydiae related to the ovine-bovine schema Antisera
Type 2
Type 1 Isolates
Sheep
Rabbit abortion (PHT-6) Mouse lung (S-mouse-4) Mouse lung (K-mouse-4) Guinea pig (Davis) CSU-4, bull semen CSU-5, bovine abortion (Utah) CSU-7, lamb feces CSU-9, ewe (aborting) feces CSU-12, lamb (polyarthritis) spleen CSU-15, sheep blood CSU-17, lamb (still born) gut CSU-18, lamb (still born) brain (Utah) CSU-3, calf feces CSU-6, bovine-sporadic encephalomyelitis (Wenner) CSU-8, lamb feces (Utah) CSU-13, lamb (polyarthritis) feces CSU-20, lamb (polyarthritis) conjunctiva CSU-21, lamb (polyarthritis) conjunctiva
chlamydial types, and such infections are very common in some herds. For experimental studies, researchers must often treat the animals before challenges are initiated to assure that observed effects are produced by inoculated, not resident, chlamydiae. In our typing study, isolates from the intestinal tract have not always been the type expected on the basis of observed disease. However, in experimental studies, the type 2 isolates have been more invasive and produced arthritis and conjunctivitis, whereas the type 1 isolates have produced abortions. Numerous experimental studies with sheep and cattle have shown that chlamydial isolates recovered from diseased animals of one species can produce similar disease in the other. Thus, chlamydiae recovered from aborting cattle have produced abortions in sheep (10). Fraser and Berman (4), among others, have noted an antigenic similarity between abortion isolates from different hosts. Our study demonstrates that chlamydial strains from abortions of sheep and cattle are either antigenically identical or very closely related. Expansion of these studies could enable us to devise a rational system for typing chlamydial isolates, based upon antigenic structure. It should be emphasized that some chlamydiae apparently associated with naturally occurring abortions and capable of producing abortion under experimental circumstances
Sheep polyLW-613
abortion Fitz-65
LW-508
21 24 20 48 15 21 19 20 25 17 20 25
54 55 56 25 11 11 28 32 51 47 59 54
-
-
-
-
-
-
-
-
-
-
80 34
12 29
-
-
24 60 41
25 50 36 54
13 -
arthritis LW-646
126
-
could not be typed in this system, indicating either a lack of sensitivity or the more likely possibility that other serotypes exist and simply were not represented among those strains used to produce antisera. The two serotypes were very sharply divided, although there was some variation within serotypes. It was possible with only a few sera to type isolates as belonging to type 1 or type 2: a single broadly reactive serum gave positive results with all type 2 strains tested, whereas at least two antisera were required for type 1 strains. The demonstration that some isolates recovered from rabbits, mice, and guinea pigs were type 1 isolates, coupled with the knowledge of interspecies transfer of these agents, suggests that some of these isolates merely reflect introduced rather than naturally occurring infections. It is known that chlamydiae of type 1 or type 2 are found in the bovine (or ovine) intestinal tract and may be excreted in the feces. The peak titers reached in feces are high, on the order of 105 to 107 mean lethal doses/g of feces; therefore, considering that an average bovine produces up to 50 pounds (ca. 22.7 kg) of feces a day, the environmental contamination could be quite extensive. In addition, the conditions associated with these chlamydial infections in guinea pigs have not been suggestive of naturally occurring infec-
VOL. 11, 1975
SEROTYPING OF CHLAMYDIA
tions; the cataclysmic die-off observed in young guinea pigs is more indicative of a recently introduced infection than of a successful, welladapted host-parasite relationship (7). For many years, the guinea pig has been considered the host of choice in isolation attempts for chlamydiae of bovine or ovine origin. The fact that the isolates associated with the epizootic in guinea pigs are antigenically identical to some of the chlamydiae recovered from the larger mammals suggests the possibility that proximity of the animals in a vivarium setting may have resulted in the introduction of the parasite. The same reasoning may hold true for the rabbit and mouse isolates, although these rodents are naturally much more resistant to the chlamydiae. However, the possibility that the strains were introduced through environmental contamination should be considered. More chlamydiae recovered from these species will have to be studied before this point can be settled. The effect of passage on the antigenic structures measured in the plaque reduction test is not known. However, the results of this and previous studies (3) suggest antigenic stability during prolonged passage in yolk sac or mice. Recent isolates from parakeets, turkeys, or cattle with sporadic encephalomyelitis have been antigenically indistinguishable from isolates from the same sources, but with 20- to 34-year histories of laboratory passage. Our observations suggest a very real possibility of developing a rational and useful method of typing plaque-forming chlamydiae. This system is independent of host species, a significant advance because chlamydiae have been recovered from virtually every species where they have been sought.
907
ACKNOWLEDGMENTS This investigation was supported in part by Public Health Service grants CC-00553 (from the National Communicable Disease Center) and AI-11881 (from the National Institute of Allergy and Infectious Diseases), and by the World Health Organization. LITERATURE CITED 1. Ata, F. A., E. H. Stephenson, and J. Storz. 1971. Inapparent respiratory infection of inbred Swiss mice with sulfadiazine resistant, iodine-negative chlamydiae. Infect. Immun. 4:506-507. 2. Banks, J., B. Eddie, J. Schachter, and K. F. Meyer. 1970. Plaque formation by Chlamydia in L cells. Infect. Immun. 1:259-262. 3. Banks, J., B. Eddie, M. Sung, N. Sugg, J. Schachter, and K. F. Meyer. 1970. Plaque reduction technique for demonstrating neutralizing antibodies for Chlamydia. Infect. Immun. 2:443-447. 4. Fraser, C. E. O., and D. T. Berman. 1965. Type-specific antigens in the psittacosis-lymphogranuloma venereum group of organisms. J. Bacteriol. 89:943-948. 5. Parker, H. D., W. W. Hawkins, and E. Brenner. 1966. Epizootiologic studies of ovine virus abortion. Am. J. Vet. Res. 27:869-877. 6. Schachter, J., J. Banks, N. Sugg, M. Sung, J. Storz, and K. F. Meyer. 1974. Serotyping of Chiamydia. I. Isolates of ovine origin. Infect. Immun. 9:92-94. 7. Storz, J. 1964. Uber eine natiirliche Infektion eines Meerschweinchenbestandes mit einem Erreger aus der psittakose-lymphogranuloma Gruppe. Zentralbl. Bakteriol. Parisitenkd. Infektionskr. Hyg. Abt. 1 Orig. 193: 432-446. 8. Storz, J. 1966. Psittacosis-lymphogranuloma infection of sheep. J. Comp. Pathol. 76:351-362. 9. Storz, J., E. J. Carroll, L. Ball, and L. C. Faulkner. 1968. Isolation of a psittacosis agent (Chlamydia) from semen and epididymis of bulls with seminal vesiculitis syndrome. Am J. Vet. Res. 29:549-555. 10. Studdert, M. J., and D. G. McKercher. 1968. Bedsonia abortion of sheep. I. Aetiological studies. Res. Vet. Sci. 9:48-56. 11. Wenner, H. A., G. S. Harshfield, T. W. Chang, and R. W. Menges. 1953. Sporadic bovine encephalomyelitis. II. Studies on the etiology of the disease, isolation of nine strains of an infectious agent from naturally infected cattle. Am. J. Hyg. 57:15-29.
