다람쥐 (Eutamias sibiricus asiaticus)를 사용한 Candida albicans의 실험적 감염에 관한 연구
(A) study on experimental infection of Korean chipmunks (Eutamias sibiricus asiaticus) by candida albicans
1751년 John Hill에 의하여 Candids가 최초로 관찰되었으며 Berkhout(1923)에 의하여 C
andida라 재명명된 이래 현재까지 100여종이 보고되어 있다. 이중Candida albicans만이
병원성을 나타낸다고 알려져 왔으나 근래에 와서 타Candida종들도 질병을 야기할 수 있다
는 보고가 있으며 각종 진균증의 감염 증가추세와 더불어 캔디다증 역시 증가하는 현상을
나타내고 있다. 이러한 진균증의 증가추세는 항생제의 남용, 면역억제제의 사용, 각종
종양 및 면역결핍성 질환 등 여러가지 소인에 의한다고 보고되어 있다.
현재까지 각종 진균증의 원인균에 대한 적당하고 우수한 실험동물이나 Candida species
에 대한 실험동물에 관한 연구는 별로 찾아볼 수 없으며 학자들 간에도 서로 다른 의견들
이 있는 실정이다.
따라서 본 연구에서는 연세의대 미생물학교실에서 연구 개발하여 현재까지 항산군증에
대하여 좋은 실험동물로서 보고된 한국산 다람저(Eutamias sibiricus asiaticus)를 사용
하여 세계적으로 널리 분포되어 있으며 심재성 진균증을 야기하는 진균의 일종인 Candida
albicans에 대한 감수성 여부를 규명하고 실험동물로서의 이용가능성 여부를 규명할 목
적으로 실험에 착수하여 다음과 같은 결과를 얻었다.
1. 정맥을 통하여 다람쥐에 Candida albicans를 감염시켰을 경우 LD^^50 는 1ml당 5.7
×10**4 cell 이었으며 다람쥐에서 100% 사망율을 나타낸 1ml당 3.2×10**5 cell에서의
2. 정맥내로 주사한 다람쥐의 직접도말검경 및 배양성적에서는 균접종 4일 후부터는 신
장에서만 균검출이 가능하였다.
3. 각 장기에서의 생균수측정 결과는 신장을 제외하고는 균접종 1일내지 2일 이내에 최
고에 달하였다가 급속히 감소하였으나 신장에서는 31일까지도 균의 관찰이 가능하였다.
4. 혈액학적 검사성적에 있어서 백혈구의 수는 균접종전에 비하여 균접증 4일에 4배의
5. 병리조직학적 소견을 보면 접종 초기에는 각 장기에서 조직 변화없이 군체의 관찰이
가능하였으나 균접종 31일에서는 신장에서 심한 다발성국소 농양 및 괴저를 초래한 현상
을 관찰함과 동시에 많은 균사체가 발견되었다.
이상의 실험결과를 종합하여 볼 때 한국산 다람쥐는 Candida albicans에 대하여 감수성
을 가지고 있는 동시에 실험동물로서의 가능성을 내포하고 있다고 사료된다.
In 1751, John Hill observed yeast-like organisms harvested from rotting
vegetation, which he named Monilia. But, the genus Monilia was erected by Persoon
in 1797 to encompass certain species of fungi isolated from rotting fruit. In 1923,
Berkhout reclassified the genus Candida and this name was accepted as a "nomen
conservandum'by the 8th Botanical Congress at Paris in 1954.
It is generally recognized that Candida albicans is the only species of Candida
known to be pathogenic to man and to a number of laboratory animals, but recently
it has been found that all of the Candida species may be involved in any from of
candidiasis. Presently, Candida albicans is one of the normal flora of the
alimentary tract, mucous membrane, oral cavity and skin of many mammals. The
incidence of human disease caused by this organism has increased steadily in recent
years due to the wider use of immuno-suppressive drugs and broad spectrum
antibiotics. The variety of predisposing factors, the range of the clinical
disease, and the poor antibiotic chemotherapy now avilable have made candidasis a
serious clinical problem. The need to understand the immunity, host-parasite
relationship and pathogenesis involved in human diseases due to Candida albicans
has made it desirable animal model for candidasis that mimics the systemic disease
seen in human.
Several animal models from disseminated candidiasis have been described. Baine et
al. (1974) used the rabbit to study systemic candidiasis and estab1ished that the
infection is of a chronic nature. Hurley and Winner (1963) described the
histological picture of experimental Candida albicans infection in the tissue of
mice. But up untill now, a properly susceptible and sensitive animal model for
experimental systemic candidiasis has not been found.
For this reason, the author has also studied the course of an experimental
Candida albicans infection in the Korean chipmunks (Eutamias sibiricus asiaticus)
in order to establish whether this animal can be used as an experimental animal
Materials and Methods
1. Experimental organism: Candida albicans ATCC 7491 was obtained from H.
Miyazaki (Juntendo University, Tokyo, Japan). It was maintained in our laboratory
by transfers on Sabouraud's glucose agar slant.
The morphological and biochemical characteristics of Candida albicans were
verified by microscopic observation and sugar fermentation reactions.
2. Animals: Wild chipmunks were obtained. They were maintained on a nutritional
diet and their adaptability to caged life was observed for 2 months prior to
inoculation with fungal suspension. Also, white ICR-mice were obtained from the
Institute of Leprosy, Japan and were used in all of the control studies.
1. Challenge Procedure: Aliquots of the stored Candida albicans suspension
diluted in saline were prepared to obtain the proper dose of administration. 0.2 ml
of the appropriate suspension were injected into the tail vein. Otherwise, 0.5 ml
of the suspension were injected intraperitoneally.
2. Enumeration of the Candida albicans Viab1e Unit: Chimmunks were sacrificed,
under aseptic condition. The appropriate organs were removed and weighed and placed
in tissue homogenizers. Sterile saline was added. Each organ was homogenized and
then number of Candida albicans viable units in the homogenate was determined by
the pour plate dilution method, using Sabouraud's glucose agar. Colony forming
units (CFU) were determined by counting the colonies used as a source of the
3. Histopathological Study: Experimental animals Were sacrificed at 24 hours, 48
hours and 31 days after intarvenous inoculation of approximately 3.2×10**3
cell/ml. Sections of brain, lung, heart, liver, spleen and kidney were studied
after staining with hematoxylin eosin and Periodic acid-Schiff's reagent.
4. Hematological Study: Experimental chipmunks were infected with 3.2×10**3
cell/ml, and 0.5ml of whole blood were obtained daily for 5 days by cutting tail
vein. Blood was placed in tubes containing 0.3% sodium citrate solution, and white
blood cell(WBC), red blood cell (RBC) and hematocrit counts were determined with
Hema-Count TM System Model MK-3 type.
Results and Conclusions
1. Mortality Rate and Histopathological Study: In an attempt to produce a
disseminated infection, up to 3.2×10**5 cell/ml of Candida albicans were given
intravenously. With this inoculum, death of all animals was observed within 24
hours. The LD^^50 was determined as 5.7×10**4 cell/ml. Between the inocula of
2.0×10**4 cell/ml and 7.2×10**4 cell/ml mortality rose sharply, increasing from
10% to 90%.
Autopsies of animals given lethal and sublethal doses of Candida albicans
intravenous revealed disseminated microabscesses or inflammatory cell infiltrations
throughout the kidney, heart, lung, liver and spleen. Also, Candida albicans could
be cultured from these organs in the early stage of infection and cells in the
mycelial phase were demonstrated histopathologically in the renal and myocardial
abscesses after 31 days.
2. Course of Infection: For the study of the course of infection over time, a
sublethal dose of Candida albicans was given (3.2×10**4 cel1/ml) and animals were
autopsied at 24, 48, 72, 96, 120 hours and 31 days after injection, spleen, liver,
lung, heart and kidney were cultured. Over the next 5 days, colony counts revealed
a decreasing number of viable organisms in all tissues except the kidney. Between
24 hours and 48 hours the decline was rapid: between 96 hours and 120 hours all
nonrenal organs became sterile.
Although the initial renal colony counts was similar to colony counts in other
organs, there was gradual increase in renal colony count over the first 2 days of
infection, with maximal counts of viable organism of 7.0×10**5 CFU/gm tissue at 3
days. Subsequently, there was a gradual decline in colony count. By day 31, the
colony counts was 4.8×10**3 CFU/gm tissue.
3. Hematological Study: Paralleling the inefection, leukocytosis was observed 24
hours after injection and continued to rise until 4 days, when the total count of
(18.05±4.26)×10**3 WBC/cmm was seen. Blood cultures were positive for the
infecting organism for the entire 5 days period of the blood collection.
4. In summary of the above results, the chipmunk appears to be one of the most
susceptible to Candida albicans among all the experimental animals known to date.
Therefore this animal can be adopted as an expermental animal model for candidiasis