病原大腸菌に関する細菌学的研究 : 人・動物・その他自然界由来の病原大腸菌とその血清学的性状を中心として

食品衛生の重要な目的は，安全でかつ無害な食品を生産し，供給することにある。とりわけ，その中での食品と微生物，特に細菌との関係は，細菌性食中毒，経口伝染病，変質（腐敗，変敗）等に大きく関連し，食品衛生上の重要な問題となっている。特に食中毒は，食品の安全性と云う立場から見て，食性急性病害の中で，経口伝染病と共に最も普遍的で重要なものであり，そのうち細菌性食中毒は，食中毒の中でも最も発生頻度が高く，重要視されている。細菌性食中毒はその発生機序から見て，サルモネラや腸炎ビブリオ等の感染型，ブドウ球菌やボツリヌス菌等の毒素型，又セレウス菌や腸球菌等の中間型の3型に分類されている。この感染型の一つにここ数年来重要視されてきた病原大腸菌がある。 そもそも大腸菌（Escherichia coli）は人や動物の腸管内に正常菌叢の一種として常在し，又糞便汚染に起因して広く自然界や食品材料等に分布している。これらの大腸菌は，その腸管外感染において，一次的ないし二次的に化膿性疾患や敗血症等の原因となり得ても，食中毒の主たる原因になることはまずない。この様な正常大腸菌とは異なり，乳幼児の伝染性下痢症，あるいは児童，成人の急性胃腸炎や赤痢様腸炎を惹起する抗原型の一群の大腸菌が，所謂病原大腸菌（Enteropathogenic Escherichia coli）と云われている。 病原大腸菌による食中毒は，食物の中で大量に増殖した本菌を摂食する為に起り，症状はサルモネラ食中毒に類似している（サルモネラ型）。ただし一般にサルモネラ食中毒の場合よりはやや軽症のことが多いが，乳幼児に感染する際は，かなり激しい症状を呈し，赤痢とほとんど変らないと云われている（赤痢型）。又本菌は人から人へ感染し，発病するので，きわめて危険であり，この場合は食中毒としてではなく，伝染病として取扱う必要があると指適されている。 我国で病原大腸菌による食中毒事件は，腸炎ビブリオやサルモネラ，ブドウ球菌食中毒よりもやや少ないが，毎年かなり発生している。昭和42年の厚生省統計を例にとれば，発生件数こそ少ないが，細菌性食中毒の中で占める患者数の割合は，サルモネラの16.5％，ブドウ球菌の14.7％をはるかにしのぎ，腸炎ビブリオの39.7％に次いで24.1％の多きに達している。しかし本菌検索の繁雑さの為，本菌検索を実施していない検査機関もあり，又本菌赤痢型病原大腸菌は，赤痢菌との間に同一抗原もしくは共通抗原を有するものもあり，症状は赤痢に類似する為に，過去において，本知が赤痢菌と見誤られた場合もあり，本菌食中毒の実態はかなりの数に及んでいるものと思われる。 病原大腸菌の最初の発見者は，英国のBray（1945）で，死亡率の高い乳幼児下痢症の流行に際し，その原因として特殊な大腸菌（Bacterium coli neapolitanum）を報告したことに始まり，これに続いてKauffmannを中心とした北欧学者による大腸菌の血清学的分類は，病原大腸菌の究明に寄与したことは大きい。 かくして1950年以降，多くの研究者によって乳幼児下痢症及び胃腸炎を中心として病原大腸菌の検索が行なわれ，1972年までに18種血清型が報告されるに至ったが，最近更に約10種の新しい血清型が追加検討されつつある。 乳幼児胃腸炎由来の病原大腸菌は，児童，成人にも起病性が認められる。我国では乳幼児はほとんど家庭で保育される為，外国の様に大きな社会問題になる様な集団感染はあまり見られない。その為にここ10数年来我国では，病原大腸菌の研究は主として食中毒起因菌として関心が向けられてきた。又人の病原大腸菌の中には，人に起病性を示すばかりでなく，牛の乳房炎，仔牛，鶏，仔豚の下痢あるいは敗血症等にも関係し，起病性に人獣の共通性が認められるのもある。 病原大腸菌による下痢-食中毒は，以前からかなり多かったものと思われるが近年本菌検査法の進歩につれて，次第にこの下痢-食中毒の実態が明らかにされその重要性が広く注目される様になってきた。しかしながら本菌下痢-食中毒は今後サルモネラやブドウ球菌食中毒と同様に更に重要視されるであろうと推測されるにも拘らず，本菌の疫源，特に自然界における生態はサルモネラと同様であろうと云われているだけで，現在それを裏付けするものはなく，正確なことは不明である。これは本菌に関して適当な選択分離培地がなく，又病原大腸菌と一般大腸菌との鑑別には，ただ血清学的型別以外に方法がない為であろう。以上のことから著者は，食品衛生の将来における病原大腸菌の来たるべき位置に鑑み，本菌群の自然界における分布状態を正しく把握することは，人への感染の疫源を明らかにし，病原大腸菌による下痢-腸炎並びに食中毒の予防上重要な問題であると考え，病原大腸菌による汚染源，更に人と動物の相互関係を明かし，公衆衛生に寄与すべく本社の所在と態様を動物及び自然界から分離された大腸菌を中心に研究した。 1967年8月から1970年2月にわたる期間において，病原大腸菌の疫学調査を人，牛，馬，豚，愛玩犬，野犬，鶏，猫，緬羊，家兎の各糞便，河川水，海水，井戸水，浄化槽放流水，屠場内下水，屠場廃水，市販カキ，養殖カキ及び天然カキを対象に実施し，分離菌を中心に本菌の選択的増菌培地，選択的分離培地の比較検討，分離株の各種薬剤感受性試験並びに抗体因子吸収試験を行ない考察した。1）資料2,041例より15,044株の大腸菌を分離し，そのうち本菌陽性材料は109例（5.3％）で，15種血清型187株（1.2％）の本菌が検出された。2）本菌が検出された資料は，市販カキ（29.2％），猫（17.9％），屠場内下水（13.6％），牛（7.9％），野犬（7.1％），屠場廃水（6.7％），豚（6.3％），人（3.6％），浄化槽放流水（3.3％），河川水（2.2％），海水（2.1％）であった。しかし，馬，愛玩犬，鶏，緬羊，家兎，井戸水，養殖及び天然カキから本菌は検出されなかった。3）分離菌15種血清型187株の内訳はO-112a･c:K66（B11）29株（15.5％），O-128:K67（B12）28株（15.0％），O-136:K78（B22）21株（11.2％），O-125:K70（B15）20株（10.7％），O-26:K60（B6）18株（9.6％），O-111:K58（B4）16株（8.6％），O-127a:K63（B8）12株（6.4％），O-143:KX_1（B）11株（5.9％），O-28a･c:K73（B18）10株（5.3％），O-86a:K:61（B7）7株（3.7％），O-55:K59（B5）5株（2.7％），O-124:K72（B17）4株（2.1％），O-119:K69（B14）3株（1.6％），O-126:K71（B16）2株（1.1％），O-86:K62（L）1株（0.5％）の順であり，O-44:K74（L），O-144:KX_2（B），O-146:K89（B）は検出されなかった。4）人糞便や水系資料から本菌を検索する場合，Dihydrostreptomycin Sulfateを4μg./ml添加した普通ブイヨンにて増菌（37℃，一夜）後，4及び8μg./ml添加したMacConkey Agarにて分離すれば，発育上多少本剤に影響を受ける本菌があるが，従来の本菌分離法に比較し検出率の上昇が期待できる。5）分離菌187株につき9種薬剤に対する感受性試験を実施したところ，Chloramphenicol，Colistin，Polymyxin B，Kanamycin，Paromomycinに対しては強い感受性を示し，Tetracycline系薬剤は中等度で，Streptomycinに対してはかなり耐性を示す菌が多かった。6）分離菌15種血清型187株のうち，5種血清型57株の吸収試験を実施したところ，O及びK凝集素が完全に吸収され，その結果O及びK凝集反応で陰性となったものは57株中10株（17.5％）で，他の47株はO抗原の一部あるいはK抗原の一部に本菌標準株とわずかな抗原構造の相違が見られた。 以上のごとく，乳幼児下痢症あるいは児童，成人の急性胃腸炎，赤痢様腸炎の起因菌の一つである病原大腸菌の自然界における所在を調査した結果，本菌群の自然界における生態はかなりサルモネラに近い分布の様相を呈するが，しかしその動物の種類によってはかなりの宿主特異性が見られ，特に人の環境の中で飼育され，その為に人の食生活等に鋭敏な影響を受けやすい猫や豚に下痢-腸炎由来の病原大腸菌と同一抗原を有する本菌の保有率がさわめて高く，しかもその血清型は下痢-腸炎，及び食中毒からかなり高率に検出されるO-111:K58（B4），O-125:K70（B15），及びO-128:K67（B12）等であることは重要視される。しかしながら本菌の自然界における分布はサルモネラに近いとは云いながらも，我国の下痢-腸炎，及び食中毒時において検出頻度の最も高い血清型，即ちO-124:K72（B17）やO-44:K74（L）等においては，人のみに対する一種の宿主特異性が見られるのではないかと推測される。この様に本菌は人から人へ，あるいは人から動物へ，又逆に動物から人へと菌が循環し，特に動物においては，猫や豚が本菌下痢-腸炎，あるいは食中毒時の一つの重要な汚染源，あるいは媒介者と思考されるので，本菌による下痢-腸炎，あるいは食中毒予防の一手段を考える際には，これらの動物を無視することはできない。 又動物由来や環境由来を中心とした病原大腸菌は，人の下痢一腸炎由来の本菌に比較し，部分抗原がわずかに異なるものが多く，この点は本菌疫学上重要な問題であり，更にこの種の菌の病原性が今後重要視されるものと思考される。The important objects of food sanitation are production and supply of safe and innocuous foods. Among them, the relationship between foods and microorganisms, especially, as bacteria are related to bacterial food poisoning, oral infectious disease, and spoilage (putrefaction and deteriolation), is attaching great importance to food sanitation. It is well known that Escherichia coli (E. coli) is to be distributed extensively in the intestinal contents of man and animals as normal microflora. The E. coli does not yet recognized the pathogenic activity, but several types of E. coli are inferring to be pathogenic to man or animals, these types of E. coli are called "Enteropathogenic E. coli". On the pathogenicity of E. coli, Jensen (1897) was firstly reported that the causative agent of the "white scours" of a calf was E. coli, and Adam\u27s report (1927) of infants gastroenteritis associated with E. coli was the first one for the present enteropathogenic E. coli. Goldschmidt (1933) was studied strains of E. coli isolated from infants gastroenteritis thoroughly by serological and ecological methods, but the most investigators were consigned these works to oblivion at that time. By the bacteriological report of Bray (1945), it was responded to gastroenteritis-E. coli relationship, consequently, these reports of Adam and Goldschmidt were realized. Bray (1945) isolated E. coli "bacterium coli neapolitanum in classificational name of E. coli at that time" from many inpatients at the prevalence of infants gastroenteritis in a hospital in England. Soon after Bray\u27s report, there were similar reports of Varela et al (1946), Giles et al (1948), Smith (1949) and Taylor et al (1949). But the serological classification of E. coli by Kauffmann and his co-workers in Northern Europe (especially in Copenhagen) were really great to the cause of investigation of the enteropathogenic E. coli. Thus, from 1950, the enteropathogenic E. coli was isolated from infants gastroenteritis by many investigators, and was found 18 serotypes of the enteropathogenic E. coli untill today. But, unknown serotypes of the enteropathogenic E. coli existent, in 1973, 10 new serotypes of the enteropathogenic E. coli were supplemented. The enteropathogenic E. coli isolated from infants gastroenteritis was recognized the pathogenicity to adults. In the last 10 years in Japan, the studies of the enteropathogenic E. coli have been made progress for contribution to the direction of food poisoning. Several types of the enteropathogenic E. coli show not only pathogenic to man but also cause mastitis in cattle and diarrhoea or septicaemia in calf, fowl and young pig. These bacterial types are recognized in common in the both man and animals. But the report on the distribution of the enteropathogenic E. coli in healthy animals and in the nature except humans are little in Japan and other foreigns up to now. Because, there is no selective medium of the enteropathogenic E. coli, and the identification for the enteropathogenic E. coli and non-pathogenic E. coli has to test by serological method. In this time, I report on the distribution of the enteropathogenic E. coli in man, animals and other sources and its pollution movement.MATERIALS AND METHODS1. Isolation of the enteropathogenic E. coli in feces, waters and oysters From August 1967 to February 1970, a total of 15,044 E. coli strains isolated from feces of healthy humans, cattle, horses, hogs, pet dogs, stray dogs, fowls, cats, sheep and rabbits, and river water, sea water, well water, septic tank water, sewages in the Nagasaki City abattoir, waters from digestion tank of the Nagasaki City abattoir, oysters in market and natural oysters, were examined for isolation of the enteropathogenic E. coli. The serological identification of the enteropathogenic E. coli were as follows:1) At first, agglutination were carried out with OK mixed antiserum on a slide glass, and next, the agglutinated strains firmly within 30 seconds were examined similarly with single OK antiserum.2) About the positive strains of No. 1), agglutinations were carried out with O antiserum on a slide glass, and were ascertained the existence of K antigens.3) About the negative strains of No. 2), the organisms were incubated at 37℃ for 15 hours in Nutrient broth and heated at 100℃ for 1 hour, and a drop of concerned O antiserum added to 0.5 ml of this broth, were examined agglutinations in a test tube at 50℃ overnight. The positive strains with the naked eye were examined its quantitative agglutinations of antigen in vitro.4) At the quantity test of K antigen, the organisms incubated at 37℃ for 15 hours in Nutrient broth used for K antigen directly, and quantitative agglutinations were examined with K antiserum in vitro ( after 2 hours reacted at 37℃, let it alone overnight in dark and cold place ).5) At the quantity test of O antigen, the organisms incubated at 37℃ for 15 hours in Nutrient broth heated at 100℃ for 1 hour and used for O antigen, and quantitative agglutinations were examined with O antiserum in vitro at 50℃ overnight.6) The antiserum did dilute by two-fold method. Dilution ranges were from 5X to 640X in case of K antiserum, O antiserum were from 100X to 6,400X. In this time, the agglutinin titers for the commercial antiserum were 160X in the K antiserum and 1,600X in the O antiserum, I concluded to the enteropathogenic E. coli strains that the isolates indicated the titer of 80X and over in case of K antiserum and 800X and over in case of O antiserum.2. 1) Selective effect of dihydrostreptomycin sulfate ( DHS ) on isolation of the enteropathogenic E. coli The 18 standard strains of enteropathogenic E. coli consisting of 18 serotypes ( E1-E18 ), the 114 enteropathogenic E. coli isolated strains belonging to 14 serotypes, and 104 common E. coli strains isolated from human feces, 62 common E. coli strains isolated from river waters and 110 common E. coli strains isolated from hog feces, were examined its sensitivity of dihydrostreptomycin sulfate ( DHS ). In the present study, the basal medium used was MacConkey agar, and various concentrations of DRS added to MacConkey agar. And these enteropathogenic and common E. coli strains incubated at 37℃ overnight in Nutrient broth. The cultures were inoculated on the DHS MacConkey agar and incubated at 37℃ for 20 hours. The states of bacterial growth were observed.2) The effect on growth in dihydrostreptomycin sulfate ( DHS ) broth of the enteropathogenic E. coli 18 standard strains and 114 isolated strains of enteropathogenic E. coli, and 20 common E. coli strains isolated from human feces, were examined its sensitivity of DHS broth. The used media were Nutrient, LB, BGLB and EC broths in commercial.3. Antibiotics sensitivity of the enteropathogenic E. coli isolates A total of the 187 enteropathogenic E. coli strains isolated from various sources were examined its sensitivity to 9 different antibiotics. Each 1 ml of Nutrient broth cultures of the 187 strains incubated at 37℃ overnight was inoculated again to Nutrient broth and incubated at 37℃ 4-5 hours. A drop of the cultures dropped on a Heart Infusion agar plate by 1 ml pipette and extended by sterile-L glass stick. After dried, disc containing each antibiotics placed on the plate gently and let it alone room temperature 1 hour, and incubated at 37℃ overnight. The diameter of a produced inhibitory zone was measured. The used 9 different antibiotics were as follows: Tetracycline (T), Demethylchlortetracycline (Td), Oxytetracycline (O), Chloramphenicol (C), Colistin (K), Streptomycin (S), Polymyxin B (Xp), Kanamycin (Ka) and Paromomycin (H).4. Analysis of the antigen of the enteropathogenic E. coli isolates Absorption tests of 57 strains consisting of 5 serotypes isolated from various sources were examined. Serotype, O-111:K58(B4) strain isolated from cattle, O-112a.c:K66 (B11) isolated from hog, O-125:K70(B15) isolated from human, O-128:K67(B12) isolated from hog and O-136:K78(B22) isolated from cat, were prepared antisera by hyperimmunization in 5 rabbits. These 5 antisera were absorved K and O agglutinins by the enteropathogenic E. coli standard strains. These absorved antisera used for quantitative agglutinations in vitro of 57 strains consisting of 5 serotypes. The dilution of antisera was carried out by two-fold serial dilutions from 3X in case of K antisera and from 10X in case of O antisera. The agglutinin titers of 5 different rabbit antisera were about 1,600X in case of O antisera and about 160X in case of K antisera.RESULTS1. Distribution of the enteropathogenic E. coli in feces, waters and oysters 15,044 E. coli strains isolated from various sources were examined for identification of the enteropathogenic E. coli. The results are summarized as follows:1) Number of the enteropathogenic E. coli positive samples were 109 (5.34%), and 187 strains (1.24%) consisting of 15 serotypes were isolated.2) The distribution of the 15 enteropathogenic E. coli serotypes were as follows ; O-112a.c:K66(B11) (15.5%), O-128:K67(B12) (15.0%), O-136:K78(B22) (11.2%), O-125:K70(B15) (10.7%), O-26:K60(B6) (9.6%), O-111:K58(B4) (8.6%), O-127a:K63(B8) (6.4%), O-143:KX_1(B) (5.9%), O-28a.c:K73:(B18) (5.3%), O-86a:K61(B7) (3.7%), O-55:K59(B5) (2.7%), O-124:K72(B17) (2.1%), O-119:K69(B14) (1.6%), O-126:K71(B16) (1.1%) and O-86:K62(L) (0.5%). Both types O-112a.c:K66(B11) and O-128:K67(B12) were isolated in higher rate. In this time, O-44:K74(L), O-144:KX_2(B) and O-146:K89(B) were not isolated.3) Serotype O-128:K67(B12) was isolated from 9 kinds of samples, O-125:K70(B15) was isolated from 7, O-127a:K63(B8) was isolated from 6, O-112a.c:K66(B11) was isolated from 5, O-26:K60(B6) and O-28a.c:K73(B18) were isolated from 4, O-55:K59(B5), O-86a:K61(B7), O-124:K72(B17), O-136:K78(B22) and O-143:KX_1(B) were isolated from 3, and O-111:K58(B4) and O-126:K71(Bl6) were isolated from 2.4) Serotype O-86:K62(L) was isolated only from dog, and O-119:K69(B14) was isolated only from humans.5) Serotypes O-112a.c:K66(B11) and O-125:K70(B15) were isolated from 2 hogs, O-55:K59(B5) and O-128:K67(B12) were isolated from 1 hog, O-86:K62(L) and O-128:K67(B12) were isolated from 1 dog, O-55:K59(B5) and O-128:K67(B12) were isolated from 1 dog, O-26:K60(B6) and O-136:K78(B22) were isolated from 1 cat, and O-111:K58(B4) and O-128:K67(B12) were isolated from 1 cat. From March 1969 to February 1970, the enteropathogenic E. coli strains isolated from normal and watery contents in the hog caeca, and sewages and waters from digestion tank in the Nagasaki City abattoir, were examined for its seasonal variation and quantitative relationship of coli-aerogenes group. The results are summarized as follows:1) Of normal and watery contents, the organism-positive contents were more than negative contents, and of the organism-negative contents, watery contents were more than normal contents in number of coli-aerogenes group. But, of the organism-positive contents, the difference of number of coli-aerogenes group was not recognized between normal and watery contents.2) Of normal contents, the isolation rate of the organisms was higher in spring (from March to May ) through the year.3) Sewages and waters from digestion tank in the abattoir, the isolation rate of the organisms were higher in summer (from July to August) through the year.2. Selective effect of dihydrostreptomycin sulfate (DHS) on isolation of the enteropathogenic E. coli The present study was carried out to confirm selective effect of dihydrostreptomycin sulfate on the isolation of the enteropathogenic E. coli from humans, animals and river water, in the light of Ramirez\u27s report that media containing DHS were highly effective as selective substance for isolation of the enteropathogenic E. coli from normal feces and sewage. The results are summarized as follows:1) Of the enteropathogenic E. coli standard strains, the growth of serotypes O-26:K60(B6), O-28a.c:K73(B18), O-44:K74(L), O-86:K62(L), O-111:K58(B4), O-119:K69(B14), O-124:K72(B17), O-125:K70(B15), O-126:K71(B16), O-127a:K63(B8), O-136:K78(B22), O-144:KX_2(B) and O-146:K89(B) were normal, but O-55:K59(B5), O-86a:K61(B7), O-112a.c:K66(B11), O-128:K67(B12) and O-143:KX_1(B) were slightly inhibited on the DRS MacConkey agar (2-10 μg. level per ml).2) Of the enteropathogenic E. coli isolated strains, almost of strains grew on the DHS MacConkey agar (10 μg. level per ml). Of these, the growth of O-55:K59(B5), O-86a:K61(B7), O-128:K67(B12) and O-143:KX_1(B) as well as O-26:K60(B6), O-28a.c:K73(B18), O-86:K62(L), O-111:K58(B4), O-119:K69(B14), O-124:K72(B17), O-127a:K63(B8) and O-136:K78(B22) were normal, but O-112a.c:K66.(B11) and O-125:K70(B15) were slightly inhibited on the DHS MacConkey agar.3) Of non-pathogenic E. coli isolates, 42.3% of strains from human were inhibited by 4 μg. level per ml of DHS, 76.0% by 6 μg. per ml and 77.9% by 8 μg. per ml, and none of strains from river waters were inhibited by 4 μg. level per ml, 45.2% by 6 μg. per ml and 58.1% by 8 μg. per ml; on the other hand, strains of hogs were slightly inhibited by 4-8 μg. level per ml of DHS MacConkey agar.4) All of the enteropathogenic E. coli standard strains grew by 4 and 6 μg. level per ml, and 72.2% of strains grew 8 μg. per ml of DHS MacConkey agar. Of the enteropathogenic E. coli isolated strains, 99.1% of strains grew by 4 μg. per ml, 96.5% of strains grew by 6 μg. per ml, and 93.0% of strains grew by 8 μg. level per ml of DHS MacConkey agar.5) Of non-pathogenic E. coli isolates, 60% of strains were inhibited by 4 μg. level per ml of DHS Nutrient broth.6) Of the enteropathogenic E. coli standard strains, the growth of 88.9% of strains were normal by 4 μg. level per ml of DHS Nutrient broth.7) In the examination of fecal specimens of hogs, the combined use of DHS Nutrient broth and DHS MacConkey agar resulted in normal average rate of detection of the enteropathogenic E. coli.8) From these results, it is presumed that the use of a combination of DHS Nutrient broth (4 μg. level per ml) and DHS MacConkey agar (4, 6 and 8 μg. level per ml) will yield a higher percentage for isolation of the enteropathogenic E. coli from human feces and waters except hog feces than do any other medium alone.3. Antibiotics sensitivity of the enteropathogenic E. coli isolates A total of the 187 enteropathogenic E. coli strains isolated from various sources were examined its sensitivity to 9 different antibiotics. The results are summarized as follows:1) The highly effective compounds in the sensitivity tests were chloramphenicol, colistin, polymyxin B, kanamycin and paromomycin. Moderative inhibition was shown in tetracycline, demethylchlortetracycline, oxytetracycline and streptomycin.2) There was little difference in the sensitivity to all antibiotics between the strains from humans and from animals.3) It is noted that tetracyclines- and streptomycins-resistant strains were obtained from only feces of hogs.4) Of all the strains tested, 81 strains (43.3%) were resistant to antibiotics, 1 strain (0.5%) was resistant to 5 kinds of antibiotics, 12 strains (6.4%) were resistant to 4, 18 strains (9.6%) were resistant to 3, 11 strains (5.9%) were resistant to 2, and 39 strains (20.9%) were resistant to 1.5) The serotypes of antibiotics-resistant strains in the isolates were as follows; serotypes O-26:K60(B6) and O-112a.c:K66(B11) isolated from hogs were resistant to tetracyclines and streptomycin. O-111:K58(B4) isolated from cattle, O-136:K78(B22) isolated from cats and O-143:KX_1(B) isolated from human and dogs, were resistant to streptomycin.4. Analysis of the antigen of the eateropathogenic E. coli isolates Absorption tests of 57 isolated strains consisting of 5 serotypes were examined. The results are summarized as follows:1) As a results of the agglutinins were observed completely by the enteropathogenic E. coli standard strains, both O and K negative agglutinations were found in 10 strains consisting of 3 serotypes.2) Other 47 strains were slightly recognized the difference of a certain sections of O only or K antigen structures from its enteropathogenic E. coli standard strains.3) In both O and K agglutinations, 10 negative strains consisting of 3 serotypes were as follows; 2 strains of serotype O-111:K58(B4) isolated from cats, 5 strains of O-125:K70(B15) isolated from hogs and 3 strains of O-128:K67(B12) isolated from hogs.DISCUSSION AND CONCLUSION There exists considerable literatures on ecological investigation of the enteropathogenic E. coli in man, but little work has been done to study its distribution in animals and in the natural world. In this time, numerous strains of E. coli isolated from animals and the natural world were examined serotypes of the enteropathogenic E. coli which causes diarrhoea or gastroenteritis and food poisoning in man. They have distributed widely in human living environments and in animals, especially the cat and dog. It was recognized the relationship between the serotypes isolated from many sources and the serotypes isolated from diarrhoea, gastroenteritis and food poisoning, on that account, it is presumed that these are important problems for food sanitation. In case of compared with the antigen structure of the enteropathogenic E. coli standard strains and the enteropathogenic E. coli strains isolated from animals or in the natural world were recognized to be slightly different, in a certain portion of the antigen structure (for example, parts of O or K antigen) from the antigen structure of the standard strains. These points are attached great importance to the ecology of the enteropathogenic E. coli. Moreover, the pathogenicity of these strains are attached great importance for furthe