Veterinary bacteriology : a treatise on the bacteria, yeasts, molds, and protozoa pathogenic for domestic animals

Front matter

arieieaton pee reeiiie Ae ee et ener

ABORATORY IRIDGE, SURREY.

A TREATISE ON THE

Preface To The Second Edition

THE present volume is a revision of the Veterinary Bacteriology prepared by the senior author.

- The rapid advance which has been made in the science of bacteriology during the past five years has necessitated a complete revision of the text. Many chapters have been completely rewritten and several new chapters added. The organisms have likewise been regrouped in ‘accordance with more recent conceptions of relationships.

R. E. BUCHANAN,

CHARLES Murray.

Iowa State CoLiuecH, Ames, Iowa.

September, 1916.

P46 & oa a ¢

Preface

THE present volume is a revision of the lectures on veterinary bacteriology given during the pastsix years to classesin the Division of Veterinary Medicine in the Iowa State College. It constitutes a serious attempt to put in usable form that fund of knowledge concerning bacteriology which the student of veterinary medicine. should master. It is in no sense a text on pathology, and discussion of purely pathological subjects has been minimized as much as possible. The intention has been to confine attention as far as practicable to those topics that unquestionably lie in the province of bacteriology. This has been defined to include a discussion of immunity and of the pathogenic bacteria, yeasts, molds, and protozoa.

The book is not intended to serve as a manual of laboratory practice, hence detailed discussion of methods and technic has been omitted. Methods of significance in diagnosis or treatment are given in greater detail in the discussion of specific organisms.

Several organisms causing diseases of man not transmissible to lower animals have been included. In all cases they are closely related to organisms having significance to the veterinarian, they cause diseases which are commonly confused with somewhat similar diseases of lower animals, or they are valuable as illustrations of methods of immunization, treatment, or diagnosis. Such organisms are relatively few in number.

A group system of discussion of the pathogenic bacteria has - been adopted. The classification used has proved very helpful in my own classwork. The groupings used are not entirely satisfactory, in part due to the fact that some of the species have not been adequately described and differentiated in the literature. An effort has been made to point out the deficiencies in our present knowledge, both to give a better balanced presentation of the subject and to stimulate interest in the solution of the problems.

10 PREFACE

The pathogenic protozoa constitute a group which is particularly difficult to treat adequately, largely due to the rapid growth of the subject. Relatively few of the forms, moreover, are of immediate interest to the North American student.

; R. E. BucHANAN,

Iowa State CouLuece, Amgs, Iowa.

Section I Morphology, Physiology, And Classification Of Bacteria 7

Definition of Bacteriology, 17.—Scope of Bacteriology, 17.—Scope of Veterinary Bacteriology, 19.—The Microscope and Its Influence, 19.—Nature and Classification of Microdrganisms, 21.—Spontaneous Generation, 21.—Relationships of Microérganisms to Fermentation and Decay, 22.—Relationships of Microérganisms to Disease, 22.—Development of Laboratory Methods, 23.—Development of Theories of Immunity, 24.—Development of Sanitary Science and Preventive Medicine, 24.

CHaprer Il.—MorrHoLtocy AND RELATIONSHIPS OF MICROORGANISMS CONCERNED IN DISEASE PRODUCTION................ Te Bard 26

Position of Pathogenic Microérganisms, 26.—Differentiation of Animals and Plants, 26.—Subdivisions of the Thallophytes, 27.—Morphology of Bacteria, 28.— Shape of Bacteria, 28.—Grouping of Bacterial Cells, 29.—Size of Bacteria, 31.— Histology and Structure of Bacteria, 32.—Reproduction in Bacteria, 36.—— Morphology of the Yeasts, Saccharomycetes, and Blastomycetes, 38.—Form, Size, and Grouping of Yeasts, 39.—Histology and Structure of the Yeasts, 39.—Yeast Protoplasm and Cell Inclusions, 39.—Reproduction in Yeasts, 40.—Morphology of the Hyphomycetes or Molds, 41.—Form and Size of Hyphomycetes or Molds, 41.—Histology and Structure of Molds, 42.—Reproduction of Molds, 43.— Morphology of the Protozoa, 44.—Form and Size of Protozoa, 45.—Histology, 45.— Reproduction, 45.

Food Relationships of Microérganisms, 46.—Composition of the Cell, 46.— Sources and Kinds of Foods, 46.— Moisture Relationships of Microérganisms, 47.— Respiration of Microorganisms, 48.—Temperature Relationships of Microérganisms, 49.—Optimum Temperature, 49.—Minimum Temperature, 49.—Maximum Growth Temperature, 49——Growth Temperature Range, 49.—Thermal Death-point, 49.—Light Relationships of Microérganisms, 50.—Effect of Electricity on Bacteria, 51.—Relationships of Microérganisms to Chemicals. 52.—Chemotaxy, 52.—Tropisms, 53.—Influence of Reaction of Medium on Growth, 53.—Antiseptics and Disinfectants, 54.—Theories of Action of Antiseptics and Disinfectants, 54.— Disinfectants and Antiseptics in Common Use, 54.—Adjustment of Organisms to Osmotic Pressure, 56.—Symbiosis, Antibiosis, and Commensalism, 57.—Pigment Production by Microérganisms, 58.—Light Production by Microérganisms, 59.— Fermentation and Enzyme Production, 59.

CuaptTer [V.—Cuances or Economic SIGNIFICANCE Broucut ABOUT BY NON-PATHOGENIC: ORGANISMS. (oe Se Sa. sea oe 68 Production of Alcohol, 64.—Production_ of Acids, 64.—Decay and Putrefaction, 66.—Reduction Processes in Inorganic Compounds, 68.—Oxidation of Inorganic Compounds, 69.—Miscellaneous Changes, 76.

CHAPTER V.—CLASSIFICATION OF MIcROORGANISMS..............00-- ver

Discussion of Principles of Nomenclature, 77.—Classification of Bacteria, 78.— Key to the Genera and Higher Groups of Bacteria, 79.—Discussion of the Bacterial Genera, 80.—Streptococcus, 80.—Diplococcus, 80.—Sarcina, 80.—Staphylococcus, 81.—Micrococcus, 81.—Bacillus, 82.—Vibrio, 82.—Spirillum, 83.— Nocardia, Actinomyces, and Actinobacillus, 83.—Classification of Yeasts, 84.— Classification of Molds, 84.

12 . CONTENTS

Section II Laboratory Methods And Technic

CrAprer .Vi-—STERILIZATIONS = 690 Was.

Sterilization by the Flame, 85.—Sterilization by Hot Air, 85.—Sterilization by Streaming Steam, 86.—Sterilization by Steam Under Pressure, 87.—Sterilization at Temperatures Lower Than Boiling-point, 89.—Sterilization by Addition of Chemicals, 89.—Sterilization by Filtration, 89.

CuHapTeR VII.—CuLTURE-MEDIA AND THEIR PREPARATION........

Use of Normal Solutions of Acid and Alkali and Methods of Expressing Reactions, 91.—Nature of Nutrients Required by Bacteria, 92.—Liquid Media, I2.== Bouillon or Beef Broth from Meat, 93.—Bouillon or Broth from Beef Extract, 93.—Sugar-free Broth, 93.—Sugar Broth, 94.—Glycerin Broth, 94.—Serum Broth, 94.—Dunham’s Solution, 94.—Beerwort, 94.—Milk, 94.—Petruschky’s Lackmus Molke, 94.—Barsiekow’s Medium, 94.—Hetsch’s Medium, 95.— Synthetic Media, 95.—Liquefiable Solid Media, 95.—Nutrient Gelatin, 95. —Other Gelatin Media, 96.—Nutrient Agar, 96.—Blood-serum Agar, 96.— Other Agar Media, 96.—Endofuchsin-agar, 97.—Léffler’s Malachite Green-safranin-pure-blue Agar, 97.—Drigalski-Conradi Litmus Nutrose Agar, 97.— Non-liquefiable Media, 98.—Potato, 98.—Other Vegetable Media, 99.—Blood-serum, 99.—Egg Medium, 99.

Acid Production, 101.—Alkali Production, 101.—Gas Production, 101.—Reduction Processes, 102.—Indol Production, 103.—Thermal Death-point, 104.— Efficiency of Disinfectants, 104.—Phenol Coefficient, 105.

CHaptTerR LX.—Microscopic EXAMINATION AND STAINING METHODS. .

Oil Immersion Objectives, 106.—Measuring Bacteria, 107.—Examination of Living Bacteria—Hanging Drops, 107.—Staining Methods, 108.—Mordants, 108.—Formulas of Some of the Commonly Used Stains, 109.—Preparation of a Stained Mount, 109.—Spore Stain, 110.—Stain for Acid-fast (Acid-proof) Organisms, 111.—Wirth’s Stain for Much Granules, 111.—Flagella Stain, 112.— Gram’s Staining Method, 113.—Capsule Stains, 113.—Muir’s Stain, 113.— Johne’s Stain, 113.—Raebiger’s Stain, 114.—Blood and Protozoan Stains, 114.— Wright’s Stain, 114.—Giemsa’s Stain, 115.—Negri Bodies, 115.—Lentz Method, 115.—India-ink Method, 116.

CyapTrerR X.—Mertuops or SECURING PuRE CULTURES OF BACTERIA.

Dilution Method, 117.—Isolation by Smearing, 117.—Direct Isolation, 117.— Isolation by Plating, 118.—Isolation by the Use of Heat, 119.—Isolation by the Use of Differential Antiseptics or Disinfectants, 119.—Isolation by Animal Inoculation, 119.

CHAPTER XI.—Strupy or BACTERIAL CULTURES............ or at ora

Cultural Characters, 120.—Agar Stroke, 120.—Potato, 120.—Blood-serum, 121.— Gelatin Stab, 121.—Nutrient Broth, 121.—Milk, 121.—Litmus Milk, 122.— Gelatin Plate Colonies, 122.—Colonies on Agar Plates, 123.—Physiologic Characters, 125.

Section III Bacteria And The Resistance Of The Animal Body To Disease

Infectious Diseases, 126.—Contagious Diseases, 127.—Avenues of Infection, 127. —Virulence, 129.—Koch’s Postulates, 129.—Animal Inoculation, 130.—Methods of Animal Inoculation, 131.—Types of Infectious Diseases, 132.

CONTENTS 3h}

Cuaptrer XIII.—Iwmunity. GENERAL DISCUSSION................. 134

Immunity, 134.—External Resistance to Infection, 134.—Variations of Individuals in Susceptibility to Disease. Predisposing Factors, 135.—Types of Immunity, 135.—Natural Immunity, 135.—Acquired See 136.—Active Acquired Immunity, 136.—Acquired Passive Immunity, 138.—Theories of Immunity, 138.—Theory of Exhaustion, 138.—Noxious Retention Theory, 139.— Metchnikoff’s Theory of Phagocytosis, 139.—Ehrlich’s Humoral Theory, 139.— Duration of Immunity, 140.—Antigens and Antibodies, 140.—Antibodies as Factors in Acquired Immunity, 140.

CuHapTeR XIV.—ANTITOXINS AND RELATED ANTIBODIES.............. 142 Antibodies of Ehrlich’s First Order, 142.—Toxins, 142.—Antitoxins, 144.— Constitution of the Toxin, 147.—Constitution of Antitoxin, 147.—Diagrammatic Representation of Toxin and Antitoxins, 148.—Preferential Union of Toxins with Body-cells, 148.—Antitoxins of Commercial Importance, 149.— Manufacture of Diphtheria Toxin and Antitoxin, 149.—Preparation of Tetanus Toxin and Antitoxin, 156.—Preparation of Other Toxins and Antitoxins, 158.— Anti-enzymes, 158.—Other Antibodies Related to Antitoxins. 159.

CHAPTER XV.—AGGLUTINATION AND PRECIPITATION..............--- 160

Antibodies of Ehrlich’s Second Order, 160.—Differentiation of Precipitation and Agglutination, 160.—Agglutination, 160.—Precipitins, 167.

CuapTer XVI.—CyrTotysins, INcLUDING BACTERIOLYSINS, AND HEMOL- CUCTANGSR Pie Maca ot eee RS Reet acne fas on Ag Soe RN Re Bi, ad 170

Antibodies of Ehrlich’s Third Order, 170.—Cytolysins, 170. —Group Cytolysins, 173.—Bacteriolysins, 174.—Hemolysins, 175.—Fixation of Complement and Its Utilization, 176.—Cytotoxins, 178.—Conglutination, 178.

CHAPTER XVII.—OPSONINS AND PHAGOCYTOSIS. . oe ee P80

Opsonins, 181.—Opsonic Index, 183.—Autogenic Vareeee 187. sate: DAsonic Immunization, 189. —Leukocytic Extracts, 189.—Aggressins, 189.

CHAPTER XVIII.—ANAPHYLAXIS AND HYPERSUSCEPTIBILITY.......... 192

Phenomenon of Arthus, 192.—Serum Sickness in Man, 192.—Theobald Smith Phenomenon, 193. —Vaughn’ s Split Proteins, 193.—Mechanism of Anaphylaxis, 193.—Relationship of Anaphylaxis to Certain Body Reactions, 196.—Bacterial Anaphylaxis, 196.

Section IV Pathogenic Microorganisms Exclusive Of The

PROTOZOA CHAPTER XIX.—Grovuprps or PATHOGENIC MICROORGANISMS.......... 198 CHAPTER XX.—THE GROUP OF STREPTOCOCCI. . os . 200

Classification of Streptococci, 200. Dh esaomee te Bieoio 201. Waites coccus Equi, 209.—Streptococcus Gallinarum, 212.—Streptococcus Vaginitidis, 214.—Streptococcus Abortus, 216. —Streptococcus Mastitidis Sporadice, 216.— Streptococcus Sp., 217 Streptococcus Lacticus, 217.

Diplococcus Pneumonie, 220. esintecens! Meningidia: 293. eT ilecoume Intracellularis Equi, 226.—Diplococcus Gonorrheee, 226.

Pear XX STAPHYLOCOCCUS: GROUP) 20 tic! ehiacs Sowa ae are. 229

Staphylococcus Aureus, 229.—Staphylococcus Albus, 233.—Staphylococcus Niele 234.—Staphylococcus (Pyogenes) Bovis, 234. Staphylococcus Ascoormans, 234.

Saaeran, <1 =—Micrococcus :-GRopes.the. cea. -2ee he hayes 2) 2d Micrococcus Melitensis, 237.—Micrococcus Caprinus, 239.

14 CONTENTS

PAGE Graprern” X XTV.—ANTHRAX. GROUP) Lee eee ee eee 241 The Group of Aérobic Spore-producing Bacilli, 241.—Bacillus Anthracis, 242.— Bacillus Lactimorbi, 252.

CHAPTER XX V.—BLACKLEG—TETANUS GROUP............02-+-0+00- 255

Key to the More Important Pathogenic Members of the Tetanus-Blackleg Group of Bacteria, 256.—Bacillus Tetani, 256.—Bacillus Chauvei, 262.— Bacillus Gastromycosis Ovis, 267.—Bacillus Welchii, 269.—Bacillus (Edematis, 272.—Bacillus of Ghon-Sachs, 275.—Bacillus Enteritidis Sporogenes, 276.—Bacillus Sp. of Novy, 276.—Bacillus Sp. of Hibler, 276.—Bacillus Botulinus, 276.

CHAPTER XXVI.—PASTEURELLA, OR HEMORRHAGIC SEPTICEMIA Group 279

Common Characters of Group, 280.—Bacillus Avisepticus, 282.—Bacillus Suisepok 286.—Bacillus Bovisepticus, 290.—Bacillus Cuniculicida, 291.—Bacillus estis, 291.

CHAPTER XXVII.—Doa DISTEMPER GROUP................-++e-00-- 295

Bacillus Bronchisepticus (Bronchicanis), 295.

Cuarrmn +X. Vill =-GLANDERS GROUP} 2.522400 ee eee 297 Bacillus Mallei, 297.—Bacilli of Selter, Babes, and Kutscher, 308.

CHAPTER X XIX.—INTESTINAL OR COLON-TYPHOID GROUP............ 309

Subgroup I.—Colon Subgroup, 310.—Bacillus Coli, 311.—Bacillus Acidi Lactici, 315.—Bacillus Communior, 316.—Bacillus Coscoroba, 316.—Bacillus Lactis Aérogenes, 316.—Bacillus Cloace, 317.—Organisms Associated with Calf Scours or Calf Diarrhea, 317.—Capsulated Pathogenic Organisms, 319.—Bacillus Pneumonie, 319.

Subgroup II.—Intermediate, Hog-cholera, Enteritidis, or Gartner Subgroup, 320.— Bacillus enteritidis, 321.—Bacillus Choleree Suis, 324.—Bacillus Typhi Suis, 328. —Bacillus Voldagsen, 328.—Bacillus Paratyphosus, 328.—Bacillus Psittacosis, 329.—Bacillus Typhi Murium, 330.—Bacillus Pullorum, 331.

Subgroup IIT.—Typhoid—Dysentery Subgroup, 332.—Bacillus Typhosus, 332.— Bacillus Dysenteriz, 336.

CHAPTER XXX.—BovVINE ABORTION BAcILLUS GROUP............... 339 Bacillus Abortus, 339.

Cuaprer XXXI.—Bacinuvs NECROPHORUS GROUP! 22 0.50 ae ee eee 344 Bacillus Necrophorus, 344.

CuAprur XXX 1L—FLUORESCENT GROUP. 6 4 eee ee 349 Bacillus Pyocyaneus, 349.

CHAPTER XX XIII.—DIPHTHERIA-PSEUDOTUBERCULOSIS GROUP........ 352

Bacillus Pseudotuberculosis, 353.—Bacillus Diphtheriez, ,358.—Bacillus ‘ Hoffmanni, 363.—Bacillus Xerosis, 363.

CHapTrer XX XIV.—SwIneE ERYSIPELAS GROUP.........-.---e0+ eee 364 Bacillus Rhusiopathiz, 364.—Bacillus Murisepticus, 368.

CuaptTerR XX XV.—HEMOGLOBINOPHILIC, OR INFLUENZA GROUP....... 370

Bacillus Pyogenes, 370.—Bacillus Influenze, 374.—Bacillus Pertussis, 374.— Bacillus of Koch-Weeks, 374.

CHaprer XX XVI.—Acip-rast Group... ol. oo. el ea eee BIB ED

Bacillus Tuberculosis, Paratuberculosis, 396.—Bacillus Lepre, 397.—Non-pathogenic Acid-fast Bacteria, 398.—Bacillus Smegmatis, 398.— Dung Bacillus, Grass Bacillus of Moeller, Butter Bacillus, etc., 399.

Guaprirn XXX VIL—Vinrio Groups. ae eee ee eee 400 Vibrio Metchnikovi, 400.—Vibrio Cholerse, 402.—Non-pathogenic Spirilla, 404.

CONTENTS

Cultivation of Spirochetes, 408.—Classification of Spirochetes, 408.—Spirochseta Obermeieri, 409.—Spirocheta Duttoni, 411.—Spirocheta Kochi, 413.—Spirocheta Anserina, 413.—Spirocheta Theileri, 415.—Spirocheta Pallida, 416.— Spirocheta Pertenuis, 419.—Spirocheta Hyos, 419.—Other Spirochetes, 420.

Classification of Actinomyces, 421.—Actinomyces Bovis, 424.—Actinomyces Nocardii, 427.—Actinomyces Capre, 429.—Actinomyces Madure, 430.— Actinomyces of Other Infections, 431.

Cm ei rice ie DLAGTOMYCETHS. sta. Mors in. ot. cera a a oh roe Pah

Blastomyces Farciminosus, 433.—Blastomyces Dermatitidis, 435.—Blastomyces Coccidioides, 438.

Cuirrer <L1.—-Monp orn HYPHOMYCETE GROUP. ..2....6 00sec ees

Aspergillus, 441.—Aspergillus Fumigatus, 443.—Aspergillus Flavus, 446.— Aspergillus Niger, 447.—Other Species of Aspergilli, 448.—Penicillium, 448.— Fusarium, 449.—Fusarium Equinum, 450.—Sporotrichum, 452.—Sporotrichum Beurmanni, 452.—Trichophyton, 456.—Trichophyton Granulosum, 458.— Trichophyton Felineum, 458.—Trichophyton Equinum, 458.—Trichophyton Caninum, 459.—Microsporum, 459.—Microsporum lLanosum, 460.—Microsporum Felineum, 460.—Microsporum Equinum, 461.—Achorion, 461.—Achorion Muris, 461—Achorion Galline, 461.—Oidium Albicans, 463.

Section V Pathogenic Protozoa

CuapterR XLII.—Structurse, RELATIONSHIPS, AND CLASSIFICATION OF EL Bie Ea DZ Ole see rey Meter ems 2 Py 6 Oat A gs So 1 oa PROC ala eee Structure of the Protozoa, 464.—Classification of the Protozoa, 466.

The Genus Trypanosoma, 467.—Morphology, 468.—Cultiyation of Trypanosomes, 470.—Method of Disease Production, 470.—Examination and Staining Methods, .470.—Trypanosoma Equiperdum, 471.—Trypanosoma Evansi, 473.—Trypanosoma Brucei, 474.—Trypanosoma Equinum, 476.—Trypanosoma Dimorphon, 478.—Trypanosoma Congolense, 478.—Trypanosoma Pecaudi, 479.—Trypanosoma Cazalboui, 480.—Trypanosoma Theileri, 481.—Trypanosoma Gambiense, 481.—Trypanosoma Lewisi, 482.—Trypanosoma Hippicum, 483.—The Genus Herpetomonas, 484.—Herpetomonas Donovani, 484.—Leishmania (Herpetomonas?) Infantum, 485.—Leishmania Tropica, 485.

CuHapTerR XLIV.—PatTHocEnNtc PRoTozoA OF THE CLASS RHIZOPODA....

The Genus Entameba, 487.—Staining Methods, 488.—Methods of Isolation and Cultivation, 488.—Entamceba Coli, 489.—Entamceba Histolytica, 490.—Entameeba Tetragena, 493.

ere POROLOA Ty al. eich ls ae eda We ina

The Genus Piroplasma, or Babesia, 495.—Babesia Bigemina, 495.—Babesia Mutans, 497.—Babesia Equi, 497.—Babesia Ovis, 498.—Babesia Canis, 498.— Babesia (Piroplasma) Gibsoni, 500.—Babesia (Piroplasma) Commune, 500.—

Theileria, 502.—Theileria Parva, 502.—The Genus Plasmodium, 502.—Plasmo-° dium Vivax, 502.—Plasmodium Malariz, 504.—Plasmodium Immaculatum and Falciparum, 504.—The Genera Proteosoma, Halteridium, and Hemoproteus, 505.— The Genus Anaplasma, 505.—Anaplasma Marginale, 505.—The Genus Leucocytozoén, 507.—The Genus Eimeria (Coccidium), 508.—Eimeria Avium, 509.— Himeria Stiede, 511.—Eimeria Bovis, 511.—Himeria Faurei, 513.—Isospora Bigemina, 513.

CHapteR XLVI.—Parasitic Protozoa OF THE CILIATA............. Protozoan Commensals of the Rumen and Cecum, 514.—Balantidium Coli, 517.

16 CONTENTS

Section VI

INFECTIOUS DISEASES IN WHICH .THE SPECIFIC CAUSE IS NOT CERTAINLY KNOWN

CHAPTER XLVII.—DiIsEASES PRODUCED BY UNKNOWN ORGANISMS.....

Bacterial or Protozoan Relationships of Ultramicroscopic Organisms, 519.—Virus of Pleuropneumonia, 520.—Virus of Foot-and-mouth Disease, 521.—Virus of

Rinderpest or Cattle Plague, 522.—Virus of Hog-cholera, 524.— Virus of Horse.

Sickness, 526.—Virus of Infectious Anemia of the Horse, 526.—Virus of Dog Distemper, 528.—Virus of Fowl Plague, 528.—Virus of Epithelioma Contagiosum, 529.—Virus of the Poxes, 530.—Virus of Yellow Fever, 531.—Virus of Epidemic Infantile Paralysis, 531.—Virus of Rabies, 532.—Virus of Infectious Agalactia of Sheep and Goats, 535.—Virus of Guinea-pig Plague, 536.—Virus of Fowl Leukemia, 536.—Virus of Certain Chicken Tumors, 536.

Section VII Bacteria Of Water And Food

CuapTreR XLVIII.—BactTeria oF WATER AND WATER PURIFICATION.. Water Purification, 542.

CHarpTeR XLIX.—Mitx. Its Constituents, CONTAMINATION, AND HX AMINATION? (8. cactecet be ctr aera matteo a one oe ne

Influences Which Determine the Ultimate Bacterial Content, 550.—Standards for Production and Distribution of Certified Milk, 553.—Hygiene of the Dairy Under the Supervision and Control of the Veterinarian, 554.—Transportation, 559.— Veterinary Supervision of the Herd, 559.—Bacteriologic Standards, 561.

CHAPTER L.—BAcCTERIA AS THE CAUSE OF Murat PoIsonING

BrBrrioGRAPHIC INDEX (s 50%. See ee ee hoe i a eee

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LOGY. PHYSIOLOGY, AND CLASSIFICATION OF BACTERIA 3

Introduction

BacTERIOLOGY is commonly defined to include a consideration of three distinct groups of minute living organisms: the true bacteria, the molds, and the pathogenic protozoa. Some authorities have objected to the inclusion of a discussion of forms other than the true bacteria under the heading of bacteriology, and have proposed that the term microbiology be used instead. In accordance with this latter conception, the term microbe includes the bacteria, the molds, and the protozoa, and the science of microbiology includes the corresponding subdivisions, bacteriology, mycology, and protozodlogy. As most commonly used, however, the term “bacteriology” is regarded as a synonym of “microbiology,” and in this text this usage will be followed. )

The reasons for including the bacteria, the molds (particularly those pathogenic to animals), and the pathogenic protozoa under bacteriology may be stated briefly as follows: All three groups ‘must be studied by very similar methods. All three contain organisms which are capable of bringing about pathologic conditions in man and animals. The microscopic unicellular animals, known as protozoa, are known to produce disease in some cases, and have been studied largely by means of the laboratory technic developed 2 17 by the bacteriologist. ‘The boundaries between the groups of the bacteria on the one hand and protozoa on the other are likewise far from distinct. In many cases it would prove impossible from a clinical examination alone of a new disease to determine whether it is caused by the invasion of true bacteria or of protozoa. It is evident that there are many practical difficulties in differentiating the bacteria and protozoa.

Furthermore, the line of demarcation between the bacteria and fungi (including the molds, mildews, smuts, rusts, toadstools, puffballs, etc.) is very poorly defined. Particularly is it easy to find all intergradations between the bacteria and those groups of fungi commonly known as yeasts and molds. It appears, therefore, that because of difficulties in differentiation and because of the relationships indicated that a consideration of bacteria, yeasts, molds, and protozoa may all be included under the title of bacteriology.

Parasitology is that branch of science commonly defined to include a discussion of animal parasites, such as the mites, lice, nematodes, and similar types. Sometimes it is held to include consideration of the pathogenic protozoa and the parasitic molds. To this extent the fields of bacteriology and parasitclogy would therefore overlap.

Although bacteriology is one of the youngest of the sciences, nevertheless it has grown so rapidly that many divisions and subdivisions have come to be recognized.

Medical bacteriology may be defined as that branch of bacteriology which treats of those microérganisms (including the true bacteria, molds, and protozoa) that produce disease in the animal body or are related directly or indirectly to the maintenance of health. Agricultural bacteriology, with its subdivisions—sovl bacteriology, dairy bacteriology, and plant bacteriology—includes a consideration of all organisms of importance in soil fertility, in production and distribution of dairy products, in disease causation in plants, and to a certain degree in domestic animals. Sanitary bacteriology has for its field the methods of disease prevention based upon the knowledge of the organisms causing disease and the manner in which they spread. Systematic bacteriology discusses the classification and relationships of organisms. Immunology con-

INTRODUCTION 19 siders the resistance and susceptibility of the body to disease and the means which may be used to increase such resistance.

It is evident from the preceding definitions that the various divisions of bacteriology overlap to a considerable degree.

Veterinary bacteriology may be defined to include that portion of medical bacteriology which concerns those microérganisms (bacteria, yeasts, molds, or protozoa) which affect the health of domestic animals. The history of veterinary bacteriology is closely linked with that of general medical bacteriology, for many of the diseases of man are transmissible to animals and vice versa. lt should be remembered that both are merely subdivisions of a great science, concerning which it is important that the student should gain something of a perspective view, particularly with reference to its history and development. This development has

4a, dices <a Bo a Ss = 7 ————al

Fig. 1.—Leeuwenhoek’s drawings of bacteria: A, B, Bacilli, probably; C—D, path of movement; EH, cocci; F, Leptothrix, probably; G, spirillum.

been so rapid, and so many of the important discoveries have been made within recent years, that it is frequently difficult to determine their relative importance. However, certain facts and personalities stand out so conspicuously that they are deserving of brief consideration.

The Microscope and its Influence.—The existence of living plants or animals smaller than can be seen by the unaided eye was conjectured by several of the Greek philosophers and physicians who used such theories in their speculations on the origin and cause of fermentation and disease. Until the discovery of the microscope such speculations were without any basis in fact.

Leeuwenhoek (1632-1723), in the course of his examinations of a great variety of natural objects by means of the somewhat crude lenses of his own manufacture, chanced to observe the presence of motile and motionless microdrganisms in the tartar from teeth and in various decaying organic materials. His correspondence with the Royal Society of London and the figures published leave no doubt but that he actually observed bacteria. These drawings are of such historic interest that they are here reproduced. / Each advance in the efficiency of the microscope was followed by an advance in our knowledge of the microorganisms, although speculation frequently outran the ability to see clearly. The com- * pound microscope has proved to be indispensable in the study of these forms. Since the introduction of this instrument the degree of magnification, the clearness of definition, and the mechanic ar- ‘rangements for accurate focusing have been gradually improved until at the present time the homogeneous oil immersion objective, the compensating ocular, and the Abbé condenser are in constant use in the laboratory, and enable us to secure readily magnification to 1500 diameters or more. During the last several decades there has been little increase in magnification, due to two reasons. The greater the magnification the more convex and consequently the smaller must be the lenses used in the objectives, and the more difficult becomes their grinding and adjustment. Furthermore, the physicist tells us that a clear view, with determination of the size and shape of microscopic objects, cannot be obtained when the objects examined are smaller than one-half the wave length of the rays of light in which they are examined. There is thus a seemingly insurmountable barrier set to an indefinite increase in magnification. | A recent advance has been made through the development of the ultramicroscope. This has made visible objects much smaller than those which had been previously observed. A bright gleam of light from an arc or similar source is passed across the darkened field of the microscope, and the light is reflected to the eye from any particles that may be in suspension. These objects are seen in the same manner that minute particles of dust are made visible in a bright ray of light that enters a darkened room. The use of the ultramicroscope has not as yet added many facts of value to our knowledge of the bacteria.

_ INTRODUCTION | 21

Nature and Classification of Microorganisms.—Leeuwenhoek, | whom we have seen to be the first observer of bacteria, contributed ‘very little to a knowledge of their essential nature. F. Miller © (1786) worked out a simple classification, but did not differentiate ‘between: bacteria and protozoa. To him we owe several of the group names applied to bacteria, such as bacillus, vibrio, spirillum. Ehrenberg (1795-1875), with the improved microscope and lenses at his command, prepared the first logical classification of bacteria. Cohn (1828-1898) elaborated and modified Ehrenberg’s classification. He differentiated the true bacteria from the protozoa, and his arrangement is the basis for the classification used most extensively at present. With the continued improvement in the microscope and laboratory technic, more careful studies of structure, form, and relationships have been rendered possible, and many classifications and groupings for bacteria have been suggested. The difficulty in finding morphologic characters that are accurate indices to true relationships has made the subject a troublesome one. The classification of bacteria most commonly in use at present is that of Migula, published in 1897 in Engler and Prantl’s “Synopsis of the Genera of Plants.” As will be seen from the discussion recorded in Chapter V, under the heading of Classification, even this system is not wholly satisfactory.

Spontaneous Generation.—In ancient times and even during the middle ages it was generally held by the philosophers and scientists that living things, animals, and plants, could arise de novo. Among the first observations that created doubt in man’s mind as to the validity of this belief was that of Francisco Redi, who covered meat with gauze to protect it from flies, and found that maggots did not develop in it spontaneously, but arose from the eggs which the flies deposited on the screen. This pointed the path for other similar studies, and it was not long before the idea of spontaneous generation of the higher forms of life was aban- _doned. When the microscope revealed the presence of myriads of microdrganisms in all decaying or putrefying materials, it was concluded that these organisms arose without progenitors of their own kind, but directly from the organic materials of their surroundings. Boiling was believed to certainly destroy all life, a2 VETERINARY BACTERIOLOGY yet it was found that boiled decoctions would not always remain free from microérganisms. The theory of spontaneous generation of these bacteria was opposed by some and supported vigorously by others of the best scientists of the time. Experiments were carefully planned and a great variety of materials used, paving the way for the development later of the laboratory technic of the bacteriologist. The sterilizing action of heat, the antiseptic action of certain chemicals, and the value of the cotton plug as a bacterial filter were demonstrated. The theory of spontaneous generation as a topic of contention practically disappeared about 1860. This was largely due to the efforts of Pasteur, who, by a long series of ingenious experiments, overthrew the last defense of the supporters of the theory. The dictum, omne. vivum ex vivo (all life from life), is universally accepted at the present time, and the controversy has little but historic interest.

Relationships of Microérganisms to Fermentation and Decay.— As has been previously noted, some of the early philosophers hazarded the opinion that decay might be caused by invisible living beings of some kind. The causal relationship of microorganisms to decay and particularly to fermentation was first definitely established by the work of Louis Pasteur (1822-1895). He found the production of alcohol and carbon dioxid from sugar was due to a yeast, that milk soured because of the activity of bacteria, and that many of the familiar changes in organic substances were accomplished by microdrganisms. His conclusions were strenuously opposed and ridiculed by the great German chemist, Liebig. Doubtless the necessity for meeting the attacks of the latter and of establishing his points beyond possibility of refutation led him to devise and develop many of the laboratory methods in common use at the present time. As a result of Pasteur’s work the fundamental importance of bacteria in the transformation of nitrogen and carbon compounds in nature, the disposal of waste, the purification of water, the enriching of the soil, and many of the changes in the manufacture of foods have been established.

Relationship of Microorganisms to Disease.—The probable causal relationship of microdrganisms of some kind to disease was argued as long ago as 1762 by Plenciz, of Vienna. His

INTRODUCTION 23 theories were not generally accepted, and it was not until 1840 that Henle proposed what we have come to call the germ theory of disease. He never succeeded in proving his point satisfactorily because of the lack of proper methods and technic. Many other writers within the next few years discussed the theory and numerous facts were adduced in favor of it. The majority of medical practitioners, however, put very little faith in it. The argument that certain organisms were always present was met with the statement that these organisms were the result and not the cause of the disease. Davaine (1863) practically demonstrated by inoculation experiments the causal relationship of a bacillus he found in the blood of diseased animals to anthrax. Pasteur (1865) proved the cause of a silkworm disease to be a protozoan parasite. Koch and Pasteur later cultivated the anthrax organism in the laboratory and showed beyond a doubt its relationship to the specific disease. Improved laboratory technic cleared up the cause of many diseases within the next decade or two. The discovery of the Bacillus tuberculosis by Koch (1882) marks the real beginning of bacteriologic science. The knowledge of protozoa as a cause of disease lagged somewhat behind that of bacterial infections. Evans (1880) described the trypanosome of surra and transmitted the disease by inoculation experiments. In 1882 Laveran observed the Plasmodium malarie, the cause of malaria. | Development of Laboratory Methods.—Progress was delayed in the study of objects as minute as the bacteria because of the lack of proper methods for their isolation, observation, and identification. Culture-media in which the pathogenic microérganisms could be grown were used by Pasteur and Koch. To the latter we are indebted (1882) for our knowledge of the solid media which can be used for the isolation of organisms from mixed cultures. The importance of this contribution can hardly be overestimated, for the use of pure cultures lies at the very foundation of all modern bacteriologic investigation. This one discovery accounts in large measure for the rapid advance made during the next two decades in the identification of the organisms producing disease. The use of aniline dyes in rendering cells and their structure more plainly visible under the microscope we owe to Weigert, but the application to bacteriology was made by Koch. Since their introduction successive advances in staining technic have in every instance been followed by the discovery of new organisms related to disease. The microscope, liquefiable media, and anilin dyes constitute the trio of most important factors in the development of the science of bacteriology.

Development of Theories of Immunity.— Knowledge that one attack of certain diseases generally prevented a recurrence and that diseases could not be indiscriminately transferred to all species of animals has existed ever since the foundation of medicine. Many theories have been advanced to account for this phenomenon. A few of the names of investigators who have put the facts into logical form for presentation and study should be considered. Metchnikoff conceived that the white blood-corpuscles and some other body cells acted as scavengers and destroyed microérganisms in the blood. This theory in modified form furnishes to-day the logical basis for many of the operations of the practitioner. Von Behring (1890) published results of studies on the diphtheria bacillus in which he recounted the discovery of the specific toxin of this organism and a specific antitoxin. He laid the foundation for the present-day ‘ humoral ” theory of immunity, which supplements so well the phagocytic theories of Metchnikoff. Ehrlich has correlated and coérdinated the various facts of the humoral theory and has made substantial additions toit. He has created a terminology which has been quite generally accepted and has proved most useful in discussion of the subject. So extensive have been researches in the field of immunity during the last two decades (since 1890) that it has assumed almost the rank of a codrdinate science. ee

Development of Sanitary Science and Preventive Medicine.— In 1858 Murchison formulated the so-called pythogenic theory of disease—1.e., that disease is caused by the emanations arising from decaying or putrefying organic matter, and by the consumption of such materials in water and food. This theory was quite commonly accepted, and its practical applications form the basis for our modern sanitary science. The disposal of sewage and refuse, the purification of drinking-water, and adequate systems of plumbing were advocated and adopted before the germ theory of disease