: Qlfl z.t I i Ujii ..I "' I Cornell University Librar« QR 121.K28 Bacteria and their relaWons to da^^^^^^^ 3 1924 003 232 257 DATE DUE DEMCO 38-297 ^ •-tJu-kRxAAj>jujuvAiC'^ I^aX Olm-UUS^ o BACTERIA AND THEIR RELATIONS TO DAIRYING, LECTURE BY SIMEON C. KEITH, Jr., BOSTON, MASS. Delivered at the Maine State Dairy Meeting at Bangor, December 2, 1897. / ^ / A BACTERIA AND THEIR RELATIONS TO DAIRYING. By Simeon C. Keith, Jr., Boston, Mass. Among the most numerous and wide-spread of all living things is a group of small plants that have undoubtedly existed for ages and yet have escaped discovery until comparatively recent times. I refer to the organisms called bacteria which are more commonly known as germs. They were discovered some two hundred years ago, by a Dutch mechanician who constructed a magnifying glass that was so far superior to anything ever before made, that with it he was the first to see in putrefying liquids, such as beef-juice, etc., little animals as he called them, because many of them had the power of motion. Little more was known about them, however, until the beginning of the present century, when the forms were roughly classified and a hint at the truth arrived at, namely: that the germs found in putrefying liquids were the cause of the spoiling. It was gen- erally supposed, however, that putrefactive substances, like meat, etc., spoil spontaneously, in other words that the germs had their origin directly from, the matter in which they were found. This idea of spontaneous generation was generally held up to the time Pasteur, who finally disproved it by show- ing that matter that was subject to spoiling, never did so unless bacteria from without were introduced into it, or as he expressed it, life always proceeds from pre-existing life. As I have pre- viously said, the bacteria are plants and are closely related to the molds and yeasts which we are all more or less familiar with. They are, furthermore, the simplest in structure of all the plants in the world, having as they do neither root, stem nor leaf. They consist simply of a very minute case filled with living matter, which is called protoplasm. Yet these little living cells are capable of nourishment, growth and reproduc- tion, the essential functions of all life. The number of shapes bacteria may have is very Hmited, in fact, there are only three fundamental forms of bacteria and these may be described as ball shape, rod or sausage shape, and spiral or corkscrew shape. A B O CZZ3 Fig. I— Types of Bacteria. A — Micrococcus. B— Bacillus. C— Spirillum. The bacteria are exceedingly small and in general may be said to be about one twenty-five thousandth of an inch in diam- eter. If a common sausage and a bacterium could be magni- fied alike, so that the bacteria would be as large as sausages, the sausage itself would be about three miles long and 2,500 feet in diameter. Up to the present time, some fifteen hundred species of bacteria have been described, which number pirobably represents, however, only a part of the varieties that really exist. Out of the known kinds there are few that are really detrimental to our health, only about iifty in all, while the remainder are either useful or harmless. You have proba- bly been wondering, by this time, how it is possible for us to distinguish so many varieties, when there are only three forms to go by? While I cannot enter into this particular subject in detail, I will say that we find differences in bacteria, mainly from studying the effect on various substances in which they grow; in milk, for instance, some germs produce souring, some a rennet action and others a gaseous fermentation. Other differences are found in a similar way by growing the germs on other substances, so that in a complete description of a bacterium, we have beside the shape and size, some ten other differences, which are mainly of function. The bacteria increase in numbers by a simple splitting of the cell into two or more, and under favorable conditions a single generation is completed in about twenty minutes so that in the course of five hours, starting from a single germ and allow- ing that one cell separated into two each twenty minutes, we should have over 250,000 bacteria produced as the result. A . 3 a_ ( ) Fig. II— Showing method of reproduction in haoteria by transverse division of the cell. A, B, 0, etc., successive stages of the reproduction of a bacillus during two generations. The soil seems to be the normal habitat for most bacteria, and in the top layers of it billions to each handful are not unusual numbers. As we pass into the lower layers of the soil, we find the number of bacteria growing less and less, and at a depth of about six feet there are practically none. I call especial attention to bacteria in the soil, for here is the real source of many of the bacteria found in water (as the water washes the germs from the soil) also of the normal bacterial of the air (the drying of the soil and its being blown by the winds into the air.) Having seen what the bacteria are, let us see how they effect the dairyman. Now milk from a normal, healthy cow, if drawn under proper conditions, is free from a very undesirable prop- erty which most milk has, that is, it will not spoil and is there- fore free from bacteria. If, however, care is not taken in the experiment, the milk soon spoils, and the reason is, that the milk in the first place is a good food for bacteria to live upon, and secondly, that some bacteria got into the milk. Milk as it is delivered in the city is swarming with these bacteria, and is consequently partially decayed. It is not unusual in city milk to find from five tO' ten millioni to each cc. (A cubic centi- meter being about half a thimbleful.) These bacteria are trace- able to various sources, one of the principal being the dust of the stable. Compared with outside air, the air of the stable is particularly rich in bacteria, and when the milker begins his task, often hay, which is well known to be full of dust, has just been pulled down from the loft and possibly fed to the cattle; then again I have often seen hay hanging through loose plank- ing, over the cows, and at times the cows backs are well nigh hidden from view with hayseed, etc. All of this dust has its effect on the milk, causing it to spoil and furthermore to be very dirty. This source of trouble is easily remedied by mak- ing a rule to never move hay in a stable for some hours before milking is begun, and further by sheathing up the ceiling of the tie-up. Of course I only offer this suggestion when it is impossible tO' keep the cows in a separate building, from that in which the hay is kept, — this being the ideal plan. Another cause of the infection of milk, and further, perhaps one of the most objectionable ones, in many respects, is from cow-dung. The decomposed and digested food of animals is ooqe of the richest sources of certain bacteria, and these great numbers persist in the dung to such an extent, that an exceed- ingly small amount of it is sufiScient to inoculate and spoil a Fig. 3— (Eaw inilk, 7,741 colonies). Fig. 4 — Normal milk, no colonies. Photographs of gelatin plate cultures showing the relative numbers of bacteria In equal quantities of ordinary milk and normal milk (condition of milk in cows udder). whole pailful of milk. We have all been in stables where cows were improperly cared for, and seen them in many instances almost covered with dried excrement. A farmer can do no better thing to lower the quality of his dairy products, than to Fig. 5— Petri plate exposed two minutes out of doors. Contains six colonies. Flo. 6— Petri plate exposed two minutes in barn. Contains ill colonies. Fio. 7— Petri plate exposed two minutes under cow being milked. Contains 1,800 colonies. Photograpbs of gelatin plate cultures— showing the relative numbers of bacteria In air outdoors, in a barn and under a cow while being milked (each white spot represent^ the result of growth of a"gingle bacterium settling on the gelatin during the two minutes exposure.) 8 be lax in this particular, and I cannot emphasize this point too stronig-ly, for I am convinced that it requires more attention than it is receiving to-day, as when dry, the excrement is easily dislodged from its tetraporary resting place, tO' find its way to the milk-pail. Again it sometimies gets there from the cow switching her tail, and sometimes the tail itself gets into the milk. Keep the cow clean. Card her and care for her, and have a couple of clean cloths ready, so that before milking you can carefully wipe off the udder, thus removing any loose hairs and dirt that may be there. Do this and see if you are not more than repaid for your trouble, in that your milk and dairy products will be better for it, and further that you will be setting the ex- ample for others. Personal cleanliness is the next subject I wish to call your attention to and it is in some respects the most important of all. We can consume milk infected with bacteria from many sources without harm, but when the germs of disease are there, it is time for us to take warning. Now there has been a great deal of talk about Bovine Tuberculosis and rightfully so, too, I believe. But a factor that is little recognized is possibly doing more harm than the tuberculosis in spreading disease, especially in our large cities, that depend as you know on the country for their milk supply. Disease may be introduced by the men that handle the milk from its start in the country to its delivery in the city to the consumer, and every person handling such milk may add his or her share to the disease-dealing qualities of it. Several of the worst epidemics of typhoid fever in Massachusetts have' been traced by Prof. William T. Sedgwick of the State Board of Health, to a contaminated milk supply. This can be to a great extent prevented by suitable care and if a rule could be adopted, that before milking or handling milk, the hands of the person be carefully washed and the nails cleaned, I am sure that it would be a long step forward in securing what we want at the present day, pure, clean and safe food. Aside from the sanitary point of view, the point of cleanliness itself is worth thinking about, for I am sure that you will admit that you would hardly want your wife to make bread with hands in the condition that you and I have seen milkers' hands, which often get washed with the milk as you know; and after all, milk is a food as well as bread. Milk utensils deserve a word, in that they, too, when improp- erly cleaned, or made in such a way that it is impossible to clean them, add their share of bacteria infection to milk. All utensils, therefore, should be cleaned very carefully and, if pos- sible, sihould be sterilized with live steam before using them. Dr. Russell of the Wisconsin Experiment Station recommends that all seams in crevices in pails and cans, be filled up flush with solder, and I can heartily recommend the proceeding, for the point of a dirty can alone, is enough when the case is aggravated, to cause very bad results in the dairy. You will see then that milk is a very susceptible liquid to infection from bacteria from various sources, and if we had to drink water containing as much filth and bacteria as milk contains, we should certainly criticise the health authorities strongly. Bear- ing these facts in mind, you will note that the cleaner you are in the dairy, the more you reach the ideal, normal condition of milk, and as a result the quality of your dairy products will be raised correspondingly, both from a sanitary and money stand- point, and it is my hope that you may act along the lines that I have indicated, for my observation shows that until this is done, no great advance can be made in the dairy industries in this or any other state. Ques. Does milk drawn from a cow infected with tubercu- losis contain tuberculosis bacteria? Ans. It may or may not. Cows infected with tuberculosis of the udder are certainly dangerous animals to have, but I do not think there is any method by which we can tell whether a cow has tuberculosis of the udder or not to a certainty without killing her, and subjecting the udder to experts. Ques. Would it not be very difificult to find the bacteria? Ans. It is impossible to find them by microscopical examin- ation. The way we have proven their presence is this : a small portion of the milk taken from a tuberculous cow has been injected into healthy Guinea pigs, and after a time those Guinea pigs developed the disease of tuberculosis in so marked a degree that there can be no doubt that the milk must have had the germs' of tuberculosis in it. Ques. May you not try a great many experiments of that sort and have the tuberculosis show itself in but very few? 10 Ans. Yes, indeed. I do not think that twenity-five per cent of the cows that respond to the tuberculin test have tuberculosis of the udder. Ques. Do cows have tuberculosis without having the lungs afifected? Ans. They do certainly. It is not necessary that the source of the disease sihall be in the lungs. There are a great many cases of tuberculosis of human beings in which the disease is not in the lungs at all. It may be in the alimentary canal the stomach, or the intestines. Ques. Is the beef of an animal diseased with tuberculosis healthful? Ans. I dt> not think it is unheathful if it is thoroughly cooked. Cooked bacteria are harmless. Ques. Can you tell us how tuberculin is manufactured? Ans. Tuberculin is made from a pure culture of the bacilli of tuberculosis which are obtained from people or animals that have died from the disease. Generally a piece of the lung, or a piece of diseased tissue, is taken, and by a tedious method we get a pure culture of the typical bacteria from it. Tlien this is inoculated into a flask of bouillon, and in that it develops, producing a toxine or poison, which is the active principle of the bacillus. The bacillus itself is not so damaging in many ways as the poison produced by it. The poison is separated from the germs and, when mixed with glycerine, forms tuberculin. The real, active principle of tuberculin is the poison produced by the germ when growing under artificial conditions in a culture medium. A Pasteur filter is used to separate the germs from the toxine. Ques. What effect does tuberculin have on the animal? Ans. Upon a healthy animal it does not have any effect as far as we know, if it is properly prepared. If, however, we have a cracked filter, and some of the germs get through, we are very apt to give the animal tuberculosis. But tuberculin from, reli- able laboratories contains no germs of tuberculosis, and is o^nly the pure poison. When that is injected into a cow having tub- erculosis, a number of hours afterwards there will be a 'rise of temperature, and that rise of temperature is the indication of the disease. II Ques. Is the rise of temperature in proportion to the severity of the disease ? Ans. I think not. Ques. How many degrees does the temperature rise? Ans. Only a very little. Ques. Do the germs of tuberculosis increase rapidly? Ans. They increase very slowly. Ordinary bacteria multi- ply once every twenty minutes, whereas you would not get more than one division in twenty-four hours in tuberculosis. There would be practically no more germs of tuberculosis in milk at the end of the time in which it would be used than when first drawn from the udder. In the preparation of antitoxine for diphtheria, the same pro- cess is followed as in the preparation of tuberculin up to that point, but instead of stopping there an antitoxine is made by inoculating horses with some of the diphtheria toxine every day, or every two days, and gradually increasing the dose until the horse can finally stand eruough to kill a dozen horses if given them at first. Very small doses are given at first, but after a few months the horses will get so that they can stand immense doses, and their system gets into a condition in which the blood has the power of neutralizing some of the poison. The great danger in a case of diphtheria is from the poison that is produced by the germs in the throat, and the antitoxine is injected into the system to neutralize that poison. No one who has ever seen the workings of antitoxine can doubt its efficacy for an instant. If two Guinea pigs be taken, and enough toxine is injected into them to kill both, and then one of them is given a dose of anti- toxine, in twenty-four hours the one that has received the toxine only is dead, and the other, that has received the toxine plus the antitoxine, is as well as ever it was. Ques. Does injecting tuberculin into a cow have any effect on the milk usually? Ans. I think not, because the milk glands are really separate from the other organs of the body. They are only supplied with blood which nourishes the cells of the milk glands. These cells swell up and burst, and the liquid flowing out of the cells is the milk. I do not think the milk would be affected unless the dosing was kept up too- long. 12 Ques. Is it possible tO' tell what stage the tuberculosis has reached in the animal by the use of tuberculin? Ans. It is not, because very mild cases seem to respond as readily to the tuberculin test as very severe ones. In fact, there are some cases in which diseased animals do not seem to respond, and I think there are occasionally some instances where healthy animals do respond. I iii