7.3.6: *Bacteriology*

Crofton, W. M.. Pulmonary Tuberculosis: Its Diagnosis, Prevention and Treatment. (Philadelphia: P. Blakiston’s Son & Co., 1917). 1-7.

CHAPTER I.

BACTERIOLOGY.

The tubercle bacillus, the cause of tuberculosis, belongs to a group of micro-organisms having the generic name of Streptothrices or Discomycetes, since they include a small mycelial stage in their life histories.

// how do we define something? //

In the lesions they occur as bacilli 2-5 p. to 5 p. in length and about 3 in thickness. They are straight or slightly curved, and usually stain evenly along their length. Quite commonly, however,

// taxonomies based on vague descriptions //

unstained areas are left, giving a somewhat beaded appearance. Sometimes a slight swelling at one end is seen, and frequently, in tubercular sputum for instance, one sees little groups of granules staining characteristically like the bacilli,

// in absence of the illustration //

// of the photograph //

// the author tries to define vision //

that is exhibiting ‘ acid fastness,’ not being decolorised by treatment with 25 per cent. sulphuric or other strong acid when stained.

Now and then in the lesions one finds the bacilli forming short filaments, sometimes branched. When injected under the dura mater of a rabbit or into a solid organ like the kidney, spherical masses some times form consisting of radiating filaments with clubbed ends. These ends do not exhibit acid fastness, but stain by the Gram-Weigert method.

// various methods of staining are called for //

// dependent on the time and quality of the bacillus //

// which are being distilled //

In old cultures quite considerably branched filaments may form, and one frequently comes across long, slender, non-acid fast, tapering bacilli, sometimes in young, but especially in old egg medium cultures.

// various media need to be managed //

// various material are needed to feed the bacilli //

In lesions, too, non-acid fast tubercle bacilli occur, and non-acid fast granules.

By far the best method for exhibiting acid fastness is the Ziehl-Neelsen staining process ; whilst in the non-acid fast stages the microbe is best stained by Gram’s method, or one of its modifications, such as Much’s (vide Appendix).

// implicit in this writing is a foregrounded knowledge //

// that we, of course, know the processes of staining //

// and the various scientists who developed these methods //

There are two chief types of the tubercle bacillus which infect man, viz., the Human type and the Bovine type. The latter is as a rule shorter, thicker, and more regular than the human type, when obtained from cultures. It grows more slowly on culture media and is much more virulent for oxen and rabbits than the human type.

CULTIVATION—The Human Type.—On inspissated blood serum it first appears as little, somewhat heaped-up granular masses, which gradually spread by wavy margins until they coalesce to form a wrinkled, dull yellowish skin, which turns more buff-coloured with age.

// it is so odd to me //

// how much management of the living //

// is required in this discourse //

On Dorset’s egg medium, with or without glycerine, the growth often becomes heaped up into granular masses having a cheesy consistency.

// that one must cultivate the bacilli //

// raise them in their constructed environment //

// like a farm animal (and not unlike the animals they raise) //

// (to infect, kill, and inspect) //

In glycerine veal broth it forms little white masses which fall to the bottom, While On the surface a white pellicle forms, which may spread up on the side of the glass.

The Bovine Type.—This bacillus grows much slower as a rule, but eventually forms similar heaped-up cheesy masses on Dorset egg medium. Glycerine is said to inhibit its growth, but I have found that it grows well enough on this medium, especially if when making the primary cultures a piece of the infected tissue is left on the medium. It is well to do this in all cases, whether the microbe is human or bovine. If the primary culture is being made from sputum after treatment with antiformin without passage through a rabbit or guinea-pig, fresh human blood in the medium is always an advantage.

Like other microbes, there is a marked difference in the virulence of the microbes in various strains. One strain of bovine bacillus I have largely used will produce generalised tuberculosis and death of rabbits in from seventeen to thirty days with as small a dose as 25 millions given intravenously ; while another strain took two months or more.

// on the bright side, we are getting really good at killing rabbits //

In lupus vulgaris strains of low virulence both of the human and bovine type have been obtained. Both human and bovine types have been isolated from tuberculosis of the lungs in man. There is no difference in the type of disease they produce. Not infrequently the infection is mixed.

The rapidity of infection in oxen and rabbits is the chief criterion for distinguishing the two types. A subcutaneous injection of human tubercular material into a cow merely produces a local lesion which afterwards heals, while bovine material produces a local and general infection and death.

In rabbits, too, an intravenous injection of bovine bacilli produces a rapidly fatal generalised tuberculosis.

An intraperitoneal injection produces a rapid general peritonitis and generalised tuberculosis. Besides the tubercle bacillus, other microbes, either in pure culture or in various combinations, are invariably found in the sputum of patients suffering from pulmonary tuberculosis. The kinds generally found are those that commonly produce nasal catarrh, bronchitis, pyorrhea alveolaris, and tonsilitis.

// i’m cutting a list of microbes //

//

// from this source //

// for sake of space //

It must not be forgotten that, besides being open to infection along the respiratory tract, the lungs share with the spleen and liver the distinction of being one of the chief sites for the filtering off and phagocytosis of microbes, so that the tubercular lesions may be infected secondarily through the blood-stream.

By far the most common combination to find is the Micrococcus catarrhalis and streptococci. Staphylococci and streptococci are often found working together too, and the pneumococcus generally has some other microbe helping it along. The small Gram-negative non-motile bacillus is very common and very poisonous. Bacillus pyocyaneus and Bacillus coll are rare, as is the true influenza bacillus. As we shall see later, it is much safer for treatment purposes to treat all microbes that grow at 37 deg. C. as infecting the patient and not to consider a microbe which has not been described as not being pathogenic. Microbes have an exceptional faculty for becoming pathogenic if the resistance of the tissues is lowered.

While we may identify a particular microbe by its morphology and cultural characteristics, we may be still completely ignorant as to its toxicity for the human being.

// all the gesticulations to describe a certain ignorance //

// but imply the value of future research //

// on the certainty that knowledge can be gleaned //

The toxicity of various strains differs most remarkably. The difficulty in getting effective antisera against the pneumococcus, meningococcus, etc., demonstrates quite clearly that the antibodies produced against one strain are practically useless against another.

This is quite easily understandable. The mere fact that the microbe is multiplying in the patient’s tissues means that it has completely adapted itself to its environment, that is, has developed a ferment (toxin) that can break down that patient’s protoplasm.

// this logic assumes that presence is always already a problem //

// that the body cannot be a host //

// but always a victim //

But that particular strain of microbes might be quite helpless in the environment of another individual until, if it survived, it had after many generations produced a toxin capable of breaking down the new individual’s protoplasm ; this toxin must differ more or less in quality from what it was in the first individual. The consequence of this is that for the purposes of treatment by vaccines one must make the vaccine from the patient’s own strain of microbes.

// it is worth noting that vaccines were different //

// than our contemporary ones //

It seems to me much better to grow all our microbes for vaccine purposes on fresh human blood-agar, since it is probable that they lose toxicity least when grown on medium containing fresh human blood.

// like creates like //

Of course it would be ideal if the blood used was that of the patient. Most of the microbes infecting the chest grow best on medium containing fresh human blood. The reaction of the medium must be + 10, and it must not have been heated over 100 deg. C. during preparation.

It will be clearly understood, then, that the following descriptions are of the morphology and cultural characteristics of typical members of main groups, the variations of type inside which are infinite.

// needing some boundaries //

// visual or otherwise //

// for an object in motion //