According to their staining-reactions bacteria may be very conveniently grouped in three classes: 1, Staining with Gram-Weigert’s method; 2, Not staining with Gram-Weigert’s; 3, Staining with the tubercle-bacillus method (acid-resisting).
1. BACTERIA STAINING BY THE GRAM-WEIGERT METHOD.
Weigert’s modification of Gram’s method, as given above for the staining of fibrin, is the best for the staining of bacteria that stain by this method. (See Fibrin, Chapter [XXVI].) The differentiation with aniline-xylol is slower and safer than with alcohol. Acetone-xylol (1:5) has been recommended in place of aniline-xylol. Wolbach recommends the use of a 5-10 per cent colophonium-alcohol for differentiation. Contrast staining with watery Bismarck brown, dilute carbol-fuchsin or eosin may be carried out if desired. The aniline-xylol may be saturated with eosin and the section stained during the differentiation. Carbol-gentian-violet may be used instead of aniline-gentian-violet; it keeps much better than the latter.
Staining by Gram’s Method (Gram-positive).
Staphylococcus pyogenes aureus.
Staphylococcus pyogenes albus.
Staphylococcus pyogenes citreus.
Streptococcus pyogenes.
Micrococcus tetragenus.
Diplococcus pneumoniæ.
Bacillus aërogenes capsulatus.
Bacillus of diphtheria.
Bacillus of anthrax.
Bacillus of leprosy.
Bacillus of tetanus.
Bacillus of tuberculosis.
Bacillus of rhinoscleroma.
Bacillus of mouse septicæmia.
Bacillus of swine erysipelas.
Oïdium albicans.
Mycelium of actinomyces.
2. BACTERIA NOT STAINING BY GRAM’S METHOD.
For the bacteria belonging to this class Löffler’s methylene-blue, carbol methylene-blue, a watery solution of methylene-blue or gentian-violet, Leishman’s or Wright’s modification of Romanowsky’s methylene-blue eosin method (see page [290]), Unna’s alkaline methylene-blue solution preceded by eosin after Zenker’s fixation (see page [260]), aniline gentian-violet, Zieler’s method and carbol fuchsin are most commonly used as stains. Wolbach advises the use of a 5-10 per cent acetone-colophonium solution for the differentiation of Gram-negative bacteria in tissue fixed in formol.
1. Löffler’s Methylene-blue.
1. Saturated alcoholic solution of methylene-blue 30 cc.; potassium hydrate solution (1 in 10,000) 100 cc.
2. Stain 5 minutes to 24 hours.