Staphylococci, pneumococci, and streptococci are probably the most common of the bacteria to be found in nonspecific conjunctivitis and keratitis. The usual cause of acute infectious conjunctivitis, especially in cities, seems to be the Koch-Weeks bacillus. This is a minute, slender rod, which lies within and between the pus-corpuscles (Fig. 125), and is negative to Gram's stain. In smears it cannot be distinguished from the influenza bacillus, although its length is somewhat greater. The diplobacillus of Morax and Axenfeld gives rise to an acute or chronic blepharo-conjunctivitis without follicles or membrane, for which zinc sulphate seems to be a specific. It is widely distributed geographically, and is common in many regions. The organism is a short, thick diplobacillus, is frequently intracellular, and is Gram-negative (Fig. 126). A delicate capsule can sometimes be made out.
| FIG. 126.—The diplobacillus of Morax and Axenfeld (from a preparation by Dr. Harold Gifford). |
Early diagnosis of gonorrheal ophthalmia is extremely important, and can be made with certainty only by detection of gonococci in the discharge. They are easily found in smears from untreated cases. After treatment is begun they soon disappear, even though the discharge continues.
Pseudomembranous conjunctivitis generally shows either streptococci or diphtheria bacilli. In diagnosing diphtheric conjunctivitis, one must be on his guard against the xerosis bacillus, which is a frequent inhabitant of the conjunctival sac in healthy persons, and which is identical morphologically with the diphtheria bacillus. The clinical picture is hence more significant than the microscopic findings.
Various micro-organisms—bacteria, molds, protozoa—have been described in connection with trachoma, but the specific organism of the disease is not definitely known.
THE EAR
By far the most frequent exciting causes of acute otitis media are the pneumococcus and the streptococcus. The finding of other bacteria in the discharge generally indicates a secondary infection, except in cases complicating infectious diseases, such as typhoid fever, diphtheria, and influenza. Discharges which have continued for some time are practically always contaminated with the staphylococcus. The presence of the streptococcus should be a cause of uneasiness, since it much more frequently leads to mastoid disease and meningitis than does the pneumococcus. The staphylococcus, bacillus of Friedländer, colon bacillus, and Bacillus pyocyaneus may be met in chronic middle-ear disease.
In tuberculous disease the tubercle bacillus is present in the discharge, but its detection offers some difficulties. It is rarely easy to find, and precautions must always be taken to exclude the smegma and other acid-fast bacilli ([p. 35]), which are especially liable to be present in the ear. Rather striking is the tendency of old squamous cells to retain the red stain, and fragments of such cells may mislead the unwary.
PARASITIC DISEASES OF THE SKIN