Gill (1938, 1942), Whalen (1938), and Dobes (1943), have also emphasized the

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1 EXTERNAL OTITIS, WITH ADDITIONAL STUDIES ON THE GENUS PSEUDOMONAS1 S. B. SALVIN2 AND M. L. LEWIS3 Naval Medical Research Institute, National Naval Medical Center, Bethesda 14, Maryland Received for publication July 23, 1945 Bacterial or fungous infections of the ear canal have been recognized and described repeatedly. However, there has been a pronounced difference of opinion as to the principal etiologic organisms and the exact sources of infection. Since the authors were in contact with many cases of external otitis, a study of 100 consecutive new or acute cases was undertaken in order (a) to determine the relative frequency of fungi and bacteria as infective agents, (b) to learn of any possible relationship between the severity of the condition and the type of organism isolated, and (c) to provide material for further investigations on the characteristics of the principal pathogenic organism or organisms. No cases of chronic otitis externa were included in this series. I Some investigators (Minchew, Collins, and Harris, 1940) claim that there is no appreciable difference in the bacterial flora of pathologic ear canals as compared with that of the normal, and therefore that fungi (chiefly members of the genus Aspergillus) are the important etiologic organisms. Others, such as Gill (1938, 1942), Whalen (1938), and Dobes (1943), have also emphasized the importance of fungi in this disease. On the other hand, the results of Williams, Montgomery, and Powell (1939) indicate that bacteria are the most prominent organisms in diseased ear canals, with fungi present in only a small minorityof cases. A few authors have indicated the possible role of Pseudomonas types as the causative agent in otitis externa (Morley, 1938; Dagget, 1942; Davis, 1943). Materials and Methods After the ear canal had been sponged with 70 per cent alcohol and dried with sterile cotton, samples for culturing were obtained by scraping the epithelium with a small, sterile curette and by streaking the resultant material on three different media: Saboraud's maltose agar (for the isolation of fungi), 0.5 per cent glucose blood agar (for the cultivation of hemolytic bacteria), and Difco nutrient agar (for the isolation of less fastidious organisms). The tubes and plates were then incubated at room temperature for 24 to 96 hours before examination. The resulting growth, when fungal, was examined after fixation and staining in a 1 The opinions or assertions contained herein are the private ones of the writers and are not to be construed as official or reflecting the views of the Navy Department or the naval service at large. 2 Lt. (j.g.), H (S), U.S.N.R. 'Lt., H(S), U.S.N.R. 495

2 496 S. B. SALVIN AND M. L. LEWIS lactophenol cotton blue solution; when bacterial, after staining with methylene blue and Gram's stain. Some of the isolated bacteria, notably members of the genus Pseudomonas, were further studied. Data were obtained from each of the patients concerning (1) his original home locality, (2) age, (3) sex, (4) race, (5) history of previous ear pathology, (6) present residence, (7) recent or pertinent water contacts, including swimming pools, and (8) symptoms of disease at the time of first reporting. In each case, in order to standardize therapeutic methods, the treatment was the same- 'namely, gentle cleansing of the ear canal followed by application of tincture of merthiolate to the affected area and dusting with a powder consisting of two parts of sulfathiazole, two parts of sulfanilamide, and one part of sodium perborate. No additional- treatment was used. In those instances in which pain was intense, hot compresses were applied for 30 minutes four times a day until pain was relieved. Results Of the 100 cases observed, 44 were limited to the right ear, 30 to the left, and 26 involved both ears. Of those that had otitis externa in the left ear alone, 9 were left-handed, whereas the rest, who had right ears or both ears pathologic, were right-handed. Five per cent of the patients were colored, the rest white, although 18 per cent of the personnel aboard were colored. The ages, as shown in graph 1, varied from 17 to 48 inclusive, with the great majority occurringi the 17- to 23-year-old group. Of interest, especially in view of the simple, relatively mild medication used, are the data of the severity of the infection and the time for cure. Symptoms were classified according to the amount of swelling, discharge, and pain, with additional notes concerning the presence of itching and the color of the discharge. Each patient was examined every 24 to 48 hours, and the initial dates of onset and disappearance of pathologic symptoms were noted. The results (graph 2) show that the time for complete cure, symptomatically and bacteriologically, varied from a minimum of 4 days to a maximum of 29, with the mean at 11.2 days. Of those ears from which fungi were isolated the time varied from 4 to 14 days, with the mean at 4.5 (graph 3). The ears from which species of Pseudomonas were isolated required from 4 to 29 days, with the mean at 12.7 days (graph 4). Those individuals who had a previous history of otitis externa were cured in a mean time of 8.9 days, whereas those who had not were cured in a mean time of 12.3 days (graphs 5 and 6). Bacterial infections also produced more severe symptoms of pain, swelling, and discharge than those of fungi, there being but slight difference in the effect of different bacteria (graph 7). Attempts were made to identify all the organisms obtained from the infected canals. Of the 100 cases, bacteria alone were isolated from 84, fungi alone from 8, and a mixture of fungi and bacteria from 8. Of the 16 fungal isolates, 1 was a species of Monotospora; 4 were Actinomyces israeli; 3, Aspergillus niger; 4, Aspergillus flavus; and 4, Aspergillu8 terreus (table 1). Of the patients from whose ears bacteria were isolated, 45 had Pseudomonas

3 EXTERNAL OTTS z W I 0 hi U. 5 6is- Ot- IHE L I %^ * so aa A 6 E GRAPH 1.! VW 0 ILLUSATION OF TE NumBER OF INDIVIDUALS Or AGES FROM 17 To 49 with OTITS EXTERNA GRPh 2. TIME IN DAYS ILLusTRATIoN OF THE TIME REQUIRED FOR CuBE FROM EXTERNAL OTTS 10 K.5 L t ; o0 5 lb TIME IN DAYS GWPH 3. ILLUsTATION OF THE TImz REQUIRED FOR CURE IN THosE FROM WHOs Em FUNGI WERE ISOLATED

4 498 S. B. SALVIN AND M. L. LEWIS sp. ;27,Skaphylococcus albus; 14,unidentified diphtheroids; 9,viridans streptococci; 9, Chromobacter sp.; 2, Sarcina lutea; 2, hemolytic streptococci; and 1, Staphylococcus aureus (table 2). 2 W I0 GnAPH 4. i L IIIli:i :l L 2 S IS 20 5 TIME IN DAYS ILLuSTRAnToN OF THE TIME REQUIRED FOR CURE IN THOSE FROM WHOSE EARs P8seudomona SP. WERE ISOLATED TINE IN IDAYS Gi&PH B. ILLusqTAToN OF THTIME FOR CuR AMONG THOs8EWHO HIAD PviouBny HAD ExTERWNAL OTITIS GRAPE 6. (l TIME IN DAYS ILLUSTRATION OFTHi TiME FOR CURE AMONG THOSEWHOHADNOT PREvIOUSLY HAD EXTERNALOTITIS Cultures were taken from 25 normal ear canals in the same way as from patho logic ones, and yielded the following results: gram-negative rods, 17; Staphylococcus albus, 16; and no organism, 4. Fungi were not isolated from normal ear cas.

5 EXTERNALOTT4 499 Analysis of Data When the foregoing data are analyzed, several deductions can be made. The time for the cure of a fungous infection of the ear canal is noticeably less than that of a bacterial infection, notwithstanding the current opinion of the marked severity of mycotic invasions of the ear. The ease with which fungus in the ear canal was eradicated was in marked contrast, for example, to the definite persistence of some of the Pseudomonas sp. infections, this occurring during the midsummer months when the mean temperature was 82.4 F and the average relative humidity 78.7 per cent. These fungous infections usually had a fairly copious, colored discharge, and exhibited relatively little pain and swelling. As shown in graphs 5 and 6, those individuals who had a history of otitis externa were cured on the average in less time (8.9 days) than those who had no 00 e Xo z0 go c3c P Ohio hi Ohi SUGHT MODERATE SEVERE ASSERT SUGHT MODERATE S AEREASSERT SUIHT MODERATE SVERE ABSEMT 7 A 7 a -7 e GRAPH 7. ILLUSTRATION OF THE SYMPTOMS OF EXTERNAL OTITIS CAUSED BY (A) Pseudomonas Sp., (B) FUNGI, AND (C) OTHER ORGANISMS ISOLATED history (12.3 days). This may be significant, although it is pointed out here merely to suggest possibilities for future control of the ailment. No causal relationship was found between individual age and the occurrence of external otitis, since, as was to be expected from naval personnel, most of the patients were in the 17- to 26-year age bracket. Also, no unusual results were seen in the number or type of recurrence in the "cured" cases, wherein only 9 per cent of the patients returned with very mild infections during a period of 3 months following the termination of the original infection. The type of organism that was isolated from the diseased ear was noticeably different from that found in the normal ear. Of course, according to the experiments completed, there is no certainty that the organisms isolated were the causative ones, but the very fact that the flora differs is an indication that the

6 {i00 S. B. SALVIN AND M. L. LEWIS organisms concerned are either primarily or secondarily related to the onset of the disease. Of outstanding interest are the small percentage of fungi obtained and the relative ease with which they responded to treatment. Pseudomonas sp., which occurred in 45 per cent of the diseased canals and in none of the normals, was the most frequently isolated organism and the one associated with the cases least responsive to treatment. Staphylococcus albus, which was the most common organism in normal ears, was isolated from 27 per cent of the pathologic ears, although frequently it occurred with,other forms. A yellow Chromobacter sp. TABLE 1 Fungi isolated from infected ear canals (100 patients) IDENTITY 01 ORGANISM NMBERO1 PATIENTS Actinomyces israeli... 4 Aspergt'lus terreus... 4 Aspergillus flavus... 4 Aspergillus niger... 3 ) onotospora sp... 1 TABLE 2 Bacteria isolated from infected ear canals (100 patients) NO. O1 PATIEnT ROM WEOCISOLATED IDENTITY 01 ORGANISM1 0.In pure In mixed Total cuyture culture isolations Pseudomonas sp Staphylococcus albu Diphtheroids Viridans streptococei Chromobacter sp Sarcina lutea Hemolytic streptococi Staphylococcusaure was also found in 9 per cent of the diseased canals, generally in conjunction with other bacteria. II Since Pseudomonas sp. was most frequently isolated from diseased ear canals, further studies were made of this organism. Pseudomonas aeruginosa has been recognized as a potential human pathogen for many years, and yet little is known about its properties. Its most striking characteristic is its formation of pyocyanin, a chloroform-solubl, nonfluorescent, blue pigment. However, there is a

7 EXTERNAL OTITIS 501 striking difference of opinion as to its fermentative action and its other biochemical characteristics. For example, on page 20 of the pamphlet of the Enteric Pathogen Laboratory, National Naval Medical Center (1944), there is the statement, "Pseudomonas aeruginosa is easily recognized culturally due to the fact that with the exception of a slight and transient acidity in glucose, all carbohydrate media are rendered alkaline." Moltke (1927) and Bergey et al. (1939) drew similar conclusions, but others such as Topley and Wilson (1936) and Stitt et al. (1938) believe that glucose alone is attacked. Clara (1934), on the other extreme, claimed that his isolate of P. aeruginosa fermented glucose, galactose, levulose, salicin, mannose, arabinose, xylose, mannitol, and glycerol. Elrod and Braun (1942) follow an intermediate path in asserting that only glucose, xylose, and arabinose were fermented. Biochemical studies were therefore made (1) to study the extent of the fermentative activity of 56 isolates of Pseudomonas sp.; (2) to determine the exact type or types of Pseudomonas sp. isolated from the ear according to Bergey's classification of this genus; and (3) to compare strains obtained from four different sources, namely, diseased ear canals, pathologic stools, drinking water, and soil. The cultures tentatively identified as Pseudomonas aeruginosa because of the production of the pigment pyocyanin were isolated from the following sources: 13, from diarrheal stools, in which no other established enteric pathogen could be found; 28, from pathologic ear canals; and 2, from chlorinated well water. Thirteen other isolates were made from soil, and they all were included as P. fluorescens because of the presence of fluorescein and the absence of pyocyanin. Each isolate was first examined for motility after 24-hour growth in Difco nutrient broth at 37 C, and all were established as definitely possessing that character. These observations on the motility of the organisms were further substantiated by 24-hour growth at 37 C on a semisolid medium made by the mixture of two solutions: one consisting of 80 g bacto gelatin in 600 ml of water; and the other of 5 g sodium chloride, 10 g bacto peptone, 3 g Liebig's beef extract, 4 g bacto agar in 400 ml of water. Again, all the organisms showed definite motility, with isolates S-1 and S-2 forming additionally a contrastingly large amount of blue-green pigment. After 21 days' incubation at room temperature in 1 per cent peptone water, none of the 56 isolates formed hydrogen sulfide or indole. After 5 days' growth at 37 C in Difco nultrient broth containing 0.1 per cent potassium nitrate, 6 of the 13 P. fluorescens group and 21 of the 43 P. aeruginosa cultures reduced nitrate to nitrite when tested by the Griess-Ilosva method. None of the cultures showed any evidence of the formation of.nitrogen gas in Durham tubes. Ten per cent gelatin stabs of the isolates were made and kept at room temperature for 28 days. All the P. aeruginosa group that reduced nitrate liquefied gelatin with infundibuliform type of growth in 3 to 15 days, whereas those that did not reduce nitrate either displayed a stratiform-filiform type of liquefaction (8 in number) or none at all (2 in number). Three of the P. fluorescens group showed a stratiform-filiform type of liquefaction, and the rest none at all, with

8 5020. B. SALVIN AND M. L. LEWIS no apparent correlation between nitrate reduction and the type of liquefaction. Each of the isolates was grown in Difco nutrient broth at both 42 C and 5 C, according to the suggestions of Seleen and Stark (1943). All of the isolates showed heavy growth at 42 C with the exception of the soil series, which showed no growth after 5 days' incubation. At 5 C, on the contrary, the soil group exhibited light to heavy growth after 31 days, whereas the rest of the isolates showed either very scanty growth or none at all. When the different organisms were inoculated onto potato plugs, which had previously been soaked in 1 per cent sodium carbonate for 30 minutes, growth was luxuriant in all cases after 7 days at room temperature, with most of the pyocyanin-producing forms exhibiting a brown, yellow, and blue-green pigmentation, and the others a pale to deep yellow one. Similarly, when the isolates were grown in litmus milk at room temperature for 7 days, peptonization, clotting, and an alkaline medium were produced by most of the pyocyaninforming groups, and merely atl alkaline medium by all but one of the soil isolates. Fermentation studies were made on the 56 strains of Pseudomonas sp. wherein the following carbohydrates were tested: adonitol, arabinose, dextrin, glucose, dulcitol, fructose, galactose, glycerol, inositol, inulin, lactose, maltose, mannitol, mannose, raffinose, rhamnose, sorbitol, starch, sucrose, trehalose, and xylose. Since Pseudomonas sp., when growing in proteinaceous media, produces ammonia, which in turn would mask the formation of acid, a medium was used in which ammonia production was at a minimum. This synthetic medium, suggested by Elrod and Braun (1942), consisted of 0.2 g magnesium sulfate, 0.1 g calcium chloride, 0.2 g sodium chloride, and 0.2 g dipotassium phosphate per liter of distilled water. As an example, 43 of the isolates were grown both in Difco phenol red broth (proteose-peptone no. 3, 10 g; bacto beef extract, 1 g; sodium chloride, 5 g; and bacto phenol red, g per liter) and in the Elrod-Braun synthetic medium with either one of several sugars added, and the fermentative activity was compared. The results clearly demonstrate that, since in the phenol red broth only 18.6 per cent of the isolates in glucose and 81.4 per cent in xylose acidified the solution, as contrasted with 95.3 per cent in the synthetic medium, the fermentative reactions of a species of Pseudomonas should not be studied in the presence of organic nitrogen. The 43 isolates which produced pyocyanin all fermented glycerol; with the exception of 2 strains, all fermented arabinose, glucose, galactose, mannose, and xylose; but none acted upon adonitol, dextrin, dulcitol, fructose, inositol, inulin, lactose, maltose, mannitol, raffinose, rhamnose, sorbitol, starch, sucrose, or trehalose. On the other hand, the 13 soil isolates, none of which produced pyocyanin, all fermented glucose and galactqse; 9, arabinose; 8, mannose; 10, xylose; and none acted upon adonitol, dextrin, dulcitol, fructose, glycerol, inositol, inulin, lactose, maltose, mannitol, raffinose, rhamnose, sorbitol, starch, sucrose, or trehalose. In order to observe the action of the isolates on blood, 0.5 ml of 2 per cent suspensions of washed beef corpuscles in sterile physiological saline were inoculated and incubated at 37 C for 24 hours. All of the P. aeruginosa group

9 EXTERNAL OTITIS hemolyzed the red blood cells; the P. fluorescens group did not. When pour plates were made with 5 per cent defibrinated beef blood agar, all the pyocyaninproducing forms showed in 24 hours at 37 C a distinct hemolysis of the beta type, with a zone of hemolysis of 1 mm or less, whereas the soil forms were characterized after 96 hours' incubation at 37 C by a slow diffuse decoloration of the hemoglobin with heavy green pigment production. When these experiments were repeated on human blood, similar results were obtained. DISCUSSION 503 Evidence was produced that Pseudomonas sp. was isolated from cases of external otitis, and not from normal ear canals. For expressing quantitatively this association between a disease and a possible causative agent, the calculation of X2 is frequently most advantageous (Hill, 1942). From the formula X2 (O E)2 - E in which 0 is the observed result and E the expected result, X2 can be determined, and from that data the probability (P) of each agent being the causative one in the disease calculated. Thus, according to the figures obtained for the frequency of each of the microorganisms isolated from both normal and diseased ears, the probability of Pseudomonas sp., which was isolated in 45 per cent of the pathologic cases, being the causative agent of external otitis just by chance is much less than 1 in 10,000; of Staphylococcus albus, 1 in 2,000; of fungi, 3 in 100; of diphtheroids, about 1 in 10; of viridans streptococci and Chromobacter sp., about 12 in 100; of hemolytic streptococci and Sarcina lutea, about 1 in 2; and of Staphylococcus aureus, about 3 in 5 (table 3). Pseudomonas sp. is therefore most outstanding as the probable causative agent of otitis externa. Although the value for P in the case of Staphylococcus albus is high, its significance decreases when the general prevalence of this organism on open surfaces and on normal tissues is taken into account. Of foremost interest is the determination of these species of Pseudomonas. According to the classification of Bergey et al., the 52 cultures may be grouped into the following categories: (P. aeruginosa, 21; class II, 9; class III, 12; class IV, 5; and class V, 5 strains. Since the activities of most of these 52 isolates differed from those species of Pseudomonas described by Bergey et al., classes II, III, IV, and V could not be identified, but are closely related to P. septica, P. schuylkilliensis, P. ovalis, and P. incognita, respectively. Since even within a single class fermentative differences occur, each one of these categories may not contain a single species. Further examination of the available literature disclosed that the existing data for the classification of the genus Pseudomonas is incomplete, and in some cases contradictory and confusing. The present definitions of the Pseudomonas group are therefore so inadequate as to make the proper identification of many isolates impossible. Since all but two of the pyocyanin-producing isolates fermented arabinose,

10 504 S. B. SALVIN AND M. L. LEWIS glucose, galactose, mannose, and xylose, the fermentation of these sugars should be considered in the formation of a sound biochemical pattern for this group. This uniform ability of pyocyanin-producing bacteria to ferment arabinose, glucose, galactose, mannose, and xylose, with the formation only of acid, warrants the testing with these sugars of future Pseudomonas sp. isolations that are derived both from saprophytic and pathologic sources. Future data may then permit some etiologic correlation between the true natural reservoirs of pyocyanin-producing organisms and their occurrence in human pathologic processes. The irregularity of some activities, such as the reduction of nitrates to nitrites, the liquefaction of gelatin, the formation of various pigments on potato slants, and the action on litmus milk, strongly indicate the existence of different strains within this pyocyanin-producing group. Further investigations of the antigenic composition should therefore be made in an attempt to find a satisfactory serologic schema whereby each, strain could be identified by its antigenic components TABLE 3 Probability of pathogenicity of organisms ORGANISM X2 P Pseudomonas sp <.0001 Staphylococcus albus Fungi Diphtheroids Viridans streptococci Chromobacter sp Hemolytic streptococci Sarcina lutea Staphylococcus aureus alone, or by its antigenic composition plus these differential biochemical and metabolic characteristics. In addition, the pyocyanin-producing Pseudomonas sp. effected true beta hemolysis on blood agar plates, whereas the non-pyocyanin-producing isolates were not able to produce any degree of hemolysis. On the basis of this metabolic property, therefore, it is logical to propose that more consideration be given to these pyocyanin-producing strains as potentially etiologic agents in human disease. This characteristic is also offered as a means of differentiating in culture the pyocyanin-producing forms from those that do not produce this pigment. Since, as a general rule, parasitic bacteria are mesophiles that grow best at the temperature of the living host, usually 37 C, the pyocyanin-formers may be considered as belonging to a potentially parasitic group. This is in direct contrast to the non-pyocyanin-formers which were psychrophilic and were isolated from saprophytic sources. The pyocyanin-producing bacteria behaved as mesophiles in that they thrived at both 42 C and 25 C, whereas their growth was markedly inhibited at 5 C. The non-pyocyanin-producing isolates behaved as

11 EXTERNAL OTITIS psychrophiles, as there was no evidence of stasis at 5 C and as they failed to grow at 42 C. This characteristic of different growth rates at 42 C and 5 C is offered as another difference in metabolic properties between the two groups of Pseudomonas strains. SUMMARY 505 One hundred consecutive acute cases of external otitis were examined for the possible etiologic organisms. From 45 per cent of the patients' ears, Pseudomonas sp. was isolated, whereas only 16 per cent had fungi. The rest showed a variety of bacterial types. From none of the 25 normal ears were either fungi or Pseudomonas sp. isolated. Studies were conducted on the biochemical and metabolic activities of 56 isolates of Pseudomonas, obtained from diseased ear canals, pathologic stools, well water, and soil. In general, only 6 carbohydrates of 21 tested were fermented with the formation of acid only, namely, arabinose, glucose, galactose, glycerol, mannose, and xylose. The genus was divisible into two distinct groups according to differences in (a) the production of pyocyanin, (b) the liquefaction of gelatin, (c) action in litmus milk, (d) the response to temperature extremes, (e) the production of pigment on potato slants, (f) the hemolysis of red blood corpuscles, and (g) acid formation in glycerol. These two groups could be further subdivided according to other minor variations in biochemical activity. The isolates from the soil were in a different group from those obtained from pathologic sources. It was impossible to identify the isolates specifically because of the inadequlacy of the information in the available literature. ACKNOWLEDGMENTS The authors express their appreciation and thanks to J. R. Poppen, Captain, MC, U.S.N., for his aid in making the foregoing experiments possible; to W. A. Marmor, Lt. Cmdr., MC, U.S.N.R., for his assistance in obtaining the isolates from pathologic ear canals; and to Professor W. H. Weston, Harvard University, Cambridge, Massachusetts, for his co-operation in the identification of some of the fungal isolates. REFERENCES BERGEY, D. H., et al Manual of determinative bacteriology. 5th ed. Williams & Wilkins Co., Baltimore. CLARA, F. M A comparative study of the green-fluorescent bacterial plant pathogens. Cornell Univ. Agr. Expt. Sta., Mem., 159. DAGGETT, W. I Desquamative otitis externa in Malta. J. Laryngol. Otology, 57, 427. DAVIS, E. L Mycotic ear infections at an advanced allied base. Med. J. Australia, 2, DoBEs, W. L Moniliasis of the external ear canal. Southern Med. J., 36, ELROD, R. P., AND BRAUN, A. C Pseudomonas aeruginosa; its role as a plant pathogen. J. Bact., 44, Enteric Pathogen Laboratory Pamphlet. Naval Medical School, National Naval Medical Center, Bethesda, Md.

12 506 S. B. SALVIN AND M. L. LEWIS GiLL, W. D Mycotic infections in otolaryngology. Southern Med. J., 31, GILL, W. D Otitis externa. Ann. Otology Rhinol. Laryngol., 51, HILL, A. B Principles of medical statistics. 3d ed. The Lancet, Ltd., London. MINCHEW, B. H., COLLINS, B. E., AND HARRIS, M. M External ear disease with special reference to the fungous type. Southern Med. J., 33, MOLTKE, Contributions to the characterization and systemic classification of * Bacterium proteus vulgaris (Hauser). Munksgaard, Copenhagen. MORLEY, G Otitis externa: "Hot-weather ear." Brit. Med. J., I, 373. SELEEN, W. A., AND STARK, C. N Some characteristics of green-fluorescent pigment-producing bacteria. J. Bact., 46, STirT, E. R., CLOUGH, P. W., AND CLOUGH, M. C Practical bacteriology, haematology, and animal parasitology. 9th ed. The Blakiston Co., Philadelphia. TopiEy, W. W. C., AND WILSON, G. S The principles of bacteriology and immunity. 2d ed. William Wood and Co., Baltimore. WALEN, E. J Fungous infections of the external ear. Am. Med. Assoc., Trans. Sect. Laryngol. Otology Rhinol., WILLIAMS, H. L., MONTGOMERY, H., AND POWELL, W. A Dermatitis of the ear. J. Am. Med. Assoc., 113,