Opportunistic infections of the lungs

Review

OPPORTUNISTIC INFECTIONS OF T H E L U N G S Harry I. Lurie, B.Sc., M.B., B.Ch., M.R.C. Path.,* and Richard J. Duma, M.D/f

Abstract In this review we describe the most common opportunistic infections of the lung, particularly emphasizing their diagnosis in the living patient and in autopsy material. The review is not intended to be complete and detailed but is written with the specific object of being a practical aid to the pathologist. Included are brief discussions of the clinical manifestations and radiologic appearance when these data may be o f help in reaching a diagnosis. Also included is information about the value, use, and significance of sputum stains and culture, as well as serologic tests. Emphasis is placed on tissue reactions, the morphologic appearance of the organisms in the tissues, and their staining characteristics. Intentionally omitted are the more sophisticated procedures not generally available in hospital laboratories, such as immunofluorescence and agar gel immunoelectrophoretic techniques.. Because the infections are opportunistic, occurring in patients with an altered or deficient immune system, the clinical manifestations, serologic reactions, and tissue response are often "atypical" and may differ from the classic descriptions.

In 1962 The Committee of the International Symposium on Opportunistic Fungus Infections I suggested that the term opportunistic fungi be used to designate ubiquitous saprophytes and occasional pathogens tlmt invade the tissues of man or animals with predisposing diseases such as diabetes and leukemia or predisposing conditions such as roentgen therapy and antibiotic drugs. The Committee agreed that the term opportunist also be used to designate a fungus that infects even a heahhy person when a favorable opportunity presents itself. At the symposium Dr. John P. Utz 2 defined opportunistic

infections as those caused by organisms that adapt themselves to take advantage of the circumstances of the moment; the organisms may be either truly pathogenic or heretofore supposedly saprophytic or nonpathogenic. We consider both definitions to be too broad, tbr probably every infection occurs when the circumstances and conditions are favorable; even pneumococcal pneumonia in an alcoholic who had spent a wintry night on a park bench would be in this category. As yet there are no clearcut limitations to what should be included in the group of opportunistic infections.

*Professor of Pathology, Medical College of Virginia, Virginia Commonweahh University, Richmond, Virginia. -{-Assistant Professor of Medicine, DMsion of Infections Diseases, Department of Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia.

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We have not attempted to define these limitations, but have decided to include in this review what we consider to be the most common and most important infections of the lung occurring in those circumstances mentioned by the Committee, viz., candidosis, aspergillosis, phycomycosis, cryptococcosis, histoplasmosis, nocardiosis, gram positive and gram negative bacterial infections, cytomegalic inclusion disease, and pneumocystosis. In such infections pathologists often encounter problems in defining the causal organism(s): The clinical pathologist is confronted with such questions as the significance of an organism isolated from sputum or the value and interpretation of serologic tests; the anatomic pathologist may have difficuhy in identifying the causal organism in'either biopsy or autopsy material. In an attempt to assist pathologists dealing with these problems, we shall describe the clinical and pathologic manifestations of these opportunistic infections of the lung, the morphology of the organisms in the tissues, and various diagnostic procedures available. T h e tissue reactions and morphologic features are summarized in the table on the opposite page. T h r o u g h o u t this review certain general principles should be kept in mind in evaluating opportunistic infections. (1) Bec,ause of the frequent presence of an altered host response, one should not be misled by aberrant or "atypical" clinical or pathologic findings. Such variations from "normal" depend upon the degree of impairment of the host response. (2) For the same reasons serologic tests may be confusing. (3) Since many infections develop in the wake of previous infections, residual tissue reactions or damage may complicate pathologic interpretation. (4) Prior or concomitant chemotherapy may have killed the primary pathogen so that it can no longer be cultured and identified. Also subsequent overgrowth by saprophytic organisms may occur and add to interpretative difficulty. (5) Since opportunistic infections are often mixed;" careful evaluation of all isolates is mandatory before final conclusions are drawn. Gram stains of sputum, exudates, and imprint smears from biopsy or necropsy material are invaluable in estimating the relative importance or significance of the various isolates

and in the selection of correct cultural procedures. CANDIDOSIS Previously C. albicans was considered tile only pathogenic member of the genus Candida. However, it is now generally recognized that several other species may be pathogenic under certain circumstances. Because species identification is laborious and time-consuming, it is fortunate that the lesions caused by the various biotypes appear to be indistinguishable both clinicall)" and pathologically. The clinical picture of pulmonary candidosis simulates that of bacterial infection and may vary from patchy to confluent broncho- or lobar pneumonia. However, the sputum is mucoid or gelatinous and may be blood streaked; only in the event of secondary bacterial infection does it appear purulent. The radiologic picture is as variable as the clinical one and usually cannot be distinguished from that of bacterial infections. T h e disease may be confined to the lungs or disseminate or spread to the hmgs from a primary site elsewhere, such as the gastrointestinal tract. Before the diagnosis can be considered, the fimgus must be isolated and identified. Sampling is critical, for Candida may be fotmd not only within the "normal" mouth but also at times within the respirator)' tree as a saprophyte, commensal, or apparent "nonpathogen." Procurement contanfinants are frequent, and it must be emphasized that an isolate per se is not diagnostic. Concomitant bacterial invaders must also be evaluated, because the)" may be more responsible for pathologic change than the fungus. A Gram stain of sputum, biopsy, or necropsy material combined with aerobic and anaerobic cuhures for bacteria from the same site may be helpfifl in this regard. Serologic and skin tests are available. Stallybrass3 concluded that Candida precipitins are formed only in response to systemic infections and are not found in the sera of heahhy persons or patients with superficial candidosis. However, Taschdjian et al.4 obtained positive precipitin reactions in 8 per cent of their con-

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HUMAN PATHOLOGY--VOLUME 1, NUMBER 2 June 1970 trois, which included both "normal" people and patients with cutaneous candidosis; two patients with terminal Candida septicemia gave negative reactions. T h e usual tissue response to Candida is the same as that to any pyogenic organism, i.e., an acute inflammatory reaction with polymorphonuclear leucocytes predominating in the form o f microabscesses. ha sections stained with hematoxylin and eosin, pale blue yeast-like bodies and pseudohyphae can be seen between pals cells. Witlt appropriate special stains, such as periodic acid-Schiff (PAS) and methenamine silver, oval blastospores are clearly visible, measuring 3 to 6 p. in length (Fig. 1). The)' have thin walls and many show buds. Pseudohyphae are usually present. W h e n the fungus is growing on a surface, such as the wall ot'a cavity or the pleura, or in a bronchus, a b u n d a n t true hyphae are usually present, and interspersed between them are clusters of oval spores (Fig. 2).

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Occasionally a blastospore is attached to a hypha at a point of constriction. In rare instances the tissne response is tlmt o f a giant cell granuloma. Within the giant cells blastospores and sometimes fragments o f hyphae are seen. ASPERGILLOSIS

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Figure 1. Candidosis; section of hmg abscess showing oval yeast-like bodies, some budding. 2 3 6 Pe odi acid-Schiffstain, x 1330.)

Five types of lesions have been described: intracavitary fimgal growth (aspergilloma or fungus ball), necrosis of lung tissue, hemorrhagic necrotizing pneumonia,5. Gchronic granulomatous pneumonitis, and l)seudomembranous tracheobronchitis3 Clinically and radi01ogically the pictures of aspergillosis vary with the type. In the cavitary form the clinical manifestations are those of the basic disease. T h e fungus ball does not directly affect the health o f the patient, except that healing

OPPORTUNISTIC INFECTIONS OF THE LUNGS--LuRIE, Duxla of the underlying disease may be prevented. Occasionally hemoptysis may occur. Intracavitary aspergilloma is an opportunistic infection only insofar as it occurs as a result of a pre-existing lesion. When sufficiently large, it may be diagnosed radiologically (Figs. 3, 4). The type of lesion associated with necrosis of hmg tissue may simulate pulmonary infarction; the necrotizing pnenmonic type is like that of an)' other necrotizing hemorrhagic pneumonia. The chronic granulomatons variety simulates tuberculosis. With any of these, except the fungus ball, dissemination may occur, and in such cases muhiple abscesses or granulomas appear in a variety of organs. Regardless of the type of lesion tile clinical diagnosis of asp~ergillosis rests on

finding the fungus in tile sputum, preferably from muhiple samples. However, a negative culture does not exclude the diagnosis. Fragments of hyphae and numerous spores may be seen on direct examinations, but identification still requires culture. The most commonly found species in pulmonary aspergillosis is A. fiunigatus. In some cases other species such as A. niger and A. nidulans are involved, and since these may be aerial contaminants, tile growth of a single colony or even a few colonies fi'om one specimen is not diagnostic. Skin tests and serologic examinations are of limited diagnostic value. Precipitin tests are positive in a high percentage of cases of pulmonary aspergillosis, but positive reactions have been reported with

Figure 3. Aspergilloma"fimgusball" presenti~gas an asymptomatic"coinlesion"in the right lower lobe.

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HUMAN PATHOLOGY--VOLUME 1, NUMBER 2 June 1970

Figure 4. Aspergillo,na"fimgus ball" presenting as an asymptonmtic"coin lesion"in the right lower lobe.

other fungal infections and in apparently healthy individuals.S-r'.. Some cases of proved aspergillonm have given negative reactions. 13 Intracavitary aspergilloma invariably resuhs from secondary infection of a preexisting cavity in the hmg, as in tuberculosis, bronchiectasis, or lung abscess. The

238

flmgus grows profusely, producing a dense mycelium, which almost fills tile cavity, resulting in the so-called fungus ball. It generally remains confined to this space with mininlal infiltration of the cavity wall. In the type associated with necrosis of hmg tissue histologic examination reveals

OPI'ORTUNISTIC INFECTIONS OF THE LUNGS-LumE, DUMA tim presence of muhiple foci of coagulative necrosis, each usually containing abundant nuclear debris. Blood vessels within and adjacent to tim necrotic zones are thr0mbosed. There is little or no tissue reaction to tim fungus; however, an occasional polymorphonnclear leucocyte may be present. It is of interest that when dissemination occurs, the lesions in other organs show a marked polymorphonuclear leucocyte infiltrate. In hematoxylin and eosin sections blue-staining fragments of fungal hyplme are seen in the areas of necrosis (Fig. 5). Special stains such as periodic acid-Schiff stain or metllenamine silver reveal the presence of numerous hyphae. The abundance of tim fungus is strongly indicative of aspergillosis; in no other mycotic infection are they so numerous. In addition to the necrotic areas,

Figure 5. Aspergillosis; section o f h m g s h o w i n g fragments of hyphae in necrotic tissue. Some of tile hyphae are cut at right angles and resemble spores. T h e r e is no inflanmmtory reaction. (llematoxylin and eosin staiu, x 530.)

hyphae are seen invading tim walls of blood vessels, extending into tile thrombi. Invasion of the blood vessels with resultant thrombosis may be the primary lesion and infarction secondary, or infarction may be primary and invasion secondary. The hemorrhagic necrotizing pneumonia may simulate lobar or bronchopneumonia. Diffuse consolidation of lung tissue may occur with abscess formation in some cases. Fungal hyphae are seen extending into alveolar spaces from alveolar walls. In addition, invasion of blood vessels occurs with resultant hemorrlmgic infarcts. Rarely lesions in tim lung take the form of a widespread chronic granulomatous reaction with abundant multinucleated giant cells, many of which contain plmgocytosed hyphal fragments. T h e grannlomas are surrounded by dense fibrous tissue. The lesion of pseudomembranous tracheobronchitis is uncommon. It con; sists of a focus of ulceration of the trachea or bronclms covered by a pseudomembrahe comprised of amorphous necrotic material. Embedded in this membrane and projecting into tim lumen are masses of hyphae. The morphology of aspergilli in the tissues for all types of lesions is the same. They appear as septate hyphae less tlmn 5 /_t in thickness, showing frequent Yslmped dichotomous branching (Fig. 6). Hyphae cut transversely or at a slight angle appear as round or oval structures and nmy be mistaken for the blastospores of Candida (Fig. 5). These structures are distinguishable from yeasts by their "empty" appearance in contrast to true yeasts, which stain as solid structures (Figs. 1, 2). When aspergilli grow into a cavity, as in tim case of the fungus ball, or into the lumen of the trachea or a bronctms, they may produce fruiting bodies (conidiophores). These appear as round or oval bodies covered by sterigmata and sometimes clusters of spores (Fig. 7).

PHYCOMYCOSIS

The PIwcomycetes include Absidia, Rhizopus, and Mucor. Althougll the dis-

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Figure 6. Aspergillosis; section of lung showing numerous hyl)hae, many showing dichotomous branching. (Methenamine silver stain. • 320.)

Figure 7. Aspergillosis;section of wall of cavity in lung showing three fruiting bodies (conidiophores covered with sterigmata). (Periodic acid-Schiff stain. • 530.)

ease is often r e f e r r e d to as nmcormycosis, in tissue sections t h e s e flmgi cannot be differentiated. T h e r e f o r e , unless the genus Mucor has been identified on culture, the term phycomycosis is more correct. T h e clinical and radiologic pictures are those o f p n e u m o n i a o r p u h n o n a r y infarction. Because Phycomycetes are c o m m o n aerial contaminants, their isolation f r o m s p u t u m must be r e g a r d e d with suspicion. O n the contrary, even in p r o v e d cases, s p u t u m cultures are often negative. T h e r e are no skirl tests or serologic reactions for this g r o u p o f fungi. T h e lesions in the lung are the same as those o f aspergillosis associated with necrosis. T h e s e fungi also invade blood vessels with r e s u h a n t thrombosis. T h e tissue response is that o f acute inflammation

with a p o l y m o r p h o n u c l e a r leucocyte infiltrate. Although fnngal h y p h a e can be seen in hematoxylin and eosin stained sections, m e t h e n a m i n e silver stain is better for their demonstration. Periodic acid-Schiff stain has often p r o v e d unsatisfactory. H y p h a e are f o u n d in necrotic lung tissne (Fig. 8), in areas o f acute inflammation, and in tile walls and lumens o f blood vessels (Fig. 9). T h e y are irregular in c o n t o n r , nonseptate, and up to 20/z wide. Ill contrast to Aspergillus, b r a n c h i n g is not d i c h o t o m o u s but variable and often at right angles (Fig. 10). H y p h a e lmve been mistaken for capillaries, venules, or lymplmtic vessels (Fig. 11); occasionally in hematoxylin and eosin sections their blue staining is so intense as to simulate foci o f calcification.

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Figure 8. l'hycomycosis; section of hmg showing area of necrosis with intlammatory reaction at periphery. Hyphae cut longitvdinally and transversely are seen in the necrotic tissue. (Hematoxylin and eosin stain. • 135.)

Figure 9. l'hycomycosis; section of arteriole showing fungal hyphae in the wall and within file hnnen. (ilematoxylin and eosin stain, x 320.)

Figure I0. l'h)'con~ycosis; section oflungshowing wide, irregularly contoured hyphae, one showing right angled branching. (Methenamine silver stain. • 530.)

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Figure It. Phycomycosis;sectionof hmg showing wide. irregularlycontoured, thin-walled,"enli~ty" hyphae. Some resemble capillaries; two show right angled branching. (Hematoxylin and eosin stain. • 530.)

CRYPTOCOCCOSIS

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The clinical manifestations of puhnonary cryptococcosis are usually insignificant. The infection may be entirely asymptomatic or produce a low grade fever and cough with mucoid or blood-tinged sputum. Physical signs may suggest bronclfitis or bronchopneumonia; a pleural effusion may be present. The radiologic appearance is equally variable; it may take the form of an alveolar infiltrate, nodular lesions, diffuse miliary lesions, or even suggest a neoplasm. Hilar involvement is rare. The sputum usually contains the organism. India ink preparations may be helpfifl in its demonstration. Some authors maintain that the finding of cryptococci in the sputum is diagnostic of infection. However, Reiss and Szilagyi~4 recovered the

fungus from six persons, none of whom showed any evidence of disease. There have been numerous reports concerning skin tests and serologic reactions. Skin tests may give false-positive reactions with other fungal infections.TM in Serologic tests, which include complement fixation, bemagglutination, latex fixation, agglutination, and-indirect immunofluorescent .teclmiques, have given positive reactions in cases of cryptococcosis, but reports of their specificity and sensitivity are variable. In some cases the lungs appear to be normal on gross examination, and the diagnosis is made lfistologically. Other cases may resemble broncbopneumonia, but if a knife is scraped across the cut surface of tile lung, gelatinous material may be seen on the blade. In still other cases the lesions may simulate miliary granulomas or microabscesses, and some present as subpleural nodtfles. Occasionally the lesion may take the form of a large abscess, the wall of wlfich is ill defined, irregular, and devoid of a fibrous capsule; the contents appear gelatinous or mucoid. When the diagnosis is suspected, a specimen of this material should be exanfined by the India ink method. Microscopically, there may be no inflammatory reaction or change in the lung tissue, yet alveoli may be filled with fnngal bodies (Fig. 12). When the lesions are more circumscribed, they may be surrounded by a minimal amount of loose connective tissue; dense fibrous tissue is not seen. There may be a granulomatous reaction with ifistiocytes and giant cells, many of which contain phagocytosed flmgal bodies. Rarely a polymorphonuclear leucocyte response may be present. 17 Fungal bodies are readily seen in hematoxylin and eosin sections as pale blue or pink, round or oval bodies lying free in alveolar spaces or phagocytosed by giant cells (Fig. 13). Sometimes they are faintly stained because their walls are thin. Their presence is often suggested by the appearance of a wide unstained halo surrounding each fungal cell (Fig. 14). With periodic acid-Schiff and methenamine silver stains tim enormous numbers of organisms demonstrated may be surprising (Fig. 15). The size varies considerably from 2 to 20/~ in diameter, the majority

OPPORTUNISTIC

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F i g u r e 12. Cryptococcosis; sectioq o f l u n g s h o w i n g n o r m a l - l o o k l q g alveolar wails a n d alveolar spaces packed with ftmgal bodies. ( t t e m a t o x y l i n a n d eosin stain. • 135.)

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HISTOPLASMOSIS

F i g u r e 15. Cryptococcosis; section of hmg showing numerous round or oval fnngal bodies of varying sizes. (Periodic acid-Schiff stain, x 320.)

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measuring about 7/x. Their walls are tlfin and sometimes do not slmw a double contour. Budding may be seen; the bud is round or oval. This is in contrast to that of Blastomyces, which is dome-shaped and broad based. The capsule does not stain with hematoxylin and eosin, periodic acidSchiff stain, or methenamine silver but does with mucicarmine, appearing as an irregular coating of carminophilic material on the surface of tim cell. Occasionally the capsule presents as delicate spines radiating from the cell wall into the halo. T h e irregularity of the coat!ngs and the radiations are artifacts produced by fixation, for in vivo the capsule fills the space, but after fixation it contracts. Usually the cell wall itself is strongly mucicarmine positive and under oil immersion appears as a thin carmine ring. This staining reaction is diagnostic of C. neoformans.

O f the diseases discussed in tiffs review, histoplasmosis is least often encountered as an opportunistic infection. It is similar to tuberculosis in that corticosteroids may cause reactivation or dissemination of a quiescent lesion. In the lung several types o f lesions may be f o u n d - d i f f u s e pneumonitic, miliary (Fig. 16), or cavitary. Diffuse pneumonitic or miliary lesions are usually a manifestation of generalized disease; pulmonary involvement may be overshadowed by reticuloendothelial and adrenal lesions. An aid to radiologic diagnosis may be massive hilar lymph node enlargement; pleural effusions are uncommonly rare. The cavitary form both clinically and radiologically resembles tuberculosis. In the majority of cases tile organism can be identified in the sputum both on direct and on cultural examination. Skin tests are of little value, as a positive reaction has tim same significance as that of a positive tuberculin reaction. The complement fixation test also may be of limited value, simply indicating past infection; only a rising titer may be significant. In diffuse pneumoniti s tlm alveolar spaces are filled with an organizing and fibrosing exudate of pleomorphic inflammatory cells, ts Tile most prominent cell is tile histiocyte. The miliary lesions consist of epithelioid cell granulomas with or without caseation. In the cavitary form the pathologic picture resembles tlmt of tuberculosis, viz., granulomas with epithelioid cells, Langhans giant cells, and caseous necrosis, ts The organisms are usually numerous and can be seen in hematoxylin-eosin sections (Fig. 17). They are intracytoplasmic, within histiocytes and giant cells. The cytoplasm of these cells is greatly enlarged and packed with fungal bodies. In hematoxylineosin sections the organisms appear as small, round or oval bodies about 1 to 3/x in size, each surrounded by a clear halo (Fig. 18). Periodic acid-Sclfiffand methenamine silver stains are both satisfactory. However, with these stains the yeast-like bodies appear larger (2 to 4/1,) tlmn with bematoxylin and eosin and halos are not seen (Fig. 19).

OPPORTUNISTIC

I N F E C T I O N S O F T H E L U N G S - - L u R I E , DUMA

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ttistoplasmosis; disseminated miliary pattern in a patient on long-term corticosteroid therapy.

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H U M A N P A T H O L O G Y - - V O L U M E 1, NUMBER 2 Ju~ze 1970

Figure 17. tlistoplasnaosis; section of hmg showing diffuse pneunmnitis. The cytoplasm of tile histiocytes is packed with small fungal bodies. (Hematoxylin and eosiq stain, x 320.)

Figure 18. ttistoplasmosis; section of lung showing tile cytol)lasm of tile histiocytes packed with oval fimgal bodies, each surrounded by a clear halo. (Hematoxylin and eosin stain, x 1330.)

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OPPORTUNISTIC INFECTIONS OF T H E LUNGS--LURIE, DUMA

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0 Figure 19. ttistoplasmosis; section of lung showiqg nunaerous round or oval flmg~al bodies. There is no evidence of a halo. (Methenanfine silver stain. X 1330.) NOCARDIOSIS T h e clinical manifestations o f nocardiosis may be those o f acute bronch0p n e u m o n i a o r lung abscess, but in tile more chronic f o r m they may simulate tuberculosis. Associated e m p y e m a Ires been noted, as well as p l e u r o c u t a n e o n s fistulas. Radiologic examination may show small foci o f alveolar infiltration o r large areas o f consolidation (Fig. 20). T h e lower lobes are m o r e frequently involved than the u p p e r ones. Occasionally small cavities are f o u n d and some cases present as coin lesions. Dissemination f r e q u e n t l y occnrs, especially in patients receiving corticosteroids, most often to tile brain, but any organ may be involved. ~a Patients with alveolar proteinosis a p p e a r to be particularly predisposed. 2~ T h e r e are several pathogenic species o f Nocardia, but ahnost all cases o f pulmonary nocardiosis have been caused by N. asteroides. It is t h o u g h t that N. brasiliensis

may occasionally . p r o d u c e systemic lesions. 21 T h e organism is usually present in the sputum." However, it is i m p o r t a n t to request that tile laboratory search for N0cardia, as tile specimen must be treated differently f r o m ottters. Concentration methods may kill the organism, and tlte m e d i u m must be free o f antibiotics, lit addition, Nocardia may be confused with rapidly growing mycobacteria. Opinion varies as to the significance o f an isolate o f N. asteroides f r o m tlle sputum. Hosty et al. 22 recovered it f r o m the s p u t u m o f 134 patients in whom evidence o f disease d u e to nocardiosis could not be established. Peabody and Seabury 23 considered it a c o m n t o n saprophyte. However, others lmve maintained that its presence in the s p u t u m is diagnostic o f p u h n o n a r y nocardiosis. 21, 24, z~ At present no reliable skin o r serologic tests are available. T h e gross a n d microscopic a p p e a r ance o f the lungs resembles that o f pyogenic b r o n c b o p n e u m o n i a with abscess formation. Usually fibrinous pleuriti s is present and occasionally empyemfi occurs; Histologically the picture is that o f acute b r o n c h o p n e u m o n i a with focal necrosis and abscess formation. Abscesses may become confluent and p r o d u c e large cavities. Rarely a g r a n u l o m a t o u s reaction may be observed. ~ T h e organism cannot b e s e e n in hematoxylin-eosin sections. Periodic a c i d Schiff stain is also unsatisfactory for demonstrating its presence since only portions o f a minority o f tile filaments are stained. However, either Gram's stain or m e t h e n amine sih'er usually reveals n u m e r o u s b r a n c h i n g filaments less than 1 /x in thickness. T h e y are gram positive and may appear beaded, or they may be fi'agmented and resemble bacilli or even cocci. N. asteroides is partially acid-fast and fragm e n t e d filaments may be ntistaken for mycobacteria. Tile one feature that distinguishes it f r o m bacilli, cocci, and mycobacteria is branching, which should be searched for with an oil immersion lens (Fig. 21). Acid-fastness may be variable, and to assure satisfactory staining a 1 per cent solution o f sulfuric acid should be used for decolorization. In a few cases microscopic granules may be present.

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HUMAN PATHOLOGY--VOLUME 1, NUMBER 2 June 1970

Figure 20. Nocardiosis; disseminated mtfltinodtdar lesions in a patient" with a renal transplant and" iatrogenic Cushing's disease.

These are much smaller and far less compact than those of Actinomyces, and in addition they lack terminal clubs (Fig. 22). BACTERIAL INFECTIONS

248

Opportunistic bacterial infections of the lung frequently are suprainfections and hospital acquired. They may be due to gram positive as well as gram negative organisms, although recent emPlmsis has been upon the latter, zT"2s l'atients most prone to develop such problems are those with prior underlying puhnonary disease, especially chronic obstructive lung disease. Other predisposing factors are aspiration, recent tracheostomy, exposure to ventilatory assistance and nebulization equipment, and any of the well known factors contributing to decreased host resistance.

Gram Positive Infections Since circulating humoral antibody (IGG and IGA) appears to play an important role in host defense against most pyogenie gram positive organisms, (e.g., pneumococci, streptococci, and staphylococci), deficiencies of these antibodies often result in frequent recurrent infections due to these organisms. In sinopulmonary infections a deficiency of secretory IGA may be particularly important. In a study by Duma et al. 29 at tile Massachusetts General Hospital, 66 per cent of tile "pathogenically significant" streptococcal isolates from the blood represented opportunistic infections. Such opportunism was especially evident with Lancefield group B streptococci, which often infected patients with diabetes mellitus and on occasion resulted in fatal

OPPORTUNISTIC INFECTIONS OF THE LUNGS-LuRIE, DUMA

Figure 21. Nocardiosis;sectionof hmg showing bacillary and beaded forms. One filament shows branching. (Gram stain. • 1330.)

p n e u m o n i a . Streptococcal p n e u m o n i a d u e to group A organisms has frequently followed such illnesses as measles, influenza, pertussis, or chronic p u l m o n a r y infections a n d sometimes has occurred immediately after tracheostomy.30, 3~ Characteristically, streptococcal p n e u m o nia is an acute b r o n c h o p n e u m o n i a with infiltrates and an early serosanguineous effusion, which has been misinterpreted clinically a n d radiologically as p u l m o n a r y infarction. 20 Anaerobic streptococcal infections frequently follow aspiration. A considerable a m o u n t of suppuration may be produced and multiple abscesses, cavities, a n d occasional e m p y e m a may occur. Often these organisms are obscured culturally by saprophytic bacilli or fungi; however, use of selective culture media and particularly Gram's stain will demonstrate their presence. Microaerophilic and capnophilic streptococci have also been described u n d e r similar circumstances, and their isolation may also be difficult.32 In the recent past staphylococci were c o m m o n opportunists, but the advent o f penicillinase-resistant penicillins has considerably reduced the frequency a n d seriousness of this problem. Nevertheless,

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I

Figure 22. Nocardiosis; pus smear from lung abscess showing small, loosely packed granules devoid of terminal clubs. The beaded appearance is well seen. (Gram stain. • 530.)

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Figure 23. Staphylococcal pneumonia in a patient with leukemia. The presence ~f abscesses and pneumatoceles suggests the diagnosis.

patients with influenza or cystic fibrosis are still troubled by pneumonia from these bacteria. Together with Gram stains and cultures, certain radiologic findings will assist in making the clinical diagnosis: the development of pneumatoceles (Fig. 23), the occurrence of spontaneons pneumothorax, a rapidly changing infiltrate with parafocal emphysema, and early loculation of pleural exudate? 3

Grant Negative Infections Gram negative bacillary pneumonias

250 appear to be increasing in frequency?3-'~'~

Usually they are due to muhiresistant organisms residing in tile hospital environs? t Although many of the responsible pathogens are lactose-fermenting Enterobacteriaceae (Escherichia coli, KlebsiellaEnterobacter, Proteus, Serratia, and Citrobacter), the incidence of nonfermentative organisnls is also significant, for example, Pseudomonas species (especially P. aeruginosa), Mirna-Herellea, AIkaligenes faecalis, Bordetella bronchiseptica, and Acromobacter. Clinically, there is little that is characteristic about these pneumonias except that they are often unresponsive_to antibiotic therapy and terminally infect pa-

OI'PORTUNISTIC INFECTIONS OF THE LUNGS--LURIE, DUMA tients with previously treated pulmonary disease (Fig. 24). All may be marked by tissue necrosis and suppuration. Friedlander's pneumonia (Klebsiella) appears to occur most commonly in alcoholics, diabetics, and patients with debilitating diseases36 Closely related to the bacteria of the Klebsiella-Enterobacter group are Serratia. These bacteria have been isolated in a variety of pulmonary infections, including bronchitis, bronchiectasis, lung abscess, pneumonia, and empyema? r A small percentage of Serratia produce red pigment and may give rise to "pseudohemoptysis" (red Sputum without blood). Primary Pseudomonas pneumonia, in contrast to metastatic pneumonia secondary to Pseudomonas septicemia, is usually not associated with bacteremia, and arteritis is

not the rule. Although many gram negative bacillary pneumonias are associated with pleural effusions that contain the responsible organism, E. colt appears to be unusual in being associated with extensive empyema.28 Isolation of all the aforementioned organisms is facilitated by initial plating on eosin-methylene blue (EMB) medium as well as on blood agar. The presence of highly motile Proteus species may obscure more significant pathogens, and in such situations a "stifF' or "dry" agar should be used. It must always be remembered that isolation of bacteria in the laboratory depends not on their etiologic significance but on their ability to grow under a given set of conditions on artificial media. The gross and microscopic appear-

Figure 24. llerellea lmeunloniain a hospitalized patient with chronic obstructive puhnonar)"disease in whom tracheotomyand artificialventilationhad recentlybeen carried out. Bilateraldiffusebroncholmeunlonia occurred.

251

HUMAN PATHOLOGY--VOLUME 1, NUMBER 2 June 1970 ance of tile lungs is essentially the same as that of "nonopportunistic" bacterial pneumonias, apart from the severity of the lesions. However, several exceptions are worth noting. In streptococcal pneumonia an interstitial infiltrate of mononuclear cells is often present. With Pseudomonas pneumonia unrelated to septicemic spread, abscesses containing polymorphonuclear leucocytes and hemorrhagic necrosis surrounded by mononuclear infiltrates may be noted. 2s Proteus pneumonias are similar except tlmt they are said to sbow little tendency to spread beyond the segment of lobe involved; histologically, scattered fibrosis and "exudation of endothelial and lymphocytic cells" are noted? s E. coli may also produce a predominantly interstitial mononu.clear cell infiltrate,zs but in addition atelectasis and emphysema may be prominent. In those cases due to gram positive organisms, the bacteria frequently grow as colonies in the lung; these colonies may resemble actinomycotic granules in hematoxylin-eosin sections, even to the extent of exlfibiting a layer of amorphous eosinoplfilic material on the periphery (Fig. 25). Gram's stain, however, will demonstrate the presence of rods or cocci and the absence of branching filaments.

CYTOMEGALIC INCLUSION DISEASE Respiratory disease due to cytomegalovirus is being recognized with increased frequency as an opportunistic infection of tile lungs. Such infection may be recently acquired or may represent activated latent foci. Clinical findings in such cases are freq u e n t l y absent, 3~176but if present, they usually consist of tachypnea, dyspnea, cyanosis, and patchy infiltrates throughout the lung fields. Lesions similar to varicella zoster, i.e., muhiple, small nodular densities scattered throughout the lungs, have been described as rather specific, but their occurrence has been infrequent? ~ Dissemination of the virus, as well as of tile disease, occurs; 4t necrosis of the adrenal medullaat or cortex,a2 myocarditis,39 and severe gastrointestinal ulceration have been noted. 39 Tile virus may be recovered from sputum or h m g tissue or, in the event of dissemination, from a variety of organs. Isolation is not too difficult if cuhures are made from fresh specimens on human tissue, such as fibroblasts or myometrial cells. Growtb can.be recognized in most cases by the end of 2 1 days, but observation for cytopathic effect (CPE) should

Figure 25. Gram positive bacterial pneumonia; section of hmg abscess showing the presence of a mass 2 5 2 of bacteria resemblingan actinomycoticgranule. (I lematoxylinand eosin stain. • 35.)

OPPORTUNISTIC INFECTIONS OF THE LUNGS-LumE, DUMA

Figure 26. Cytomegalic inclusion disease; section of h m g showing hyperplastic alveolar lining cells. A large intranuclear inclusion surrounded by a clear halo is seen in one cell. (Hematoxylin and eosin stain. • 1330.)

continue for up to 60 days before tile cultures are discarded. Storage or freezing of the specimen should be avoided, as either will impair isolation? 3 The pathologic significance of a viral isolate is not always clear, especially that from the upper respiratory tract, for cytomegalovirus may be recovered from saliva in the absence of disease. Serologic tests are of limited value. Complement fixing antibodies, if present, appear late in the disease. Because past infection with this organism may give weakly positive reactions, it is necessary to demonstrate a rising titer: a four-fold rise is highly significant. The possibility of cross reactions with other related viruses has not yet been excluded. Serologic results in children appear to be more meaningful than those in adtdts. On gross examination tile hmgs are somewhat firm and edematous. Diagnosis

depends on finding inclusion bodies in the alveolar lining cells. These cells are greatly enlarged, up to 40/L in diameter. Within the nucleus of such cells are large inclusion bodies, measuring as much as 17/x. They are either acidophilic or basophilic and generally are separated from the nuclear membrane by a clear halo (Fig. 26). Occasionally basophilic inclusions are seen in the cytoplasm; these are small and peripherally located. The presence of intranuclear inclusions is more meaningful. The pathologic significance of cytomegalic inclusion cells is sometimes difficult to evaluate. Despite frequent isolation of the virus from sputum and lung, characteristically tissue damage is minimal. Often only isolated cytomegalic inclusion cells are found, usually without inflammation?9.41, 4,'1At times interstitial pneumonia and associated intra-alveolar hyaline membranes may be observed? 3 In some cases despite frequent isolation of the virus, no inclusions or other lesions can be found. The interpretation of pathologic significance may be made even more difficult by either associated fungal infection (especially Candida and Aspergillus 4~ toxoplasmosis, 4'~ or pneumocystosis? ~ 46 PNEUMOCYSTOSIS

Pneumocystosis is an interstitial pneumonia due to Pneumocystiscarinii, an organism whose pathologic sign!ficance in such disease states and whose taxonomy are still unclear. The disease remains confined to the lung, and dissemination has been noted only rarely? r' 4s Early symptoms are dry cough, dyspnea, tachypnea, and fever. At this time small, bilateral infiltrates may be noted in tile lower or midlung fields. In untreated cases relentless progression occurs to involve tile entire hmg (Fig. 27), and an "alveolar capillary-block syndrome" with cyanosis appears. Pleural effusions usually are not seen and auscultatory findings are absent. Since at present the organisms cannot be cultured, diagnosis is established by microscopic examination of lung biopsy or autopsy material. Imprints should be prepared and stained with Giemsa stain, a~ Thereafter the tissue is fixed in 10 per cent formalin for histologic examination.

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Figure 27. l'neumocystosis in a patiem with tiodgkiq's disease. The disease appeared initially as bilateral lower lobe interstitial infiltrates.

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Figure 28. l'neumoc)'stosis; section of h, ng showing interstitial imeumonitis. The alveolar spaces are filled with a foamy material but contain no inflamnlatory cells. (I-lematoxylin and eosin stain. • 135.)

OPPORTUNISTIC

INFECTIONS

OF THE

L U N G S - - L u R I E , DUMA

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Figure 29. Pneumocystosis; section of lung showing numerous small cysts embedded in the foamy material within an alveolar space. (Methenamine silver stain. • 530.)

In Giemsa-stained preparations small cysts with two to eight intracystic, round or irregular bodies measuring 0.5 to 1.0/.t are seen: ~ 5~ Serologic tests have been useful in

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Europe, s2"53 but in the United States evaluation of such tests in cases of opportunistic infections lms not beencompleted. Grossly the lungs are firm, heavy, and comparatively dry. The color has been de-

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Figure 30. Pueunlocystosis; section of lung showing cysts~ some round or oval, some crescent-shaped and one cup-shaped. (Methenamhae silver stain. :~ 1331).)

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scribed variously as gray or as ranging from yellow-pink to dark red. 5~ On microscopy the diagnostic feature is the presence in the alveolar spaces of foamy eosinoplfilic material free of inflammatory cells (Fig. 28). The alveolar lining cells are hyperplastic. Bronclfioles are unaffected. In the classic case there is marked interstitial pneumonitis with tlfickening of t h e alveolar walls, which are heavily infiltrated by lymphocytes, plasma cells, and lfistiocytes (Fig. 28). In those patients in whom the immune response Ires been impaired (by drugs such as corticosteroids and azathioprine), this reaction may be reduced or inconspicuous. There is no suppuration, necrosis, or fibrosis.

With methenamine silver stain, the presence of the clmracteristic cysts can be demonstrated. These are embedded in the foamy intra-alveolar material and appear as small round bodies about 4.5/z in diameter (Fig. 29). Characteristically, many of the cysts appear to be cup shaped or crescent shaped (Fig. 30); this helps to differentiate them from other material tha~ may take up the stain. Periodic acidSchiff stain is not satisfactory, because both the foamy material and the cysts are positive. Concomitant cytomegalovirus inclusions are often found, and as might be expected the relative pathologic importance of the two is difficult to evaluate. 54"5~

REFERENCES

256

1. Committee of the International Symposium on Opportunistic Fungus Infections: Foreword. Lab. Invest., 11(11):1017, 1962. 2. Utz, J. P.: The spectrum of opportunistic fungus infections. Lab. Invest., 11(11):1018, 1962. 3. Stall)brass, F. C.: Candida precipitins. J. l'ath. Bact., 87(I):89, 1964. 4. Taschdjian, C. L., Kozinn, 1'. J., Okas, A., and Caroline, L.: Serodiagnosis of systemic candidiasis. J. Infect. Dis., 117(2):180, 1967. 5. Young, R. C., Vogel, C. L., and DeVita, V. T.: Aspergillus lobar pneumonia. J.A.M.A., 208 (7):1156, 1969. 6. Hutter, R. V. 1'., Lieberman, P. H., and Collins, H. S.: Aspergillosis in a cancer hospital. Cancer, 17:747, 1964. 7. Okudaira, M., and Schwarz,J.: Tracheobronchopuhnonary mycoses caused by opportunistic fimgi, with particular reference to aspergillosis. Lab. Invest., 11(11):1053, 1962. 8. Dronhet, E., Segretain, G., Pesle, G., and Bidet, L.: l~tude des pr6cipitines s6rigues en milieu g61os6 pour le diagnostic des aspergilloses brouchopulnaonaires. Ann. Inst. Pasteur (Paris), 105(3):597, 1963. 9. Gernez-Rieux, C., Biguet, J., Voisin, C., Capron, A., and Tran Van Ky, P.: Diagnostic immunoIogique des aspergillomes bronchopuhnonaires. Mise en &'idence d'anticorps s6riques sp6cifiques por immuno-61ectrophor&e. Presse Med., 71:1541, 1963. 10. Azuma, I., Kimura, H., Hirao, F., Tsubura, E., and Yamamura, Y.: Skin-testing and precipitation antigens front Aspergillus fitmigatus for diagnosis of aspergillosis. Amer. Rev. Resp. Dis., 95(2):305, 1967. 1 i. Stallybrass, F. C.: The precipitin test in human systemic aspergillosis. Mycopathologia, 21(3-4):272, 1963. 12. Br6nnestam, R., and Hallberg, T.: l'recipitins against an antigen extract of Aspergillus fitmigatus in patients with aspergfllosis or other

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40. Rifkind, D., Goodman, N., and Hill, R. B., Jr.: Tile clinical significance of cytomegalovirus infection in renal transplant recipients. Ann. Intern. Med., 66:1116, 1967. 41. Duvall, C. 1'., Casazza, A. R., Grimley, P. M., Carbone, P. P., and Rowe, W. P.: Recovery of cytomegalovirus from adults with neoplastic disease. Ann. Intern. Med., 64:531, 1966. 42. Nelson, J. S., and Wyatt, J. P.: Salivary gland virus disease. Medicine, 38:223, 1959. 43. Kanich, R. E., and Craighead, J. E.: Cytomegalovirus infection and cytomegalic inclusion disease in renal homotransplant recipients. Amer. J. Med., 40:874, 1966. 44. Butterick, D. D., and Roberts, L.: Generalized cytomegalic inclusion disease. Report of two eases with associated fungal infection, one involving aspergillosis, the second with candidiasis. Amer. J. Dis. Child., 110:319, 1965. 45. Vietzke, W. M., Gelderman, A. H., Grimley, P. M., and Valsamis, M, P.: Toxoplasmosis complicating malignancy. Cancer, 21:816, 1968. 46. Case records of the Massachusetts General Hospital. New Eng. J. Med., 277:39, 1967. 47. Zandanell, E.: Pneumozystisbefund ausserhalb der Lunge bei interstitieller plasmazellulfirer l'neumonie der S~uglinge und Friihgeburten. Zbl. Allg. Path., 92:74, 1954. 48. Jarnun, S., Rasmussen, E. F., Ohlsen, A. S., and S0rensen, A. W. S.: Generalized Pneumocystis carinii infection with severe idiopathic hypoproteinemia. Ann. Intern. Med., 68:138, 1968. 49. Gadjusek, D. C.: Pneumocystis carinii. Etiological agent of interstitial plasma cell pneumonia of premature and young infants. Pediatrics, 19: 543, 1957. 50. Esterly, J. A., and Warnel-, N. E.: l'neumocystis carinii pneutnonia. Arch. Path. (Chicago), 80:433, 1965. 51. Robbins, J. B.: Pneumoo~tis carinii pneumonitis. A review, l'ed. Res., 1:131, 1967, 52. Vivell, V. O.: Ein neues stabiles Antigen fiir die Serodiagnose der interstitiellen plasmazellulfiren l'neumonie der junger Sfiugiinge und Friillgeburten. Deutsch. Med. Wschr., 80: 1357, 1955. 53. Barta, K.: Complement fixation test for pneumocystosis. Ann. Intern. Med., 70:235, 1969. 54, Rifkind, D., Starzl, T. E., Marchioro, T. L., Waddell, W. R., Rowlands, D. J., anti Hill, R. B., Jr.: Transplantation pneumonia. J.A.M.A., 189:808, 1964. 55. Vogel, C. L., Cohen, M. It., l'owell, R. D., Jr., and DeVita, V. T.: l'neumocystis carinii pneumonia. Ann. Intern. Med., 68:97, 1968. Department of Pathology Medical College of Virginia Virginia Commonwealth University Richmond, Virginia 23219 (Dr. Lnrie)

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