CLINICAL MICROBIOLOGY REVIEWS, July 1996, p. 382–404 Vol. 9, No. 3 0893-8512/96/$04.0010 Copyright q 1996, American Society for Microbiology Detection of Infection or Infectious Agents by Use of Cytologic and Histologic Stains GAIL L. WOODS* AND DAVID H. WALKER Department of Pathology, University of Texas Medical Branch, Galveston, Texas 77555-0743 INTRODUCTION .......................................................................................................................................................382 STAINS FOR DIAGNOSIS OF VIRAL INFECTIONS.........................................................................................383 Direct Detection in Smears ...................................................................................................................................383 Detection in Tissue Sections .................................................................................................................................385 STAINS FOR DETECTION OF CHLAMYDIA TRACHOMATIS AND RICKETTSIAE ...................................387 Direct Detection in Smears ...................................................................................................................................387 Detection in Tissue Sections .................................................................................................................................387 STAINS FOR DETECTION OF BACTERIA..........................................................................................................389 Direct Detection in Smears ...................................................................................................................................389 Detection in Tissue Sections .................................................................................................................................392 STAINS FOR DETECTION OF MYCOBACTERIA .............................................................................................393 Direct Detection in Smears ...................................................................................................................................394 Detection in Tissue Sections .................................................................................................................................395 STAINS FOR DETECTION OF FUNGI.................................................................................................................396 Direct Detection in Smears ...................................................................................................................................396 Detection in Tissue Sections .................................................................................................................................397 STAINS FOR DETECTION OF PARASITES........................................................................................................399 Direct Detection in Smears ...................................................................................................................................399 Detection in Tissue Sections .................................................................................................................................399 CONCLUSIONS .........................................................................................................................................................400 REFERENCES ............................................................................................................................................................401 INTRODUCTION inclusion-bearing cells are observed, the patient does not have CMV pneumonia. For most patients with infectious diseases, microbiological Frequently, the histopathologic damage, the host response, isolation and identification techniques offer the most rapid and and the cultivated organism have a long-established associa- specific determination of the etiologic agent. On the other tion, lending strong support to the diagnosis. For example, hand, visualization of organisms in cytologic smears, tissue Mycobacterium tuberculosis goes hand in hand with the pres- sections, or both often adds important information and in ence of caseous granulomas. Granulomas are identified micro- some circumstances is crucial to the establishment of a timely scopically by the pathologist by the criterion of clusters of diagnosis. Microbial culture alone cannot distinguish between activated macrophages; caseous necrosis is identified by the colonization (the growth of organisms on the body surface) or, pathologist grossly by the presence of material resembling the in the case of some viruses, asymptomatic shedding and tissue curds of cottage cheese or feta cheese. Pathologic lesions as- invasion. For example, recovery of Candida albicans, a com- sociated with an organism, however, often vary, depending on ponent of the normal flora of the oral cavity, from a sputum the competence of the host immune defenses; therefore, culture does not necessarily indicate that the organism is caus- knowledge of the immune status is useful in interpreting tissue ing pneumonia; this requires identification of pseudohyphae, lesions diagnostically. It is ideal for the pathologist to know the budding yeasts, or both invading the lung parenchyma. Isola- culture results from the microbiology laboratory and to con- tion of Pseudomonas aeruginosa from a burn wound specimen sider them before finalizing a pathologic diagnosis; however, may represent colonization of the wound or a life-threatening this is not always possible. For example, mycobacterial and situation; histologic examination of tissue from the burn fungal cultures are held for several weeks, and if no organisms wound site reveals whether gram-negative bacilli are present are growing in these cultures at the time the pathologic diag- only on the dead tissue of the burn eschar or have invaded nosis must be made, which generally is within a few days, final viable tissue. Similarly, evaluation of tissue for the presence of culture results cannot be considered. compatible lesions can be an important factor in assigning an Other situations in which evaluation of smears and tissue etiologic role to an agent recovered in culture. For example, sections stained for organisms are useful include those when isolation of cytomegalovirus (CMV), a prevalent persistent multiple organisms are cultured and certain situations when agent, from a respiratory specimen such as bronchoalveolar none are recovered. When several organisms are cultivated, lavage fluid or lung tissue does not prove that it is the cause of the morphology of the predominant organism visualized in the illness; cell culture results must be considered in conjunction tissue sections can suggest the true causative agent. For exam- with clinical and pathologic data. If normal lung tissue and no ple, if a mixture of Enterococcus spp., Klebsiella pneumoniae, and Staphylococcus aureus were recovered from sputum and if histologic examination of the lung biopsy specimen revealed * Corresponding author. Phone: (409) 772-4851. only large gram-negative bacilli, obviously the most likely eti- 382 VOL. 9, 1996 CYTOLOGIC AND HISTOLOGIC STAINS FOR PATHOGEN DETECTION 383 TABLE 1. Virus-induced changes in cellular morphology observed in cytologic preparations and tissue Virus Description of cytopathic changes HSV and VZV ....................................Multinucleated giant cell (up to 100 mm) with molding of nuclei against each other, and/or infected cell with an intranuclear inclusion that fills the nucleus, pushing nuclear chromatin to the margin, or with a central dense irregular body surrounded by a clear zone and by clumped nuclear chromatin (inclusion scar) (Fig. 1 and 4) CMV.....................................................Enlarged cell with amphophilic intranuclear inclusion, often surrounded by a halo, and/or multiple granu- lar often basophilic cytoplasmic inclusions (Fig. 3); dying infected cells may appear shrunken and smudged with poorly defined inclusions (resembling inclusions of adenovirus) Adenovirus...........................................Cell with an enlarged nucleus containing an amphophilic or basophilic inclusion and thin rim of cytoplasm (smudge cell) (Fig. 5); an earlier form of inclusion resembles a HSV inclusion Human papillomavirus .......................“Balloon cell” (koilocyte): enlarged intermediate cell containing one or more hyperchromatic irregular nuclei that are surrounded by a variably sized clear area (Fig. 2); smears stained by the Papanicolau method show isolated cells or small aggregates of cells showing dyskeratotic changes with orangeophilic cytoplasm and irregular, small, dense nuclei Parvovirus B19.....................................Erythrocyte precursors with enlarged, ballooned, eosinophilic nuclei that have marginal inclusions (lantern cells) (Fig. 6) JC virus.................................................Enlargement of oligodendrogliocyte nucleus with a basophilic, eosinophilic, or amphophilic intranuclear inclusion (Fig. 7) BK virus ...............................................Large, dense, homogeneous, basophilic intranuclear inclusion that usually fills the entire nuclear envelope and has a smudgy appearance Measles virus .......................................Multinucleate giant cells with eosinophilic intracytoplasmic and sometimes intranuclear inclusions RSV ......................................................Epithelial cell with rare pink intracytoplasmic inclusions, often