Microorganisms

Published on 04/03/2015 by admin

Filed under Hematology, Oncology and Palliative Medicine

Last modified 22/04/2025

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21 Microorganisms

Plasmodium species

The following examples are representative of the developmental stages of malaria that can be seen in the peripheral blood. Detailed criteria for identification of species may be found in a parasitology text.

FIGURE 21–1A Plasmodium falciparum rings (A), including applique form (B), and platelet on RBC (C) (PB ×1000).

(Courtesy Indiana Pathology Images).

FIGURE 21–1B Plasmodium falciparum rings and crescent (banana-shaped) gametocyte (arrow) (PB ×1000).

(Courtesy Indiana Pathology Images).

FIGURE 21–1C Plasmodium malariae schizont (with 6 merozoites) (PB ×1000).

(Courtesy Indiana Pathology Images).

FIGURE 21–1D Plasmodium vivax; growing trophozoite with stippling (PB ×1000).

(Courtesy Indiana Pathology Images.)

Babesia species

FIGURE 21–2 Babesia microti (PB ×1000).

Babesia species may be confused morphologically with Plasmodium falciparum, but lack of pigment and absence of life cycle stages help differentiate Babesia spp. from P. falciparum. Another differentiating factor is the presence of extracellular organisms (Figure 21-2, arrows) that may be seen in Babesia spp. but not in P. falciparum.

Loa loa

FIGURE 21–3 Loa loa, a microfilaria (PB original magnification ×1000).

Loa loa is a microfilaria (Figure 21-3). Other microfilariae rarely may be seen in the peripheral blood.

Trypanosomes

FIGURE 21–4A Trypanosoma gambiense (Giemsa stain, PB ×1000).

FIGURE 21–4B Trypanosoma cruzi (Giemsa stain, PB ×1000).

(From Marler LM, Siders JA, Simpson A et al: Parasitology image atlas CD-ROM, Indianapolis, IN, 2003, Indiana Pathology Images.)

Trypanosomes are examples of hemoflagellates that may occasionally be encountered in the peripheral blood (Figure 21-4, A and B). Differentiating features may be found in a parasitology text.

Fungi

FIGURE 21–5A Histoplasma capsulatum in neutrophil (PB ×1000).

FIGURE 21–5B Intracellular and extracellular yeast in peripheral blood of an immunocompromised patient (PB ×1000).

FIGURE 21–5C Cryptococcus neoformans (BM × 1000) (see also Figure 24-14).

Bacteria

FIGURE 21–6A Bacilli engulfed by a leukocyte. Note vacuoles (PB ×1000).

FIGURE 21–6B Extracellular bacteria from same specimen as Figure 21-6A. Extracellular bacteria alone may indicate contamination. Presence of intracellular bacteria may rule out contamination (PB ×1000).

FIGURE 21–6C Cocci engulfed by a monocyte (PB ×1000).

FIGURE 21–6D Multiple organisms, including yeast and cocci, most likely contamination from an intravenous line (PB ×1000).

FIGURE 21–6E Anaplasma phagocytophilum in a neutrophil (PB ×1000).

FIGURE 21–6F Ehrlichia chaffeensis in a monocyte (PBx1000).

(Courtesy J. Stephen Dumler, MD, Division of Medical Microbiology, The Johns Hopkins Medical Institutions, Baltimore, MD.)

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