Color Plates

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Staphylococcus aureus in a Gram-stained smear from a colony growing on agar medium (left) and from the sputum of a patient with staphylococcal pneumonia (right). The organisms are gram-positive spheres, primarily in grapelike clusters. The pink cells in the right-hand photo are neutrophils.

Plate 1 Staphylococcus aureus in a Gram-stained smear from a colony growing on agar medium (left) and from the sputum of a patient with staphylococcal pneumonia (right). The organisms are gram-positive spheres, primarily in grapelike clusters. The pink cells in the right-hand photo are neutrophils.

Streptococcus pyogenes in Gram-stained smears. From a culture plate (left), the gram-positive organisms appear singly, in chains, and in clumps. In broth culture media (center), the characteristic long chains are seen. In a smear from an abscess (right), the organisms are primarily gram-positive cocci in long chains.

Plate 2 Streptococcus pyogenes in Gram-stained smears. From a culture plate (left), the gram-positive organisms appear singly, in chains, and in clumps. In broth culture media (center), the characteristic long chains are seen. In a smear from an abscess (right), the organisms are primarily gram-positive cocci in long chains.

Streptococcus pneumoniae in Gram-stained smears. The organisms from a colony growing on agar medium (left) are gram positive and lancet shaped and appear in pairs and short chains. In a Gram stain of cerebrospinal fluid from a patient with pneumococcal meningitis (right), the organisms are mostly diplococci. The capsule (arrow) can be seen around some bacteria, outlined by the pink proteinaceous material of the fluid.

Plate 3 Streptococcus pneumoniae in Gram-stained smears. The organisms from a colony growing on agar medium (left) are gram positive and lancet shaped and appear in pairs and short chains. In a Gram stain of cerebrospinal fluid from a patient with pneumococcal meningitis (right), the organisms are mostly diplococci. The capsule (arrow) can be seen around some bacteria, outlined by the pink proteinaceous material of the fluid.

Plate 4 Neisseria gonorrhoeae in a Gram-stained smear from a male urethral exudate appear as gramnegative, bean-shaped diplococci.

Gram-negative bacilli (Klebsiella pneumoniae) in a Gramstained smear from an agar colony (left) and a patient’s blood culture (right). In the blood specimen, the organisms are pleomorphic, varying in length from coccobacillary to filamentous.

Plate 5 Gram-negative bacilli (Klebsiella pneumoniae) in a Gramstained smear from an agar colony (left) and a patient’s blood culture (right). In the blood specimen, the organisms are pleomorphic, varying in length from coccobacillary to filamentous.

Curved, spiral, gram-negative bacilli (Campylobacter jejuni) in a Gram stain from culture. Some bacteria line up to form spirilla like chains.

Plate 6 Curved, spiral, gram-negative bacilli (Campylobacter jejuni) in a Gram stain from culture. Some bacteria line up to form spirilla like chains.

Plate 7 Spirochetes (Treponema pallidum) appear black (arrows) in a skin preparation stained with a silver stain.

Plate 8 Bacillus spp. are gram-positive bacilli with endospores. Endospores appear as clear areas within the vegetative bacterial cell (arrows).

Mycobacterium tuberculosis in an acid-fast stain of sputum (left). The acid-fast bacilli appear as red, beaded rods against a blue background (×1,000). Strains of M. tuberculosis often form ropy “cords” (center), which is considered an indication of virulence. When stained with a fluorescent dye, acid-fast bacilli fluoresce brightly against a dark background (right, × 400).

Plate 9 Mycobacterium tuberculosis in an acid-fast stain of sputum (left). The acid-fast bacilli appear as red, beaded rods against a blue background (×1,000). Strains of M. tuberculosis often form ropy “cords” (center), which is considered an indication of virulence. When stained with a fluorescent dye, acid-fast bacilli fluoresce brightly against a dark background (right, × 400).

The quellung reaction. The halo around the cells is the pneumococcal capsule, which appears to swell when the cells are treated with pneumococcal antiserum.

Plate 10 The quellung reaction. The halo around the cells is the pneumococcal capsule, which appears to swell when the cells are treated with pneumococcal antiserum.

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