Gallery: The amazing ink-proof yeast capsule

by Mike

Observed doctors and medical students as they learn about the workings of the clinical microbiology lab, I’m impressed by their love of the India ink test for cryptococcus. The way this test works is: Cryptococcus is a type of infectious yeast that looks a lot like Candida if you just do a gram stain. But it has a polysaccharide capsule around each cell (unless for some odd reason it isn’t producing a capsule), wider than the cell itself. So if you put Cryptococcus in a colored liquid, most famously a solution of India ink, the polysaccharide capsule shows up as a huge empty white area around the cell. Whereas with Candida, only the cell itself is white.

We apparently don’t use this test regularly anymore, but we still show it to people in case they need to know what it is.

Something about the India ink test just makes people happy. A lot of diagnostic microbiology uses techniques that were developed several generations ago, but this one is just so simple, requiring not “acid alcohol” or various toxic red and purple substances, but merely the simplest form of ink, developed millennia ago. And to use the phrase “India ink”, instead of “colloidal carbon” or something, is such an anachronism in the 21st century. Most of us last saw that phrase when reading some classic of literature like The Secret Garden or A Bear Called Paddington. And aside from the name, there’s something magical about seeing this invisible capsule appear around what seemed to be a normal yeast cell. Like lemon-juice ink made visible.

* * *

So here are some depictions of India-ink-stained Cryptococcus in the literature. First, camera lucida drawings from a 1935 JID paper by Rhoda W. Benham (Cryptococci — their identification by morphology and serology) that must have been a handy field guide to Cryptococcus species. The top right corners of the dishes are shaded to show how they look under India ink.

crypto-benham

* * *

Now, some photos of patient tissues directly stained with India ink.

From Wilson HM, Duryea AW (1951), Cryptococcus meningitus (Torulosis) treated with a new antibiotic, actidione®. Archives of Neurology & Psychiatry 66(4):470-480.

crypto-duryea

* * *

From Carnecchia BM, Kurtzke JM (1960), Fatal toxic reaction to amphotericin B in cryptococcal meningo-encephalitis. Annals of Internal Medicine 53(5):1027-1036.

crypto-carnecchia

* * *

From Schupbach CJ, Wheeler CE Jr, Briggaman RA, Warner NA, Kanof EP (1976), Cutaneous manifestations of disseminated Cryptococcosis. Archives of Dermatology 112(12):1734-1740. Note “Tzanck preparation”, looking for multinucleated giant cells.

crypto-schupbach

* * *

From Love GL, Boyd GD, Greer DL (1985), Large Cryptococcus neoformans isolated from brain abscess. Journal of Clinical Microbiology 22(6):1068-1070.

crypto-love-1985

* * *

From Bottone EJ, Kirschner PA, Salkin IF (1986), Isolation of highly encapsulated Cryptococcus neoformans serotype B from a patient in New York City. Journal of Clinical Microbiology 23(1):186-188.

crypto-bottone

* * *

And some images of cells grown in culture. Ending with one in color!

From Neill JM, Abrahams I, Kapros CE (1950), A comparison of the immunogenicity of weakly encapsulated and of strongly encapsulated strains of Cryptococcus neoformans (Torula histolytica). Journal of Bacteriology 59(2):263-275.

crypto-neill

* * *

From Littman ML, Tsubura E (1959), Effect of degree of encapsulation upon virulence of Cryptococcus neoformans. Proceedings of the Society for Experimental Biology & Medicine 101:773-777.

crypto-littman

* * *

From Bulmer GS, Sans MD, Gunn DM (1967), Cryptococcus neoformans I: Nonencapsulated mutants. Journal of Bacteriology 94(5):1475-1479.

crypto-bulmer

* * *

From Dykstra MA, Friedman L, Murphy JW (1977), Capsule size of Cryptococcus neoformans: Control and relationship to virulence. Infection & Immunity 16(1):129-135.

crypto-dykstra

* * *

From Chang YC, Kwon-Chung KJ (1994), Complementation of a capsule-deficient mutation of Cryptococcus neoformans restores its virulence. Molecular & Cellular Biology 14(7):4912-4919.

crypto-chang

* * *

From Doering TL (2000), How does Cryptococcus get its coat? Trends in Microbiology 8(12):547-553.

crypto-doering

* * *

From Zaragoza O, Casadevall A (2004), Experimental modulation of capsule size in Cryptococcus neoformans. Biological Procedures Online 6(10):10-15.

crypto-zaragoza-2d

* * *

From Zerpa R, Huicho L, Guillén A (1996), Modified India ink preparation for Cryptococcus neoformans in cerebrospinal fluid specimens. Journal of Clinical Microbiology 34(9):2290-2291.

crypto-zerpa

* * *

And a bonus: High-tech 3-dimensional visualization! These are 40 focal “slices” of a single cell. From Zaragoza O, McClelland EE, Telzak A, Casadevall A (2006), Equatorial ring-like channels in the Cryptococcus neoformans polysaccharide capsule.

crypto-zaragoza-3d

Advertisements