Saturday, 23 April 2011

Trichomonas hominis

Trichomonas hominis

Parasite (Flagellate)

A relatively common flagellate which may be overlooked or unrecognized during examination of fecal specimens for parasites. This organism is found worldwide in both warm and temperate climates. Its detection in fecal specimens does not seem to be related to gastrointestinal illness although it is often recovered from diarrheic stools. Trichomonas hominis is considered to be non-pathogenic.

As with Trichomonas vaginalis, there is no known cyst stage therefore it must be acquired by ingesting the trophozoite directly. The troph probably survives the acid stomach environment by ingestion along with some protective substance such as milk. After passing through the stomach, they tend to take up residence in the cecal region of the large intestine where the feed on bacteria.

Trophozoites are about 5 to 15 µm by 7 to 10 µm in size and are roughly pyriform in shape. As with Trichomonas vaginalis, they have both an axostyle and undulating membrane, which helps to differentiate them from other fecal parasites that may be present. The undulating membrane extends the entire length of the body, in contrast to that of Trichomonas vaginalis.

Diagnosis; In freshly passed stool they may be recognized by motility provided by the characteristic movement of flagella and rhythmic beating of the undulating membrane. These rather small organisms are difficult to see in the fresh specimen and are easily overlooked in stained preparations.

Both Trichomonas hominis and Trichomonas vaginalis are site specific in that neither can survive in the other’s environment. Attempts to transplant T.hominis into the vaginal were unsuccessful.

While prevalent worldwide, it is recovered with greater frequency in warmer climates and from children more than in adults. Prevention is by interrupting transmission which is accomplished though increased hygiene and improved sanitary conditions. Treatment is not warranted.

Trichomonas hominis in stool specimen (Iron-hematoxylin stain x1000)
(Click on image to enlarge for better viewing - 1024 X 768 px)

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Tuesday, 19 April 2011

Cunninghamella species

Cunninghamella species (including Cunninghamella bertholletiae)
-filamentous fungus (mould) in the order of Mucorales.

Widespread distribution primarily in sub-tropical climates - commonly found in soil, animal matter and soil. Has been isolated from cheese.

Extremely fast growing fungus producing wooly mycelia which can fill a petrie dish in 2 to 3 days. Mature matt-like surface growth appears white to grey, darkening with age. Reverse is white/pale/buff.

Cunninghamella on Sabouraud-Dextrose Agar after 48 hours incubation at 30C

  • Hyphae are broad and aseptate or rare septations
  • Sporangia are long, branched and ending in swollen vesicles about 40 µm in diameter. Vesicles on lateral branches are generally smaller.
  • Vesicles are covered with spine-like denticles, each supporting a single round to oval sporangiolum (7 µm to 12 µm).
  • Each sporangiolum contains one spore which can be smooth walled or finely echinulate (ie. is spiny or has small prickles)
  • Zygospores may be present (spherical, 25-55 µm diameter, brownish with tuberculate projections. Heterothalic.
  • Rhizoids may be seen.
Cunninghamella sporangiophore covered with sporangiola (400X, LPCB, Nikon)

Cunninghamella species sporangiophore bearing sporangiola attached to surface by a denticle.
(400X, LPCB, Nikon)
(Click on photo to enlarge for better viewing)

Cunninghamella sporaniophore with terminal vesicle. Sporangiophores dispersed revealing the denticles (arrow) by which they were attached to the vesicle. (400X, LPCB, Nikon)
(click on photo to enlarge for better viewing)

Cunninghamella sporangiospores
(Click on photo to enlarge for better viewing)
C.bertholletiae is thermophilic species with good growth at 30oC as well as at 45oC however C.elgans fails to grow a 45oC.  Growth is inhibited by cyclohexamide.

An opportunist. Cunninghamella is agent of zygomycosis known to have cause pneumonia in immunocompromised children, disseminated disease in renal transplant recipients and infected other severely debilitated patients such as those with AIDS. C.bertholletiae is considered to be the only pathogenic species. It can be distinguished from the non-pathogenic C.elegans by its ability to grow at 40-45oC.

November 3rd, 2013
I've come across another isolate of Cunninghamella and thought I'd add a few more photos.  As this isolate proved to be thermophilic, with growth at 45oC it could be definitively identified as Cunninghamella bertholletiae.  Cunninghamella elegans fails to grow at this elevated temperature.

Cunninghamella bertholletiae on SAB at 30oC after 48 & 72 hours of incubation.  As is evident, it matures and will fill the plate rapidly. (Nikon)

 Cunninghamella bertholletiae - branching sporangiophores.  Free sporangioles in upper left of photo.
 (400X, LPCB, Nikon)

Cunninghamella bertholletiae - another view of the broad septate hyphae & branching sporangiophores.  The vesicles have lost most over their sporangioles and can be seen free throughout the photo.  (400X, LPCB, DMD-108)

  Cunninghamella bertholletiae -sporangiophores with vesicles and attached sporangioles.
(400X, LPCB, DMD-108)

   Cunninghamella bertholletiae -as above. Vesicle surrounded by individual sporangiola maturing into sporangioles.  (400X, LPCB, DMD-108)

  Cunninghamella bertholletiae -mature sporangioles being dispersed from vesicle.
(400+10X, LPCB. DMD-108) 

Cunninghamella bertholletiae -broad hyphae with sporangiophore devoid of sporangioles.  Vesicle clearly shows the nubby bumps which are tuberculate projections (denticles) that cover the surface.  These were the points of attachement of the sporangioles to the vesicle.
(400+10X, LPCB, DMD-108)

  Cunninghamella bertholletiae - vesicle showing the apical surface covered with the tuberculate projections.  (400+10X, LPCB, DMD-108)

  Cunninghamella bertholletiae -a shift through the plane of focus shows the texture covering the entire surface of the vesicle, created  by the tuberculate (denticle) projections.  Unlike dimples on a golf ball, these are projections outwards from the surface.
(1000+10X, LPCB, DMD-108)

  Cunninghamella bertholletiae -broad branching, septate hyphae/sporangiophores bearing somewhat oval (I've often found 'tear-drop' shaped) sporangioles.  Here they are still attached via the tuberculate projections to the vesicle.  (1000X, LPCB, DMD-108)

Cunninghamella species computer wallpaper (1024 X 768) as posted. (Nikon)
(Click on photo to enlarge for better viewing)

Syncephalastrum species

Syncephalastrum species
-A filamentous fungus classified within the order Mucorales.

Syncephalastrum species are saprobes commonly isolated from animal dung and soil primarily in tropical or subtropical regions.

Very rapid growth - mature within 3 days. Abundant aerial hyphae gives a wooly or cotton candy-like texture. Pale to dark grey shades on the surface with a white or pale reverse.

Syncephalastrum on Sabouraud's Dextrose Agar at 72 hrs at 30C
  • Broad hyphae -septa absent or rare.
  • Sporangiophores are 10-25 µm wide, often branched, having a terminal vesicle up to 80 µm in diameter, which produce finger shaped merosporangia (4-6 µm by 9-35 µm) over the entire surface.
  • Sporangiospores (merospores) are round and formed in a linear series, between 3 to 18 in number within in the interior of the merosporangia. They are smooth in texture, pale brown, spherical to oval, ~3-7 µm in diameter.
  • Rhyzoids are usually present
Sporangiophore arising from hyphae with terminal vesicle with merosporangia radiating out from the surface. (LPCB X400)
(click on photo to enlarge for better viewing)

Mature Syncephalastrum sporangiophores (LPCB x400)
(click on photo to enlarge for better viewing)

(click on photo to enlarge for better viewing)

Syncephalastrum sporangiophore with radiating finger-like merosorangia containing individual merospores.
(click on photo to enlarge for better viewing)

Finger-like merosporangia free of sporangiophore, each containing merospores
(click on photo to enlarge for better viewing)

Considered to be non-pathogenic to humans although a case of cutaneous infection has been reported (Kalama & Thambiah 1980). May be found as a contaminant.

Sunday, 3 April 2011

Mucor Species

Mucor species

The genus Mucor is a filamentous fungus with several species, few of which grow well at 37C (body temp.) and thereby able to infect humans. Mucor species have been implicated as an agent in zygomycosis, particularly in the debilitated patient. Mucor is ubiquitous in nature, found in the soil or growing on decaying vegetative matter.

Macroscopic Appearance (Colony) ~25-30C;
Mucor is a rapidly growing fungus which will fill a culture plate in a matter of a few days with a woolly growth resembling cotton candy. New growth is white in colour but turns a greyish-brown with aging. The reverse remains a pale white.

Mucor On SAB Agar Plate 48hrs at 30C

Microscopic Morphology;
Mucor has broad hyphae which are scarcely or non-septate. Sporangiophores are long, may be branched and terminate in a round spore-filled sporangia (50µm-300µm diameter). The sporangia has a thin wall which when mature dissolves (or is disrupted) to release round or somewhat ellipsoidal sporangiospores (4µm-8µm diameter). With the spores scattered, the collumella which bore the sporangia is visible, sometimes leaving a collerette at the base of the sporangium.

Welcome to the Jungle
Sparsely septated hyphae, sporangiophores bearing sporangia (LPCB X100)
(click on photo to enlarge for better viewing)

Mucor sporangiophore bearing dematiaceous sporangia containing sporangiospores (400X)
(click on photo to enlarge for better viewing)

With spores dispersed, collumella is revealed with collarette remaining beneath (arrows)
(click on photo to enlarge for better viewing)

Mucor species are capable of producing chlamydospores.
Mucor differs from Rhizopus species in that it fails to produce rhizoids and from Absidia species by the absence of apophysis beneath the sporangium.
Mucor is inhibited by cyclohexamide.

Amphoteracin B, Ketoconazole, Itraconazole and Voriconazole have shown to have activity against Mucor, however clinical response may be variable.

Mucor species computer screen wallpaper (1025 X 768) when posted.
(click on image to enlarge for better viewing)

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Saturday, 2 April 2011

Hookworm & Trichostrongylus Ova

Hookworms & Trichostrongylus sp.
-Nematodes (Roundworms)

Ancycostoma duodenale (old world hookworm) -predominant in South-East Asia, China, India, Northern Africa and Southern Europe.
Necator americanus (new world hookworm) - America, Caribbean, Central America, Southern Africa, Polynesia -virtually World-wide.

Old & New World labels are historical and somewhat of a misnomer as geographic distribution overlap.
Hookworms are found in warm, moist areas of the world.

Adult Worms;
Adult males are about 7-11 mm long with A.duodenale usually slightly larger than N.americanus. Adult worms are rarely seen as they usually remain firmly attached to the intestinal mucosa by their mouth. A.duodenale has well developed teeth while N.americanus has cutting plates facilitating attachment. As such, diagnosis is usually made by finding hookworm eggs in stool specimens. Eggs (ova) are essentially identical for both hookworm species.

Infection is acquired through skin penetration of the filariform larvae from soil. Hookworms have hyaluronidase activity which facilitates the infective larvae penetration through skin. After penetration, the larvae are carried to the heart and then to the lungs where they enter the alveoli and migrate through the bronchi to the trachea and pharynx. Once they reach the pharynx they are swallowed and travel to the small intestine where they attach to the mucosal surface and further mature. Females usually begin to deposit eggs about 5 months after initial infection.

Eggs (~56µm to 75µm X 36µm to 40µm) that are passed in the stool are usually in the early cleavage stage and appear rather oval with broadly rounded ends and a clear space between the embryo and egg shell. Eggs will hatch within 1 to 2 days when in moist, shady warm soil. Infective filariform larvae develop within 5 to 8 days of hatching under optimal conditions and can remain viable in the soil for several weeks.

Hookworm Egg - Note broadly rounded ends, clear space around developing cells.
(click on image to enlarge for better viewing)
All photos from formalin-ethyl acetate concentrate at 400X
Clinical Disease;
Hookworm infections cause more morbidity rather than mortality. Symptoms usually are related to the larval load (how many). Infections may go unnoticed or may cause pruritus with further complication by secondary infection through scratching. Depending on the number of migrating larvae, pneumonitis may result.
Once attached to the intestinal mucosa, symptoms may include;
  • Necrosis of intestinal tissue
  • Blood loss through ingestion by the worm or direct bleeding facilitated by an anticoagulant secreted by the worm
  • Fatigue
  • Nausea & Vomiting
  • Abdominal pain
  • Diarrhea with stools that may be tinted red to black due to blood loss.
  • Chronic infections may result in anaemia from the blood loss.
Again, diagnosis is made by finding the hookworm eggs in stool samples, either in direct, concentrate or stained smears. Results should be reported as “Hookworm Ova” present as species (N.americanus, A.duodenale) cannot be determined by the egg.

Prevention & Treatment;
Sanitary treatment & disposal is the most effective way of reducing exposure to the filariform soil larvae. Wearing of shoes may also help prevent infection.
Anti-helminthic drugs such as albendazole prove effective in treatment.

Just for comparison- A Hookworm egg in the upper right compared to an Ascaris egg in the lower left of photomicrograph. Fecal concentrate at X250)
(click on photo to enlarge for better viewing)

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Trichostrongylus Species; (several species can infect humans with varying severity)
This nematode (roundworm) has worldwide distribution and is commonly found in herbivores.
Trichostrongylus species are similar to hookworms as they also take up residence on the mucosa of the small intestine however they differ in not having teeth or cutting plates.

Infections is usually acquired by ingestion of the infective larvae on contaminated plant material. Trichostrongylus larvae reach the small intestine without any migratory pathway through the lungs and mature there within 3 to 4 weeks.

The Trichostrongylus ova appear similar to Hookworm ova however they are slightly larger (~73µm to 95µm X 40µm to 50µm) and tend to have more pointed ends.
Eggs deposited in warm, moist soil may hatch as quickly as 24 hours and develop into infective larvae after about 60 hours.

Trichostrongylus Egg - Note similarity to Hookworm Egg above however end more pointed.
(click on image to enlarge for better viewing)

Trichostrongylus Egg - Note much more pointed end than Hookworm
(click on image to enlarge for better viewing)

As with the Hookworms, symptoms from Trichostrongylus infections are related to the worm burden and subsequent damage to the intestinal mucosa. Haemorrhage and desquamation may occur as with Hookworm infections.
Symptoms are not usually clinically significant unless there are large numbers of worms present.

Diagnosis is usually made through egg identification in the stool.

Prevention and Treatment;
Herbivores constantly reinfect grazing areas therefore the only effective prevention is the proper cleaning and cooking of vegetable foodstuffs. Treatment again is with anti-helmithic drugs such as albendazole.