Friday 21 November 2008

Tinea capitis:


Tinea capitis refers to dermatophytosis, a fungal infection of the scalp. Three types of in vivo hair invasion are recognized:

Ectothrix invasion is characterised by the development of arthroconidia on the outside of the hair shaft. The cuticle of the hair is destroyed and infected hairs usually fluoresce a bright greenish yellow colour under Wood's ultraviolet light. Common agents include M. canis, M. gypseum, T. equinum and T. verrucosum.

Single hair invaded by Tinea capitis (Calcofluor White Stain under Ultra Violet Microscope)
Magnification was not noted
(click on photo to enlarge for better viewing)

Endothrix hair invasion is characterized by the development of arthroconidia within the hair shaft only. The cuticle of the hair remains intact and infected hairs do not fluoresce under Wood's ultraviolet light which the physician might use in a presumptive diagnosis.. All endothrix producing agents are anthropophilic eg T. tonsurans and T. violaceum.

Favus usually caused by T. schoenleinii, produces favus-like crusts or scutula and corresponding hair loss.

Tinea capitis infection of a single hair (Calcofluor White Stain under U.V. Scope)

The fungi that instigates tinea capitis thrives in moist and wet environments, and your risk increases if you have poor hygiene, prolonged skin wetness (such as that caused by sweating), and minor scalp injuries. Oral antifungal medication and medicated shampoos, such as those that contain selenium sulfide may be necessary to eliminate the infection.

The microphotographs above are of a single human hair with the arthroconidia visible within the hair shaft. They fluoresce because they were stained using Calcofluor White prior to being placed under a microscope cover slip and slide. Viewed under a fluorescent microscope at a magnification of x800.

Thursday 20 November 2008

Neisseria menningitidis:


Neisseria meningitides, also known as meningococcus is classified as a gram negative diplococcus, meaning it stains red using the gram stain and appears as two round cells in pairs. This organism is best known for its ability to cause meningitis. Symptoms may include fatigue, fever, headache, neck stiffness to coma and death can occur in about 10% of the cases. There are several serotypes (can produce distinct antibodies in response to their invasion) and these my correlate with the geographical location one aquires the infection. Antibiotic treatment might include Cephalosporins, Erythromycin, Tetracycline or Ciprofloxacin.

The photo above is of a specimen obtained from a Lumbar Puncture (LP) where a fine needle is introduced into the spinal column in order to obtain some Cerebral Spinal Fluid (CSF). The fluid was processed in a cytospin centrifuge which concentrates the specimen onto a small spot on a microscope slide, flattening out any white cells present in the process while drawing off excess fluid. White cells may be polymorph nucleocytes or monocytes depending on the infecting agent. The white blood cells are the body’s immune response attempting to defend it from the invaders. The slide is then “fixed” to adhere the material to the slide and then stained by the “Gram” method. Neisseria meningitides will appear as single or “diplo” (two) red coloured cells, often within the white blood cells. x1000 Magnification under a light microscope

Helicobacter pylori:


Helicobacter pylori is a helical or spiral shaped bacterium which can infect the various areas of the stomach and duodenum. Infection can cause peptic ulcers, gastritis, duodenitis and perhaps even lead to cancer. Helicobacter pylori likes to live in the mucous layer of the stomach aiding it in surviving the stomach‘s acid environment. Helicobacter has enzymes which splits the urea molecule resulting in carbon dioxide and ammonia which further helps to neutralize and protect it from stomach acid.

There are several tests developed to detect the presence of Helicobacter pylori. The laboratory can look for antibodies against the organism in the blood, Helicobacter antigens in the stool itself, detecting ammonia generated by the bacteria in a “breath test”, but the definitive test is by gastric biopsy via an endoscope down the throat.

Today therapy usually is by an antibiotic such as amoxicillin, clarithromycin or metronidazole and the inclusion of a “proton pump” inhibitor such as omeprzole.

The above photomicrograph is of a gastric biopsy. A very small (<1mm dia) piece of gastric tissue is mashed onto a glass slide, fixed with heat, then stained with Basic Fuschin. Viewed under a light microscope x1000.

Wednesday 19 November 2008

Histoplasma capsulatum:

Dimorphic Fungus

is a thermally dimorphic fungus found in nature. Soil contaminated with bird droppings or excrements of bats is the common natural habitat for Histoplasma. Although it is claimed to exist worldwide, tropical areas are where this fungus is more frequently encountered. Histoplasma capsulatum is the causative agent of a systemic mycosis called histoplasmosis. The spectrum of the disease varies from an acute benign pulmonary infection to a chronic pulmonary or fatal disseminated disease. Inoculation is primarily through inhalation.

For definitive identification of the fungus, (>35C) yeast-to-mould (<35c). style="font-weight: bold; color: rgb(51, 204, 0);" size="4">

Tuesday 18 November 2008

Diphyllobothrium latum:


Diphyllobothrium latum is also known as the broad fish tapeworm. There are many different host species, mainly those carnivores which eat fish, and this includes man. These worms can reach to a length of 10 meters and can shed in the region of one million eggs per day. The eggs are ovoid with an operculum (cap) at one end and a knob at the other and measure 60 x 40 microns in size. When they are released into the intestine they are only partially embryonated and require from 8 days to several weeks for the infective coracidium to develop. When the eaten by the definitive host it passes through the stomach and the scolex becomes embedded in the mucosa of the small intestine and develops rapidly producing eggs within 10-14 days. People generally become infected when uncooked fish are eaten and it is particularly prevalent in those cultures which eat a lot of freshwater fish and prepare it by methods other than cooking.

In many cases human infections go largely unnoticed, because of the nonspecific symptoms such as intestinal discomfort, nausea, and diarrhea. However, in some cases pernicious anaemia develops which is related to the malabsorbtion of vitamin B12.

There are a large number of possible drugs available to treat this disease, the two main ones used are Niclosamide and praziquantel, both of which are highly effective.

Effective control measures include cooking fish properly or freezing the fish down below -12 C for a minimum of 24 hrs.

The photomicrograph above shows the operculated eggs of Diphylobothrium latum with the pointer pointing at the cap. A wet preparation of a concentrated faecal sample was made. x800. Fecal material and bacteria can be seen in the background.

Monday 17 November 2008

Anaerobiospirillum succiniproducens


Anaerobiospirillum succiniproducens
rarely isolated in the clinical laboratory. Septicemia appears to be the most frequently reported infection caused by Anaerobiospirillum followed by gastroenteritis. This strictly anaerobic, motile, gram-negative spiral bacterium is often mistaken for Campylobacter species when first encountered. Rapid identification is imperative as Erythromycin, effective against Campylobacter and antibiotics such as Penicillin or Metronidazole, frequently prescribed against anaerobic infections are ineffective against Anaerobiospirillum.

Entry into the body seems to be through the gastro-intestinal tract and may result in bacteraemia (bacteria in the blood). Gastrointestinal symptoms may include nausea, vomiting, abdominal pain, diarrhoea and rectal bleeding. Infection usually occurs when the patient already has some chronic underlying disorder.

The photomicrograph above is from a laboratory culture of the organism after it was initially isolated from the blood of a patient returning from overseas. A modified Leifson flagella stain was employed which stained the organisms red. The stain condensed around the very fine flagella making them visible under the light microscope. The flagella are whip like projections or tails which the organism uses to propel itself. Here you can see that there is a tuft of flagella on both ends of the bacterium. x1000 magnification.

Sunday 16 November 2008

Bipolaris specefara:


Bipolaris is a dematiaceous filamentous fungus. It is cosmopolitan in nature and is isolated from plant debris and soil. Bipolaris can infect both immunocompetent and immunocompromised host. Bipolaris is one of the causative agents of phaeohyphomycosis. The clinical spectrum is diverse, including allergic and chronic invasive sinusitis, keratitis, endophthalmitis, endocarditis, endarteritis, osteomyelitis, meningoencephalitis, peritonitis, otitis media (in agricultural field workers) and fungemia as well as cutaneous and pulmonary infections and allergic bronchopulmonary disease. Bipolaris can infect both immunocompetent and immunocompromised host.

The hyphae are septate and brown. Conidiophores (4.5-6 µm wide) are brown, simple or branched, bending at the points where each conidium arises from. The conidia, which are also called poroconidia, are 3- to 6-celled, fusoid to cylindrical in shape and are light to dark brown in color.

Amphotericin B and ketoconazole are used in treatment of Bipolaris infections. Surgical debridement may be indicated in some cases, such as sinusitis

The photomicrograph above has the indicator pointed at one of the typical poroconidia which is attached to it‘s conidophore from where it has branched off the hyphae. It is of a wet preparation stained with Lactophenol Cotton Blue and viewed under x800.

Saturday 15 November 2008

Entamoeba coli:


Enatamoeba coli is an amoeba which inhabits the human gut. It is considered to be an non-pathogenic commensal organism which along with thousands of other types of organisms makes up the normal gut flora. In the laboratory care must be taken in distinguishing the non-pathogenic Entamoeba coli from the pathogenic Entamoeba histolytica. Entamoeba can exhibit two forms, the trophozoite (troph) shown here and a cyst form which can exhibit up to 8 nuclei.

Treatment is not necessary but presence of this organism in a stool sample may indicate that a person has been exposed to a contaminated source bearing faecal matter and further investigation may be warranted.

The photomicrograph above is of an Entamoeba coli trophozoite in a concentrated faecal specimen stained by the Iron Haematoxylin method. A coarse cytoplasm is seen and the cell has a nucleus with dense unevenly distributed nuclear chromatin at it’s periphery and a central nucleolus. x1000.

Friday 14 November 2008

Sporothrix schenckii:

Note:  I first posted this photo in 2008 while bedbound and recovering from a serious injury.  I had just heard about "bloging" and was just having fun playing, never thinking at that timeabout continuing this project as 'Fun with Microbiology'.  Sadly, this celluloid film print doesn't show much detail.  To remedy this, I have uploaded a new and improved Sporothrix schenckii complex blog post which can be found by clicking HERE.  I'm sure you will find the new and improved site much more informative than this lonely photo.  Y. (May 10th, 2015)
Dimorphic Fungus

Sporothrix schenckii is one of five species of thermal dimorphic fungi of medical interest. Dimorphic basically means “two forms” as the organism can express itself as a round cell yeast (>37C) or as a filamentous fungus (<37c>
In nature Sporothrix lives as a saprophyte on wood, decaying vegetation, Sphagnum moss, animal excreta and soil. It can grow on the thorns of roses and can be inoculated into the body by a prick of the thorn. The fungus can then morph to a yeast and grow in the lymph system, manifesting itself as lesions in the lymph nodes. It is often referred to as “Rose Handler’s disease”. Sporothrix can also cause lung infections.

Antifungals such as Ketoconazole may have some effect. Itraconazole shows some promise at low doses for several months. Intravenous Amphotericin B, usually the drug of last resort for fungal infections, works poorly and slowly.

The photomicrograph above shows the fungal mycelia with typical hyphae bearing conidia. The “wet preparation” is dyed with Lactophenol Cotton Blue stain for contrast. x800.

Thursday 13 November 2008

Cryptosporidium parvum:

Protozoan Parasite

Cryptosporidium is a coccidian protozoan parasite who’s oocysts can infect humans usually by the oral-fecal route. Contaminated water is often the source of infection. In recent reports improperly washed produce was implicated as the source of infection. In immunocompetent patients, cryptosporidiosis is an acute, self-limiting diarrhoeal illness lasting about 1 to 2 weeks. Symptoms may include frequent watery diarrhoea, nausea, vomiting, abdominal cramps with low grade fever. No safe and effective therapy for cryptosporidial enteritis has been successfully developed. Since cryptosporidiosis is a self-limiting illness in immunocompetent individuals, general, supportive care is the only treatment for the illness. In immunocompromised patients (AIDS, transplants, cancer patients, the illness may be much more serious. No effective treatment is available other than to prevent dehydration and let the illness run it’s course.

The above micro photograph is of a Cryptosporidium oocyst from a concentrated stool sample stained by Carbol Fuschin, then decolourized by acid-alcohol. The oocysts are “acid fast” and resist decolorization whereas other material loses the resulting red colour. The remaining material in the slide is fecal debris and normal intestinal bacterial. x1000.

Wednesday 12 November 2008

Strongyloides stercoralis:

Parasite: Nematode

Strongyloides stercoralis is a human parasitic roundworm (Nematode) about 2.5 mm in length. The adult parasitic stage lives in tunnels in the mucosa of the small intestine. The genus Strongyloides contains 53 species and S. stercoralis is the type species. The infectious larvae penetrate the skin when there is contact with the soil. Some of them enter the superficial veins and ride the blood vessels to the lungs, where they enter the alveoli. They are then coughed up and swallowed into the gut, where they parasitize the intestinal mucosa. S. stercoralis has a very low prevalence in societies where faecal contamination of soil is rare.

Ivermectin is the drug of first choice for treatment. Thiabendazole was used previously, but owing to its high prevalence of side effects and lower efficay, it has been superceeded by ivermectin and as second line, albendazole.

The above photomicrograph is of the Strongyloides larvae in a wet preparation of concentrated fecal material. x800.

Tuesday 11 November 2008

Scedosporium inflatum:


Note: When I took this photograph, the only camera in my arsenal was a film camera.  Since then, changes have occured not only in photographic technology but in the nomencature of this genus.  This fungus previously known as Scedosporium inflatum was renamed as Scedosporium prolificans.  Please visit the new post within this blog by clicking on the link within this paragraph.  To learn more about the cameras used to take the photographs, please visit my blog post entitled 'Toys'.

Scedosporium inflatum is a filamentous fungus which is found in the severely immunodepressed including those with hematologic malignancy and recipients of allogeneic hematopoietic stem cell, heart-lung, lung, liver and renal transplants and occasionally in normal hosts as well. It can cause lesions in the sinuses, lungs, bones and central nervous system. The formation by S. inflatum of annelloconidia in wet clumps at the apices of annellides with swollen bases was found to be the most useful characteristic in differentiating this potential pathogen. Dissemination throughout the body might be prevented with combined itraconazole and fluconazole treatment. Variconazole is considered first-line treatment by some.

The above photo is of the hyphae and conidia stained with Lactophenol Cotton Blue and viewed x800.

Monday 10 November 2008

E-coli & Ascorbic Acid Electron Micrographs

Back in my university days I found employment at University Hospital in London at which I studied the effects of the antibiotic Metronidazole (Flagyl) against various bacteria (1). Metronidazole has long been established as one of the premier antibiotics with activity directed against most gram negative as well as many gram positive anaerobic bacteria. More interestingly, our research unexepectantly found that Metronidazole was able to exhibit remarkable activity against the facultative organism Gardnerella vaginalis (2). This was found to be a result of the metronidazole molecule being metabolized in the liver to both an ‘acid’ and a ‘hydroxy’ metabolite. Further experimentation showed that the hydroxy metabolite exhibited significant activity against this organism.

* * *

In the experiments using various anaerobic (oxygen hating) organisms, liquid tubed media was used to grow the bacteria and in which to dilute the antibiotic. In order to “reduce” the media, so that it was oxygen free, a variety of chemical ingredients could be added. We chose ascorbic acid and used the facultative anaerobic organism E-coli as a control. The test anaerobic organisms reacted as expected however significant changes were visible on the control E-coli bacteria as well, against which metronidazole should have no appreciable effect. The E-coli cells were visibly stressed and damaged, often showing uncharacteristic morphology such as incomplete cellular division, elongated cell forms and bifurcated ends. In a rather unexciting explanation, it was determined that this was due to the ascorbic acid content itself stressing the E-coli cells.

* * *

Regardless of this outcome, the entire process served as a learning experience and afforded me a chance to work with the university’s electron microscope. I’ve included some of those electron micrographs here. In particular I never tire of marveling at the physical and molecular structure of these fascinating bacteria. Included here is an electron micrograph of an E-coli bacterium demonstrating the cell wall structure which is responsible for it’s gram staining properties. Other smaller photos show the stressed nature of the bacteria which should have appeared as rather uniform bacilli. Various magnifications were taken and if I recall, the electrondense negative stain was phosphotunstic acid (PTA).

* * *

*all electron micrographs were taken by Yuri.

So, perhaps this is evidence that you should get your daily dose of ascorbic acid (vitamin C) as it may itself have a direct effect on bacteria in your system. You know what they say, “an apple a day keeps the doctor away” - perhaps with some truth to it.

(1) Edward D. Ralph & Yuri E. Amatnieks
Antimicrob Agents Chemother. 1980 March; 17(3): 379-382

(2) E.D. Ralph & Y.E. Amatnieks
Antimicrob Agents Chemother. 1980 July; 18(1): 101-104