1. Introduction to Microbiology
Anas Abu-Humaidan M.D. Ph.D.
Lecture 23

2. Tinea versicolor
Pityriasis versicolor, sometimes called tinea versicolor, is a common fungal infection that causes small patches of skin to become scaly and discoloured.
Pityriasis versicolor is caused by a type of yeast called Malassezia. This yeast is found on the skin of more than 90% of healthy adults, but overpopulation of the yeast causes the skin damage.
The patches may be darker or lighter than normal skin colour, or may be red, brown or pink. They tend to develop gradually and may join up to form larger patches over time.

3. Tinea versicolor
living or staying in a warm, moist environment, wearing cloths that don’t breath properly, and sweating excessively increases risk of infection
Pityriasis versicolor can sometimes be confused with vitiligo, as they both cause the skin to become discoloured in patches.
UV light can be used for diagnosis, pale greenish colour under Wood's ultra-violet light
Skin scraping then Ink and KOH staining shows yeast
Antifungal shampoos or creams can be used for treatment.

4. Overview

5. Candida albicans
Candidiasis occurs in localized and disseminated forms. Localized disease is seen as erythema and white plaques in moist skinfolds (diaper rash) or on mucosal surfaces (oral thrush).
It may also cause the itching and thick white discharge of vulvovaginitis.
Deep tissue and disseminated disease are limited almost exclusively to the immunocompromised. Diffuse pneumonia and urinary tract involvement are especially common.

6. Aspergillosis
Aspergillosis is a disease caused by Aspergillus, a common mold that lives indoors and outdoors.
Most people breathe in Aspergillus spores every day without getting sick. However, people with weakened immune systems or lung diseases are at a higher risk of developing health problems due to Aspergillus.

7. Aspergillosis
Sources of high numbers of Aspergillus spores include air conditioning units, composting and damp or flood damaged housing & hospital building projects.
Transmission occurs through inhalation of airborne conidia. A conidium, sometimes termed an asexual chlamydospore or chlamydoconidium, is an asexual, non-motile spore of a fungus.
Aspergillosis is thought to affect more than 14 million people worldwide

8. Aspergillosis
In immunosuppressed hosts: invasive pulmonary infection, usually with fever, cough, and chest pain. Infection may disseminate to other organs, including brain, skin and bone.
In immunocompetent hosts: Localized pulmonary infection in people with underlying lung disease, allergic bronchopulmonary disease, and allergic sinusitis.
Chronic cavitary pulmonary aspergillosis showing marked progression between a) 2007 and b) 2012.

9. Pneumocystis
Pneumocystis is an (yeast like) organism of low virulence, which seldom produces disease in a host with normal T-lymphocyte function.
Because it has not been possible to cultivate Pneumocystis, our knowledge is limited.
Pneumocystis pneumonia is insidious, beginning with mild fever or malaise in persons whose immune system is compromised.
Before the development of effective chemoprophylactic regimens it was present in approximately 50% of all AIDS patients at the time of initial diagnosis.
Asphyxia can lead to death in a 3- to 4-week period.

10. Cryptococcus neoformans
Cryptococcus neoformans is a fungus that lives in the environment throughout the world.
C. neoformans infections are acquired by inhaling the fungus, but are rare in people who are otherwise healthy; most cases occur in people who have weakened immune systems.
Infection can present as pneumonia-like illness, with symptoms such as cough, fever, chest pain, and weight loss
C. neoformans can also disseminate to the central nervous system (CNS) and cause meningoencephalitis. 

11. Parasitic infections الالتهابات الطفيلية
Parasitism, denotes a relationship in which one organism, the parasite, usually benefits at the expense of the other, the host.
Parasites studied in this course that cause disease are either Protozoans or helminths.
Protozoa الأوليات are microscopic, single-celled eukaryotes with a membrane-bound nucleus and organelles.
Helminths, comprising both Platyhelminthes الديدان المسطحة and Nemathelminthes ديدان أسطوانية are macroscopic, multicellular worms possessing differentiated tissues and complex organ systems; they vary in length from more than 1 m to less than 1 mm.
The majority of both Protozoa and helminths are free living, are seldom inconvenience the human race. The less common disease-producing species are typically obligate parasites.

12. Parasitic infections الالتهابات الطفيلية
Parasitic infections are much less common in developed countries, but can still happen in some populations like the impovireshed.

13. Malaria
Malaria is a mosquito-borne disease caused by a parasite. People with malaria often experience fever, chills, and flu-like illness. Left untreated, they may develop severe complications and die.
Malaria parasites are micro-organisms that belong to the genus Plasmodium.
In humans, the parasites grow and multiply first in the liver cells and then in the red cells of the blood. In the blood, successive broods of parasites grow inside the red cells and destroy them, releasing daughter parasites (“merozoites”) that continue the cycle by invading other red cells
The blood stage parasites are those that cause the symptoms of malaria, and depending on the shape of the parasite in the RBC, diagnosis can be made.
Sickle cell trait limits intensity of P falciparum infection. Other hemoglobinopathies can also exert protection.

14. Malaria

15. Malaria
Distribution is mainly in tropical areas Worldwide.
Plasmodium vivax is the most widely distributed of the four species.
Plasmodium falciparum is the dominant organism of the tropics.
Plasmodium ovale is rare
and found principally in Africa
In 2017 an estimated 219 million cases of malaria occurred worldwide and 435,000 people died, mostly children in the African Region.

16. Malaria
The life cycle in the female Anopheles mosquito begins with the ingestion of male and
female gametocytes from the circulation of a malaria-infected individual.
Rapid infection of hepatocytes
starts asexual cycle in humans
Erythrocytic cycle begins with
merozoite attachment to RBC
receptor
Trophozoites multiply in RBCs to
form new merozoites
In 48 to 72 hours, RBCs rupture,
releasing merozoites to infect new
RBCs
Intrahepatic dormancy causes
relapses with P vivax and P ovale

17. Malaria
The indications for treatment rests on several factors. These include the severity of disease, the infecting species of Plasmodium, and the part of the world in which the infection was
acquired.
Several agents can destroy asexual erythrocytic parasites. Chloroquine, has been the most commonly used.
In endemic areas, mosquito contact can be minimized with the use of house screens, insecticide bombs within rooms, and/or insecticide-impregnated mosquito netting around beds.

18. Malaria

19. Toxoplasmosis
Like the plasmodia, Toxoplasma gondii, the cause of toxoplasmosis, is an obligate intracellular parasite. Usually found in the intestine of mammals.
Can be transmitted from undercooked food, or from cat feces, and from mother to child.
More than 40 million men, women, and children in the U.S. carry the Toxoplasma parasite, but very few have symptoms because the immune system usually keeps the parasite from causing illness
If a woman becomes newly infected with Toxoplasma during or just before pregnancy, she can pass the infection to her unborn baby (congenital transmission), leading to miscarriage or congenital abnormalities.
Immunocompromised persons who were infected with Toxoplasma at some point before they become immunosuppressed are at risk for developing a relapse (reactivation) of toxoplasmosis.

21. Further reading: Sherris Medical Microbiology, sixth edition
Chapter 48-52