2025-04-14 Microbiology For The Health Sciences

Lecture 1 for Exam 4

Chapter 21 Skin Diseases

• They are eukaryotes 

• These organisms (fungi and protozoan) are becoming resistant

Fungi that invade keratinized tissue (epidermidis) are called

dermatophytes which lead to dermatomycoses.

Myco

think about fungal cells 

Derma

skin

Ringworm - Tinea corporis, T. cruris, T. capitis, T. unguium

are all contagious and usually one comes in contact with the organism from unclean environments and fomites. All can be treated with antifungal drugs but it may take many weeks. With T. pedis, one can get a secondary bacterial infection.

• Only because of the way it looks, has nothing to do with worms 

• Pick it up from gym showers 

• Be careful in nail salons - T. unguium (regulate nail salons) 

• Fomites - inanimate objects that harbor infectious agents 

• T. pedis (athlete's food) - you can get secondary infections 

Candidiasis

Candida albicans is part of the normal flora. It can cause thrush, vaginitis, infect tissues and is the most common nosocomial fungal infection. Possibility of a systemic infection in immunocompromised people.

• Superinfection 

• When you are treating someone with a lot of antibiotics, the normal flora disappears, the CA has no competition 

• Seems to resist phagocytosis 

• Any change of pH in vagina - upsets flora in vagina - leads to infection 

• Self-limiting - resolves on its own 

Candida auris

is an emerging fungal infection causing worldwide concern. It is a serious infection in hospitalized patients which often enters the bloodstream and spreads throughout the body.  It is highly resistant to antifungal drugs. Special laboratory methods are used to identify it.

• Ubicudis - find it in hospital and healthcare settings 

• No one understands where it comes from - maybe climate change? 

• Can easily go systemic - sepsis 

Vulvovaginal Candidiasis

most cases caused by Candida albicans. It is an opportunistic infection which can occur with uncontrolled diabetes, change in pH, hormone change, and long-term antibiotic therapy. 

• Any change of pH in vagina - upsets flora in vagina - leads to infection 

Trichomoniasis

is caused by a protozoan (Trichomonas vaginalis) which is transmitted sexually. It infects the urogenital tract surfaces in both males (rarely have symptoms) and females. Many cases are asymptomatic.   T. hominis (intestinal tract) and T. tenax (mouth) are normal commensals  in our body.

• Protozoan 

• self - resolving 

• Commensals 

Coccidioidomycosis

Coccidioides immitis is common in the Southwest USA and sometimes referred to as Valley Fever. Spores are inhaled which usually results in mild flu like symptoms or no symptoms at all. In tissues the organism can form a thick walled off body called a spherule filled with spores often used to diagnosis. Complications can occur such as spreading to meninges or bones.

• Breathed in spores (earthquake happens and the soil may cause spores to go all over the place) 

• Immunocompromised people 

• Flu-like symptoms 

Histoplasmosis

Histoplasma capsulatum is endemic in central and eastern US. Soil fungal spores are inhaled and mature into an actively growing yeastlike form which can survive and multiply in macrophages which circulate the organism through the body.  It is usually a mild respiratory infection but complications can arise such as pneumonia and infection in the spleen, liver, and lymph nodes.

• Inhale spores - go on to produce a vegetative yeast like structure 

• Budding yeast, hyphae (depends on the organism) 

• Can go systemic 

• People who explore caves - bats harbor the organism 

• Immunocompromised 

Pneumocystis pneumonia (PCP)

caused by Pneumocystis jirovecii (carinii) and invades lung cells. In healthy individuals there are few or no symptoms. It can cause complications if it spreads to other organs in individuals that have compromised immunity. There is a high fatality rate if people develop an infection and are not treated with antifungal agents. This organism often causes problems for people with AIDS.

• Major problem with people with HIV (back in the 1900s fungal infection in young people) 

• You have to be treated with antifungal agents 

Blastomycosis

caused by Blastomyces dermatitidis. Normal entry is through a wound or breathing endospores into the lungs. The spores mature to yeast cells which can get into the circulation via macrophages. Systemic blastomycosis can lead to extensive tissue damage.

• Spores can enter a wound or you can breathe them in 

• In soil rather hearty, not like endospores 

• You do have it be treated if systemic 

Aspergillosis

Aspergillus fumigatus infects the lungs when the spores are inhaled. The spores are often found in decaying vegetation. Can become an invasive lung infection which leads to asphyxiation.  This is another fungal infection that causes problems for people with AIDS or with an impaired immune system.

• Common soil fungus 

• Breathing down leaves and gets food from the ground 

• Yeast phase, hypahe - long projections - causes asphyxiation (clogs the lung so they cannot breathe) 

Giardiasis

Giardia duodenalis (intestinalis or lamblia) is the cause of the disease.  Cysts of the organisms are ingested and go to the small intestine where they mature to the trophozoite and adhere to the bowel wall via an adhesive (sucker) disk. It causes severe diarrhea with dehydration and can interrupt normal adsorption. The cysts are not killed by chlorination.

• Protozoal infection 

• Cysts - coming in through dirty water, contaminated - shedding the cyst out in fecal material - thats how you would get it 

• Virulence factor - adhesive disk 

• Beaver fever - they shed the cyst into the water and then you can ingest it 

• You have to filter the water to trap the cysts (bc chlorination doesn't kill it) 

• Immunocompromised people 

Amebiasis (Amebic Dysentery)

caused by Entamoeba histolytica. Can be an acute disease or chronic. Cysts are ingested and mature to trophozoites in the colon.  They can invade the intestinal mucosa and get into the bloodstream.  Intestinal lining damage can cause fecal material to get into the body cavity and cause "peritonitis".  The cysts are not killed by normal chlorine concentrations in water. A small number of the population are asymptomatic carriers of E. histolytica.

• Ent - intestinal infections 

• Amoebe - eukaryotic 

• Histo - tissue 

• Lytica - lysing 

• Very invasive - into the bloodstream

Cyclosporiasis

A more recently discovered protozoan causing an intestinal disease. Oocytes from Cyclospora cayetanensis are ingested and lead to watery diarrhea. The oocytes can be found in water or on food like berries.

• Protozoan 

• Oocytes 

• Contaminated water, berries, and food 

• Self- limiting 

Cryptosporidiosis

caused by a protozoan in the genus Cryptosporidium. The 2 main species are C. hominis and C. parvum infecting humans. Oocysts are ingested and mature into sporozoites in the small intestine. Immunodeficient individuals can have life threatening diarrhea. Contaminated water is the usual source of the organism.

• Protozoan 

• Oocysts 

• Contaminated water 

 

Visceral Leishmaniasis

sand fly bite spreads the protozoan which enters the blood stream. Common disease in the tropics.  Macrophages ingest it but the organism can survive inside and continue to multiply within it. Leishmania donovani can cause extensive damage to the liver, spleen, and kidneys if left untreated and ultimately death will result. It is becoming an opportunistic infection associated with HIV.

• Vector - sandfly bite 

• You have to be treated 

• Problem infection for people with HIV 

Malaria

is endemic in tropical areas. The protozoan enters a human from the bite of a mosquito infected with the organism.  The organism matures in stages and ultimately infects a red blood cell (RBC).  People with the sickle cell trait are protected from the organism since it cannot replicate in an altered RBC.

The infected female mosquito carries the "sporozoite stage" of the protozoan which enters the human blood stream. It travels to the liver and changes into the "merozoite stage". The liver cells rupture and the merozoites invade the RBC where they multiply.  This is the "trophozoite stage".  The RBC ruptures periodically to release new merozoites, with a simultaneous rise in body temperature. Refer to the diagram on page 346 (chapter 12) of your book for another diagram of the life cycle of the malaria parasite Plasmodium.

• Protozoan 

• Vector - mosquito 

There are 4 species of Plasmodium but Plasmodium falciparum is the species which causes the most severe disease since it can lead to blood vessel obstruction.  The protozoan is starting to become resistant to the chloroquine drug used to treat it.  The organism is best controlled by controlling the mosquito population with pesticides.  A mosquito has been developed through genetic manipulation in the lab that is now resistant to infection with the organism.  It is hoped that this mosquito can be put back into the wild where it will mate with the wild type and cause that population to no longer be able to support an infection caused by this organism.

• Plasmodium falciparum - the most lethal one 

• Prevent malaria through mosquito control 

• When the mosquito is infected it cannot harbor an infection 

• Make male mosquitoes sterile 

• Worried about releasing these new mosquitos because it may be dangerous 

Scientists are trying to develop a vaccine but the problem is finding the stage of the organism that provides protection against the infection. Mosquirix vaccine is now available for children which provides protection for a limited time.

• Vaccine is given to children - very limited - doesnt last 

• Interesting life cycle 

• Its hard to make a vaccine 

• The mosquito is where the sexual part of the organism takes place 

• The mosquito will bite the human- deliver the sporozoites 

• Go into the liver and start replicating - replicate in cells and lyse themselves off

• When they lyse themselves off they now are trophozoites - a phase that actually enters the RBC - then they lyse themselves out - the merozoites - higher fever - inflammatory response - then the fever will go down but hte organism is still replicating in the RBC

• Gametocytes - a sexual phase that happens in mosquito 

Chagas' Disease (American Trypanosomiasis)

caused by Trypanosoma cruzi and this infection is seen sporadically in the southern USA.  It is transmitted by the reduviid bug. The organism initially causes a fever and swollen glands but some people go on to a chronic form of the disease. Nerves in various organs like the heart, skeletal muscles and colon can be damaged.  If a pregnant woman is chronically infected with the organism, she can pass it on to the fetus. It is difficult to treat at the chronic stage since the trypanosome can multiply inside host cells.

• Vector - reduviid bug

• Infection is traveling North 

• Not a lot of agents to treat it 

• Releases feces that releases the organism  

• Not even aware of it until you have symptoms 

• Across the placenta 

Toxoplasmosis

Toxoplasma gondii causes this disease and it can be found in the feces of cats (eating mice that harbored the organism) as oocysts which can then infect a human. Oocysts mature to trophozoites in host cells. The organism can come from eating undercooked contaminated meat. Usually, the infection causes mild lymph node inflammation and it is a self-limiting disease.

This organism can be transferred across the placenta causing congenital defects. This organism also causes a problem for people with AIDS.  Research is currently in progress to see if there is a connection between the organism and Schizophrenia.

• We can be exposed to it in many different ways 

• Oocysts mature to trophozoites in host cells.

• Immunocompromised - travels to CNS and causes issues 

• Can cross placenta (fetal damage) 

• If mice are contaminated - they lose their fear of cats - because the organism wants to get into the cat 

  • We know the organism does alter the brain 

• People who have Schizophrenia - seem to have antibodies more than the average person - even the mother of the Schizophrenic 

  • Wondering whether the exposure has does anything to the brain 

• HIV immunocompromised people 

Cryptococcosis

caused by the budding yeast called Cryptococcus neoformans.  It is carried by birds and the organism is either inhaled or carried in through the mouth which results in a systemic infection that travels to the CNS.  The organism is a common cause of meningitis in people with AIDS.

• Breathing in actual budding yeast 

• Carried by birds - vector - as birds release fecal material - we can get exposed to it 

• Pigeons - breathing in their fecal material 

• Immunocompromised HIV people 

• You need to get treated because it reaches your CNS

Trypanosomiasis

African Sleeping Sickness is caused by a protozoan (genus Trypanosoma) and is transmitted by the bite of a tsetse fly. Human disease is caused by either T. brucei rhodesiense or T. brucei gambiense. The organism can infect all organs of the body and if left untreated the person will die from deterioration of the CNS leading to death. For many years, researchers have tried to develop a vaccine but the organism constantly changes its membrane proteins to escape the host immune system making it hard to develop a vaccine with the protecting antigens.

• Vector- bite of a tsetse fly 

• A person will die - because it attacks the CNS - go into a coma 

• Infects cattle, animals, = reservoir 

• The organism completely changes its outer coat 

• Organism has like 200 antigens 

• Antigenic Variation 

  • Infected make an antibody, organism has changed its coat membrane proteins to evade our immune system