Lecture 19: Skin Diseases (2024)

Lecture 19 with textbook info- November 22nd Chapter 21 Skin Diseases- Fungi that invade keratinized tissue (epidermidis) and colonize the hair, nails, and outer layer (stratum corneal) of the epidermis are called dermatophytes (a fungus that causes a cutaneous mycosis) which lead to dermatomyc...

Lecture 19 with textbook info- November 22nd Chapter 21 Skin Diseases- Fungi that invade keratinized tissue (epidermidis) and colonize the hair, nails, and outer layer (stratum corneal) of the epidermis are called dermatophytes (a fungus that causes a cutaneous mycosis) which lead to dermatomycoses which is a fungal infection of the skin, also known as tinea or ringworm. ◦Mycoses has to do with fungal, these are fungal cells that are specifically targeting our skin cells. Fungal and Protozoal organisms have complex life cycles (don’t need to know specific details of they’re life cycle), they are eukaryotic organisms so not a lot of anti fungal or anti Protozoal drugs to treat, they are a concern because there becoming resistant to the few anti drugs that attack it. Problems with fungal cells and Protozoa are becoming a greater problem because of ppl becoming immuno compromised like people who have HIV and progress to aids. Ringworm- ◦Appears as a circular lesion especially on scalp. ◦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 (inanimate object). Were coming in contact with more of the spore part of the organism, the spores for fungal cells are hearty, and the spores are part of the lifecycle of the organism and they’re hearty so that they can stay around in the environment. ‣ Tinea capitis, or ringworm of the scalp, is fairly common among elementary school children and can result in bald patches. The infections tend to expand circularly, hence the term ringworm Dogs and cats are also frequently infected with fungi that cause ringworm in children ‣ Tinea cruris- ringworm of the groin or jock itch. ‣ Tinea pedis- ringworm of the feet, or athletes foot. With T. pedis, one can get a secondary bacterial infection. (athletes foot) happens because you have your foot in a shoe which is a moist area, and the fungus creates an opening in the skin can lead to secondary infection and you have to take a different antibiotics. ‣ Tinea unguium (onychomycosis)- ringworm of the fingernails or toenails. ◦All can be treated with antifungal drugs but it may take many weeks bc the organism especially where there located on the skin its not easily accomplished getting drugs there and the organism has a complex life cycle so you don’t know what the antifungal drug is doing to kill it during the life cycle. Opportunistic Fungal Infection Candidiasis - ◦Candida albicans is part of the normal flora, in mouth and vagina. If your taking an antibiotic and getting treatment your disturbing the normal flora which gives the opportunity for Candida albicans to grow up because theres no competition. ‣ The bacterial microbiota of the mucous membranes in the genitourinary tract and mouth usually suppress the growth of such fungi as Candida albicans. Because the fungus is not affected by antibacterial drugs, it sometimes overgrows mucosal tissue when antibiotics suppress the normal bacterial microbiota. Changes in the normal mucosal pH may have a similar effect. Such overgrowths by C. albicans are called candidiasis. ◦It can cause thrush, vaginitis, infect tissues and is the most common nosocomial fungal infection. ‣ Newborns, whose normal microbiota have not become established, often suffer from a whitish overgrowth of the oral cavity called thrush  ◦Possibility of a systemic infection in immunocompromised people it can be a serious infection because theres not a lot of antifungal drugs to treat it. ‣ If candidiasis becomes systemic, as can happen in immunosuppressed individuals, fulminating disease (one that appears suddenly and severely) and death can result. The usual drug of choice to treat systemic candidiasis is fluconazole. ◦Has capsule which makes it resistant to macrophages attacking it. Candida auris - ◦is an emerging fungal infection causing worldwide concern. Doesn’t behave like Candida albicans, it’s very difficult to grow up, the media used for Candida albicans can’t be used for auris. ◦It is a serious infection in hospitalized patients which often enters the bloodstream and spreads throughout the body. Found in walls of room and all over the hospital, might have something to do with climate change, more hotter days and humidity which allows the organism to grow. ◦It is highly resistant to antifungal drugs, don’t know if its due to resistance genes or the drugs can’t get into organism. ◦Special laboratory methods are used to identify it. ◦Skin and mucosal infections by C. albicans are usually treated with topical applications of miconazole, clotrimazole, or nystatin. Chapter 26 Reproductive System Diseases Vulvovaginal Candidiasis – ◦most cases caused by Candida albicans. ‣ Vaginal infections by yeastlike fungi of the genus Candida—called vulvovaginal candidiasis—are the most common cause of vaginitis. ◦C. albicans often grows on mucous membranes of the mouth, intestinal tract, and genitourinary tract. ◦It is an opportunistic infection which can occur with uncontrolled diabetes, change in pH, hormone change, and long- term antibiotic therapy ◦In addition to causing vulvovaginal candidiasis, C. albicans causes oral candidiasis, or thrush. ◦The lesions of vulvovaginal candidiasis resemble those of thrush but produce more irritation: severe itching; a thick, yellow, cheesy discharge; and yeasty or no odor. ◦Any thing that allows the candida that’s normally present but its usually has competition and if the competition is gone will cause the organism to grow up and cause minor infection when there no competition. ◦It’s highly treatable. ◦This is a problem for people on longer term antibiotics Trichomoniasis ◦is caused by a protozoan (Trichomonas vaginalis) which is transmitted sexually but the organism can be part of someone’s normal flora. The anaerobic protozoan T. vaginalis is frequently a normal inhabitant of the vagina and of the male urethra. Not in everybody’s flora. ◦If the normal acidity of the vagina is disturbed, the protozoan may overgrow the normal microbial population of the genital mucosa and cause trichomoniasis. It infects the urogenital tract surfaces in both males (rarely have symptoms) and females. Many cases are asymptomatic, males don’t really have symptoms and in females there could be secretion of mucous and inflammatory response but could be asymptomatic.  ◦The infection is often accompanied by a coinfection with gonorrhea. In response to the protozoan infection, the body accumulates leukocytes at the infection site. The resulting discharge is profuse, greenish yellow, and characterized by a foul odor. This discharge is accompanied by irritation and itching. Up to half the cases, however, are asymptomatic. ◦There is 2 other types of trichomonas that is part of our normal flora ‣ T. hominis (in intestinal tract) and T. tenax (in mouth) are normal commensals in our body, not in everybody’s flora. Chapter 24 Respiratory Diseases Coccidioidomycosis - ◦Coccidioides immitis is common in the Southwest USA and sometimes referred to as Valley Fever or San Joaquin fever. ◦Spores are part of the mating cycle of the fungal cell are inhaled which usually results in mild flu like symptoms or no symptoms at all. The spores are common in soil and hearty. ◦In soil, it forms filaments that reproduce by the formation of arthroconidia. The wind carries the arthroconidia to transmit the infection. ◦Symptoms are mild and might not be recognized as a fungal infection. Most infections are not apparent, and almost all patients recover in a few weeks, even without treatment. ◦In tissues the organism can form a thick walled off body called a spherule filled with spores often used to diagnosis. If someone has a severe infection the spherule could be used as a diagnosis. Its usually self limiting. The problem is when ppl are immuno compromised and the organism gets a chance to spread. ◦Complications can occur such as spreading to meninges or bones. The signs and symptoms of coccidioidomycosis include chest pain and perhaps fever, coughing, and weight loss. ◦In less than 1% of cases, a progressive disease resembling tuberculosis disseminates throughout the body. A substantial proportion of adults who are long-time residents of areas where the disease is endemic have evidence of prior infection with C. immitis by the skin test. ◦Given the opportunity if you can’t mount a good response to the organism it can become more systemic. Histoplasmosis - ◦Histoplasma capsulatum (dimorphic fungus) is endemic in central and eastern US. It superficially resembles tuberculosis. ◦Soil fungal spores are inhaled and mature into an actively growing yeastlike form (like vegetive cell) which can survive and multiply in macrophages which circulate the organism through the body. The macrophages are the conduit spreading it to other areas of the body, usually doesn’t happen though. ◦Humans acquire the disease from airborne conidia produced under conditions of appropriate moisture and pH levels. These conditions occur especially where droppings from birds and bats have accumulated. Birds themselves, because of their high body temperature, do not carry the disease, but their droppings provide nutrients, particularly a source of nitrogen, for the fungus. Bats, which have a lower body temperature than birds, carry the fungus, shed it in their feces, and infect new soil sites. ◦It is usually a mild respiratory infection but complications can arise such as pneumonia and infection in the spleen, liver, and lymph nodes. Although the lungs are most likely to be initially infected, the pathogens may spread in the blood and lymph, causing lesions in almost all organs of the body. ◦If a person doesn’t mount a good immune response to it than it can spread and be more severe. ◦This is common in ppl that explore caves, bc the organism is associated with bird feces.  Pneumocystis pneumonia (PCP)- ◦caused by Pneumocystis jirovecii (carinii) and invades lung cells. Pneumocystis pneumonia used to be called jirovecii and carinii. Is a respiratory infection, you’re breathing in the endospores. ◦The pathogen is sometimes found in healthy human lungs. Immunocompetent adults have few or no symptoms, but newly infected infants occasionally show symptoms of a lung infection. ◦Back in early 1980s the emergency rooms were reporting young ppl with lung fungal infections and this didn’t make sense. They were the the patients who had HIV and were already immuno compromised and they wound up getting the fungal infection but it was mostly due to having HIV. ◦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. This is one of the infections ppl with AIDS can succum to. ◦In the human lung, the microbes are found mostly in the lining of the pulmonary alveoli. There, they form a thick-walled cyst in which spherical intracystic bodies successively divide as part of a sexual cycle. The mature cyst contains eight such bodies. Eventually the cyst ruptures and releases them, and each body develops into a trophozoite. The trophozoite cells can reproduce asexually by fission, but they may also enter the encysted sexual stage ◦There is few antifungal drugs so its hard to treat ppl. Blastomycosis - ◦caused by Blastomyces dermatitidis. Usually called North American blastomycosis. ◦Normal entry is through a wound and its more of a skin infection or breathing endospores into the lungs that were out in the soil. ◦The infection begins in the lungs after inhalation of conidiospores. It resembles bacterial pneumonia and can spread rapidly. Cutaneous ulcers commonly appear when the yeast are disseminated in circulating monocytes. Abscesses may form, with extensive tissue destruction. The pathogen can be isolated from pus and biopsy specimens. ◦The spores mature/germinate to yeast cells (vegetative cell) which can easily get into the circulation via macrophages and becomes a systemic infection which can lead to extensive tissue damage. ◦Few antifungal that can treat it well. ◦Systemic blastomycosis can lead to extensive tissue damage. Aspergillosis - ◦Airborne by Aspergillus fumigatus infects the lungs when the spores are inhaled. Is a common organism in the environment/soil and easily can be exposed to this. ◦Breathing in spores. ◦The spores are often found in decaying vegetation so ppl gardening are at risk. ◦Once the spores start giving actual vegetative growing part of fungus, the fungus releases long hypha extensions. This is what compromises the lung because you get these balls of tangled up hypha which cripples your ability to breathe which can become an invasive lung infection which leads to asphyxiation if not treated. ◦This is another fungal infection that causes problems for people with AIDS or with an impaired immune system. Chapter 25 Digestive System Diseases Giardiasis – ◦Giardia duodenalis (intestinalis or lamblia) is the cause of the disease. Is a Protozoal organism and can be gotten from dinking or eating the cysts of the organism which is similar to the spores of other organism, its hearty and can be found in the water or outside environment but its not actively growing but if you ingest the cyst it will make its way down to the small intestine where it matures and attaches firmly to a human’s intestinal wall. ◦Is a prolonged diarrheal disease. Sometimes persisting for weeks, giardiasis is characterized by malaise, nausea, flatulence (intestinal gas), weakness, weight loss, and abdominal cramps. The distinctive odor of hydrogen sulfide can often be detected in the breath or stools. The protozoa sometimes occupy so much of the intestinal wall that they interfere with food absorption. Basically it causes severe diarrhea with dehydration/loss of fluid and can interrupt normal adsorption. ◦Most outbreaks are transmitted by contaminated water supplies. ◦Cysts of the organisms are ingested and go to the small intestine where they mature to the trophozoite which has adhesive disks and adhere to the bowel wall via an adhesive (sucker) disk and covers the whole intestinal lining. The disks will prevent any normal absorption in the intestinal lining because it covers the whole thing, and interrupts the normal intestinal tract. ◦The cysts are not killed by chlorination. The cysts can be come in contact in outside environment so when your camping, a lot of times wild life harbors the infection. Theres not enough of them for it to be established in the drinking water but if your immuno compromised its better to boil water before drinking it. Amebiasis (Amebic Dysentery) - ◦caused by Entamoeba histolytica. Its an ameba and its intestinal. The organism can cause a lot of damage to intestinal lining, your exposed to it by cysts. The cysts mature in your body. ◦Is spread mostly by food or water contaminated by cysts of the protozoan ameba 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/lining and get into the bloodstream, and it’s referred to as histolytica tissue damage. ◦Invasive to the intestinal lining, can cause so much damage to the intestinal lining that you actually reach the lining and all of the fecal material can come into your peritoneal cavity and cause another problem. Intestinal lining damage can cause fecal material to get into the body cavity and cause "peritonitis". ◦Although stomach acid can destroy trophozoites, it does not affect the cysts. In the intestinal tract, the cyst wall is digested away, and the trophozoites are released. They then multiply in the epithelial cells of the wall of the large intestine. A severe dysentery results; the feces characteristically contain blood and mucus. The trophozoites feed on tissue in the intestinal tract. ◦The organism in some people can remain chronic, they recover from sever symptoms but go on and be chronic carriers and be asymptomatic but still potentially passing tropozoids to someone else. ◦The cysts are not killed by normal chlorine concentrations in water. A filtering system would grab out cysts but theres not enough of the cysts that would cause damage to a healthy person. ◦A small number of the population are asymptomatic carriers of E. histolytica.  Cyclosporiasis – ◦A more recently discovered protozoan causing an intestinal disease. Common contaminant in certain foods like berries or foods that don’t get cooked, outbreaks in schools or certain communities. ◦Most outbreaks have been associated with the ingestion of oocysts in water, on contaminated berries, or similar uncooked foods. The foods are presumed to have been contaminated by oocysts shed in human feces or possibly from birds in the field. ◦Responsible for series of recent diarrheal disease outbreaks. ◦It is self limiting. ◦They call them oocytes (cysts) from Cyclospora cayetanensis are ingested and lead to watery diarrhea for a few days but in some cases it may persist for weeks. The disease is especially debilitating for immunosuppressed people, such as people with AIDS. ◦The oocytes can be found in water or on food like berries. Cryptosporidiosis - ◦caused by a Protozoal in the genus Cryptosporidium. ◦The 2 main species are C. hominis and C. parvum infect humans more prevalently. ◦Oocysts are ingested in food and the oocysts eventually release/mature sporozoites in the small intestine. Not a problem unless you’re immune compromised. ◦The motile sporozoites invade the epithelial cells of the intestine and undergo a cycle that eventually releases oocysts to be excreted in the feces ◦The disease is a cholera-like diarrhea lasting 10 to 14 days. ◦The infection is transmitted to humans largely through recreational and drinking water systems contaminated with oocysts of Cryptosporidium, mostly from animal wastes, especially cattle ◦Immunodeficient individuals can have life threatening diarrhea, including people with AIDS, the diarrhea becomes progressively worse and is life-threatening. ◦Contaminated water is the usual source of the organism. Studies in the United States show that many, if not most, lakes, streams, and even wells are contaminated. The oocysts, like the cysts of G. duodenalis, are resistant to chlorination and must be removed from water by filtration. ◦Municipal drinking water is filtered at the water treatment plant to remove Giardia cysts and Cryptosporidium oocysts Chapter 23 Cardiovascular and Lymphatic Diseases Visceral Leishmaniasis - ◦sand fly bite spreads the protozoan which enters the blood stream. Common disease in the tropic countries. ◦Macrophages ingest it but the organism can survive inside and continue to multiply within it and the macrophages circulates it throughout the body, thought of as lymphatic and can even travel through lymph fluid. ◦Leishmaniasis is transmitted by the bite of female sandflies ◦Small mammals are an unaffected reservoir of the protozoans. ◦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.  Malaria - ◦Malaria is characterized by chills and fever and often by vomiting and severe headache. These symptoms typically appear at intervals of 2 to 3 days, alternating with asymptomatic periods. Malaria occurs wherever the Anopheles mosquito vector is found and there are human hosts for the Plasmodium protozoan. ◦Plasmodium vivax is widely distributed because it can develop in mosquitoes at a lower temperature and is the cause of the most prevalent form of malaria. ◦Used to be problem in the US, especially southern states because the mosquitos could survive the temp. ◦is endemic in tropical areas. The protozoan enters a human from the bite of a female mosquito because the female is taking the blood meal infected with the organism. ◦Occasionally, malaria has been transmitted by unsterilized syringes used by people injecting illegal drugs. Blood transfusions from people who have been in an endemic area are also a potential risk ◦The female mosquito wants a blood meal, shell take it from a person who has malaria and that’s how the mosquito gets 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 growing and maturing in the liver cells into the "merozoite stage". ◦The liver cells rupture and get released and the merozoites invade the RBC where they multiply. This is the "trophozoite stage" which is the stage which infects the RBC. The RBC ruptures periodically to release new merozoites, with a simultaneous rise in body temperature. When the blood cell bursts open this is where the person has the most climactic symptoms like spiking a fever and have chills, and vommitting which is an inflammatory response that’s happening when the merozoites are out in the circulation. Refer to the diagram on page 346 (chapter 12) of your book for another diagram of the life cycle of the malaria parasite Plasmodium. ◦The merozoites can be picked up by the mosquito and the mosquito is the sexual phase of the organism and the mosquito is essential for the survival of the organism. ◦The merizoids, some of them in the environment, sort of go off into becoming gametes. And the gametes are what's actually taken up by the mosquito. The cell goes through the life cycle, the sexual part of the life cycle and creates a merizoid. ◦Difficult to get a vaccine because you don’t know what stage to shoot for. They’ve tried to get proteins from every stage of the organism but it doesn’t give you good protection. Scientists are trying to develop a vaccine but the problem is finding the stage of the organism that provides protection against the infection. ◦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 and is the most pathogenic. When a person has the infection it causes a lot of damage to the blood vessels and clotting is seen and death can happen. The other strains are more mild. ◦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 and it can’t grow in the modified mosquitos. 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. ◦Mosquirix vaccine is now available for children which provides protection for a limited time. Its not great and the protection is usually for a year or two but it does help for young kids to get some immunity.  Chagas' Disease (American Trypanosomiasis) - ◦caused by Trypanosoma cruzi and this infection is seen sporadically in the southern USA. Protozoan disease of the cardiovascular system. ◦It is transmitted by the reduviid bug, looks like a fly. The organism initially causes a fever when bitten and swollen glands but some people progress and go on to a chronic form of the disease and it might take years but the organism starts doing a lot of damage to nerves. Nerves in various organs like the heart, skeletal muscles and colon can be damaged and really any tissue. The person will wind up with so much damage that nothing can be done. ◦If a pregnant woman is chronically infected with the organism, she can pass it on to the fetus which can cause damage depending on when the fetus saw the infection. ◦Its seen more now, was seem mostly in South America but now Texas and Arizona it’s moving more north now and can be due to climate change. ◦It is difficult to treat at the chronic stage since the trypanosome can multiply inside host cells it must be done in the…. Not a lot of anti Protozoal drugs to treat the organism to get rid of it. Usually the treatment that can cure a person has to happen during the invítalo infection, once they become chronic the organism sort of becomes hidden away from the añito Protozoal agents. Toxoplasmosis - ◦Toxoplasma gondii causes this disease and it can be found in the feces of cats as oocysts which can then infect a human or uncooked meat bc the oocytes might be in the actual meat and wouldn’t be sectioned if it was undercooked. Complex life cycle (don’t need to know for exam). ◦Is a disease of blood and lymphatic vessels. ◦Oocysts mature to trophozoites in host cells. Cats are part of the sexual life cycle of the organism. ◦ 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 or immuno comprised. ◦The organism seems to do something with the central nervous system. ◦When mice are infected with the organism they seem to loose they’re fear of cats, the organism seems to alter the brain chemistry/fear response in mice and the infection itself in a healthy adult is a minor issue its more of a problem in pregnancy bc it can cross the placenta and ppl who are immune compromised. ◦Research is currently in progress to see if there is a connection between the organism and Schizophrenia possibly gotten during pregnancy. ◦Ppl who have schizophrenia seem to have antibodies to the organism and it does something to the brain chemistry. Chapter 22 Nervous System Diseases Cryptococcosis - ◦caused by the budding yeast/fungi called Cryptococcus neoformans. Often found in fecal material especially pigeons. ◦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. Has to be treated. ◦The disease is transmitted mainly by the inhalation of dried, contaminated droppings. The inhaled fungi multiply in people with compromised immune systems, such as people with AIDS, disseminate to the CNS, and cause meningitis that has a high mortality rate. ◦The organism is a common cause of meningitis in people with AIDS. Trypanosomiasis - ◦Causes African Sleeping Sickness is caused by a protozoan (genus Trypanosoma) and is transmitted by the bite of a tsetse fly and affects the nervous system. The fly has the organism and is injecting it to ppl through a bite. ◦Human disease is caused by either T. brucei rhodesiense or T. brucei gambiense. ‣ Humans are the only significant reservoir for T. b. gambiense, whereas T. b. rhodesiense is a parasite of domestic livestock and many wild animals ◦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, systemic infection. If not treated you’ll go into a comma. ◦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. ◦The organism is constantly changing its outside coat protein. This organism when you mount an antibody response to the one antigens on its surface it immediately switches to another coat protein which isn’t affected by the antibody at all, the organism has at least 100 different coat proteins so its hard to get a vaccine for it. ◦Endemic organism and iIt’s seen in tropical countries and transmitted through the fly so its hard to control. Wildlife can also carry the organism, the fly can bite a cow and than is transmitted to a human. Many deaths caused by the organism.