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CHAPTER 3 More Medical Microbiology Specialties

CHAPTER 3 More Medical Microbiology Specialties. 3-2. Introduction. Subspecialties of medical microbiology Virology Mycology Parasitology. 3-3. Study of viruses Most common infectious agent in humans Contains core of genetic material surrounded by a capsid; no organelles

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CHAPTER 3 More Medical Microbiology Specialties

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  1. CHAPTER 3 More Medical Microbiology Specialties 3-2

  2. Introduction Subspecialties of medical microbiology Virology Mycology Parasitology 3-3

  3. Study of viruses Most common infectious agent in humans Contains core of genetic material surrounded by a capsid; no organelles Obligate parasite; most are destroyed by immune system Requires host cell Protein coat covering strands of DNA or RNA Virology 3-4

  4. RNA viruses For example, influenza, polio, AIDS, rabies DNA viruses For example, common cold, cold sores, warts Transmission Direct Indirect (Continues) Virus 3-5

  5. Signs and symptoms of viral infection Low-grade fever, muscle aches, general fatigue (or) Asymptomatic Treatment Rest Fluids Palliative treatment Prevention Vaccines Virus 3-6

  6. Classified by Severity and length of time present Body organs/sites affected Identification Cell culture Direct detection Multipathogen detection systems Serodiagnosis Viral Infections 3-7

  7. Not curative Lessens severity Keeps infection under control Treats viruses, such as Respiratory syncytial virus (RSV) Acquired immunodeficiency syndrome (AIDS) Hepatitis C (HCV) Severe acute respiratory syndrome (SARS) Antiviral Therapy 3-8

  8. Respiratory Syncytial Virus (RSV) Causes bronchiolitis and pneumonia Major cause of acute respiratory disease in children Treatment Ribavirin (inhibits essential nucleic acid formation) 3-9

  9. Acquired Immunodeficiency Syndrome (AIDS) Caused by retrovirus HIV Diagnosis CD4 T cell count less than 200 cells/mm³ Presentation of AIDS-defining diseases Cannot be cured Treatment Three antiretrovirals 3-10

  10. Usually asymptomatic during acute stage Usually progresses to chronic Hepatitis C (also may be asymptomatic, and may progress to liver cirrhosis or liver cancer) Has six genetically distinct types (Genotypes 1–6) Genotypes 1 and 4 are most difficult to treat Hepatitis C (HCV) 3-11

  11. Severe Acute Respiratory Syndrome (SARS) • Signs and symptoms • Fever • Headache • Body aches • Dry cough • Spread by respiratory droplets • Fatal for 30% of those infected 3-12

  12. Ebola • Signs and symptoms • Fever, sore throat, muscle pain, headache (within 2–21 days after contracting the virus) • Followed by severe vomiting, diarrhea, rash • May exhibit internal and external bleeding (Continues) 3-13

  13. Ebola • High mortality rate due to • Dehydration • Electrolyte imbalance • Kidney or liver failure • Hypotension • Supportive treatment includes • Oral rehydration • IV fluids 3-14

  14. Parasitology • Study of parasites • Unicellular or multicellular • Live in host at host’s expense • Exist in many body areas (e.g., blood, skin) • Three main classes • Protozoa • Helminths • Ectoparasites 3-15

  15. Parasites • Identified by • Name • Specific state of development • Trophozoite (feeding and growing) • Cyst (dormant) • Ova (eggs) • Larvae (immature) • Adult (mature) 3-16

  16. Protozoa • Microscopic • Most favorable host: humans • Infestation may be caused by • Ingestion of contaminated water • Penetration through skin • Insect bites • Symptoms vary according to type 3-17

  17. Giardia • Common parasite in GI tract • Transmission from people, food, or water • Signs and symptoms • Watery, foul-smelling diarrhea • Nausea, vomiting, abdominal gas, cramps • (or) Asymptomatic • Treatment • Fluids, electrolytes, antimicrobials 3-18

  18. Malaria • Caused by mosquito bite (Plasmodium) • Signs and symptoms • Mimic flu: fever, chills • Death if untreated • Diagnosis • Microscopic exam of blood of infected patient • Treatment varies with species and geographical area where acquired 3-19

  19. Helminths • Viewed upon gross examination • Survive in nature or in humans • Three main groups • Tapeworms • Flukes • Roundworms (hookworms and pinworms) 3-20

  20. Tapeworm • Acquired from ingesting improperly cooked beef or pork • Signs and symptoms • Abdominal pain • Nausea • Loss of appetite • Some types cause blindness or seizures • (or) Asymptomatic • Treatment: praziquantel or niclosamide 3-21

  21. Hookworm Acquired by walking barefoot in fecally contaminated soil Reside in host’s GI tract Signs and symptoms: nausea, vomiting, diarrhea, abdominal pain, possibly nutritional deficiencies, anemia Treatment: albendazole or mebendazole 3-22

  22. Pinworms Small, round worms Most often in children and institutionalized individuals Signs and symptoms: anal itching more intense at night Diagnosed by “tape test” Treatment: albendazole, mebendazole, (require prescriptions), pyrantel pamoate, (available OTC) 3-23

  23. Ectoparasites • External parasites with hard, segmented bodies • Feed on blood from humans/animals • Transmission of disease occurs with • Fleas, ticks, mosquitoes • No transmission of disease • Bed bugs (present economic and public health consequences) 3-24

  24. Mycology • Study of fungi • Reproduced by spores (used in identification) • No chlorophyll • For example, mushrooms, yeast, molds • Have ergosterol instead of cholesterol as in human cells • Destruction of body’s natural flora through use of antibiotics and steroids may lead to opportunistic fungal infection 3-25

  25. Fungi Most susceptible: immunocompromised patient Identification: microscopic observation or biochemical reaction testing Transmission: inhalation or ingestion of spores, or through non-intact skin Most are opportunistic in occurrence Signs and symptoms vary according to location on host 3-26

  26. Yeasts • Single-celled microorganisms • Cannot manufacture own nutrients • Thrive on organic matter in living host • Candida: most common in humans • May cause local mucous membrane infection (or) life-threatening septicemia (or) multisystem organ infection 3-27

  27. Prions • Lack nucleic acid • Resistant to routine sterilization technique • Infect nervous system • Five related diseases in humans • Creutzfeldt-Jakob Disease, Variant Creutzfeldt-Jakob Disease, Gerstmann-Straussler-Scheinker Syndrome, Fatal Familial Insomnia, Kuru 3-28

  28. Creutzfeldt-Jakob Disease (CJD) • Worldwide disease; usually fatal within one year of diagnosis • Signs and symptoms • Dementia • Difficult walking/balance • Myoclonus • Diagnosis • Based on signs and symptoms; definitive diagnosis made from examination of brain tissue sample 3-29

  29. Summary • Viral species and parasites require host • Virology: study of viruses • Virus: infectious particles containing genetic material surrounded by a capsid • Examples: RSV, AIDS, SARS • Parasitology: study of parasites • Parasite: unicellular or multicellular organism living in/on host at host’s expense • Examples: protozoa, malaria, pinworms (Continues) 3-30

  30. Summary • Mycology: study of fungi • Fungi: reproduced by spores, have a rigid cell wall and no chlorophyll • Examples: yeasts, prions, CJD • Fungal infection likely to develop in immunocompromised patient 3-31

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