bacteria, virus, parasite, fungi Flashcards

Question

what are bacteriophages?

Answer 1

a type of virus that infects bacteria. All of them are composed of a nucleic acid molecule that's surronded by a protein structure. It hijacks the cell machinery and makes it produce viral components until it bursts through lysis

Answer 2

is a highly resistant process whereby dormant bacteria are formed. This process preserves the genetic material of bacteria when conditions are lethal and inhospitable. Each normal (vegetative) cell forms one spore (dormant)

Answer 3

they are structures in the bacterial cell cytoplasm, they consist of RNA and associated proteins. Their role is to synthesize proteins. They are divided into subunits, measured by the unit Svedberg. 70S ribosomes → made up of large (50S) and small (30S) subunits 30S subunit → made up of (16S) subunit - which is used for bacterial identification

Answer 4

1- Get a specimen from a patient 2- Staining to determine whether it's gram-positive or gram-negative infection to select the appropriate antibody 3- Incubation of a small amount of specimen onto agar plates at 37 C 4- Formation of bacterial colonies Use a light microscope with an oil immersion lens (x1000) & staining to see the bacteria

Answer 5

1- Phenotypically → i.e. relating to observable physical properties e.g. - Gram stain (gram + & gram -) - Growth requirements (aerobic & anaerobic & microaerophilic) - Serologic - Mass spectrometry (protein profiling) 2- Genotypically → i.e. relating to DNA (used more in modern times) e.g. - Ribosomal RNA sequence analysis - Whole genome sequencing

Answer 6

an organism that lives in or on another organism (host) and derives its nutrients at the expense of this host. They are classified by: - Cellular structure - Life cycle - complex stages An organism which acts as an intermediate host for a parasite is known as a Vector

Answer 7

Protozoa → malaria & amoebae & flagellates - Helminths (worms) → roundworms & tapeworms & flukes - Ectoparasites (outside of body) → lice & ticks & mites

Answer 8

Protozoa are microscopic, single-celled organisms, that can be free-living or parasitic. They can multiply in humans and they transmit through two routes: 1- Live in a human's intestine → faecal-oral route 2- Live in the blood or tissue of humans → insect vector

Answer 9

Malaria is a protozoan infection, the most common cause of death by parasitic infection globally, usually found in the tropics and subtropics. It is a mosquito-borne preventable disease caused by a parasite called Plasmodium Vector → Anopheles mosquito (female) non-specific symptoms i.e. fever, chills, headache, sore throat Blood films → parasitaemia

Answer 10

a protozoan infection that causes bloody diarrhoea. It is caused by an invasion of Entamoeba histolytica in the gut wall. Contraction of infection - through ingestion of faecal matter through contaminated food i.e. Faecal-oral route Clinical relevance: - Intestinal and extra-intestinal infections - Liver abscess in late disease

Answer 11

To diagnose we look into stool samples of patients and check for worm eggs Most are transmitted through the faecal-oral route but use an intermediate vector Common in resource-poor / hygiene-poor areas 1- Nematodes → Roundworms 2- Cestodes → Tapeworms 3- Trematodes → Flatworms

Answer 12

Enterobiasis (pinworm/threadworm) → 1cm, threadlike, very common in children Causes anal itch Diagnosis → sellotape on perianal region and check for eggs under a microscope Treatment → anti-helminth tablets kill adult worms [2] Ascaris lumbricoides/Ascaris Infection → 15-35 cm, largest nematode. Often asymptomatic, may cause failure to thrive in children / blocking the small intestine & bile duct → Bowel obstruction

Answer 13

Cestodes are long, segmented tapeworms. e.g. [1] Taenia saginata (beef) [2] Taenia solium (pork) Can migrate to the brain from the gut and make cysts causing → Neurocysticercosis [3] Echinococcus - carried by dogs, wolves, foxes (intermediate host) - humans ingest eggs in dog faeces → eggs hatch and form cysts in the liver. ---------------------------------------- Eating larval cysts}} (intermediate host) that are found in raw or undercooked meat. Adult tapeworms in humans (definitive host) → eggs excreted through human stool Animals, e.g. pigs/cows, eat grass with human stool and the cycle continues. The life cycle of worms can only keep going if animals are eating grass-containing eggs i.e. poor sanitation/hygiene

Answer 14

Different species cause human infection in various body sites i.e. Blood, Lung, Liver, Pancreas, Intestines [1] Schistosomiasis, has three types: * S. haematobium (bladder) * S. mansoni (intestinal) * S. japonicum (intestinal) - endemic in tropical areas i.e. 200 million people affected annually - Acquired by swimming in infected freshwater - development in snails (intermediate host) - Swimmer's itch is a common sign - Can lead to liver failure & bladder cancer if untreated

Answer 15

they are parasites that live outside the body. Usually insects with six legs or arachnids with eight legs.

Answer 16

Through blood microscopy Thick and thin blood films under a microscope Severity of malaria → number of red blood cells infected by Plasmodium parasites We can then determine which type of treatment to use.

Answer 17

Diagnostic principles in Parasitology: (deep) [1] Definitive diagnosis → identify parasites in host tissue or faeces/urine [2] Blood microscopy e.g. thick and thin blood films for malaria [3] Stool microscopy is used to find enteric pathogens e.g. Ova, cysts and parasites [4] Helminth infection - Eosinophilia → (high eosinophil levels) - Elevated IgE → (high IgE levels to fight parasitic infections) [5] Indirect testing (antibody & antigen testing) - Serology → immune testing - Rapid diagnostic tests

Answer 18

a chemo-organotrophic eukaryote that lacks chlorophyll and forms spores. Cell wall → contains polysaccharides, often chitin or glucan, and it absorbs nutrients. Membrane → contains ergosterol - major sterol Classification is based on morphology can infect plants and animals

Answer 19

Basidiomycetes Ascomycetes Zygomycetes

Answer 20

cause skin infections one main virulence factor - an enzyme that degrades and utilizes keratin as a nutrient source. Diseases caused by these fungi - tinea, which are named according to the region they infect in the body. Causative agents: Epidermophyton - Microsporum - Trichophyton

Answer 21

they are frequent colonisers and part of the normal skin microbiota, usually found in sebum-rich areas like the scalp and chest. Their absence might be an indication of disease. but in certain conditions, they can cause superficial infections in immunocompromised individuals.

Answer 22

1- Favorable micro-environments e.g. (warm, moist areas) encourage the growth of fungi on skin and mucous membranes 2- Broad-spectrum antibacterial agents reduce competition for epithelial colonization sites in the gut 3- Immunosuppression of all types create a window of opportunity for fungal invasion

Answer 23

Iatrogenic: 'illness caused by medical examination or treatment' - Steroids - Anti-cancer chemotherapy - Solid-organ transplantation Disease processes: - AIDS - Leukaemia - Endocrinopathies

Answer 24

fungal infections caused by yeasts C. Albicans can form hyphae (filamentous form of growth) → pleomorphic fungus Clinical diseases: - Superficial → mouth, vagina, penis, skin, nails - Deep-seated → disseminated infections in immunocompromised hosts

Answer 25

1- Bacteria in competition with Candida in the gut. 2- Antibacterial added → bacteria ↓ 3- Candida overgrowth & might get access to epithelium. 4- Surgical insult → Candidia gets into the bloodstream & forms a biofilm on the catheter surface. 5- It then becomes resistant to anti-fungal treatments.

Answer 26

a type of candida infection that arises in individuals with an unusual combination of endocrine and immune dysfunction. (autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy - APECED)

Answer 27

an infection caused by a type of fungus called Aspergillus Causative species: Aspergillus fumigatus Aspergillus flavus Aspergillus nidulans (in CGD patients) Aspergillus lentulus other species on rare occasions Types of disease: simple asthma asthma with eosinophilia aspergilloma (fungal ball in lungs - Farmer's lung) invasive bronchopulmonary aspergillosis (associated with haematological malignancy - hyphae filaments penetrating lung tissue) disseminated aspergillosis Route of infection: - inhalation of conidia (spores)

Answer 28

transmitted to humans through inhalation of conidia, which germinate to hyphae (the main mode of vegetative growth) in the lung tissue. It is angioinvasive i.e. invades the walls of blood vessels

Answer 29

an infection caused by a type of fungus called cryptococcus Main causative species: (yeasts with a thick extracellular capsule) Cryptococcus neoformans Cryptococcus gattii --------------------------- Human diseases: pulmonary cryptococcosis meningitis (particularly in AIDS patients) → 1/2 million deaths each year disseminated infection in severely compromised hosts

Answer 30

results in invasion from pathogens and dissemination Diseases: Systemic candidosis Acute invasive Aspergillosis

Answer 31

results in a hyperinflammatory response (damaged tissue) Diseases: Recurrent Candida vaginitis Allergic bronchi pulmonary aspergillosis (ABPA) Dermatophytosis

Answer 32

Direct detection: 1 - Histopathology Biopsy of lung tissue → A. fumigatus hyphae Skin scraping treatment with KOH → visualise dermatophytes Direct smear with Periodic Acid Shiff (PAS) staining → fungi Vaginal smear with Calcofluor white stain → C. albicans hyphae Culture organisms and use ChromAgar Candida → detect species based on colour Germ tube test in serum → C. albicans form hyphal germ tubes -------------------- 2 - High-res CT scans Liver → Candida infection Pulmonary → Aspergillosis --------------------- Other methods: - detection of circulating fungal antigens - detection of circulating antibodies to fungi - PCR for fungal DNA - Culture of fungus from a normally sterile site - MALDI-ToF Biotyping

Answer 33

Azoles (Triazoles) and Allylamines → Target sterols Route of administration→ oral & IV & topical Mechanism of action → inhibit the production of ergosterol -------------------- [2] Echinocandins → Target wall Route of administration → IV only Mechanism of action → inhibit the production of glucan -------------------- [3] Polyenes → Target membrane Route of administration → oral & IV & topical Mechanism of action → bind to ergosterol to make pores in the membrane -------------------- [4] Flucytosine → Target DNA synthesis

Answer 34

Spectrum of activity Static or cidal IV vs oral Toxicity Antifungal Resistance Expensive Cost

Answer 35

small (20-400 nm) non-cellular organisms; their genetic element cannot replicate independently of a living (host) cell. Virion: extracellular form of a virus * Exists outside the host and facilitates transmission from one host cell to another * Contains nucleic acid genome surrounded by a protein coat and, in some cases, other layers of material Structures: [1] Icosahedral: 20 equilateral triangular faces, 12 vertices and 30 edges [2] Helical: protein binds around DNA/RNA in a helical fashion [3] Complex: neither of the above

Answer 36

they are pathogens that can only replicate inside host cells. Most viruses have a specific host range and only infect specific host cell types, this is known as tissue tropism

Answer 37

Order → Family → Genus → Species Virus families can be classified according to: 1- Virion shape/symmetry 2- Presence/absence of envelope 3- Genome structure 4- Mode of replication

Answer 38

Virus replication process: 1- Attachment to the host cell 2- Uncoating of envelope 3- Replication of Genomic nucleic acid in the nucleus 4- Nucleic acid + Proteins Insertion into membrane 5- Assembly of Virion 6- Release of Virion outside of cell

Answer 39

[1] Clearance of virus}} i.e. with no, short or long-term immunity * Hepatitis C (no lasting immunity) * Measles (long-term immunity) [2] Chronic infection * HIV, hepatitis B, hepatitis C [3] Latent infection: * Herpes Virus [4] Transformation i.e. long-term infection with altered cellular gene expression * Epstein-Barr Virus, Human Papilloma Virus

Answer 40

when a virus lies dormant (latent) in the cell after primary infection. The full viral genome is retained in the host cell, but its expression is restricted, so that few viral antigens and no viral particles are produced. This allows the reactivation of viral replication, which may or may not cause apparent disease. Reactivation is more likely to occur in immunocompromised individuals. Examples: 1- Herpes Simplex Virus 2- Varicella Zoster Virus

Answer 41

1- Modulation of cell cycle control (driving cell proliferation) 2- Modulation of apoptosis (prevention of programmed cell death) 3- Reactive oxygen species-mediated damage (some persistent viral infections can cause persistent inflammatory processes which lead to cancer via reactive oxygen species) ----------------- e.g. Virus & Cancer diseases - EBV: Burkitt’s lymphoma, Hodgkin’s lymphoma, nasopharyngeal carcinoma, post-transplant lymphoproliferative disease (PTLD) - Human herpes virus 8: Kaposi’s sarcoma, primary effusion lymphoma, Castleman’s disease - Human T-cell Lymphotropic Virus (HTLV): Adult T-cell leukaemia/lymphoma - Human Papillomavirus (HPV): cervical, anal, oropharyngeal cancers - Hepatitis B and Hepatitis C: hepatocellular carcinoma

Answer 42

[1] Whole organism - i.e. virus → electron microscopy → culture using light microscopy to see (uninfected/infected cells) ---------- [2] Part of organism – e.g. antigen, nucleic acid → antigen detection → nucleic acid detection from the sample then amplify a region of the target organism genome ---------- [3] Immune response to a pathogen – i.e. antibodies → antibody detection - determines acute/recent infection - determines prior infection/response to vaccination

Answer 43

[1] Prophylaxis (to prevent infection) [2] Pre-emptive therapy (when evidence of infection/replication is detected, but before symptoms are apparent) [3] Overt disease [4] Suppressive therapy (to keep viral replication below the rate that causes tissue damage in an asymptomatic infected patient)

Answer 44

Because there are limited viral proteins that are potential targets for antiviral drugs

Answer 45

immunisation * Vaccination * Passive immunisation with immunoglobulin ----------------- Prophylactic treatment post-exposure * Post-exposure prophylaxis in HIV ----------------- Infection prevention and control (IPC) measures * Isolation of symptomatic patients * Personal protective equipment (PPE) * Safe use and disposal of sharps ----------------- Blood/tissue / organ screening ----------------- Antenatal screening - identifying those at high risk of a disorder for prenatal diagnosis

Answer 46

* No animal reservoir or ability to amplify in the environment * clearly identifiable, with accurate diagnostic tool * No chronic carrier state * Efficient and practical intervention, e.g. vaccination * Political & social support -------------------------- Examples: Smallpox (eradicated in 1979) * Measles * Polio

bacteria, virus, parasite, fungi Flashcards

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