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54 Cards in this Set
- Front
- Back
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What are the leading infectious diseases causing mortality in Australia?
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-Respiratory
-HIV -Septicaemia -UTI/Kidney -Viral Hepatitis |
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What are explanations for the resurgence of infectious diseases in the population?
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-New patterns of trade/travel, agriculatural practices, sexual behaviours, medical interventions, overuse of atibiotics
-Breakdown of economic, social and political systems leading to weakend medical services -Emergence of new infections, zoonotic infections -Climate change; vector born diseases -Bioterrorism |
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What is the definition of epidemiology?
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Study of the occurrence, spread and control of diseases in populations
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What is the reasons for recording diseases affecting populations?
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-Indentify causes and modes of transmission
-Predict the likelihood of further infections -Identify risk factors -Plan control measures |
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Define endemic
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Disease that occurs regularly at low or moderate frequency in the population
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Define Epidemic
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Incidence of a disease clearly in excess of normal experience (ie normally 4000 cases increases to 8000)
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Define pandemic
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Epidemic that affects all or most countries in the world at the same time
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Define epizoonotics
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Outbreaks that occur in animal populations
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Define infection
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Presence of microorganisms associated with tissue destruction or inflammatory response
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Define infectious disease
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Only used when there has been a disturbance to boyd function from presence of products of microorganisms (can be mild or severe)
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Define Incubation period
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Time interval between exposure to microbe and appearance of disease
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Define communicable disease
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An infectious disease that is capable of spreading from person to person
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Define carrier
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Harbours microorganisms that are capable of causing disease in others but doesnt show any clinical symptoms
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Define pathogenicity
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Ability to cause disease; qualitative measure of disease production
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Define virulence
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-Attributes that promote pathogenicity and affect infectiousness or disease severeity
-ie High virulence pathogenic in low numbers |
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What is the biologic response gradient?
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Outlines that microbes do not always cause exactly the same disease severity and symptoms in individuals
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What are the 4 broad microbial classifications?
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Eukaryotes
Prokaryotes Atypical Bacteria Non-cellular organisms |
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What are eukaryotes?
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-Uni/multicellular
-Fungi (moulds, yeasts) -Parasites (Protozoan/metazoa) -Capable of independant life -Complex cellular structure |
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What are prokaryotic organisms?
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-Bacteria
-Classified by gram stain, shape, biochemistry etc -Can sometimes survive without a host |
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What is atypical bacteria?
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-Mycoplasma
-Chlamydia, Rickettsia -Not capable of indpendant life -Have no cell wall -Obligate intracellular parasites |
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What are non-cellular organisms?
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-Viruses
-Prions -Nucleic acid+protien coat+- envelope -Infectious protein particles |
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Why do we classify microorganisms?
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-Data on structure and classification are relevant pathways for identification and hence diagnosis and also therapy
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What is the difference between a eukaryote vs a procaryote?
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In prokaryotes;
-Nucleus absent -DNA; singular chromosome +/- plasmids -Transcription/translation can be carried out simultaneously -Lack of membrane bound organelles |
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What is responsible for encoding resistance genes?
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Plasmids
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What are the characteristics of Fungi (myceteaee)?
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-Uni or multi cellular
-Non photosynthetic -Rigid cell wall composed of chitin and glucan (carbohydrate) -Grouped into yeasts and moulds -Many medically important fungi are dimorphic ie can exist in both yeast and mould form -Ubiquitous group; saprobes, symbionts, commensuals and parasites |
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Are all fungi aquired from the environment?
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No, it is possible for it to be part of the normal flora
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How is fungi classified?
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-According to the tissue infected as well as by specific characteristics of the organism
-Superficial mycoses (athletes foot/thrush), spread via contact -Cutaneous (keratinized layer of skin, hair and nails) -Subcutaneous (involve deeper layers of the skin) -Systemic |
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What are the characteristics of yeasts?
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-Reproduce by budding
-Usually unicellular -Produce round pasty or mucoid colonies on agar -Type of fungi |
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What are the characteristics of moulds?
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-Multicellular organisms
-Consists of threadlike tubular structures (hyphae) which elongate at their tip by apical extension -Hyphae form to produce mycelium -Spores consist of sporangiospores and conidia which are small airborne and easy to inhale -Colonies formed described as filamentous, hairy and woolly |
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What are the characteristics of protazoa (parasites)?
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-unicellular
-Surfaces vary in complexity and rigidity (psuedophilia for locomotion and ingestion, flagella for locomotion, stiff pellicles for preserving cell shape) -Live either intracellular or extracellular -Intracellular; RBC, macrophage, epithelial cells; nutrients acquired by direct uptake or ingestion of cytoplasm -Extracellular; live in blood, intestine , GUT; uptake nutrients directly or ingest host cells |
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How are protozoa classified?
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-Classified largely on microscopic morphology or stage of life cycle
-Flagellates; have flagella, leishmania -Amoebid; have pseudopodia, entamoeba histolytica -Ciliates; have cilia, balantidium coli -Sporozoa; lack locomotor organs, plasmodium -Trophozoite; stage that actively feeds and multiplies -Cysts;parasite that protects itself with a protective membrane |
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How do protozoa reproduce and transmit?
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-Typically asexual reproduction by binary fission
-Sexual reproduction absent or in insect vector phase -Ingestion of water/food contaminated with the transmission stages -Transmission via sexual activity -Via insect vectors -Some transmitted from mother to foetus |
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What are some protoza that affect the CNS?
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-Amebae
-Malaria -Toxoplasm -trypanosomes |
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What are some protoza that affect the blood?
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-Malaria
-trypanosomes |
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What are some protoza that affect the intestine?
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-Cryptosporidium
-Entamoeba -Giardia -Cyclospora -microsporidia |
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What are some protoza that affect the skin?
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-Leishmania
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What are some protoza that affect the urogenital tract?
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-Trichomonas
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What are the characteristics of metazoa (helminths/worms)?
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-Multicellular organisms
-Elongated and bilaterally symmetrical -Larger than protozoa, generally macroscopic -External surface; smooth, cuticles, ridges, spines, tubercules -Often possess attachment structures anteriorly; hooks suckers teeth -Primitave nervous and excretory systems, no circulatory system, some have almentary tract -occur in tropical and sub tropical areas with most infections long lived -Divided into flat and round worms |
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How are metazoa (helminths/worms) transmitted?
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-Direct (swallowing infective stages)
-Penetration of larvae through skin -Indirect via intermediate hosts or insect vectors |
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What are the characteristics of round worms (nematodes)?
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-Cylindrical bodies
-Seperate sexes -Have complete digestive system -May be intestinal parasites or infect blood and tissues |
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What are the characteristics of flatworms?
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-Seperated into flukes (trematodes) and tapeworms (cestodes)
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What are the characteristics of flukes?
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-Type of flat worm
-More hermaphrodites -Incomplete digestive systems -Complex life cycle; snails serve as first intermediate hosts and other aquatic plants/animals serve sa second hosts |
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What are the characteristics of tapeworms?
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-Type of flatworm
-Hermaphrodites -Lack digestive system; nutrients absorbed through body wall -Complexity of life cycle varies (direct or require intermediate hosts) |
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What are the characteristics of bacteria?
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-Prokaryote
-Single celled -different shapes and sizes and stain differently -many are motile -cell surrounded by a complex cell wall +/- capsule -Reproduce by binary fission -Vary in nutrition requirements -Have many strategies to combat the human host |
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What are the characteristics of viruses?
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-Genetic material; DNA or RNA contained within a capsid
-Metabolically innert -Replicate only after infecting the host cell; parasite host's cells ability to transcribe/translate genetic information -Cause some of the most common and most serious human diseases |
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What are the characteristics of prions?
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-Lack a nucleic acid genome
-Highly resistant to disinfection and UV -Do not elicit an immune response -Transmission; ingestion of contaminated materials or via medical procedures -Small modified host derived proteinaceous particles that are misfolded.These accumulate as amyloid plaques, internalised by cells leading to tissue damage and cell death -Disease characteristics by changes in the brain (spongioform encephalopathies)and motor disturbances |
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What is meant by extracellular pathogens?
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-Reproduces and causes disease while extracellular
-eg Vibrio cholera |
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What is meant by facultatively intracellular pathogens?
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-Sometime spent extracellular and sometime spent intracellular
-Some parasites; toxoplasma, leishmania -Some bacteria; mycobacterium, brucella,listeria, shigella, salmonella |
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What is meant by obligately intracellular pathogens?
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-Have to be within a cell to survive
-Chlamydiae, rickettsiae -Viruses |
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Do all microbes require humans for spread?
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No, microbes vary in the degree of dependance of human beings, obligate parasites are those that depend on humans but not all cause disease
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What is normal flora?
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-Inhabitants of surfaces, bacteria, fungi, adapted to their local environment
-Harmless when in their usual site -Potentially pathogenic when they enter tissues (opportunic pathogens) -Derived from maternal geneital tract, skin, mouth and pharynx of close contacts, air bourne organisms, environment and food |
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What areas have more normal flora?
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Moist areas;
The majority of bacteria in the nose and throat, large intestine and vagina are anaerobes. |
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What are the advantages of normal flora?
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-Prevent colonisation by potential pathogens by producing fatty acids, releasing antibacterial factors, maintaining acid environment, occupying all available ecological niches ie outcompetes for living space
-Generate antigenic stimulation to ensure normal development of the immune system -Aid in digestion of food -Produce metabolites such as vit. K used by the host |
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What are the disavantages of normal flora?
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-Potenital to spread into previously sterile parts of the body; perforated intestine, extraction of teeth, organisms from the perianal skin asend the urethra and cause uti, medically induced (catheters)
-Overgrowth of potentially pathogenic normal flora; composition of normal flora changed (antibiotics), local environment changes (pH), immune status changes (immunocompromised) |
