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54 Cards in this Set

  • Front
  • Back
What are the leading infectious diseases causing mortality in Australia?
-Respiratory
-HIV
-Septicaemia
-UTI/Kidney
-Viral Hepatitis
What are explanations for the resurgence of infectious diseases in the population?
-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
What is the definition of epidemiology?
Study of the occurrence, spread and control of diseases in populations
What is the reasons for recording diseases affecting populations?
-Indentify causes and modes of transmission
-Predict the likelihood of further infections
-Identify risk factors
-Plan control measures
Define endemic
Disease that occurs regularly at low or moderate frequency in the population
Define Epidemic
Incidence of a disease clearly in excess of normal experience (ie normally 4000 cases increases to 8000)
Define pandemic
Epidemic that affects all or most countries in the world at the same time
Define epizoonotics
Outbreaks that occur in animal populations
Define infection
Presence of microorganisms associated with tissue destruction or inflammatory response
Define infectious disease
Only used when there has been a disturbance to boyd function from presence of products of microorganisms (can be mild or severe)
Define Incubation period
Time interval between exposure to microbe and appearance of disease
Define communicable disease
An infectious disease that is capable of spreading from person to person
Define carrier
Harbours microorganisms that are capable of causing disease in others but doesnt show any clinical symptoms
Define pathogenicity
Ability to cause disease; qualitative measure of disease production
Define virulence
-Attributes that promote pathogenicity and affect infectiousness or disease severeity
-ie High virulence pathogenic in low numbers
What is the biologic response gradient?
Outlines that microbes do not always cause exactly the same disease severity and symptoms in individuals
What are the 4 broad microbial classifications?
Eukaryotes
Prokaryotes
Atypical Bacteria
Non-cellular organisms
What are eukaryotes?
-Uni/multicellular
-Fungi (moulds, yeasts)
-Parasites (Protozoan/metazoa)
-Capable of independant life
-Complex cellular structure
What are prokaryotic organisms?
-Bacteria
-Classified by gram stain, shape, biochemistry etc
-Can sometimes survive without a host
What is atypical bacteria?
-Mycoplasma
-Chlamydia, Rickettsia
-Not capable of indpendant life
-Have no cell wall
-Obligate intracellular parasites
What are non-cellular organisms?
-Viruses
-Prions
-Nucleic acid+protien coat+- envelope
-Infectious protein particles
Why do we classify microorganisms?
-Data on structure and classification are relevant pathways for identification and hence diagnosis and also therapy
What is the difference between a eukaryote vs a procaryote?
In prokaryotes;
-Nucleus absent
-DNA; singular chromosome +/- plasmids
-Transcription/translation can be carried out simultaneously
-Lack of membrane bound organelles
What is responsible for encoding resistance genes?
Plasmids
What are the characteristics of Fungi (myceteaee)?
-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
Are all fungi aquired from the environment?
No, it is possible for it to be part of the normal flora
How is fungi classified?
-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
What are the characteristics of yeasts?
-Reproduce by budding
-Usually unicellular
-Produce round pasty or mucoid colonies on agar
-Type of fungi
What are the characteristics of moulds?
-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
What are the characteristics of protazoa (parasites)?
-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
How are protozoa classified?
-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
How do protozoa reproduce and transmit?
-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
What are some protoza that affect the CNS?
-Amebae
-Malaria
-Toxoplasm
-trypanosomes
What are some protoza that affect the blood?
-Malaria
-trypanosomes
What are some protoza that affect the intestine?
-Cryptosporidium
-Entamoeba
-Giardia
-Cyclospora
-microsporidia
What are some protoza that affect the skin?
-Leishmania
What are some protoza that affect the urogenital tract?
-Trichomonas
What are the characteristics of metazoa (helminths/worms)?
-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
How are metazoa (helminths/worms) transmitted?
-Direct (swallowing infective stages)
-Penetration of larvae through skin
-Indirect via intermediate hosts or insect vectors
What are the characteristics of round worms (nematodes)?
-Cylindrical bodies
-Seperate sexes
-Have complete digestive system
-May be intestinal parasites or infect blood and tissues
What are the characteristics of flatworms?
-Seperated into flukes (trematodes) and tapeworms (cestodes)
What are the characteristics of flukes?
-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
What are the characteristics of tapeworms?
-Type of flatworm
-Hermaphrodites
-Lack digestive system; nutrients absorbed through body wall
-Complexity of life cycle varies (direct or require intermediate hosts)
What are the characteristics of bacteria?
-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
What are the characteristics of viruses?
-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
What are the characteristics of prions?
-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
What is meant by extracellular pathogens?
-Reproduces and causes disease while extracellular
-eg Vibrio cholera
What is meant by facultatively intracellular pathogens?
-Sometime spent extracellular and sometime spent intracellular
-Some parasites; toxoplasma, leishmania
-Some bacteria; mycobacterium, brucella,listeria, shigella, salmonella
What is meant by obligately intracellular pathogens?
-Have to be within a cell to survive
-Chlamydiae, rickettsiae
-Viruses
Do all microbes require humans for spread?
No, microbes vary in the degree of dependance of human beings, obligate parasites are those that depend on humans but not all cause disease
What is normal flora?
-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
What areas have more normal flora?
Moist areas;
The majority of bacteria in the nose and throat, large intestine and vagina are anaerobes.
What are the advantages of normal flora?
-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
What are the disavantages of normal flora?
-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)