Infection Flashcards
What categories of organism cause infection
Largest to smallest: Helminths Insects Protozoa Fungi Bacteria Viruses Prions
What is a parasite
An organism which depends on another for its survival to the detriment of its host
What categories of organism are referred to as parasites
Helminths
Insects
Protozoa
What are the characteristics of endoparasites and ectoparasites
Endo: live inside of body, major cause of illness, examples are helminths and protozoa
Ect: live outside the body, minor symptoms but can transmit other infections, examples are fleas, lice, bed bugs and ticks
What are protozoa and what are the types
Unicellular organisms
Too small to see by eye
Some have complex lifecycles involving more than 1 host
Amoeba
Sporozoa (malaria)
What are helminths and what are the characteristics of the different types
Complex organisms
Some have complex lifecycles involving more than 1 host
Cestodes: (tapeworms) segmented, flat
Trematodes: (flukes) unsegmented, flat
Nematodes: (round worms) cylindrical, have digestive tract with lips, teeth and anus
What are the two types of fungal infection and their characteristics
Yeats: single cells which bud
Moulds: filamentous strands
Some can switch between yeast and mould
What are bacteria
unicellular organisms Prokaryotes Cell membrane Cell wall No nucleus Reproduce asexually
What is a gram stain
Looks at cell wall because bacteria cell walls vary in composition with some retaining crystal violet stain and others not
Gram-positive: purple
Gram-negative: pink
What are viruses
Dependent on infection of host cell for metabolism and replication
Contain protein core, surrounding genetic material, protein coat and outer membrane
Very small
Can only be seen with powerful microscopes
What are the three categories of viral infection
Acute
Chronic
Latent
What are prions
Smallest infective agents
Not a living organism
Proteins are abnormal and accumulate, mainly in neural tissue
Very difficult to destroy
What is an endogenous infection and what is an example
Infection comes from normal flora; usually starts in normal place and moves to the wrong place resulting in an infection
Cystitis (UTI): caused by gut flora moving into urinary tract, most commonly E.coli (gram negative bacteria)
What is exogenous infection
Comes from another organism or something in the outside environment
How can endogenous infection happen
Migration
Perforation
Blood spread
How can exogenous infection happen and what are examples of each route
Contact: direct (Impetigo); indirect (MRSA)
Injury: trauma (Tetanus); bites (malaria)
Airborne (influenza virus)
Oral: food (food poisoning); water
Blood-borne (hepatitis)
Sex (chlamydia)
Mother-to-baby /vertical (Herpes, rubella)
What pathogen factors affect response to infection
Infectious dose
Direct infection cells/tissues
Virulence factors and toxins
Resistance to antibiotics
What patient factors affect response to infection
Environment
Barriers to infection
Genetics
What are examples of bacteria
Staphylococcus aureus
Streptococci
Escherichia coli
Tuberculosis
What are examples of Viruses
Rhinovirus (common cold)
Influenza
Hepatitis B/C
HIV
What are examples of Fungi
Candida
Tinea
What are examples of parasites
Malaria
Hookworm
What do each white blood cell type suggest if elevated
Neutrophil: bacterial infection
Lymphocyte: viral infection
Eosinophil: parasitic infection
What is the CRP test
C-reactive protein is a marker of inflammation, can show if someone is improving or deteriorating
What are UandEs
Urea and electrolyte levels (kidney function)
What are LFTs
Liver function tests
What tests do microbiologists do with the samples sent to the lab
Antibody detection Microscopy Culture Antibiotic sensitivity testing PCR Antigen detection
What is the IgM antibody
Initial antibody response
Appears within a week and usually disappears after a few months
What is the IgG antibody
Later antibody response
Appears 10-14 days
Persists throughout life as part go immunological memory
Useful to test whether you are immune to an infection
What are antimicrobials
Any drug that kills microorganism
What are antibiotics
A chemical substance derived from a mould or bacterium that can kill microorganisms and cure bacterial infections
What is desired of an antimicrobial
Selective toxicity
Bacteriocidal (kills bacteria) rather than bacteriostatic (inhibits its growth)
No resistance
Good pharmacokinetics
No side effects
Not inactivated by enzymes secreted by microbes or by the host
What are the categories of antibiotic action
Cell wall synthesis (---illin, ceph---, ---penem) DNA replication (quinolone) Folic acid (trimethoprim) Protein synthesis (cindamycin)
What are broad spectrum vs narrow spectrum antimicrobials
Broad: kill lots of different organisms, may also kill out natural flora
Narrow: kills few specific organisms
What is antibiotic stewardship
Using antibiotics wisely to make sure we aren’t overprescribing antibiotics and thereby increasing resistance
