Week 2 - Microbiology Flashcards
What is a microorganism
An organism/replicating entity that is of microscopic size
What is microbiology
The study of micro-organisms (or macroscopic for example some worms) their relationships with humans
3 types of cellular microorganisms
Bacteria
Protozoa/other parasites
Fungi
2 types of acellular microorganisms
Viruses and prions (are more like deviated proteins)
5 features of prokaryotes
No membrane bound nucleus
Transcription and translation are coupled (i.e not in ribosome and nucleus)
Single, circular chromosomal DNA
Additional DNA carried in plasmids
Usually bacteria
4 features of eukaryotes
DNA is held in chromosomes inside membrane bound nucleus
Translation and transcription processes are compartmentalised
Cytoplasm is rich in membrane bound organelles
Cellular organisms other than bacteria
How is DNA found in bacteria
Long, circular form sometimes with plasmids in addition
What else surrounds the membrane around the bacteria
Cell wall
Thick capsule
How do bacteria reproduce
Via binary fission (asexual reproduction by separation into 2 bodies)
What makes bacteria gram-positive
Thick layer of peptidoglycan on cell wall so crystal violet remains
What makes bacteria gram-negative
Thin layer of peptidoglycan on cell wall
What makes bacteria gram-stain unreliable
Very small bacteria, atypical life cycle, atypical structure, don’t have complex wall
What can be used when bacteria are gram stain unreliable
PCR
Microscopy
Alternative staining/culture techniques
What counter-stains the gram negative bacteria
Safranin
2 examples of gram positive coccus bacteria
Streptococcus aureus
Streptococcus pneumoniae
2 examples of gram positive rods
Listeria monocytogenes
Corynebacterium diphtherie
2 examples of gram negative cocci
Nisseria meningiditis/gonnorrhoeae
2 examples of gram negative rods
escherichia coli
salmonella species
What is a commensal organism
One that uses food supplied internally/externally without establishing a close relationship - mutualistic
3 benefits of natural flora from birth
Immune stimulation
Metabolic waste products - vitamins K and B
Competition and natural by-products inhibit the establishment of infection
5 sites of colonisation of bacteria
Colon (most diverse and large in number)
Skin
Distal GI tract
Upper resp
Distal urethra
Name 7 sterile body sites
Blood, tissue, organ systems
Central nervous system
Exposed conjunctivae
Female reproductive tract down to the cervix
Lower respiratory tract
Sinuses, inner and middle ear
Renal system down to postural urethra
Define a parasitic infection
Establishment, persistence and reproduction of an infectious agent at the expense of a host
Opportunistic infection
Infection by less virulent infection that ubiquitous in the environment but might cause harm in immunocompromised individuals
Nosocomial infection
Hospital acquired infection
Carrier state
A host that has an infection that is inapparent throughout it’s course and has no symptoms - can be chronic or transient
Endotoxins
lipopolysaccharide - forms the outer part of the cell membrane of gram negative bacteria
Exotoxins (super antigens)
Produced by gram positive intracellularly and released by mature toxins on infection
For example
streptococcus aureus
streptococcus pyogenes
What do exotoxins cause
Non-specific polyclonal T cell stimulation
Toxic shock syndrome
Factors that determine whether patients will develop an infection
Age
Gender
Ethnicity
Personal hygiene
Nutrition
Other medical conditions
Immunocompromise due to condition or medication
Presence of bionic materials e.g plastic/metal - vascular endothelium is designed to reject any bacteria or foreign objects therefore organisms can target these metals and plastics since easy to stick to
Why might faecal samples need to be decontaminated
due to diverse flora present
Example of testing you might do on faecal sample
latex agglutination to determine whether any antigens or antibodies are present
What is sepsis
Physiological response to severe infection when the body responds improperly to infection. Involves cytokine cascades, free radical production and vasoactive mediators
Name the 6 forms of cocci
Coccus
Diplococci
Staphylococci
Streptococci
Tetrad
Sarcina
Name 4 forms of bacilli
Simple bacillus
Diplobacilli
Streptobacili
Palisades
