Microbiology Flashcards
What are Protozoa
Unicellular eukaryotes
Many are Free-living
Often with parasites
What are eukaryotes
Cellular organisms with membrane bound organelles
DNA in the form of chromosomes in a nucleus
Complex metabolic function
example of protozoa
trypanosomiasis (chagas disease)
malaria
cryptosporidium
Toxoplasma gondii
how big are protozoa generally
2-100 micrometers
what does Bordetella pertussis cause
whooping cough
how to streptococcus cause infection
release Streptolysin O toxin
haemolysis
what shape is streptococci and staphylococci
strep = line of circles
staph = bunch of circles
what is a protkaryote
single-celled organism that lacks a nucleus, and other membrane-bound organelles.
compare gram positive and negative bacteria
Gram negative have 2 membranes separated by a very thin layer of peptidoglycan which cannot sustain the gram stain leaving it its natural histological pink colour.
Gram positive microbes have a very thick peptidoglycan wall which can hold the stain, leaving it purple.
explain the structure of peptidoglycan (3)
Peptidoglycan is a polymer of N-acetyl muramic acid (NAM) and N-acetyl glucosamine (NAG)
crosslinked via amino acid pentapeptides and anchored to the cell wall.
what part of bacteria does penicillin attack
the cross linking of the peptidoglycan in cell walls
compare flagella and Pili
Flagella rotate in different directions to propel the bacteria in a direction
Pilli have sticky ends that adhere to host surfaces and contract to bring closer
both for movement of bacteria
what is a pathogen
disease causing organism
what is a commensal
an organism that lives freely in a host that does not cause disease in normal circumstances
what is an opportunistic pathogen
a commensal that is usually harmless but under certain circumstances e.g. immunocompromised - leads to disease
name some commensals, where they are found and their opportunistic diseases
Staph aureus - found in nasal passages = MRSA, endocarditis
Staph Epidermidis - found on skin = catheter related sepsis
how many bacteria are in 1g of GI tract
1000,000,000
give the structure and gram stain of E. Coli
gram negative rod
commensal
how do we test for mycobacterium and why
It is impervious to gram staining due to waxy cell wall
unusual cell wall containing mycolic acid - higher melting point that have a waxy nature - can survive in lungs
Ziehl-Neelsen acid-fast staining procedure: mycobacteria in red.
An example of this would be M.Tuberculosis.
compare the structure of a gram negative wall and a acid fast wall
gram negative have 2 membranes separated by a thin layer of peptidoglycan
acid fast walls contain mycolic acid making it waxy
how would we test for M. Tuberculosis or M. Lepore
Ziehl-Neelsen acid-fast test under microscope
red rods
what was the first pathogen related to a disease
m. Leprae
what is the carrier state and why is it important
asymptomatic carriage of pathogenic bacteria
it increases the spread of the disease quickly before people realise they have the disease. Half of gonorrhoea and chlamydia is asymptomatic and even less so in women. But with larger effects on women.
why does washing hands prevent spread of typhoid fever and what causes this (3)
Salmonella Typhi causes Typhoid fever
Small amounts of this are kept in the gall bladder which is then excreted
Washing hands after going to the toilet stops spread