Flashcards in Microbiology 1 and 2 - Nature of infection, systemic bacteriology 1 Deck (81)
List of microorganisms in increasing size
What type of names do all organisms have?
A genus name and a species name
What type of diseases does prion proteins cause?
Give an example.
Transmissible Spongiform Encephalopathies (brain infection)
Mad cow disease (Crutzefelt Jacob Disease)
Problem with prion proteins?
Cannot be reliably removed by sterilisation
What type of organism is a virus?
What is it surrounded by?
"obligate intracellular parasite"
A capsomere (protein coat)
Diagnosis of viral infections?(3)
Difference between the genetic material contained within viruses and bacteria?
Viruses = DNA or RNA
Bacteria = DNA and RNA (one double stranded chromosome with some genetic material sometimes stored within plasmids)
What surrounds a bacteria in terms of walls, etc.?
What does a bacteria use for adhesion and movement?
Adhesion: Pilli and fimbriae
Bacterial shapes? (3)
Can spirochaetes be stained using the gram method?
No but they have a gram negative structure
Gram stain reactions?
Gram positive = purple
Gram negative = pink
Difference between gram positive and gram negative?
Gram positive cell wall contains a thick layer of peptidoglycan compared to a thin layer between the cytoplasmic membrane and outer membrane in gram negative bacteria
What 2 organisms do not stain well?
Mycobacterium tuberculosis (causes TB, has a waxy coat)
Treponema pallidum (spirochaete that causes syphilis)
Where in the body is there a natural bacterial flora? (5)
Lower small intestine
Skin (resident and transient flora)
What is commensalism?
Where one organism benefits from the relationship without affecting the other (commensal is part of the normal flora)
An organisms that will cause infection in an immunocompromised individual
Degree of pathogenicity of an organism (i.e. how easily can an organism cause disease)
How does bacteria replicate?
What do they require to replicate? (4
)How quickly can bacteria replicate in ideal growth conditions?
Correct temp. (usually 37 for human pathogens)
correct pH (about 7.4)
Every 20 minutes
3 main types of atmosphere?
Aerobic (growth in presence of oxygen, many aerobic organisms will also grow in anaerobic conditions but less well)
Microaerophillic (reduced O2 and enriched with CO2)
Anaerobic (no O2, "anaerobes" are strict anaerobes)
Why does bacteria make us ill?2 types of these?
Many produce toxins (enzymes)
Exotoxin (mainly gram positive, produced side cell and exported out)
Endotoxin (mainly gram negative, part of GN cell wall)
What do toxins produced from bacteria do?
Interact with cells of the immune system causing release of cytokines
Damage RBCs and WBCs, make small blood cells 'leaky", decrease BP, affect blood clotting and eventually lead to sepsis and septic shock
What type of organisms tend to form spores?2 examples
Gram positive bacilli (put DNA in thick coat = can't replicate but can survive for long time)
Clostridium sp. (e.g. C. difficile)
Bacillus sp. (e.g. Bacillus anthracis)
How does a spore develop? (3 stages)
Calcium dipliconate accumulates
Diagnostic methods for bacteria?
Microscopy (same day)
Culture (48 hours)
Detection of antigens (e.g. in urine)
Detection of antibodies (e.g. serology) - same day
PCR (same day) for NAATs (detection of DNA/ RNA through nucleic acid amplification tests
Streptococcus pneumoniae causes?
Pneumonia and meningitis
Streptococcus pyogenes (group A strep.)
Skin (e.g. necrotising fascitis), throat infecitons (e.g. tonsillitis - if rash present = scarlet fever), peurperal sepsis = severe life threatening infection in pregnant and post natal women)
Group B strep.?