microbiology Flashcards
What are common side effects of all antibiotics
Nausea, vomiting, diarrhoea - all disrupt guts natural flora
side effects of gentamycin
Renal and vestibulocochlear
S.E of metronidazole?
reacts with alcohol
S.e of ciprofloxacin?
tendonitis
What antibiotics increase risk of C diff
avoid the 4 C’s
ciprofloxacin, cephalosporins, co-amoxiclav and clindamycin
What antibiotics are to be avoided in pregnancy
Trimethoprim and metronidazole are to be avoided in the first three months of pregnancy
Gentamycin, tetracycline and fluoroquinolones are to be avoided all together !!
Pathogen?
harmful organism
commensal?
organism that is part of the normal flora
opportunistic pathogen
Only cause infection in the immunocompromised
Contaminant
organism that has gotten into a culture by accident
pathogenecity
ability of the microorganism to produce disease
virulence
the degree in which a pathogen can do harm
How does bacteria replicate?
binary fission - start off as one and then divide
What are the three types of atmosphere bacteria can grow in?
aerobic - in presence of oxygen
microaerophillic - reduced O2 increased CO2
anaerobic - without O2
What are the two different types of toxins?
Exotoxin - released from gram positive cell from within and exocytosed out
endotoxin - released from gram negative cell and is part of the cell wall
What do fungi like moulds and yeasts release? (what conditions can arise out of these)
moulds - spores and hyphae (aspergillus)
yeasts - single cells that reproduce by budding - candida
What is the antibiotic of choice for staph aureus
flucloxacillin
Describe the way in which a fever forms
antigen attacks macrophage
releases cytokines
travel up to the anterior hypothalamus of the brain
release prostaglandin E
increases body temp to above normal
body thinks its cold so starts to shiver
pathogens grow more slowly in increased heat
What is the first line antibiotic of coliforms?
gentamicin
What is the first line treatment for infections caused by anaerobes?
Mentronidazole
What are some properties of mycobacteria?
thixy waxy outer coat, involved in TB and ziehl neelson stain is used - acid fast bacilli
What are the three different ways of gene transfer in bacteria?
Transformation - DNA from dead bacteria taken up by living bacteria and incorporated in the genetic part of cell
conjugation - sex plius produced by one bacteria through which a plasmid can be transferred
Transduction - viruses infecting bacteria can transfer bits of DNA from one bacteria to another
What are the five I’s of infection?
mother to infant, inoculation, ingestion, inhalation and intercourse
Describe the chain of infection
starts with infectious microbe, reservoir, portal of exit, mode of transfer, portal of entry, susceptible host
Define bactericidal and bacteriostatic
kill bacteria and inhibit bacteria growth
What are the antibiotics that work on the cell wall?
Penecillin, cephalosporins (ceftriexone) and glycopeptides (vancomycin)
Describe the cell wall of gram positive and negative organisms
positive - Cell wall has thick layer of peptidoglycan and a single phospholipid bilayer
negative - Cell wall has two phospholipid bilayers and a thin layer of peptidoglycan
What does penicillin inhibit?
Is it bactericidal?
Is it a beta-lactam antibiotic
Inhibits cell wall synthesis by preventing cross linking of peptodiglycan subunits
bactericidal
beta- lactam antibiotic
When is flucloxacillin used?
Skin and wound infections, cellulitis
What are some properties of cephalosporins?
inhibit what?
inhibit cell wall synthesis
bactericidal
beta lacatam
may induce C. diff
Glycopeptides? (vancomycin) - cell wall what?
what are they only effective against?
cell wall active antibiotic binds to end growing chain - prevents cross linking and weakens bacterial cell wall
bactericidal
only effective against gram +ve
What are the antibiotics that inhibit protein synthesis?
macrolides (clarithromycin) - bacteriostatic
tetracyclines (doxycycline) - bacteriostatic
aminoglycodsides (gentamycin) - bactericidal
When are macrolides particulary useful?
they are lipophyllic and especially useful for infections that hide from the hosts immune system
What are some side effects of tetracyclines - doxy (broad spectrum)
Broad spectrum - destruct intestinal flora leading to an increased risk of secondary infection
can permanently stain the teeth of kids
What are aminoglycosides mainly used for ?
gram negaives aerobes - coliforms and pseudomonas aeruginosa
What are some antibiotics that work on bacterial DNA
metronidazole, trimethoprim and fluroquinolones
When is metronidazole used?
true anaerobic infections - strand breakage of bacterial DNA
How does trimethoprim work?
inhibits bacterial folic acid synthesis
How does a fluoroquinolone work?
Prevent supercoiling of bacterial DNA - restricted use due to C diff
What are the 6 stages of viral replication?
attachment - interact with specific receptors in target cell
entry - endocytosis
uncoating - viral nucleic acid released from capsid
nucleic acid and protein synthesis - host ribosomes used + host polymerases
assembly - nucleic acid and proteins packed together
release - budding ( doesnt kill, virus released with envelope)
lysis - virus accumulates until cell burst - kills cell
Why are cytotoxic T lymphocytes useful?
recognise proteins on cell surface as being foreign and will signal infect cell to commit suicide so virus doesn’t spread
What is selective media?
specific substance that permits growth of one organism over anotehr
Differential media
incorportation of chemicals that facillitate identification
What is the process of becoming septic?
small blood vessles become leaky and loose fluid into surrounding tissue
lower blood volume requires heart to work harder to maintain oxygenation of tissues
less blood supply to vital organs
clotting system is activated which uses up clotting factors and increasing the risk of bleeding
What is the structure of a virus
nucleic acid genome
protein capsid
lipid envelope associated with virus proteins
How do you detect a viral infection
PCR - antigen swab test
host response - IgG or IgM
