Session 1 And 2 Flashcards
(31 cards)
Describe the basic infection model.
Pathogen infects patient; pathogens mechanism of infection begins; infection is identified and managed; outcome varies depending on management (get better or worse/death).
Which fungi are unicellular and which are multicellular?
Yeast are uni-, mounds are multi-.
Which parasites are unicellular and which are multicellular?
Protozoa are uni-, helminths are multi-.
Classify bacteria, fungi and parasites as either prokaryotic or eukaryotic.
Bacteria: prokaryotes
Fungi: eukaryotes
Parasites: eukaryotes
What is contiguous spread of infection?
Pathogen moves from a part of the body where it is usually found to one where it isn’t and results in infection
What is innocuous spread of infection?
Infection due to inoculation, e.g. surgical site infections or infection from splinter injuries.
WHat is infection via ingestion?
Infection due to eating/drinking a pathogenic microorganism.
What does infection by ingestion usually result from?
Fecal-oral transmission.
What is infection via inhalation?
Infection due to breathing in a pathogen as a droplet or aerosol.
What is infection via a vector?
Infection caused by contact with an organism carrying a pathogen.
What is infection via vertical transmission?
Infection transmitted to a baby from its mother in utero, delivery or breastfeeding.
By what mechanisms may a pathogen cause infection?
By directly damaging cells, causing inflammation, via endotoxins release.
Usually damage is due to hosts inflammatory response.
How can antimicrobials be classified?
By type of organism they act on; bactericides/bacteriostatic properties; broad/narrow spectrum; by target site; by chemical structure.
What are the ideal features of an antimicrobial agent?
Selective toxicity; few adverse effects; able to reach site of infection; both oral and IV formation availability; long half-life; no interference with other drugs.
How does penicillin operate?
Inhibits transpeptidase enzymes so crosslinking in the cell wall cant occur. An imbalance between synthesis and degredation results causing the cell wall to become more fluid so the cell dies.
What is penicillin effective against and why?
Gram positive bacteria, particularly streptococci, staphylococci, clostridium and listeria.
Not effective against gram negative bacteria as they have a protein layer outside their peptidoglycan layer in the cell wall so penicillin is blocked from attaching.
What is vancomycin’s mechanism of action?
It binds to amino acid residues in the cell wall which prevents penicillin-binding protein from attaching. This prevents cross-links from forming so the cell wall becomes more fluid and the cell dies.
What is vancomycin effective against and why?q
Gram positive bacteria, gram negative bacteria have a different method of cell wall synthesis so vancomycin is ineffective in them.
What infections is vancomycin typically used against?q
Severe sepsis, MRSA, severe skin, bone and LRT infections.
How do fluoroquinolones work?
Target enzymes involved in DNA replication in bactaeria, usually DNA gyrase in gram -ve bactaeria and topoisomerase in gram +ve bactaeria.
By what mechanisms may antibiotic resistance occur?
Drug may be inactivated; target enzyme may be altered; antibiotic uptake may be altered.
How can antibiotic sensitivity be tested for?
Using disc sensitivity testing: if growth is inhibited then the microbe isn’t resistant.
How can the minimum inhibitory concentration of an antibiotic be determined?
Use test tubes containing known concentrations of antibiotic and introduce the organism to them. If a turbid broth is formed then growth isn’t inhibited
What is penicillin mainly effective against?
Streptococci.
