Microbiology D Flashcards
what does selective toxicity mean and how is this achieved
Antimicrobials are intended to be drugs that kill microorganisms but do not harm the host cells
Antibacterials Selectively toxic by targeting:
- Cell wall
- Protein synthesis
- Process of DNA supercoiling
- Folate metabolism
name two bacteria classes that act on the cell wall
- Beta-lactams
2. Glycopeptides
name two bacteria classes that act on the cell wall
- Beta-lactams:
- penicillins
- Penicillin/ beta-lactamase
inhibitor combinations
- Cephalosporins
- Monobactam
- Carbapenems - Glycopeptides
name some bacteria classes that are protein synthesis inhibitors
macrolides
aminoglycosides
tetracyclines
quinolones - DNA supercoiling
others - folate metabolism
what is a bacterias spectrum activity. what is meant by broad spectrum
The range of bacteria that a given antibiotic is able to kill
Antibiotics effective against a large variety of medically important organisms
describe the start smart then focus guidelines for infection treatment
Start smart:
- Do not start antibiotics in the absence of clinical evidence of infection
- Thorough drug allergy history*
- Rapid assessment for Sepsis
- Comply with local guidelines [microguide app
- Document diagnosis and treatment
- Document review and stop date
- Obtain cultures prior to starting treatment
Then focus: Clinical review, ideally with microbiological results at 48-72 hours: Document decisions: 1. Stop 2. IV to oral switch 3. change antibiotic 4. Continue 5. OPAT (Outpatient Parenteral Antimicrobial Therapy) Document all decisions
how do you Take a thorough allergy history
What drug
When did you take it (i.e. What age were you)
How long after taking the drug did the adverse reaction start (type 1, IgE reactions tend to be immediate)
Describe the reaction (paying attention to the appearance of rash- urticarial rash tends to be caused by histamine and so may be IgE mediated)
what drug is ok to give after a life threatening reaction to penicillin
Monobactam Aztreonam
what drugs are ok to give after a non-life threatening reaction to penicillin
Cephalosporins
Cefuroxime, Ceftriaxone
Monobactam Aztreonam
Carbapenems
Meropenem, Ertapenem
name two drugs used for Herpesvirus infections and how they work
Aciclovir
Ganciclovir
Nucleoside analogues: faulty DNA
Aciclovir: HSV and VZV
Ganciclovir: CMV
name the drug prescribed for influenza and how does it work
Oseltamivir
can be used for people with influenza or prophylaxis
Inhibitor of Neuraminadase enzyme:
Neuraminadase promotes viral
release and spread from respiratory cells
name some of the drugs prescribed for Hepatitis B and C and how do they work
Hepatitis B:
Tenovovir
Peginterferon alfa
Hepatitis C
Peginterferon alfa
Ribavarin
- Tenovovir: analogue of adenosine: a nucleoside reverse transcriptase
inhibitor - Peginterferon alfa: naturally
occurring cytokine with wide variety of antiviral properties - Ribavarin: Analogue of
Guanosine: broad antiviral activity, including RNA viruses. Toxic.
Multiple modes of action
name two drugs prescribed for Respiratory syncytial virus and how do they work
Palivizumab
Ribavarin
Palivizumab: Monoclonal antibody
Given as prophylaxis to children at
risk of serious RSV infection
name some drugs used in treatment of HIV
Reverse transcriptase inhibitors: - Nucleoside RTI: Zidovudine Tenovovir - Non-nucleoside RTI: Efavirenz
Protease inhibitors:
Lopinavir
Ritonavir
Integrase inhibitors:
Raltegravir
Fusion inhibitors:
Enfuviritide
describe Highly Active Anti Retroviral Therapy (HAART)
management of HIV
Multiple agents limit development of resistance
Backbone of 2 Nucleoside RTI
Plus one other agent (PI, Non Nucleoside RTI, integrase inhibitor)
Define herd immunity, vaccine adjuvant, passive immunotherapy
List the characteristics of a good vaccine.
Distinguish different types of vaccine preparations (live and inactivated) and compare their advantages and disadvantages.
List side effects of vaccine
Identify vaccines on the current UK vaccination schedule
Give examples of patient risk groups that require additional vaccinations
Give examples of post exposure vaccination
.
Define herd immunity
Concept of herd immunity – level of immunity at which an infectious agent can no longer continuously circulate (R becomes <1)
what’s the difference between dead or live vaccines
All vaccines should contain at least one of the protective antigens of the microbe.
Dead vaccines generally less effective than live
Live:
- microbes with artificially reduced virulence (‘attenuated’)
- microbes with naturally reduced virulence for humans
Dead:
- Inactivated virus
- subcellular fragments/ Sub-unit vaccines
- Toxoids
- Genetically engineered recombinant vaccines.
list some Pros and Cons of Live Attenuated Vaccines
Advantages:
- Good immunogens
- Induce long-lived, appropriate immunity
- Tend to produce mucosal immunity
- May offer alternative routes (e.g. oral)
Disadvantages:
- Labile: Cold chain vital for live vaccines
- Potentially unstable genetically (possible reversion to virulence)
- Not possible to produce in all cases - trial and error
- Contamination possible (e.g SV40 virus) in poliovirus vaccine
- Inappropriate/accidental vaccination to at risk groups (immunosuppressed and pregnant) may pose risk
list some Pros and Cons of Live Attenuated Vaccines
Advantages:
- Good immunogens
- Induce long-lived, appropriate immunity
- Tend to produce mucosal immunity
- May offer alternative routes (e.g. oral)
Disadvantages:
- Labile: Cold chain vital for live vaccines
- Potentially unstable genetically (possible reversion to virulence)
- Not possible to produce in all cases - trial and error
- Contamination possible (e.g SV40 virus) in poliovirus vaccine
- Inappropriate/accidental vaccination to at risk groups (immunosuppressed and pregnant) may pose risk
list some Pros and Cons of Inactivated Vaccines
Inactivated whole virus- Poliovirus, Rabies, inactivated HAV
Advantages:
- Stable
- Little or no risk (if properly inactivated)
Disadvantages:
- Not possible for all viruses; denaturation may lead to loss of antigenicity and adverse affects, e.g. measles, RSV.
- Not as effective at preventing infection as live viruses (mucosal immunity - IgA).
- May only protect for a short period protect
describe Sub-Cellular (Sub-Unit Vaccines)
Subcellular fractions can be used as vaccines if protective immunity is directed against a particular part of an organism
list the Pros and Cons of Sub-unit Vaccines
Advantages:
Selected virus proteins or peptides used so:
- Completely safe, except for rare adverse reactions.
- Specific Antibody and T cell reactions can be selected.
- Can be made using recombinant DNA techniques
Disadvantages:
- Tend to be the least effective.
- (Relatively) poor antigenicity (especially short peptides)
- Vaccine delivery (carriers/adjuvants needed)
describe Toxoid Vaccines
- Bacterial toxins – proteins realised by bacteria which induce inflammatory responses
- Toxoids: inactivated toxins (usually by formaldehyde) so no longer toxic, but still induce protective antibody
- Two toxoids: diphtheria and tetanus- among the most successful and widely used of all vaccines.
- In combination with killed Bordetella pertussis, they constitute the triple vaccine, DTP (diphtheria, tetanus, pertussis).
- Pertussis acts as an ‘adjuvant’ as well as a specific vaccine.
describe some proven concerns with vaccine safety
Live attenuated vaccines:
- Insufficient attenuation - Reversion to wild type
- Administration to immunodeficient patient & Persistent infection
- Contamination by other viruses
- Fetal damage.
Non-living vaccines:
- Contamination by toxins or chemicals
- Allergic reactions
- Autoimmunity.
Genetically engineered vaccines:
??Possible inclusion of oncogenes - hasn’t been proven
list some at risk groups for vaccines
- Immunodeficiency
- HIV positive
- Asthma
- Chronic Lung Disease
- Congenital Heart Disease
- Definite hypersensitivity- Severe or Generalised Reaction to Preceding Dose
- Down’s Syndrome
- Avoid live vaccines in pregnancy
- Small For Dates infants
- Premature infants
Give examples of post exposure vaccination
Examples: MMR in measles exposures, HBV vaccination in HBV exposure
describe the use of passive immunisation with immunoglobulin
to prevent infection after exposure (e.g. rabies, tetanus)
to minimise its severity (varicella, measles in immunodeficient children).
Primary treatment (e.g diphtheria)
