Session 4 ILOs - HIV/Antibiotics Flashcards
Understand the relevance of HIV in a global and UK context (5)
- No change in numbers over the last decade
- Still many millions of people living with HIV
- TB & HIV go hand in hand globally
- Substantially fewer deaths due to HIV in the UK compared to globally
- If left untreated, it leads to AIDS and unusual infections such as oral candidasis, Kaposi’s sarcoma and pneumocystis pneumonia (PCP)
Apply the infection model to a patient with HIV and AIDS
Pathogen - Virus (human immunodeficiency virus)
Patient - Flu like illness 2-4 weeks after virus enters body ie fever, headache, muscle ache
Mechanism of infection - sexual contact/IV drug use/vertical transmission
Process of infection - replication in host cells
Management - antiretroviral drugs
Patient outcomes - chronic infections or death (if chronic infections left untreated)
Outline a classification of antimicrobials
Describe the concept of antimicrobial stewardship
- Coordinated interventions designed to improve and measure the appropriate use of antimicrobials by promoting
- the selection of the optimal antimicrobial drug regimen
- dose
- duration of therapy
- and route of administration.
- Antimicrobial stewards seek to achieve
- optimal clinical outcomes related to antimicrobial use
- minimize toxicity and other adverse events
- reduce the costs of health care for infections
- and limit the selection for antimicrobial resistant strains
Describe the principles of transmission and prevention with regard to HIV
Transmission: (5)
- Occurs through contact of infected bodily fluids with mucosal tissue, blood or broken skin
Examples:
- Sexual contact (most common)
- Transfusion (rare in UK)
- Contaminated needles (IV drug use e.g.)
- Perinatal transmission (during childbirth, transplacental, through ingestion of breast milk)
HIV transmission = affected by type of exposure, viral level in blood, condom use and breaks in skin or mucosa
Prevention: (7)
- Increase condom usage
- Medical circumcision
- ARV treatment use as prevention
- Pre-exposure prophylaxis (HIV Prevention meds)
- Post-exposure prophylaxis
- Wide-spread testing/screening
- Prevention of mother to child transmission (prevention of vertical transmission)
Describe the principles of HIV structure and replication (including the 4 stages of infection)
Human Immunodeficiency virus:
Structure/details: (9)
- Retrovirus
- 2 Strands of single stranded RNA
- It infects cells with CD4 surface receptors (T-helper lymphocytes and monocytes/macrophages and dendritic cells)
- Has surface antigens (gp120 and gp41)
- 3 key enzymes (integrase, reverse transcriptase) protease)
- Viral Envelope (lipid)
- Capsid
- Reverse transcriptase
- Glycoprotein
Replication:
- Free virus in the blood binds to CD4 receptors (on T-helper lymphocytes and monocytes/macrophages and dendritic cells)
- Virus penetrates the cell and empties it’s contents
- ssRNA are converted into dsDNA by reverse transcriptase enzyme
- Viral DNA is integrated into the host’s DNA by integrate enzyme
- When the cell divides, the viral DNA is read and long chains of viral proteins are made and come together
- Immature virus pushes out of the cell, taking some of the cell membrane with it and the it breaks free of the cell
- Protein chains are cut by the protease enzyme into individual proteins that combine to make a working virus
4 stages of infection:
- Primary infection / seroconversion
- Latent infection
- Symptomatic infection
- Severe infection / AIDS
Describe the principle of AIDS
AIDS - when CD4+ count drops below 200 cells/μL and opportunistic infections begin to take hold.
AIDS (Acquired Immunodeficiency Syndrome) is the term used to describe the most advanced stage of HIV infection when the patient has become ‘immunodeficient’ (or fully immunocompromised).
- Patient now susceptible to serious complications from previously harmless infections, opportunistic pathogens (organisms that are not usually pathogenic in those with normal immune systems) and malignancies.
- E.g.Pneumocystis pneumonia or candidiasis
- Death is not caused by the HIV virus itself but through conditions like these.
Describe the principles of antibiotic resistance and it’s impact on antimicrobial prescribing
- A consequence of natural selection and random mutation of bacteria
3 types of antimicrobial resistance:
- Intrinsic
- Naturally resistance - the bacteria have no target for the drug to work on e.g. a penicillin can’t act on a microbe without a cell wall as this is its site of action. - Acquired
- this is done either through mutation or horizontal gene transfer. - Adaptive
- Organism responds to stress - The bacteria only are resistant when exposed to an antibiotic as they adapt to the environment
Antimicrobial resistance is increasing, with few new antimicrobial medicines coming to market. Can lead to:
- Treatment failure
- Prophylaxis failure
- Economic costs
Describe the principles of HIV testing and treatment
Blood test (serology) = test anyone with unusual symptoms (ie chronic weightless or diahorrhea) or if a high rate of HIV in community or any STI
- Serology
- Antibody/Antigen test (main test)
- Detects antibodies against HIV
- Detects HIV antigen itself
- May get false negative if performed too early - wait 4 weeks - PCR test - used for follow up/treatment response
- Detects HIV nucleic acid
- Highly sensitive so detect very early infection but very expensive with slow results (so not used for initial HIV testing) - ‘Rapid tests’ for HIV antibody
- Detects antibodies against HIV
- Can be blood test (finger prick) or oral (saliva) (home testing or postal kits)
- May get a false positive result (need to confirm with serology)
Treatments (ARV drugs - target enzymes in replication) = start ASAP:
- Give 2 reverse transcriptase inhibitors and 1 other drug option e.g. protease inhibitor
Outline measures to ensure the appropriate use of antimicrobials
Assess:
- Necessity of antibiotics
- Whether they can be taken orally rather than IV
- Appropriateness to use specific rather than broad targeting antibiotics
- Need for authorisation from microbiology(some antimicrobials are restricted)
Describe the mechanism of action of the main group of antimicrobials
