Advanced Microbiology Flashcards
(Antivirals) What are the 3 groups of Nucleoside Reserve Transcriptase Inhibitors (NRTI)?
1) AZT (azidothymide) = inhibits HIV replication
2) Zidovudine & Lamivudine = pyramidine analogues
3) Abacacir, Tenofovir = purine analogues
(Antivirals) What are 2 examples of Non-nucleotide Reverse Transcriptase Inhibitors (NNRTI)?
Efavirenz
Nevirapine
(Antivirals) What are 2 examples of Protease Inhibitors (PIs) and what are these used for?
a) Atazanine/ Darunavir/ Ritonavir = HIV (they all sound like names)
b) Paritaprevir/ Grazoprevir = HCV
(Important Antivirals) What is Aciclovir and what is it used for?
Aciclovir- Nucleoside analogue, Herpes Simplex virus (HSV) & Varicella Zoster Virus (VZV)
(Important Antivirals) What are the following used for?
a) Ganciclovir
b) Oseltamivir/ Zanamavir
c) Ribavirin
d) Interferons
a) Ganciclovir = Cytomegalovurus (CMV)
b) Oseltamivir/ Zanamavir = Influenza (neuraminidase inhibitor)
c) Ribavirin = RSV, HCV, HEV
d) Interferons = Hep B virus cure!
What does Highly Active Anti-Retroviral Therapy (HAART) consist of?
2xNRTIs & NNRTI
or 2xNRTIs & boosted PI
(Antibiotics) Give an example of a Glycopeptide (formulary B antibacterial NON beta-lactam)
Vancomycin, teicoplanin (can also give in penicillin allergy)
- GRAM POSITIVE activity (staph, strep, enterococci)
- Most gram negative are intrinsically resistant becuase their outer membranes are impermeable to to large glycopeptide molecules)
- Treats meningitis caused by methicillin-resistant S. aureus
- 1st line treatment for skin/ bloodstream infections, endocarditis.
- Vancomycin has renal toxicity
(Antibiotics) What are the 4 Protein Synthesis Inhibitors?
a) Gentamicin/ amikacin (aminoglycosides)
b) Macrolides, Lincosamides, Streptogramins (MLS antibiotics)
c) Tetracyclines
d) Oxazolidinones
(Antibiotics) Give an example of an Aminoglycoside (Formulary B antibacterial NON beta-lactam, also a type of Protein Synthesis Inhibitor)
Gentamicin - binds to 30s ribosomal subunits
- GRAM NEGATIVE BACILLI (including pseudomonas)
- covers staphylococci, poor streptococcal (but synergism)
- Can cause nethro/oto toxicity
- IV/IM, topical
(Antibiotics) Give an example of a Macrolide (Formulary B antibacterial NON beta-lactam, also known as MLS antibiotics)
Give an example of a Lincosamide.
Macrolide- ery/clari/azi-thromycin
- GRAM POSITIVE organisms (strep, staph)
- limited gram negative cover (azithromycin will cover GN)
- covers ATYPICAL organisms (intracellular), like for chlamydia, legionella
Lincosamide= Clindamycin (bind to 50s ribosomal subunit)
(Antibiotics) Give an example of a Tetracycline (a type of Protein Synthesis Inhibitor)
Tetracycline, doxycycline, tigecycline (broader spectrum)
- Bind to 30s ribosomal subunit
- inhibit translation by interfering with binding of tRNA to rRNA
(Antibiotics) Give an example of an Oxazolidinone (a type of Protein Synthesis Inhibitor)
Linezolid
- Inhibits initiation of protein synthesis
- Binds to 50s ribosomal subunits
(Antibiotics) What is Flucloxacillin used for?
MRSA (penicillinase-resistant penicillin)
(Antibiotics) What are the 2 types of DNA synthesis inhibitors?
a) Trimethoprim & Sulphonamide
b) Quinolones & Fluoroquinolones
(Antibiotics) How do Trimethoprim & Sulphonamide work? (DNA synthesis inhibitors)
They both inhibit folate synthesis- a precursor for Purine synthesis.
Trimethoprim- commonly treats UTIs
Trimethoprim + Sulphonamide- combination used in treatment for some protozoal infections & resistant bacterial infections.
(Antibiotics) How do Quinolones & Fluoroquinolones work? (DNA synthesis inhibitors, and Formulary B antibacterial NON beta-lactams)
Quinolones- eg) Ciprofloxacin, levofloxacin. (inhibit DNA gyrase and topoisomerase IV) (Effective against bacteria only)
Fluoroquinolone-
a)CIPROFLOXACIN (early): GRAM NEGATIVEs, staphylococcal/ ‘atypicals’. Poor streptococcal/anaerobic activity
b) LEVOFLOXACIN (late): GRAM POSITIVEs, streptococci, ‘resp FQ’ as cover resp tract infections.
(Antibiotics) Give an example of a RNA Synthesis Inhibitor.
Rifampicin: RNA polymerase inhibitor, prevents mRNA synthesis (cornerstone of anti-TB chemotherapy)
Give 2 examples of Antibacterial Cell Membrane Agents?
Colistin (GRAM NEGATIVES)
Daptomycin (GRAM POSITIVES)
Give 3 examples of Antifungal Cell Membrane Agents?
1) Azoles (clotrimazole, fluconazole)
2)Terbinafine
3) Amphotericin B
(2&3 are to do with ergosterol, a component of fungal cell walls)
What is an Antifungal agent?
Echocandins eg)Anidulafungin, Caspofungin, Micafungin.
What is Clindamycin used for? (example of Forulary B antibacterial NON beta-lactam)
- GRAM POSITIVE organisms (staph, strep), anaerobes
- Anti-toxin action
- Highly associated with C diff infection
- ORAL/IV
What is Metronizadole used for? (example of Forulary B antibacterial NON beta-lactam)
- Bacteria, anaerobes
- Parasites! (protozoa, helminths)
What are the 3 Formulary B antibacterials beta-lactams?
1) Penicillins: benzylpenicillin, flucloxacillin, amoxicillin
2) Beta-lactam/ Beta-lactamase inhibitor combinations: coamoxiclav, tazocin
3) Cephalosporins: cephalexin, cefuroxime, cefotaxime.
Give 3 examples of Beta-lactamase enzymes (enzymes that hydrolyze beta-lactams, resulting in resistance to beta-lactam antibiotics)
1) Staphylococcal beta-lactamase = resistant to some penicillins
2) ‘Extended Spectrum Beta-lactamase’ (ESBL) = resistant to penicillins & cephalosporins
3) Carbapenemases (eg NDM1) = carbapenems
What are Beta-lactam/ Beta-lactamase inhibitor combinations (BLBLI) and give 2 examples of these?
V broad spectrum, predispose to C dif. (dont end in -illin, so penicillin allergy may be missed)
a) Augmentin- increases the spectrum of amoxicillin
b) Tazocin- increases the spectrum of piperacillin
What are 5 examples of Formulary B antibacterials NON beta-lactams?
1- Aminoglycosides (gentamicin) 2- Macrolides (ery/clari/azi-thromycin) 3- Glycopeptides (vancomycin) 4- Quinolones (ciprofloxacin & levofloxacin) 5- Tetracyclines (doxycycline)
What is Leucocyte Esterase an indicator of?
Enzyme produced by neutrophils.
Positive in: Chlamydia, urethritis, TB, bladder tumours, nephrolithiasis, corticosteroid use.
What are Nitrites an indicator of?
Some bacteria reduce urinary nitrates to nitrites.
Positive nitrites: infection, but negative nitrite test doesn’t rule out UTI.
(Formulary B antibacterials Beta-lactams) Give a general description of Penicillins, and what are 4 types?
Bacericidal Cross reaction with other beta-lactams (cephalosporins, carbapenems) 1- Penicillin G & V 2- Flucloxicillin 3- Amoxicillin 4- Tazocin
What are Penicillin G and Penicillin V?
What are they used for?
-Penicillin G (benzylpenicillin, IV/IM)
-Penicillin V (phenoxymethylpenicillin, ORAL)
Both are narrow spectrum, destroyed by beta-lactamases.
Best used for= Streptococci (S pneumoniae, S pyogenes)
= also covers anaerobes
=covers some GNC (N meningitidis, N gonorrhoeae)
What is Flucloxicillin and what is it used for?
(spectrum broader than Penicillin G) (not destroyed by staphylococcal beta-lactamase)
Used for= Staphylococci (not MRSA)
=many anaerobes, most streptococci
What is Amoxicillin and what is it used for?
(spectrum broader than Penicillin G) (destroyed by staphylococcal beta-lactamase)
Used for= streptococci, enterococci, some GNB
What is Tazocin and what is it used for?
(step up from amoxycillin, will cover more GNB)
Anti-pseudomonal activity
Broad spectrum= staphylococci (not MRSA), streptococci, enterococci, anaerobes, pseudomonas, GNB & GNC.
Doesnt cross BBB
What is ‘sensitivity testing’?
Culture micro-organisms in the presence of antimicrobial agent.
Determine whether minimum inhibitory concentration (MIC) is above ‘breakpoint’ level.
What are some clinical consequences of antibiotic resistance?
1- Meticillin-resistant Staphylococcus aureus (MRSA)
2- Vancomycin/ glycopeptide resistant enterococci (VRE/GRE)
3- Enterobacteriaceae resistant to many things, such as carbapenems, beta-lactams (amoxicillin, gentamicin) etc
Examples of Live Immunisations in active immunity?
MMR, BCG, Yellow Fever, Varicella
Examples of inactivated organisms in active immunity vaccine?
Pertussis, typhoid, IPV
Examples of inactivated toxins in active immunity vaccine?
Diptheria, tetanus
Difference between primary and secondary immune response?
Primary Immune Response: develops in weeks following first exposure- mainly IgM antibody
Secondary Immune Response: is faster & more powerful- mainly IgG antibody
Describe briefly how antibodies produce immunity.
- Antibodies produced from B lymphocytes
- Antigen binds to variable region of antibody (Ig)- triggers CLONAL EXPANSION
- IgM production, followed by IgG
- IgG binds tightly to antigen, simultaneous complementary binding facilitates the destruction of the antigen-bearing microorganisms
- Infection resolves, IgG decline
- Immunological memory from some remaining IgG producing B lymphocytes
What is the susceptible population?
The number of secondary cases caused by each infectious person.
Why would a white blood cell count be useful in an infection test?
Can be raised in infection, but poor specificity (sepsis can lower WCC)
Neutrophils typically raised in bacterial infection
Lymphocytes typically raised in viral infection
What is Seroconversion?
Change from negative to positive result from one test to a subsequent test
What are 4 methods of sterilisation?
1) HEAT (moist= autoclave) (dry= oven)
2) CHEMICAL
3) FILTRATION
4) IONISING RADIATION (used for single use disposable equipment)
What is antisepsis?
This is disinfectant applied to damaged skin or living tissue, needs to be minimal toxicity.
What are the 3 methods of DECONTAMINATION?
1- STERILISE (destroys all microorganisms including spores. For all reusable surgical equipment)
2- DISINFECT (reduces microorganisms to a level that is nolonger harmful. For items that will contact mucous membranes or contaminated with bodily fluids)
3- CLEAN (removal of dirt/ organic matter using water and detergent. For items that only contact intact skin)
What level of decontamination for…
a) syringe needle
b) flexible endoscope
c) central venous catheter insertion site
d) surgical instrument reprocessing
e) surgeon’s hands
a) Sterilisation (disposal after use)
b) High level disinfectant
c) Disinfection (antisepsis)
d) Sterilisation
e) Washing
What is Encephalitis caused by?
Usually viral (Herpes virus) (it is inflammation of the brain)
What are Rhino-sinusitis (sinusitis) and sore throats (pharyngitis) usually caused by?
Majority are viral.
Secondary bacterial infections (end throat swabs only if evidence of bacterial)
What are some pathogens that cause Diarrhoea?
Viruses: norovirus, rotavirus
Bacteria: Salmonella, Shigella, E Coli
Parasites: Cryptospordium, Giardia
C dif infection
What are the 4 tests for H pylori?
H Pylori antibody test H Pylori stool antigen Urea breath test Biopsy urease test STOP PPIs before testing
How do you diagnose Endocarditis?
Three sets of blood cultures should be taken at different times during the first 24hours (same with Vascular Graft Infections)
What are viral Hepatitis (Hep A,B&C) investivations based on?
Based on Serology
Serology comprises Antigen & Antibody detection
What spikes in Hep C infection? (looking at serology)
Alanine Transaminase
