Week 06 - Microbiology

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mewinstanley@googlemail.com
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130459
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Week 06 - Microbiology
Updated:
2012-02-02 09:21:05
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microbiology
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MTB, HIV, STIs etc
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  1. Name 3 gram positive cocci?
    • Staphylococcus aureus
    • CoNS
    • Group A strep [scarlet fever]
    • B-haemolytic strep
    • Strep Pneumoniae
    • Enterococci
    • Strep Viridans
  2. Name 3 gram negative cocci?
    • Neisseria Meningitidis; mild sore throat → meningitis
    • Neisseria Gonoccocus
    • Moraxella Catarrhalis
  3. Name 3 Gram positive Bacilli?
    • Listeria → bacteraemia & meningitis [v young & old]
    • Clostridia species → C. Diff, C perfingens, C tetani
  4. Give 3 gram negative bacilli?
    • E.Coli
    • Klebsiella
    • Salmonella
    • H. Influenzae
  5. Define Viruence?
    Virulence = ability of organism to cause disease [ability to invade host tissue
  6. What is a pathogen?
    Microbial organism that can produce symptomatic disease
  7. What is non-sterilising immunity?
    • when a Pt grows up in a disease endemic area
    • initial infection → symptoms
    • subsequent infections have a decreasing severity of symptoms [asymptomatic]
    • but pathogen still in blood
    • e.g. malaria
  8. Outline the pathogenesis of MTB infection
    • Mycobacterium Tuberculosis
    • [inhaled droplet spread]

    • Inhaled droplets
    • 95% individuals → dromant lesions
    • replicate in macrophages
    • Reactivation of MTB [HIV, immunosuppression, smoking]
    • disease progresses to cavitating MTB
    • cavities open onto bronchi facilitating spread via coughing
    • 5% get full blown TB after 1st infection
  9. Outline the range of disease caused by MTB
    • Miliary TB
    • Lots in both lung feilds
    • looks like millet seed [CXR]

    • CNS TB
    • Tuberculomata across brain
    • epileptic fits & space occupying lesions

    Renal TB
  10. Describe a granuloma
    Formed when pathogen cannot be digested

    • Central necrosis
    • epitheliod cells [macrophages]
    • Giant cells
    • Lymphocytes [outermost, mainly T cells]
  11. Outline the Ix of suspected MTB?
    • Imaging
    • CXR → apical destruction & cavity formation

    • B/C
    • ZN stain for acid fast bacilli

    • Mantoux RXN/ Heaf test
    • inject MTB cell walll extract into dermis
    • ?prev infection → area of inflammation
    • no RXN? → no previous exposure
    • not perfect, some cross reactin w BCG
  12. What is the Tx for MTB?
    MTB is RIPE for Tx

    • Rifampicin → red urine, CYP450 inducer
    • Isoniazid
    • Pyrazinamide
    • Ethambutol

    • 6m R & I
    • Drop P & E if sensitive to RI after 2m
  13. What is the most common cause of community acquired pneuomonia?
    Name 2 other typical organisms.
    Most common → Strep Pneumoniae

    • Typicals
    • Haemophilus influenzae
    • Mraxella Catarrhalis
  14. Give 4 risk factors for CAP?
    • ^ alcohol intake
    • Smoking
    • Immunosuppression
    • Existing airway disease [COPD/ Asthma]
    • Influenza infection
  15. What are the S&S of CAP?
    What would be found O/E?
    • S&S
    • Productive cough
    • Fever
    • Pleuritic chest pain

    • O/E
    • Lobar consolidation
    • Coarse creps
    • ^vocal resonance
    • Dull percussion
  16. Outline the Tx of CAP
    Amoxicillan [beware resisitance, check travel Hx]

    • Unsuccessful?
    • Co-amoxiclav
    • Clarithromycin
    • Doxicyclin
  17. What are the atypical causes of Pneumonia?
    Mycoplasma Pneumoniae → flu symptoms, insiduous onset, Tx = Macrolides [clarithromycin]

    Legionella Pneumonia → contaminated water supply, headache & fever, Tx = macrolides

    Chlamydia Pneumonia

    Chlamydia Psittaci

    Coxiella Burnetti
  18. How is the severity of pneumonia assesed?
    CURB65

    • Confusion
    • Urea >7mmol/l
    • RR >30
    • BP → sys >90, dia <60
    • Age >65

    Scor >3 = admission, ^^mortality
  19. Which classes of antibiotics inhibit cell wall synthesis?
    • Beta-Lactams
    • Glycopeptides
  20. Which classes of antibiotics inhibit Nucleic Acid synthesis?
    • Flouroquinolones
    • Rifampicin
    • Nitrofurantoin
  21. Which classes of antibiotics inhibit protein synthesis?
    • Aminoglycosides
    • Tetracyclines
    • Macrolides
    • Loncosamides
    • Fusidic Acid
    • Mupirocin
    • Chloramphenicol
    • Metronidazole
  22. Which antibiotics inhibit folate?
    Trimethoprim
  23. For the betalactams give some examples, MoA & sensitivities
    • Penicillins → pen/ amoxicillin etc
    • Cephalosporins → cephtriaxone
    • Carbopenems → meropenem

    • MoA
    • inhibit bacterial cell wall synthesis

    • Sensitivities
    • most gram +ve
    • MSSA = resistant to pen & amox
    • Enterococci = resistant to all cephalosporins
    • P aeruginosa = resistant to all [except → tazocin, meropenem & cephtazidime]
  24. For Glycopeptides give some examples, MoA, & sensitivites
    e.g. Vancomycin/ Teicoplanin

    • MoA
    • Inhibit cell wall synthesis
    • bactericidal

    • Sensitivities
    • Only gram +ves
  25. For the aminoglycosides give some examples, MoA & sensitivities
    e.g. Gentamicin/ Streptomicin

    • MoA
    • Inhibit protein sythesis → irreversibly bind to 30S ribosomal unit
    • bactericidal

    • Sensitivities
    • mostly gram neg
    • esp sepsis
  26. For the tetracyclines give some examples, MoA & sensitivities
    e.g. tetracycline, doxycycline

    • MoA
    • Inhibit protein synthesis → reversibly bind to 30S ribosomal unit
    • bacteristatic

    • Sensitivities
    • Staph & strep
    • some gram -ve [NO e. coli]
    • active against intracellular organisms [chlamydia, coxiella burnetti, plasmodium]
  27. For the Macrolides give some examples, MoA & sensitivities
    e.g. Erythromycin, Clarithromycin

    • MoA
    • reversibly bind to 30S ribosomal unit → inhibit protein synthesis
    • Bacteristatic

    • Sensitivities
    • ~mycobacteria [not MTB]
    • Erythromycin → CAP, Campylobacter gastroenteritis
    • Calrithromycin → CAP, H. Pylori, mycobacter
  28. Ouline the features of influenza virus? [Virology]
    How is type A classified?
    • Orthomyxoviridae
    • Segmented virus

    • 3 subtypes [A, B & C]
    • A = Pandemic Flu
    • A & B = 8 RNA segments, cause epidemics
    • C = 7 RNA, milder

    • Classification of type a
    • Haemagluttinin → cell entry [16 types], antigenic drift
    • Neurominidase → exit cells [9 types]
    • e.g. H5N1
  29. What are the symptoms & complications of flu?
    • Incubation ~1-4d
    • 'flu like symptoms' → fever, malaise, sore throat, joint pain

    • Complications
    • pneumonia [secondary bacterial infections]
    • Bronchitis
    • otitis media etc
  30. How is 'flu treated?
    Usually suportive

    • Oseltamivir [tamiflu]
    • Neurominidase blocker
    • pre-exposure prophylaxis in at risk groups [pregnant]

    • Amantidine
    • soon after Pc
    • A/E → CNS & GI

    • Vaccine
    • Inactivated/subunit
    • trivalent [2 A strains & 1 B]
  31. Outline the Life cycle of HIV?
    • ssRNA retrovirus
    • reverse transcribed into host DNA → latent infection
    • mainly in T4 [also DC & macrophages]
    • antiretrovirals only target circulating virus.
  32. What are the seroconversion symptoms of HIV?
    Seroconversion = development of detectable antibodies [i.e. finding out your HIV+]

    • Fever
    • Sore throat
    • Rash
    • Also → headache, lymphadenopathy, myalgia
  33. Give 4 AIDS defining symptoms
    • Palatal Kaposis Sarcoma [purple macules, herpes virus]
    • Oesophageal Candida
    • Oral KS
    • Gingivitis
    • Apthous Ulcers
    • Cerebral Toxoplasmosis
    • CMV retinits → Late stage
    • MTB
  34. What are the different types of antiviral therapies available for HIV infection?
    Reverse Transcriptase inhibitors → nucleoside analogoues or allostearic inhibitors

    Protease inhibitors → e.g. Atazanivir

    Integrase inhibitors

    Fusion inhibitors

    Co-receptor binding inhibitors → maraviroc [block CCR5 receptor]

    Aim of therapy is to decrease viral load.
  35. How does bacterial resisitance evolve?
    • Spotaneous Mt in selective environment
    • confers advantage
    • rapid proliferation → resisitant
  36. What are the 4 mechanisms of drug resisitance in bacteria?
    Alter drug target → block antibiotic/ create new target

    Alter access to drug → decrease cellular permeability

    Enzymatic inactivation → destroy/alter anti-b

    New metabolic pathway → bypass inhibited RXN
  37. How are resistant genes spread between bacteria?
    • Plasmids
    • Transposons
    • Integrons

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