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68 Cards in this Set
- Front
- Back
What are the features of a gram +ve cell wall? |
- Proteins - Teichoic Acid - Lipoteichoic Acid - Peptidoglycan |
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How can gram stain differentiate between +ve and -ve? |
+ve shows as purple-blue -ve shows as red |
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What are the features of a gram -ve cell wall? |
- O Polysaccharide / Lipopolysaccharide (Endotoxin) - Porins - Proteins - Lipid A (innermost part of LPS) |
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Survive on drying? |
+ve Yes -ve No |
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Produce spores? |
+ve Yes -ve No |
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What do all gram -ve have in their cell wall? |
Lipopolysaccharide (endotoxin) |
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Name three gram +ve rods? |
- Clostridium - Bacillus - Diptheria / Listeria |
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Name some gram -ve rods? |
- Enterobacteriacaea - Pseudomonas - Legionella - Haemophilus Influenzae - Bacteroides |
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Pathogenic mechanisms of E.Coli? |
- LPS binds to LPS binding protein which binds to cell surface molecules eg. TLR4 - Stimulates pro-inflammatory cytokines (TNFα / IL-1 / IL-6) - Small capsule is antiphagocytic - Iron binding proteins scavenge iron |
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Two types of E.Coli? |
- ETEC - Enterotoxigenic (Traveller's Diarrhoea) - EHEC - Enterohaemorrhagic (colitis / Blood diarrhoea) |
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What infections can E.Coli cause? |
- 80% of community acquired UTI - Pyelonephritis (from urinary tract -> kidney) - Intraabdominal infections - Septic shock / bloodstream - Pneumonia |
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Drugs for E.Coli treatment? |
- Amoxicillin if sensitivity confirmed (<50%) - UTI / Communty acquired severe sepsis - Trimethoprim / Nitrofurantoin - Hospital acquired severe sepsis - Tazobactam / Pipericillin - Aminoglycosides (sometimes for severe sepsis) |
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What type of bacteria is salmonella? |
- Non-lactose fermenting gram -ve rod - Enteric fever types (typhoid) |
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Pathogenic factors of Pseudomonas Aeruginosa? |
- Heat tolerant - Endotoxin - Exotoxin A / Elastase / Leucocidin - Iron binding proteins - (Produces pyocyanin - green pigment) |
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Who is extremely susceptible to Pseudomonas infection? |
- Those with mucus accumulation ie CF |
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What infections can Pseudomonas Aeruginosa cause? |
- Neutropenia - UTI (instrumentation) - Pneumonia - Skin & soft tissue - Eye keratinitis - Endopthalmitis |
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Where does Pseudomonas Aeruginosa typically transmit from? |
- Unclean water - Contaminated equipment - Poor quality drinking water |
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Which drugs should be used to treat Pseudomonas? |
- Fluoroquinolone (Aproflaxin) only oral agent - Pipericillin / Tazobactam for hospital acquired severe sepsis - Gentamicin if severe |
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What are the pathogenic factors of Haemophilus influenzae? |
- Large polysaccharide capsule (types a-f) but b is most invasive therefore vaccine as a child - IgAse inactivated IgA on mucosal surfaces - Adhesins in cell wall promote colonisation |
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Where does HI mostly colonise? |
- Mucosal surfaces - Mostly the Upper RT |
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What infections does Haemophilus cause? |
- Invasive - Meningitis / Pneumonia / Cellulitis / Epiglottitis (pain swallowing food) Non-invasive - Blood cultures -ve / Otitis media / Conjunctivitis |
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Which drugs are used to treat Haemophilus? |
- Amoxicillin - 15% resistant - Co-Amoxiclav if resistant - Rifampicin given as chemoprophylaxis when other children <5y/o in the family |
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How do you get E.Coli |
Eating / drinking food / contact with human / animal faeces contamination |
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How does haemophilus spread? |
- Usually harmless in the nose and throat - Can spread to blood --> infection |
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What are bacteroides and what drug are some sensitive to? |
- Most common bacteria in body (faeces) - Anaerobes are sensitive to Metranidazole |
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How do Neisseria species replicate? |
- Unable to survive outside of the body - Survive and replicate inside neutrophils |
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Where can Legionella Pneumophila be found? |
- Gram -ve rod in freshwater aquatic environments - Infection by aerosol contaminated water |
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What can Legionella cause and how can it be detected? |
- Severe community acquired Pneumonia - Legionella urinary antigen is +ve for 7-10 days post symptoms |
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How does Helicobacter Pylori affect the host? What conditions does it cause? |
- Colonises stomach & lives under mucus - Produces urease to increase local pH - CagA associated with virulence - Gastritis / Duodenal Ulceration / Gastric Lymphoma |
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How is Helicobacter detected? How is it treated? |
- Antigen detection in the stool - PPI + Dual / triple antibiotics required for erad. |
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What are the Staph Aureus virulence factors (not inc. exotoxins)? |
Surface Protein A which binds the Fc portion of IgG and is therefore anti-phagocytic Secreted Coagulase which deposits fibrin around bacteria in tissues |
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Which exotoxins do Staph Aureus produce? |
- Haemolysins - Enterotoxins (short lived, profuse vomiting) - Exfoliatin - PVL (vs neutrophils) - TSST (IL-1 / 2 / TNF) |
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What drugs are used to treat Staph Aureus? |
- 90% of strains are resistant - Flucloxacillin & Co-Amoxiclav effective - Macrolides (Erythromycin & Clarithromycin) in penicillin allergy |
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What is special about MRSA resistance? |
- Has mecA gene - altered penicillin binding sequence - Low affinity for all B-Lactams - Frequently has macrolide resistance |
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What is Strep Pyogenes' main virulence factor? |
M Protein in its cell wall is anti-phagocytic |
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What can Strep Pyogenes cause? |
- Suppurative infections - ENT - Pharyngitis / Tonsilitis / Sinusitis - Puerpal Fever (& scarlet fever) - Skin - Impetigo / Cellulitis / Necrotising fasciitis - Streptococcal toxic shock (SpE superantigen) - Acute Rheumatic fever - Acute Glomerulonephritis |
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What is the difference between Staph Aureus & Strep Pyogenes toxic shock? |
Unlike Staph Aureus toxic shock, blood cultures are usually positive |
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What are the mnemonics to remember SA Vs SPy manifestation? |
SA produces HEEPT SPy causes SEPSS AA |
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What are the mnemonics to remember SA Vs SPy manifestation? |
SA produces HEEPT SPy causes SEPSS AA |
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How does SPy cause Acute Rheumatic Fever? |
- 2-3 weeks post acute streptococcal pharyngitis / scarlet fever in 5-15 year olds - Fever / rash / polyarthritis / pancarditis |
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Which parts of the body are most affected in Acute Rheumatoid Fever? |
- Heart Valves - Basal Ganglia - Joints |
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How does SP cause Acute Glomerulonephritis? |
- 3 weeks after SP in 2-6 y/o - Fluid overload - Oedema / Hypertension / Oliguria |
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Which drugs are used to treat SPy? |
- Group A strep are 100% sensitive to penicillin
- Erythro / Clarithro / Vanco |
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Distinctive features of Strep Pneumoniae? |
- Pneumolysin (alpha haemolysis on blood agar) - Cell wall contains C-Polysaccharide & Pneumococcal teichoic acid |
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What is the effect of C-Polysaccharid? |
- Induces C-reactive protein production in the host - Non-specific marker of INFLAMMATION |
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What can SPn cause? |
- Upper respiratory (sinusitis) - Lower respiratory (pneumonia) - CNS (meningitis) |
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Who's most at risk of SPn infection? |
- Hyposplenic / Splenectomised |
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What is the current preventation / treatment for SPn? |
- 2 Vaccines - 7 valent conjugate as part of childhood imm. - 23 valent polysaccharid for adults at risk of invasive |
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What famous disease can Bacillus cause? |
Bacillus --> Enterotoxins & Anthracis --> Anthrax |
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Name a coagulase +ve and a -ve? |
+ve - Staph Aureus -ve - Staph Epidermis |
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Distinctive properties of the Clostridium species? |
- Ubiquitous - Produce exotoxins with diverse effects |
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What is the mechanism by which C Dif works? |
- Spores ingested germinate and infect colon - Enterotoxins produced --> inflammatory diarrhoea / collitis |
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How does C Tet work? |
- Gains entry through wound - Tetanospasmin prevents inhibitory neurotransmitter release - Lockjaw |
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How does C Bot work? |
- Ingested from contaminated food - Imported to CNS and inhibits ACh release at NMJ --> Paralysis |
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What are the Mycobacterium Tuberculosis pathogenic factors? |
- Replicates inside macrophages - Mycolic acid stimulate host sensitivity |
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What is the hose response to MT? |
- Antibodies formed but ineffective - Mycobacterial antigens presented on surface - Lymphokine contribute to tissue damage and attract activated macrophages |
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How is MR transmitted? |
- Exposure to droplet nuclei - Cumulative <8h required - Extrapulmonary --> any system - 85% involve lower RT - BCG ONLY PARTIALLY PROTECTIVE |
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What antibiotics are used to treat TB? |
2 Months Rifampicin / Isoniazad / Pyrazinamide / Ethambutol 4 Months Rifampicin / Isoniazad |
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What can Treponema Pallidium cause? |
- Syphillis - Lyme Disease |
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What are the problems with Treponema identification? How is it transmitted? |
- Cannot be gram stained so viewed by dark ground microscopy - Congenital / Sexual transmission |
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Phases of Syphillis? |
1' - Genitals / mouth chancre 2' - 2-8w post primary systemic illness due to dissemination Latent - 2/3 do not progress & may last years 3' - Late - CV / neurosyphilis / gummatous |
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How is Syphilis treated? |
Penicillin |
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What are the hallmark symptoms of congenital syphilis? |
Hutchinson's Triad - Hutchinson's Teeth - Barrel Shaped / Notched incisors - Deafness - Interstitial Keratitis |
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What are the distinctive feature of Mycoplasma Pneumoniae? |
- Contain sterols not peptidoglycan - No gram stained but can be slow cultured |
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How can Mycoplasma Pneumoniae be detected? |
Ig< |
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Distinctive features of Chlamydia species? |
- Intracellular and reuire host cell ATP to replicate - Not visible on gram stain |
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What diseases can Chlamydia Trachomatis cause? |
- STI --> Urethritis - Eye infection --> Blindness |
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What diseases are cause by Chlamydia Psittaci / Pneumoniae? |
Pneumonia (both) PCR for diagnosis |