Title | Sketchy Micro Notes - No pictures |
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Author | Rux Bog |
Course | Medicine |
Institution | Queen's University Belfast |
Pages | 158 |
File Size | 1.5 MB |
File Type | |
Total Downloads | 76 |
Total Views | 152 |
Written notes of Sketchy's Micro videos. No pictures included due to copyrights...
Sketchy Notes
MedSN 1
Bacteria Gram Positive COCCI
2
Staph Aureus (+) Features: 1. 2. 3. 4. 5.
Small, yellow colonies. Beta Hemolytic Catalase Positive Coagulase positive Ferments Mannitol a. Positive (Yellow) b. Negative (Pink)
Reservoir: 1. Nasal mucosa 2. Skin
Pathogenesis: 1. Protein A a. Binds Fc portion of IgG, inhibits phagocytosis. 2. TSST-1 (Superantigen) 3. Coagulase 4. Exfolatins (Scalded skin syndrome) Diseases: 1. Postviral Pneumonia a. After influenza usually b. Patchy infiltrates on x ray 2. Abscesses 3. Septic arthritis a. Most common cause 4. Endocarditis a. Acute in nature b. Affects Tricuspid 5. Food poisoning 6. Osteomyelitis a. Most common cause 7. Toxic Shock Syndrome 8. Scalded skin Syndrome
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Treatment: 1. Nafcillin 2. Vancomycin (MRSA)
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Staph Epidermidis (+) Features: 1. 2. 3. 4. 5. 6.
Coagulase (-) Catalase (+) Urease (+) Contaminates blood cultures Makes biofilms on artificial valves Novobiocin sensitive
Reservoir: 1. Skin Diseases: 1. Affects prosthetic joints (enemy of orthopedic surgeons) 2. Endocarditis (artificial valves) Treatment: 1. Vancomycin a. Replace valves too in case of endocarditis
5
Staph Saprophyticus (+) Features: 1. 2. 3. 4.
Coagulase (-) Catalase (+) Urease (+) Novobiocin resistant
Diseases: 1. UTIs in sexually active females
6
Strep Pyogenes (+) (GROUP A STREP) Features: 1. Catalase negative 2. Encapsulated a. Hyaluronic acid in capsule 3. Beta hemolytic 4. Bacitracin sensitive Pathogenesis: 1. M protein a. Virulence factor for Rheumatic fever and Post streptococcal glomerulonephritis 2. Hyaluronic acid a. Not immunogenic 3. Streptococcal pyogenic exotoxin (SPE) a. SPE A, C: Scarlett fever, Toxic shock-like syndrome (TSLS) b. SPE B: Necrotizing fasciitis 4. Streptolysin O a. Hemolysin b. ASO antibodies (ASO titer) 5. Streptokinase a. Converts plasminogen to plasmin b. Breaks fibrin clots c. Spreading factor 6. DNAse Diseases:
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Divided into as follows: Impetigo Pyogenic Infections
Pharyngitis
Diseases
Cellulitis/Erysiplas Scarlet Fever Caused by SPE
TSLS Necrotizing Fascitis Rheumatic Fever
Sequelae PSGN
Pyogenic Infections: 1. Pharyngitis 2. Impetigo a. Honey-crusted lesions on skin 3. Cellulitis 4. Erysiplas a. Superficial cellulitis with well-demarcated borders b. Most common cause Caused by SPE: 1. Scarlet Fever a. Strawberry tongue b. Widespread rash that spares face 2. TSLS a. Superantigen 3. Necrotizing Fascitis a. Caused by SPE B b. Surgical emergency c. Sometimes amputation done Sequelae: 1. Rheumatic fever 2. PSGN
8
Rheumatic Fever: 1. M protein (main virulence factor) a. Interferes opsonization (inhibits phagocytosis) b. Very antigenic i. Leads to immune response ii. Antibodies made against self antigens iii. The self antigen is in myosin in muscles iv. Hence, affecting heart (mitral valve) v. This process is called molecular mimicry c. If pharyngitis is immediately treated, RF doesn’t occur. d. Symptoms (JONES): i. Joints: Polyarthritis ii. : Valvular damage, myocarditis, pericarditis. iii. Nodules: Subcutaneous iv. Erythema Marginatum: Rash with thick borders v. Sydenham’s chorea: Involuntary movement of hands and face Post Streptococcal Glomerulonephritis: 2. M12 serotype 3. Symptoms: a. Dark brown (cola colored) urine b. Facial edema 4. Occurs 2 weeks after streptococcal infection
Differences between RF and PSGN Rheumatic Fever
PSGN
Occurs after pharyngitis
Doesn’t occur if pharyngitis is treated
Treatment: 1. Penicillin (Beta lactam drugs)
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Can occur after pharyngitis or any other superficial infection like impetigo Occurs, no matter if the strep infection is treated or not
Strep Agalactiae (+) (GROUP B STREP) Features: 1. 2. 3. 4. 5. 6.
Cause serious infections in newborns Hydrolyze hippurate (hippurate test +) Beta Hemolytic Encapsulated Bacitracin resistant CAMP test (+) a. Increasing zone of hemolysis when plated with staph aureus b. Arrowhead hemolysis
Transmission: 1. Newborn infected during birth Diseases: 1. Neonatal meningitis a. Most common cause 2. Neonatal sepsis 3. Neonatal Pneumonia Treatment: 1. Penicillin Prevention: 1. Penicillin is given intrapartum to mother tested positive for strep agalactiae infection through vaginal and rectal swab at 35 weeks of pregnancy.
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Strep Pneumoniae (+) (GROUB B STREP) Features: 1. 2. 3. 4. 5. 6.
Encapsulated (polysaccharide capsule) Alpha hemolytic Optochin sensitive Bile soluble Lancet-shaped diplocci Sickle cell (asplenia) patients are more susceptible to Encapsulated bacterial infections such as S. pneumonia
Pathogenesis: 1. Polysaccharide capsule a. Major virulence factor 2. IgA Protease a. Helps in invading mucosa b. Reduces host defenses Diseases: Diseases are given the mnemonic MOPS. S. pneumonia is #1 cause for all of these.
MOPS
Meningitis
Otitis Media
Pneumonia
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Sinusitis
Pneumonia o Lobar pneumonia o Infiltrates lower lobes o Rust colored sputum
Treatment: 1. Macrolides (erythromycin) 2. Ceftriaxone Prevention: There are two vaccines available: 1. Adult Vaccine (PPV, pneumococcal polysaccharide vaccine) 2. Pediatric Vaccine (PCV, pneumococcal conjugate vaccine)
Adult Vaccine 23 of most common capsular serotypes Not conjugated with protein T-cell independent response due to no protein conjugation
Pediatric Vaccine 13 of most common serotypes Conjugated with protein T-cell response due to protein conjugation
IgM produced
IgG produced
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Viridans Streptococci (+) (GROUP B STREP) Features: 1. 2. 3. 4.
Non-Encapsulated Bile insoluble Optochin resistant Alpha hemolytic
Diseases: 1. Dental carries 2. Subacute infective endocarditis a. Affects already damaged heart valves b. It adheres to platelets through dextran and attacks damaged heart valves c. Most commonly involved valve is Mitral Valve i. Mitral valve common due to higher risk of following diseases in general population: 1. Mitral prolapse 2. Rheumatic Fever
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Enterococcus (+) 1. E. faecalis (more common) 2. E. faecium (more dangerous) Features: 1. Bile insoluble 2. Grow in 6.5% NaCl Diseases: Mnemonic: “do U
trees”
1. Urinary Tract Infections 2. Endocarditis 3. Biliary tree infection Treatment: 1. Vancomycin resistant enterococci a. Linezolid b. Tigecycline
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Bacteria Gram positive RODS
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Bacillus Anthracis and Baccilus Cereus(+) Features: 1. Rods in chains 2. Obligate aerobe 3. Encapsulated a. Protein capsule i. Poly D-glutamate 4. Spore forming 5. Potential biowarfare agent Pathogenesis: 1. Edema Factor (EF) a. Acts as adenylate cyclase b. Increases cAMP c. Causes fluid to move in extracellular fluid (edema) d. Leads to inhibition of host defenses e. Hence, prevents phagocytosis 2. Lethal Factor (LF) a. Kills cells by acting as a protease b. Cleaves MAP kinase i. MAP kinase is a signal transduction protein ii. It is involved in control of cell growth iii. Hence, LF causes tissue necrosis Diseases: 1. Cutaneous anthrax a. Black eschar with erythematous border 2. Pulmonary anthrax (wool sorter’s disease) a. Caused by spores that are inhaled from wool while dealing with it and they germinate in lungs. b. Presents first as non-specific pulmonary symptoms like dry cough, fever etc c. Eventually leads to mediastinal hemorrhagic lymphadenitis i. It presents as widened mediastinum on X ray Treatment: 1. Flouroquinolones 2. Doxycycline
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Bacillus Cereus (+) Same features as bacillus anthrax. It causes food poisoning (vomiting and diarrhea after eating reheated rice)
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Clostridium Tetani (+) Features: 1. Anaerobe 2. Spore-forming Reservoir: 1. Soil 2. Rusted Nails Transmission: 1. Punctured wound/trauma Diseases: It causes spastic paralysis. 2 important diseases are: 1. Risus Sardonicus (evil grin) or Lock Jaw Syndrome 2. Opisthotonus (exaggerated arching of back) Pathogenesis: 1. Spores germinate in tissue and produce tetanus toxin which moves retrograde to CNS 2. Name of toxin is tetanospasmin a. Acts as protease b. Cleaves SNARE protein i. It leads to prevention of exocytosis of neurotransmitters in synapse 1. Neurotransmitters are GABA and glycine a. GABA and glycine are released from Renshaw cells Prevention: 1. Toxoid vaccine a. Conjugated with protein to increase immune response b. It is a vaccine to toxin, not organism.
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Clostridium Botulinum (+) Features: 1. Spore-forming 2. Obligate anaerobe Transmission: 1. Improperly canned food (in adults) 2. Honey (in infants) Pathogenesis: 1. Adults: a. Toxin absorbed by gut b. Cleaves SNARE protein c. Leads to prevention of exocytosis of Ach in the synapse d. Leads to flaccid paralysis 2. Infants: a. Infants don’t have normal intestinal flora to outcompete any ingested botulinum spore like adults do b. Ingestion of honey leads to spore going into gut where the spore produces the toxin c. Leads to flaccid paralysis Diseases: 1. In adults: a. Flaccid paralysis i. Descending ii. Early symptoms include ptosis and diplopia 2. In Infants: a. Floppy Baby Syndrome i. More common than adult botulism
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Clostridium Difficile (+) Features: 1. Nosocomial infection 2. Spore-forming 3. Obligate anaerobe Diseases: 1. Clindamycin-associated diarrhea 2. Colitis 3. Pseudomembranous colitis Pathogenesis: 1. Exotoxin A a. Attaches to brush border of intestine b. Causes inflammation and cell death c. Leads to watery diarrhea 2. Exotoxin B a. Disrupts cytoskeleton by depolymerizing actin b. Also leads to production of yellowish gray exudate which forms a pseudomembrane that covers colonic mucosa Lab Diagnosis: 1. Visualize pseudomembrane a. Histologically b. Endoscopically 2. Stool examination for toxin a. Toxin causes the disease, not the organism Treatment: 1. Metronidazole 2. Vancomycin
20
Viridans Streptococci (+) (GROUP B STREP) Features: 1. 2. 3. 4.
Non-Encapsulated Bile insoluble Optochin resistant Alpha hemolytic
Diseases: 1. Dental carries 2. Subacute infective endocarditis a. Affects already damaged heart valves b. It adheres to platelets through dextran and attacks damaged heart valves c. Most commonly involved valve is Mitral Valve i. Mitral valve common due to higher risk of following diseases in general population: 1. Mitral prolapse 2. Rheumatic Fever
13
Enterococcus (+) 1. E. faecalis (more common) 2. E. faecium (more dangerous) Features: 1. Bile insoluble 2. Grow in 6.5% NaCl Diseases: Mnemonic: “do U
trees”
1. Urinary Tract Infections 2. Endocarditis 3. Biliary tree infection Treatment: 1. Vancomycin resistant enterococci a. Linezolid b. Tigecycline
14
Bacteria Gram positive RODS
15
Bacillus Anthracis and Baccilus Cereus(+) Features: 1. Rods in chains 2. Obligate aerobe 3. Encapsulated a. Protein capsule i. Poly D-glutamate 4. Spore forming 5. Potential biowarfare agent Pathogenesis: 1. Edema Factor (EF) a. Acts as adenylate cyclase
b. Increases cAMP c. Causes fluid to move in extracellular fluid (edema) d. Leads to inhibition of host defenses e. Hence, prevents phagocytosis 2. Lethal Factor (LF) a. Kills cells by acting as a protease b. Cleaves MAP kinase i. MAP kinase is a signal transduction protein ii. It is involved in control of cell growth iii. Hence, LF causes tissue necrosis Diseases: 1. Cutaneous anthrax a. Black eschar with erythematous border 2. Pulmonary anthrax (wool sorter’s disease) a. Caused by spores that are inhaled from wool while dealing with it and they germinate in lungs. b. Presents first as non-specific pulmonary symptoms like dry cough, fever etc c. Eventually leads to mediastinal hemorrhagic lymphadenitis i. It presents as widened mediastinum on X ray Treatment: 1. Flouroquinolones 2. Doxycycline
16
Bacillus Cereus (+) Same features as bacillus anthrax. It causes food poisoning (vomiting and diarrhea after eating reheated rice)
17
Clostridium Tetani (+) Features: 1. Anaerobe 2. Spore-forming Reservoir: 1. Soil 2. Rusted Nails Transmission: 1. Punctured wound/trauma Diseases: It causes spastic paralysis. 2 important diseases are: 1. Risus Sardonicus (evil grin) or Lock Jaw Syndrome 2. Opisthotonus (exaggerated arching of back) Pathogenesis: 1. Spores germinate in tissue and produce tetanus toxin which moves retrograde to CNS 2. Name of toxin is tetanospasmin a. Acts as protease b. Cleaves SNARE protein i. It leads to prevention of exocytosis of neurotransmitters in synapse 1. Neurotransmitters are GABA and glycine a. GABA and glycine are released from Renshaw cells Prevention: 1. Toxoid vaccine a. Conjugated with protein to increase immune response b. It is a vaccine to toxin, not organism.
18
Clostridium Botulinum (+) Features: 1. Spore-forming 2. Obligate anaerobe Transmission: 1. Improperly canned food (in adults) 2. Honey (in infants)
Pathogenesis: 1. Adults: a. Toxin absorbed by gut b. Cleaves SNARE protein c. Leads to prevention of exocytosis of Ach in the synapse d. Leads to flaccid paralysis 2. Infants: a. Infants don’t have normal intestinal flora to outcompete any ingested botulinum spore like adults do b. Ingestion of honey leads to spore going into gut where the spore produces the toxin c. Leads to flaccid paralysis Diseases: 1. In adults: a. Flaccid paralysis i. Descending ii. Early symptoms include ptosis and diplopia 2. In Infants: a. Floppy Baby Syndrome i. More common than adult botulism
19
Clostridium Difficile (+) Features: 1. Nosocomial infection 2. Spore-forming 3. Obligate anaerobe Diseases: 1. Clindamycin-associated diarrhea 2. Colitis 3. Pseudomembranous colitis Pathogenesis: 1. Exotoxin A a. Attaches to brush border of intestine b. Causes inflammation and cell death c. Leads to watery diarrhea 2. Exotoxin B a. Disrupts cytoskeleton by depolymerizing actin b. Also leads to production of yellowish gray exudate which forms a pseudomembrane that covers colonic mucosa Lab Diagnosis: 1. Visualize pseudomembrane
a. Histologically b. Endoscopically 2. Stool examination for toxin a. Toxin causes the disease, not the organism Treatment: 1. Metronidazole 2. Vancomycin
20
Clostridium Perfringens (+) Features: 1. 2. 3. 4.
Obligate Anaerobe Spore-forming Double zone of hemolysis on Blood Agar Presentation with a. Motorcycle accidents b. Deep wounds in military combat
Reservoir: 1. Spores in soil Diseases: Two diseases: 1. Gas gangrene a. Gas is produced by organism under the infected tissue when it consumes carbohydrates b. The underlying mechanism is related to Alpha toxin i. This toxin is a lecithinase ii. This means it lyses lechithin in cell membranes and disrupts them iii. If it disrupts RBC membrane, it causes hemolysis (this is the reason behind double zone of hemolysis on blood agar) c. Crepitus or crackles are heard on palpation 2. Food Poisoning a. Due to ingestion of large amount of spores b. Spores germinate in the gut and release toxin i. This is unlike other microbes which germinate OUTSIDE the gut (e.g C. botulinum in canned food, bacillus cereus in reheated rice etc) Treatment: 1. Gas gangrene: a. IV Penicillin G 2. Food Poisoning: a. Self resolving
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Corynebacterium Diphtheriae (+) Features:
1. Club-shaped (V or Y formation) 2. Contains metachromatic granules a. These dye red with aniline dye b. Rest of the cell stays blue Transmission: 1. Respiratory droplets Pathogenesis: 1. Diphtheria toxin has two components a. A subunit is active b. B subunit is binding 2. Toxin causes ADP ribosylation of elongation factor 2 (EF-2) a. This leads to inhibition of ribosomal function and hence, inhibition of protein synthesis b. Also, it leads to production of dirty gray exudate which forms a pseudomembrane on oropharynx mucosa Diseases: 1. Diphtheria has following characteristics a. Pseudomembrane i. May spread to larynx and trachea and cause airway obstruction ii. May also cause lymphadenopathy (Bull’s neck) 2. Cardiotoxicity a. Myocarditis b. Arrhythmia c. Heart block 3. Local Paralysis: a. Starts in posterior pharynx (Myelin damage) b. May lead to other cranial nerve deficits c. Mechanism involves attack of toxin on myelin sheath of nerve fibres Lab Diagnosis: 1. Swab pseudomembrane on following: a. Tellurite agar b. Loeffler’s medium 2. Elek’s test a. To differentiate between toxic and non-toxic strains i. In vitro assay on filter paper that has anti-toxin 22
ii. If toxin binds, there is a reaction and the test is positive i.e. the strain is toxic Prevention: 1. Toxoid vaccine a. Inactivated exotoxin conjugated with protein to increase immune response b. Powerful IgG response c. Often given with vaccines of Clostridium tetani and acellular pertussis (DTaP) Treatment: 1. Passive immunity (Antitoxin)
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Listeria Monocytogenes (+) Features: 1. 2. 3. 4.
Facultative intracellular Cold growth Beta Hemolytic Motile a. Extracellular motility: tumbling motility due to flagella b. Intracellular motility: actin rocket motility, rapidly polymerizes actin against bacterial wall and propels itself in the opposite direction 5. Catalase (+)
Reservoir: 1. Unpasteurized milk 2. Soft cheese Diseases: 1. Listeriosis a. Common in pregnancy i. May lead to early termination or disease in newborn 2. Meningitis a. Neonatal i. 3rd most common cause b. Elderly and immunocompromised Treatment: 1. Ampicillin
Campylobacter Jejuni (-) Features: 1. Oxidase (+) 2. Curved gram negative bacteria (the other being Vibrio and Helicobacter) 3. Thermophilic (42oC) Reservoir: 1. Intestinal tract of other animals such as poultry Transmission: 1. Fecal-oral route Diseases: 1. 2. 3. 4.
Bloody diarrhea Invasive bacteremia Reactive arthritis Guillain-Barre Syndrome a. Demyelination of peripheral nerves b. Ascending paralysis
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Vibrio Cholera (-) Features: 1. 2. 3. 4. 5. 6.
Endemic to developing countries Comma shaped bacteria Oxidase (+) Acid labile Grows in alkaline medium V. vulnificus and V. parahemolyticus can contaminate oysters
Transmission: 1. Fecal oral transmission Pathogenesis: 1. Vibrio cholera doesn’t invade mucosa a. Fimbriae attachment is observed b. Cholera toxin is released which causes the symptoms 2. Cholera toxin a. Binds to and activates adenylate cyclase (Gs Pathway) b. Increases cAMP i. Increase in water in lumen 1. PERFUSE watery diarrhea (sometimes even 10L per day) Treatment: 1. Oral rehydration with electrolytes
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Helicobacter Pylori (-) Features: 1. Oxidase (+) 2. Curved gram negative rod 3. Urease (+) a. Splits urea into NH3 and CO2 i. NH3 neutralizes the acidity of stomach Lab Diagnosis: 1. Urea breath test a. Patient swallows urea labeled with radioactive carbon b. CO2 produced (if urease positive organism is present in stomach) has radioactive carbon in it which can be detected in breath 2. Biopsy during endoscopy a. The biopsy taken is directly checked by rapid urease test Diseases: 1. Ulcers a. Duodenal ulcers most common (95%) 2. Increases the risk of adenocarcinoma of stomach 3. May also cause lymphoma of mucous associated lymphoid tissue (MALT) a. Also called maltoma Treatment: 1. Triple therapy regimen a. Proton Pump Inhibitors b. Macrol...