Bacteria Flashcards
Staphylococcus Aureus: what is it and what 4 tests are positive, where is it found and what does it cause, and what protein acts as its virulence factor?
- beta-hemolytic gram (+) coccus that is Catalase (+), Coagulase (+) and can ferment Mannitol (yellow)
- part of normal nose and skin flora that can cause bacterial pneumonia of the UPPER respiratory tract w/patchy infiltrate on X-Rays
- also acquired from contaminated mayo and meats
- Protein A (part of cell wall) prevents opsonization
Staphylococcus Aureus: what 3 findings is it the most common cause of (SA,O,E), what 4 clinical findings does it cause, and what 3 things does its exotoxin cause?
- most common cause of septic arthritis, adult osteomyelitis, and infective endocarditis
- causes impetigo (honey crust), furuncles, carbuncles, and cellulitis
- exotoxins cause: scalded skin syndrome, toxic shock syndrome, and rapid onset food poisoning (1-8 hours –> vomiting)
Staphylococcus epidermidis & saprophyticus: what are they and what 2 tests are positive for them, and what are the clinical implications of each?
- gram (+) cocci that are Catalase (+), Urease (+), and Coagulase (-)
SE: part of normal flora on skin; infects implants, catheters, and heart valves (MCC endocarditis); produces a biofilm that helps it stick
SS: UTIs in sexually active females (second most common cause)
Group A Streptococcus: what is it, what 3 clinical findings does it commonly cause, and what 3 things is its exotoxin associated with?
- gram (+) cocci that produce a Hyaluronic Acid capsule (no immune response) and is Beta hemolytic
- cause impetigo (honey crust), strep throat, and is the most common cause of skin infection (cellulitis)
- exotoxin associated with Scarlet Fever, Toxic Shock Syndrome (SPE A/C), and Necrotizing Fasciitis (SPE B)
What 3 things does the Group A Strep exotoxin produce in Scarlet Fever?
- strawberry tongue, pharyngitis, and a “sandpaper” rash that spares the palms/soles/face
How is the Group A Strep protein M associated with Rheumatic Fever?
- caused by untreated Strep A pharyngitis
- protein blocks phagocytosis and complement; leads to CROSS-REACTIVE Abs that cause pancarditis and mitral valve stenosis
- MOLECULAR MIMICRY with the heart
JONES criteria and Rheumatic Fever
J - joints (migratory polyarthritis)
O - myocarditis
N - subQ nodules (on extensor surfaces)
E - erythema marginatum (hive-like “C” shape)
S - Syndenhams chorea (rapid hand/face movements)
Post Strep A Glomerulonephritis
- immune complex deposition in glomeruli that causes renal damage and nephritic syndrome
- causes “cola-colored” urine and nephritic syndrome several weeks after
- follows pharyngitis OR tissue infection
How is Strep A pharyngitis diagnosed and what are two other virulence factors for Strep A? (SSD)
diagnose: antibodies against Strepolysin O (hemolytic virulence factor)
- other virulence factors: streptokinase (plasminogen to plasmin) and DNAses
Streptococcus agalactiae (Group B Strep): what is it and what 3 things is it positive for, how does Bacitracin affect it compared to Group A Strep, and what are the 3 clinical findings it causes (MSP)?
- encapsulated gram (+) cocci that is hippurate (+) and CAMP (+) –> (inc. hemolytic zone when plated with S. Aureus), and Beta hemolytic
- Bacitracin INSENSITIVE (Strep A is Bacitracin SENSITIVE)
- most common cause of neonatal meningitis, sepsis, and pneumonia (screen moms at 35-37 weeks)
Streptococcus pneumonia: what is it and what are 3 major findings for it, what does its protease do, and what 4 things is it the most common cause of? (MOPS)
- encapsulated gram (+) lancet-shaped diplococci that is ALPHA hemolytic, OPTOCHIN sensitive, and is bile-soluble
- causes lobar pneumonia (rust sputum) and has IgA protease that cleaves IgA Abs
- is the most common cause of meningitis, otitis media, pneumonia, and sinusitis
- sickle cell patients are more susceptible to infection
Streptococcus viridans: what is it and what are 3 major findings for it, what two things do S. mutans/sanguinis cause, and how do they use Dextrans?
- non-encapsulated gram (+) cocci that is ALPHA hemolytic, OPTOCHIN insensitive, and is bile-insoluble
- mutans and sanguinis cause tooth decay and cavities (normal mouth flora) and can cause bacterial mitral valve endocarditis
- uses DEXTRANS to adhere to platelets and enamel
Enterococcus faecalis and faecium (Group D Strep): what are they and what two things do they grow in, and what 3 things do they commonly cause (UEB)?
- gram (+) cocci (faecium is most dangerous) that grow in 6.5% hypertonic saline and in bile salts
- commonly cause UTIs, endocarditis, and biliary tree infections
Bacillus anthracis and cereus: what is it, what does it cause cutaneously and pulmonarily, and what two exotoxins does B. anthracis have?
- encapsulated (poly-y-D-glutamic acid) gram (+) spore forming bacilli that form chains and is obligate aerobe
- causes cutaneous anthrax (necrotic lesion w/erythematous ring, edema, and eschar)
exotoxins:
- Lethal Factor - cleaves MAP Kinase (no cell growth)
- Edema Factor - inc. cAMP (edema)
- Wool Sorter’s = inhaled form causing hemorrhagic mediastinitis (chest X-Ray shows widened mediastinum or pleural effusions)
What two clinical findings does ingesting Bacillus cereus cause and what is it commonly associated with?
- ingestion of preformed toxin causes early onset food poisoning (6 hours) and watery vomit/abdominal cramps (6-15 hours)
- usually associated with eating reheated fried rice
Clostridium tetani: what is it and how is it introduced into the body, how does it travel and what does its toxin do, and what 3 clinical findings does it cause?
- gram (+) spore-forming bacilli that are obligate anaerobes associated with barbed wire puncture wounds and rusty nails (inactive spores in soil)
- travels retrograde up the spinal cord; tetanus toxin cleaves SNARE proteins (no GABA or Glycine from Renshaw cells = no motor cell inhibition)
- causes spastic paralysis of neck/back/spine, Risus Sardonicus (evil grin) and Lockjaw
Clostridium botulinum: what is it and what is it associated with, how does it cause paralysis, and what are some of the first signs of infection?
- gram (+) spore-forming bacilli that is an obligate anaerobe associated with improperly canned foods
- cleaves SNARE proteins that prevent Ach release from presynaptic terminal
- cause descending flaccid paralysis starting from cranial nerves –> causes ptosis/diplopia
- infantile form from ingesting spores from honey (GI tract is not properly colonized yet)
Clostridium difficile: what is it and how is it spread, what is it clinically associated with, and what do its two toxins (AB) cause?
- gram (+) spore-forming bacilli that is an obligate anaerobe commonly spread by Clindamycin use w/improper handwashing –> WASH YOUR FUCKING HANDS YOU PLEB
- commonly associated with nosoconial diarrhea (diagnose with detection of exotoxins in stool)
Exotoxin A: bind brush border = watery diarrhea
Exotoxin B: depolymerize actin = pseudomemb. colitis
Clostridium perfringens: what is it and how is it commonly spread, what three clinical findings does it cause (GG/FP/WD), and how is it characterized when it is plated on agar?
- gram (+) spore-forming bacilli that is an obligate anaerobe (in dirt/dust) commonly associated with motorcycle accidents and deep penetrating combat wounds
- causes gas gangrene (clostridial mynecrosis) via ALPHA TOXIN (lecithinase that cleaves membranes and RBCs)
- ingestion of spores causes late onset food poisoning (watery diarrhea)
- produces a double zone of hemolysis on plating
Corynebacterium diphtheriae: what is it and what does it look like, what 4 clinical findings does it cause, and what does it look like on agar?
- gram (+) bacilli (NO SPORES –> Resp. Droplets) that form V/Y-shaped chains and have metachromatic granules that stain red (rest of bacilli stain blue)
- toxin inhibits EGF-2 via ADP ribosylation and causes pseudomembrane formation of tonsils and throat, lymphadenopathy (“Bulls Neck”), and is cardiotoxic
- can also cause demyelination causing paralysis in posterior pharyngeal wall and soft palate
- grow as dark black colonies on cysteine-tellurite agair
What test is used to differentiate between toxogenic and non-toxogenic C. diphtheriae?
ELEK test
Listeria monocytogenes: what is it and how is it transmitted, what test is it positive for, and what two populations does it commonly cause meningitis in?
- facultative intracellular gram (+) bacilli that are WEAKLY beta hemolytic and having tumbling motility outside cells and rocket motility inside cells
- Catalase (+); survives in freezing temps (milk, cheese)
- pregnant women at risk (no soft cheese) and is the third leading cause of neonatal meningitis
- also a common cause of meningitis in adults older than 60 yo
Acintomyces israelii: what is it and where is it commonly found, and what 3 clinical findings does it present with?
- gram (+) filamentous branching bacilli that is an obligate anaerobe commonly found in the mouth
- usually infect after JAW TRAUMA causing abscesses in the face and neck, and cutaneous sinus tracts
- hard yellow (sulfur) granules drain from the sinus tract
Nocardia asteroides: what is it and where is it found, what two tests are positive for it, and what 4 clinical findings does it cause?
- gram (+) filamentous branching bacilli that is an obligate aerobe (in soil) that stain acid-fast (Carbol-Fuchsin); commonly infects immunocompromised
- Catalase (+), Urease (+)
- causes lung cavitations, pneumonia w/lung abscesses, ring-enhancing lesions in brain, and cutaneous lesions
What is Nocardia asteroides commonly misdiagnosed as?
Tuberculosis
Neisseria commonalities: what are they, what two mediums do they grow on, and what are their two virulence factors?
Bonus: who is at inc. risk of infection from Neisseria?
- gram (-) diplococci that is Oxidase (+)
- grows on Chocolate Agar and Thayer Martin Agar (VPN) –> cannot grow on Blood Agar
- increased susceptibility in people with MAC deficiencies
Virulence Factors: IgA protease and pili (antigenic var.)
