Gram positive Bugs

Question 1

Define the bug that is

• Novobiocin resistant
• Novobiocin sensitive

Answer 1

• Stapholococci Saprophyticus
• Stapholococci Epidermidis

Question 2

Define the bug that is

• Optochin resistant
• Optochin sensitive
• Bacitracin resistant
• Bacitracin sensitive

Answer 2

• Streptococcus viridans
• Streptococcus pneumoniae

​

• Streptococcus group B
• Streptococcus pyogenes (group A)

Question 3

• what is the term for organisms that form green ring around colognies on blood agar?
• What forms a green ring around colonies on blood agar?
  • provide 2 distinguishing features

Answer 3

• Alpha-hemolytic organisms
• Streptococcus pneumoniae
  
  • Catalase neg
  • Optochin sensitive
• Streptococcus Viridians
  
  • Catalase neg
  • Optochin resistant

Question 4

• What is the term for organisms that form clear area of hemolysis on blood agar?
• Name the 4 organisms that form clear area of hemolysis on blood agar
  • give 2 distingusihing characterisitics

Answer 4

• Beta hemolytic bacteria
• Staphylococcus aures
  
  • Catalase +, coagulase +
• Streptococcus pyogenes group A
  
  • Catalase -, Bacitracin sensitive
• Streptococcus agalactiae group B
  
  • Catalse -, Bacitracin resistant
• Listeria monocytogenes
  
  • Tumbling motility, meningitis in newborns, unpasteurized milk.

Question 5

Presentation

Gram positive cocci in clusters, Protein A (virulance factor) bings to Fc IgG inhibiting complement activation and phagocytosis. Commonly colonizes the nose.

• Define organism
• Causes

Answer 5

• Staphylococcus aureus
• Causes
  
  • Inflammatory disease
    
    • skin infections, organ absecesses , pneumoniae (often after influenza virus infection), endocarditis, and osteomyelitis
  • Toxin-mediated disease
    
    • toxic shock syndrome (TSST-1), scalded skin syndrome (exofoliative toxin), rapid onset food poisoning (enterotoxins)
  • MRSA (methicillin resistant S. aureus infection)
    
    • important cause of serious nosocomial and community acquired infections, resistant to methicillin and nafcillin b/c of altered penicillin-binding protein.

Question 6

Toxin mediated disease

• TSST is a superantigen that bings to what 2 receptors and results in what?
  
  • Presents as fever, vomiting, rash, desquamation, shock, end-organ failure
• Use of what predisposes to toxic shock syndrome

Answer 6

• 2 receptors: MHC II and TCR receptor
  
  • results in: polyclonal T-cell activation
• Vaginal and nasal tampons

Question 7

Define the organisms that:

• infects prosthetic devies and IV catheters (by producing adherent biofilms)
• Component of normal skin flora
• contaminates blood cultures
• Novobiocin sensitive

Answer 7

Staphylococcus epidermidis

Question 8

Food poisioning

• S. aures food posioning due to ingestion of what?
• What is the incubation time?
• Enterotoxin heat stable or liable
• Is it destroyed by cooking?
• How does it form abscess?

Answer 8

**Food poisioning **

• S. aures food posioning due to ingestion of what? pre-formed toxins
• what is the incubation time? 2-6 hrs (short time)
• Enterotoxin heat stable or liable
• is it destroyed by cooking? No
• How does it form abscess? Forms a fibrin clot aronud self

Question 9

Define the organism that:

• is the second most common cause of uncomplicated UTI in young women (first is E. coli)
• Novobiocin resistant

Answer 9

Staphylococcus saprophyticus

Question 10

Define the organism that

• Most common cause of
  
  • Meningitis
  • Otitis media
  • Pneuomia
  • Sinusitis
• Lancet shaped, gram+ diplococci, encapsulated IgA protease.
• Optochin sensitive
• **Pneumococcus: **
  
  • ​Assocaited with rusty sputum, sepsis in sickle cell anemia, and splenectomy
• No virulence w/o capsule

Answer 10

Streptococcus pneumoniae

Question 11

Define the organism that

• Is alpha hemotylic and optochin resistant
• Which organism is found in the normal flora of the orpharynx and cause dental caries
• Which organism cause bacterial endocartidits at damaged valves
  
  • what is its MOA

Answer 11

• Viridans group streptococci
• Streptococcus mutans
• ​Streptococcus sanguis
  
  • *​sanguis= *blood
  • MOA: makes dextrans, which bind to fibrin platelet aggregates on damaged heart valves.

Question 12

Define the organism that:

• Causes
  
  • pyogenic: pharyngitis, cellulitis, impetigio
  • toxigenic: scarlet fever, toxic shock like syndrome, necrotizing fasciitis
  • immunologic: rheumatic fever, acute glomerulnephritis
• Bacitracin sensitive
• Antibodies to M protein enhance host defenses against _ _ but can give rise to rheumatic fever
• ASO titer detects recent infection of this organism

Answer 12

Streptococcus pyogenes

(Group A streptococci)

Question 13

Define

• Jones critieria
• Pharyngitis can result in what 2 things?
• Impetigo more commonly precedes what?
• Scarlet fever

Answer 13

• Jones critieria
  
  • Joints (polyarthritis), heart (carditis), Nodules (subcutaneous), Erythemia marginatum (pink rings on trunk), Sydenham chorea (rapid uncoordinated movements)
• Pharyngitis–> fever and glomerulonephritis
• Impetigo: precedes glomerulonephritis than pharyngitis
• **Scarlet fever: **scarlet rash with sandpaper like texture, strawberry tongue, circumoral pallor

Question 14

Define the organism

• Bacitracin resistant, B-hemolytic colonise vagina, cause pneumonia, meningitis, & sepsis: mainly in BABIES!
• hippurate test +
• Produces CAMP factor
  
  • define
• When do you screen pt and what do you give them?

Answer 14

• Streptococcus aglacteria (group B strep)
• CAMP factor: enlarges the area of hemolysis formed by S. aureus.
• Screen: 35-37 weeks
  
  • Patients with + culture receive intrapartum penicillin prophylaxis.

Question 15

Define the organism that:

• is a normal colonic flora that is penicillin G resistant and cause UTI, biliary tract infections, and subacute endocarditis (following GI/GU procedures).
• what is Lancefield grouping based off of?
  
  • what is included in this group?
• VRE (vancomycin resistant enterococci) are an important cause of nosocomial infection.

Answer 15

• Enterococci (group D streptococci)
• _Lancefield group: _based on differences in the C carbohydrate on the bacterial cell wall, variable hemolysis.
  
  • Enterococci and the non enterococcal group D streptococci

Question 16

• Enterococci hardier than nonenterococcal group D: what can it grow on?
• Define
  
  • Entero, faecalis, strepto, coccus

Answer 16

• 6.5% NaCl and bile (lab test)
• Entero= intestine, Faecalis= feces, strepto= twisted, coccus= berry

Question 17

Define the organism that:

• Colonies the gut, can cause bacteremia and subacute endocarditis in colon cancer pts.

Answer 17

• Streptococcus bovis (group D streptococci)

Bovis in the blood= cancer in the colon

Question 18

Define the organism that:

• Causes disease via exotoxin encoded by B-propharge
  
  • protent exotoxin inhibots protein produciton synthesis via ADP-ribolsylation of EF-2
• Symptoms include
  
  • pseudomembranous pharyngitis (graish which membrane) with lymphadenopathy, myocarditis, and arrhythmias.
• Lab diagnosis:
  
  • gram + rods, with metachormatic (blue and red) granules & Elek test for toxin
• How is it prevented?

Answer 18

• Corynebacterium diphtheriae
• Vaccine: toxoid vaccine prevents diphtheria

Question 19

Corynebactrium (coryne- club shaped) presents with black colonies on cystine-tellurite agar

Define what ABCDEFG stand for

Answer 19

• A= ADP-ribosylation (it inhibits protein syn)
• B= beta-prophage
• C= Corynebacterium
• D= Diptheriae
• E & F= Elongation factor 2
• G= Granules (blue and red)

Question 20

Some bacteria can form spores at tehend of the stationary phase when nutrients are limited

• Spores are highly resitant to heat and chemicals
  
  • have what in their core?
• Do they have metabolic activity?
• how do you kill spores?

Answer 20

• dipicolonic acid
• no metabolic activity
• autoclave to kill spores (this is done to surgical equipment by steaming at 121^oC for 15 min).

Question 21

• Define the spore forming gram positive bacteria found in soil
• Define other spore formers

Answer 21

• Bacillus, anthracis, Clostridium perfringens, Clostridium tetani
• B. cerus, C. botulinum, Coxiella burnetti

Question 22

G+, spore forming, obligate anaerobic bacilli

Produces tetanospasmin, and exotoxin causing tetanus. Tetanus toxin (and botulinum toxin) are proteases that cleave releasing proteins for neurotransnmitters

Causes spastic paralyis, trimus (lock jaw) and risus sardonicus

• Define the organism
• MOA

Answer 22

• C. tetani
• MOA:
  
  • Tetnus is tetanis paralysis
  • Blocks glycine and GABA release (both of these are inhibitory neurotransmitters) from Renshaw cells in spinal cord

Question 23

G+ spore forming obligate anaerobic bacilli

Produces a preformed, heat labile toxin that inhibits ACh release at the neuromuscular junction, causing botulism. _ flaccid paralysis_

• In adults: disaese is caused by ingestion of preformed toxin
• In babies: ingestion of spores in honey causes disease (floppy baby syndrome)

Answer 23

C. botulinum

Question 24

G+ spore forming obligate anaerobic bacilli

Produces alpha toxin (lecithinase), a phospholipase that can cause myonecrosis (gas gangrene) and hemolysis

Answer 24

C. perfringens

Question 25

G+ spore forming obligate anaerobic bacilli * Produces 2 toxins: * Toxin A: enterotoxin, bings to the brush border of the gut * Toxin B: cytotoxin causes cytoskeletal disruption via actin depolymerization --\> pseudomembranous colitis--\> diarrhea * often 2^o to antibiotic : define the antibiotics * How is this disease diagnosed? * Treatment

Answer 25

* **Organism:** * C. difficile* * **Antibiotics:** Clindamycin and ampicillin * **Diagnosed: **detection of one or both of the toxin in stools. * **Treatment: ** * metronidazole or oral vancomycin. * for recurring cases: fecal transplant may prevent relapse.

Question 26

**Anthrax** * is caused by what organism? * define morphology * what is unique about its cell wall?

Answer 26

* *Bacillus anthracis* * Gram +, spore forming rod (produces anthrax toxin) * only bacterium that contains polypeptide capsule (contains D-glutamate).

Question 27

Pt presents with * boil like lesion--\> ulcer with black eschar (painless, necrotic)--\> uncocmly progresses to bacteremia and death

Answer 27

cutaneous anthrax

Question 28

Pt presents with * inhalation of spores--\> flu like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock. * Define woolsorter's disease

Answer 28

* Pulmonary anthrax * **Woolsorter's disease:** inhalation of spores from contaminated wool.

Question 29

# Define the organism that: causes food poisoning, spores survive cooking rice, keeping rice warm results in germination of spores & enterotoxin formation * Emetic type usually seen with rice and pasta, nausea and vomiting w/in 1-5 hr, caused by what preformed toxin? * Diarrhea and GI pain w/in 8-18 hr.

Answer 29

* *B. cereus* * Emetic type caused by: cereulide (a preformed toxin)

Question 30

# Define the organism that is a facultative intracellular microbe; acquired by ingestion of unpasteurized dairy products and deli meats, via trasplacental transmission, or by vaginal transmission during birth. form rocket tails (via actin polymerization) that allow them to move through the cytoplasm and into the cell membrane, thereby avoiding antibody. * Characteristic tumbling motility: only gram postive to produce what? * Can cause * amnionities, septicemia, and spontaneous abortion in pregnant women, granulomatosis infantiseptica, neonatal meningitis, meningitis in immunocompormsed pt mild gastroenteritis in healthy individuals. * What is the treatment?

Answer 30

* *Listeria monocytogenes* * only G+ to produce LPS * Treatment: * gastroenteritis usually self-limited * **ampicillin** for * infants * immunocompromised pt * elderly in empirical treatment of meningitis.

Question 31

Long branching filments resembling fungi * G+ anarobe, not acid fast, normal oral flora * causes: oral/facial abscesses that drain thorugh the sinus tract, forms 'yellow sulfur granules' * Treatment? * G+ aerobe, acid fast, weak, found in soil * causes: pulmonary infection in immunocompromised and cutaneous infections after trauma in immunocompetent * Treatment?

Answer 31

* Actinomyces * Penicillin * Nocardia * Sulfonamides

Question 32

Mycobacterium tuberculosis * PPD + vs PPD - * Interferon gamma release assay (IGRA)

Answer 32

* PPD * PPD +: current infection, past exposure, or BCG vaccinated * PPD -: no infection or anergic (steroids, malnutrition, immunocompromised) and in sarcoidosis * IGRA (Interferon gamma release assay * is a more specific test * has fewer false positives from BCG vaccination.

Question 33

# Define the organism All are acid fast organisms * TB often resistant to multiple drugs * pulmonary TB like symptoms * Causes disseminated, non-TB disease in AIDS; often resistent to multiple drugs * What is its prophylactic treatment?

Answer 33

* *Mycobacerium tuberculosis* * *M. Kansasii* * *M. avium-intracellulare* * Prophylactic treatment: **azithromycin**

Question 34

TB symptoms include fever, night sweats, weight loss, and hemoptysis * Cord factor in virulent strains inhibits _\_\_\_\_\_\__and induces release of _\_\_\_\_\_\_\__. * What inhibits phagolysosomal fusion?

Answer 34

* Inhibits macrophage maturation and induces release of TNF-alpha. * Sulfatides (surface glycolipids).

Question 35

# Define the organism that * is an acid-fast bacilus that likes cool temperature (infects skin and superficial nerves- 'glove and stocking' loss of sensation) and cannot be grown in vitro. Reservoir in US armadillos.

Answer 35

*Mycobacterium leprae*

Question 36

Hasen dsease has 2 forms * One that presents diffusely over the skin, with leonine (lion like) facies, and is communicable * define the disease and patho * One that is limited to a few hypoesthetic hairless skin plaques * define the disease and characterized by what * What is the treatment?

Answer 36

* Lepromatous * characterized by _low cell-mediated_ immunity with a humoral Th2 response. * **treatment: **dapsone, rifampin, and clofazimine for 2-5 yrs * Tuberculoid * characterized by high cell-mediated immunity with a largely Th1-type immune response * **treatment: **dapsone and rifampin for 6 mo