Micro (Gram +)

Question 1

Which Staphylococci are Novobiocin resistant? Which are sensitive?

What Streptoocci are Opticin sensitive and resistant? What about Bacitracin?

Answer 1

” On the office’s “staph” retreat, there was NO StRESs. : NOvobiocin—Saprophyticus is Resistant; Epidermidis is Sensitive.

OVRPS (overpass). Optochin—Viridans is Resistant; Pneumoniae is Sensitive

B-BRAS: Bacitracin—group B strep are Resistant; group A strep are Sensitive.

Question 2

What organisms are α-hemolytic bacteria

Answer 2

Form green ring around colonies on blood agar A . Include the following organisms: ƒ Streptococcus pneumoniae (catalase ⊝ and optochin sensitive)
ƒ Viridans streptococci (catalase ⊝ and optochin resistant)

Question 3

What bugs are B hemolytic

Answer 3

ƒ Staphylococcus aureus (catalase and coagulase ⊕)
ƒ Streptococcus pyogenes—group A strep (catalase ⊝ and bacitracin sensitive)
ƒ Streptococcus agalactiae—group B strep (catalase ⊝ and bacitracin resistant)
ƒ Listeria monocytogenes (tumbling motility, meningitis in newborns, unpasteurized milk)

Question 4

Gram + bacteria. Has a Protein A virulence factor taht binds Fc-IgG and inhibits complementa activation. Lives in Nose

What diseases does it cause?

Answer 4

Staph. Aureus

Question 5

You and your roomate come back from a lunch hosted by school and both start vomitting profusely. Ingestion of what preformed toxin would cuase that rapid of onset?

Answer 5

S. aureus food poisoning due to ingestion of preformed toxin–>short incubation period (2–6 hr) followed by nonbloody diarrhea and emesis. Enterotoxin is heat stable not destroyed by cooking.

Question 6

A teamate of yours was playing soccer and got elbowed right in the nose. The trainer packed his nose and has him ice to help with the swelling. The next day at school your buddy wasn’t there and you were told he was taken to the ER last night- he has a fever of 101 and was vomitting and covered in a rash. What bug is responsible and what is the mechanism responsible for the pts symptoms

Answer 6

TSST is a superantigen that binds to MHC II and T-cell receptor, resulting in polyclonal T-cell activation. Staphylococcal toxic shock syndrome (TSS) presents as fever, vomiting, rash, desquamation, shock, end-organ failure. Associated with prolonged use of vaginal tampons or nasal packing. Compare with Streptococcus pyogenes TSS (a toxic shock– like syndrome associated with painful skin infection).

Question 7

Infects prosthetic devices (e.g., hip implant, heart valve) and intravenous catheters by producing adherent biofilms. Component of normal skin flora; contaminates blood cultures. Novobiocin sensitive.

Answer 7

Staph. Epidermidis: Gram +, Catalase +, Coag - and Novobiocin resistant

Question 8

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

Answer 8

Staphy. Saphrophiticus

Gram +, Coag +, Cat -, Novo resistant (Cow don’t get UTIs)

Question 9

Strep. Pneumo is implicated in many common disesase: which are they?

What does this bug look like?

Answer 9

S. pneumoniae MOPS are Most OPtochin Sensitive.

Meningitis, Otitis Media, Pneumonaie, Sinusitis

Lancet-shaped, gram-positive diplococci: Encapsulated. IgA protease.

Question 10

You are treating a little boy that is in the office becaues his mother says his H.influenza virus “is back”. He was in the week before and tested + for H.flu, was given antiB and sent home. Your PE is significant for diffuse lobar consolidation on both sides as well as rusty sputum which he coughed on your face.

What is the Dx?

What’s the key virulence factor?

Answer 10

Streptococcus pneumoniae

pneumococcus is associated with “rusty” sputum, sepsis in sickle cell disease and splenectomy.

No virulence without capsule.

Question 11

α-hemolytic. They are normal flora of the oropharynx that cause dental caries (Streptococcus mutans) and subacute bacterial endocarditis at damaged heart valves (S. sanguinis). Resistant to optochin, differentiating them from

S. pneumoniae, which is α-hemolytic but is optochin sensitive

Answer 11

Viridans group streptococci

Question 12

Pneumonics to remember the Viridians group streptococci

Answer 12

Sanguinis = blood. Think, “there is lots of blood in the heart” (endocarditis).

S. sanguinis makes dextrans, which bind to fibrin-platelet aggregates on damaged heart valves.

Viridans group strep live in the mouth because they are not afraid of-the-chin (op-to-chin resistant).

Question 13

Group A Strep.Pyogenes causes many diseases, name as many as you can:

Answer 13

ƒ Pyogenic—pharyngitis, cellulitis, impetigo, erysipelas
ƒ Toxigenic—scarlet fever, toxic shock–like syndrome, necrotizing fasciitis
ƒ Immunologic— rheumatic fever, acute glomerulonephritis

Question 14

Bacitracin sensitive, β-hemolytic, pyrrolidonyl arylamidase (PYR) ⊕.

What bacteria does this describe

Answer 14

Streptococcus pyogenes (group A streptococci)

Question 15

Antibodies to ________ enhance host defenses against S. pyogenes but can give rise to rheumatic fever.

_______detects recent S. pyogenes infection.

Answer 15

M protein

ASO titer

Question 16

Little boy comes to the office with a diffuse rash on his face as seen below

What bacteria is responsible for this?

What other skin associations are associated?

Answer 16

Streptococcus pyogenes (group A streptococci)

pharyngitis, cellulitis, impetigo, erysipelas

Question 17

Little girls comes to the office with her mother who is very concerned as she said her daughter has been recently peeing blood. Her daughter has a bad sore throat a few days before. What bacteria is involved?

titers would be elevated in this patient?

Answer 17

Streptococcus pyogenes (group A streptococci)

ASO titer detects recent S. pyogenes infection.

Pharyngitis can result in rheumatic “phever” and glomerulonephritis.

Impetigo more commonly precedes glomerulonephritis than pharyngitis.

Question 18

Little boy comes in with a rash all over his body, rough texture. On PE you see a strawberry tongue. What bacteria is responsible? What other body systems may become involved?

Answer 18

Streptococcus pyogenes (group A streptococci)

may see subsequent desquamation and glomerulonephritis

Question 19

What are the Jones criteria?

Is be bactiera Bacitracin resistant or sensitive?

Answer 19

J♥NES (major criteria for acute rheumatic fever):

Joints—polyarthritis ♥—carditis–Nodules (subcutaneous) Erythema marginatum Sydenham chorea

Streptococcus pyogenes (group A streptococci)

Question 20

Screen pregnant women at 35–37 weeks of gestation. Patients with ⊕ culture receive intrapartum penicillin prophylaxis

Answer 20

Streptococcus agalactiae (group B streptococci)

–Group B for Babies!

Question 21

Bacitracin resistant, β-hemolytic, colonizes vagina; causes pneumonia, meningitis, and sepsis, mainly in babies.

Answer 21

Streptococcus agalactiae (group B streptococci)

Question 22

What is the mechanism of action of infection of Group B strep?

Answer 22

Produces CAMP factor, which enlarges the area of hemolysis formed by S. aureus. (Note: CAMP stands for the authors of the test, not cyclic AMP.) Hippurate test ⊕.

Question 23

are normal colonic flora that are penicillin G resistant and cause UTI, biliary tract infections, and subacute endocarditis (following GI/GU procedures).

Answer 23

Enterococci (E. faecalis and E. faecium)

Question 24

________ is based on differences in the C carbohydrate on the bacterial cell wall. Variable hemolysis.

VRE (vancomycin-resistant enterococci) are an important cause of _______

Answer 24

Lancefield grouping

nosocomial infection.

Question 25

hardier than nonenterococcal group D, can grow in 6.5% NaCl and bile (lab test).

Entero = intestine, faecalis = feces, strepto = twisted (chains), coccus = berry.

Answer 25

Enterococci

Question 26

Colonizes the gut and can cause bacteremia and subacute endocarditis and is associated with colon cancer.

Answer 26

S. gallolyticus (S. bovis biotype 1)

Bovis in the blood = cancer in the colon.

Question 27

Symptoms include pseudomembranous pharyngitis (grayish-white membrane A ) with lymphadenopathy, myocarditis, and arrhythmias.

Dx and method of disease

Answer 27

Causes diphtheria via exotoxin encoded by β-prophage.

Potent exotoxin inhibits protein synthesis via ADP-ribosylation of EF-2.

Question 28

Lab diagnosis based on gram-positive rods with metachromatic (blue and red) granules and ⊕ Elek test for toxin.

Answer 28

Corynebacterium diphtheriae

Question 29

What are the ABCDEFG of Corynebacterium diphtheriae

Answer 29

ADP-ribosylation β-prophage Corynebacterium Diphtheriae Elongation Factor 2 Granules

Question 30

What are the benefits to spores and

Answer 30

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

Spores are highly resistant to heat and chemicals. Have dipicolinic acid in their core. Have no metabolic activity. Must autoclave to potentially kill spores (as is done to surgical equipment) by steaming at 121°C for 15 minutes.

Question 31

What disease is associated with the following bacteria that produce spores?

Bacillus anthracis

Bacillus cereus

Clostridium botulinum

Clostridium difficile

Answer 31

Bacillus anthracis: Anthrax

Bacillus cereus: Food Poisoning

Clostridium botulinum : Botulism

Clostridium difficile : Antibiotic-associated colitis

Question 32

What disease is associated with the following diseases

Clostridium perfringens

Clostridium tetani

Coxiella burnetii

Answer 32

Clostriudium Perfringen : Gas Gangrene

Clostridium tetani: Tetanus

Coxiella burnetii: Q fever

Question 33

Produces tetanospasmin, an exotoxin causing tetanus. Tetanus toxin (and botulinum toxin) are proteases that cleave SNARE proteins for neurotransmitters. Blocks release of inhibitory neurotransmitters, GABA and glycine, from Renshaw cells in spinal cord.

Causes spastic paralysis, trismus (lockjaw), risus sardonicus (raised eyebrows and open grin).

How do we treat this?

Answer 33

Prevent with tetanus vaccine. Treat with antitoxin +/− vaccine booster, diazepam (for muscle spasms).

*Gram-positive, spore-forming, obligate anaerobic bacilli.

Question 34

Gram-positive, spore-forming, obligate anaerobic bacilli.

Answer 34

C. difficile , C. perfringens ,C. botulinum

Question 35

Produces a preformed, heat-labile toxin that inhibits ACh release at the neuromuscular junction, causing botulism. In adults, disease is caused by ingestion of __________. In babies, ingestion of spores in honey causes disease (floppy baby syndrome). Treat with ______

Answer 35

preformed toxin

antitoxin

(Botulinum is from bad bottles of food and honey (causes a flaccid paralysis)

Question 36

Produces α toxin (lecithinase, a phospholipase) that can c_ause myonecrosis_ (gas gangrene and hemolysis.

Answer 36

C. perfringens: Perfringens perforates a gangrenous leg.

Question 37

Produces 2 toxins. Toxin A, enterotoxin, binds to the brush border of the gut.

Toxin B, cytotoxin, causes cytoskeletal disruption via actin depolymerization–> pseudomembranous colitis –> diarrhea.

Answer 37

C. difficile

Question 38

Often 2° to antibiotic use, especially clindamycin or ampicillin. Diagnosed by detection one or both toxins in stool by PCR.

Answer 38

C. difficile

Question 39

Caused by Bacillus anthracis, a gram-positive, spore-forming rod that produces anthrax toxin. The only bacterium with a

Answer 39

polypeptide capsule (contains d-glutamate).

Question 40

What happens when you inhale antrax?

Answer 40

Inhalation of spores flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock.

Question 41

Causes food poisoning. Spores survive cooking rice. Keeping rice warm results in germination of spores and enterotoxin formation.

Emetic type usually seen with rice and pasta. Nausea and vomiting within 1–5 hr. Caused by cereulide, a preformed toxin.

Diarrheal type causes watery, nonbloody diarrhea and GI pain within 8–18 hr.

Answer 41

Bacillus cereus

Question 42

Facultative intracellular microbe; acquired by ingestion of unpasteurized dairy products and cold deli meats, via transplacental transmission, or by vaginal transmission during birth.

Answer 42

Listeria monocytogenes

Question 43

How does Listeria avoid antibodies?

Answer 43

Forms “rocket tails” (via actin polymerization) that allow intracellular movement and cell-to-cell spread across cell membranes, thereby avoiding antibody.

Question 44

Can cause amnionitis, septicemia, and spontaneous abortion in pregnant women; granulomatosis infantiseptica; neonatal meningitis; meningitis in immunocompromised patients; mild gastroenteritis in healthy individuals.

Answer 44

Listeria monocytogenes

Question 45

Both are Gram Positive anf form long, branching filaments resembing fungi

1. Gram positive Anaerobe and not acid fast
2. Gram positive Aerobe and acid fast (weak)

Answer 45

1. Actinomyces
2. Nocardia

Question 46

Gram + anaerobes, not acid fast and are found in normal oral flora.

Causes oral/facial abscesses that drain through sinus trats and forms yellow “sulfur granules”

Answer 46

Actinomyces

Question 47

Gram + Aerobe, Acid Fast (weakly) and found in soil

Causes pulmonary infections in immunocompromised and cutaneous infections after trauma in immcucompetent.

Tx with Sulfonomides

Answer 47

Nocardia

Question 48

Viral particles isolated from the nasal exudate of a 10 yr male shown to lose their inefectivity once exposed to ether. It can be concluded that the viral particles are most likely:

Answer 48

Enveloped

Ether and organic solvents dissolve lipid bilayer that makes up outer viral envelope

Question 49

1. TB often resistant to drugs
2. pulmonary TB-like symptoms
3. causes disseminated non-TB disease in AIDS; often resistant to mult drugs

Answer 49

Mycobacterium TB

M.Kansasii

M.Avium-intercellulare (prophy tx with azithromycin)

Question 50

_____ in virulent strains of TB inhibits macrophage maturation and induces release of TNF-alhpa.

Answer 50

Cord factor

Question 51

What three situations would yield a PPD + test?

Answer 51

current infection with TB

Past exposure

BCG vaccination

Question 52

When would individuals test - for PPD?

What test is more specific then PPD for TB?

Answer 52

If no infection or anergic (steroids, malnutrition, immunocompromised) and in sarcoidosis

Interferon Gamma release assay (IGRA) is more specific; has fewer false + from BCG vaccination

Question 53

Compare and Contrast Primary and Secondary Tuberculosis

Answer 53

Primary tuberculosis: seen as an i_nitial infection_, usually in children. The initial focus of infection is a small subpleural granuloma accompanied by granulomatous hilar lymph node infection. Together, these make up the Ghon complex. In nearly all cases, these granulomas resolve and there is no further spread of the infection.

Secondary tuberculosis: seen mostly in adults as a _reactivation of previous infectio_n (or reinfection), particularly when health status declines. The granulomatous inflammation is much more florid and widespread. Typically, the upper lung lobes are most affected, and cavitation can occur.

Question 54

What two things make up a Ghon complex?

What does this represent?

Answer 54

a parenchymal subpleural lesion, often just above or just below the interlobar fissure between the upper and the lower lobes, and enlarged caseous lymph nodes draining the parenchymal focus.

THis is seen in primary TB

Question 55

Pt comes into clinic after recently visiting friends down south. They were hunting exotic animals, like armidillos, obviously. Months later his wife notices several plaques on his back.

What immune response is going on?

What’s the disease?

What do you tx the pt with?

Answer 55

Pt has Tuberculoid Leprosy

This is High-Cell mediated immunity with mostly TH1 type immune response

Tx: multidrug: Dapsone and Rifampin for 6 months

Question 56

You and your friend volunteered to go to Brazil and work at a free clinic for a month. You are working with a pt that rough rasied lesions over his face and complains of tingling in his fingers and toes. What part of the immune system is most active in this diesase?

What is the tx recommended?

Answer 56

Leprosy: often diffuse over skin, lion like facies and communicable

Low cell mediated but HUMORAL Th2 response

(lions are Humorous 2)

Tx: Dapsone, Rifampin and Clofazimine for 2-5 yrs

Question 58

12 yo boy comes to docotr with fever, chills and rash that started in the AM. Two days prior he had a sore throat and his temp is 101. You note a diffuse erythematous rash on chest and abdomen that blanches with pressure as well as 1-2 mm papules. The throat is erythemaotus with gray-white tonsilar exudate and the tongue is bright red.

Dx and bug responsible?

What may this pt look like in a week?

What complications do we worry about?

Answer 58

Scarlet fever from Group A Strep Pyogenes

Dt pyrogenic exotoxins

Can see desquemation of the rash towards the end of the first week, often starts at armpits, groin and tips of fingers

Can predispose you to Acute rheumatic fever and Glomerulonephritis

Question 59

What is the bacteria responsible for causing black ulcers and Hemorrhagic mediastinis?

What is special about it’s capsule?

Answer 59

Bacillus anthracis: on culture it forms long chains and looks serpintine

produces antiphagocytic capsule that is unique; has D-glutamate instread of polysaccaride