Gram (+) Rods

Question 1

Spore forming aerobe, zoonosis with no vector, associated with cattle that can lead to a cutaneous disease with edematous eschar

Answer 1

Bacillus anthracis

Edema factor and lethal factor released from anthrax toxin cause the eschar

Question 2

Patient presents with pneumonia. Upon chest xray, there is mediastinal widening. Patient was recently at major sporting event. If not treated within 48 hrs, this disease is almost invariably fatal.

Answer 2

Bacillus anthracis - mediastinal widening due to hemorrhagic lymphadenitis

Inhalational spores have potential for biowarfare agent

Question 3

Spore forming aerobe, associated with Chinese restaurants, rapid onset vomiting and diarrhea due to preformed emetic toxin

Answer 3

Bacillus cereus

Question 4

Anaerobic, spore former, produces toxin that blocks release of glycine and GABA in spinal synapses, leaving excitatory neurons unopposed

Answer 4

Clostridium tetani

Question 5

Associated with dirty puncture wounds and progresses from lockjaw to diffuse rigid paralysis

Answer 5

Clostridium tetani

Question 6

What is the treatment of tetanus?

Answer 6

TIG (hyperimmune human globulin) to neutralize toxin + antibiotics (metronidazole or penicillin)

Question 7

Floppy baby syndrome

Answer 7

Clostridium botulinum

buzzword: honey

Question 8

Anaerobic, spore former, heat labile, produces toxin that blocks the release of ACh at the neuromuscular junction

Answer 8

Clostridium botulinum

Question 9

Why shouldn’t you treat botulism with antibiotics?

Answer 9

In adults: there is no active infection! Just ingested preformed toxin

In infants: antibiotics will lyse the bacteria, releasing toxin and causing a potentially fatal toxemia

Thankfully, there is a trivalent antitoxin available

Question 10

Anaerobic, spore former, non motile, produces an alpha toxin that is a lecithinase which causes massive hemolysis and tissue destruction

Answer 10

Clostridium perfringens

Toxin identified by Nagler reaction

Question 11

Traumatic accident, contamination of wound with soil, tense tissue, fever

Answer 11

Clostridium perfringens - gas gangrene

Question 12

What is the treatment of gangrene due to Clostridium perfringens?

Answer 12

• debridement
• delay closure of wound for as long as possible (since C. perfringens is anaerobic)
• clindamycin + penicillin
• hyperbaric chamber

Question 13

Food poisoning, enterotoxin disrupts ion transport which causes a watery diarrhea that resolves within 24 hrs, associated with reheated meat dishes

Answer 13

Clostridium perfringens

Question 14

Which is more common in the U.S., adult or infant botulism?

Answer 14

Infant

Question 15

Anaerobic, spore former, normal flora of colon, toxins produced that are associated with antibiotic use and pseudomembranous colitis

Answer 15

Clostridium difficile

Question 16

Which antibiotics put patients at most risk for developing Clostridium difficile infection?

Answer 16

broad spectrum - clindamycin, cephalosporins, amoxicillin, ampicillin

Question 17

What is the treatment for Clostridium difficile?

Answer 17

metronidazole

Question 18

Anaerobic, spore-former, stormy fermentation in milk media, shows double zone of hemolysis

Answer 18

Clostridium perfringens

Question 19

Most common cause of meningitis is a renal transplant or cancer patient

Answer 19

Listeria monocytogenes

Question 20

Aerobic, non spore former, beta hemolytic, facultative intracellular, tumbling motility, cold growth

Answer 20

Listeria monocytogenes

Question 21

What is the manifestation of transplacental transmission of listeria monocytogenes? Neonatal acquisition?

Answer 21

Transplacental: granulomatous infantisepticum (disseminated granulomas with central necrosis) - tell mom to stay away from deli meat and soft cheese!

Neonatal: septicemia and meningitis

Question 22

Aerobic, non spore former, club-shaped, toxin produced that inhibits protein synthesis by interfering with elongation, toxoid vaccine, most commonly infects throat (gray pseudomembrane), heart (myocarditis), and nerve (recurrent laryngeal nerve palsy)

Answer 22

Corynebacterium diphtheriae

Question 23

Grows gray to black colonies in V or L or “Chinese letter formation” on tellurite medium. Can distinguish toxigenic from non toxigenic strains with Elek test.

Answer 23

Corynebacterium diphtheriae

Question 24

Toxin producing strains of corynebacterium are present in an individual due to?

Answer 24

transduction of toxin via a beta-prophage, and toxin is then produced by lysogeny

Question 25

Anaerobic, branching rods, non-acid fast, normal flora in gingiva or female genital tract, grows in tissues with low oxygenation, colonies resemble molar tooth

Answer 25

Actinomyces israelii

Question 26

Lumpy jaw, draining abscess with sulfur granules

Answer 26

Actinomyces israelii

Question 27

How do brain abscesses due to Actinomyces differ from those due to Nocardia (both branching G+ rods)?

Answer 27

Actinomyces: solitary
Nocardia: multiple foci

Question 28

Aerobic, branching rod, partially acid fast, reservoir in soil or dust, causes a cavitary bronchopulmonary disease that looks very similar to TB

Answer 28

Nocardiosis asteroides

Question 29

Aerobic, branching rod, partially acid fast, causes a cellulitis with a draining abscess and granules after traumatic implantation

Answer 29

Nocardiosis brasiliensis

Question 30

What is the preferred treatment for Nocardia infection?

Answer 30

sulfonamides or TMP-SMX

(usually will show up as TB-like symptoms with choices of a bunch of TB drugs + sulfonamides… Pay close attention to description of partially acid fast or branching rods)

Question 31

Acid fast, obligate aerobe, facultative intracellular, stains fluorescent apple green on Auramine-rhodamine stain, grows in 2-3 weeks on Lowenstein-Jensen medium, produces niacin, heat sensitive catalase

Answer 31

Mycobacterium tuberculosis

Question 32

Describe the pathogenesis mechanisms for Mycobacterium tuberculosis

Answer 32

• Sulfatides that inhibit phagosome/lysosome fusion
• Cord factor that inhibits leukocyte migration and disrupts cellular respiration
• Tuberculin that causes a delayed Type IV HSN reaction and induces cell mediated immunity
• no toxins! All damage is done by immune system

Question 33

Replication in alveolar macrophages (Ghon focus), transportation to regional lymph nodes (Ghon complex), granulomas formed to wall off organisms

Answer 33

Primary pulmonary TB

Question 34

Reduction of host T cell immunity and erosion of granulomas into airway with potential for dissemination

Answer 34

Reactivational TB (when disseminated, “miliary”)

Question 35

Diagnosis of TB?

Answer 35

• PPD skin test, if positive proceed to CXR
• Microscopy of sputum
• slow growing culture

Question 36

Cause of pulmonary infection in AIDS patients with CD4 counts < 50

Answer 36

M. avium-intracellulare (diagnosis nonchromogen)

M. kansasii (diagnosis photochromagen)

Question 37

Cause of lymphadenitis from contaminated water sources that will cause a solitary cervical LN in kids

Answer 37

M. scrofulaceum (diagnosis scotochromogen)

Question 38

Cause of soft tissue infection in tropical fish enthusiasts

Answer 38

M. marinum (diagnosis photochromagen)

Question 39

Acid fast rod, obligate intracellular parasite, prefers cooler parts of body, transmitted via nasal discharge, causes a disease that leads to sensory loss

Answer 39

Mycobacterium leprae

Question 40

Lepromin test +, few organisms in tissue, causes granuloma formation and subsequent nerve damage, macular lesions

Answer 40

Tuberculoid leprosy - if strong CMI (TH1) is present

Question 41

Lepromin test -, many organisms in tissue, causes nerve damage due to growth of bacteria in cells, nodular lesions, leonine facies

Answer 41

Lepromatous leprosy - if weak CMI (TH2) is present

Question 42

Diagnosis and treatment of leprosy?

Answer 42

Dx: punch biopsy of lesions and acid fast stain, cannot culture

Tx: dapsone + rifampin (add clofazimine in lepromatous type)