Bacterial Skin Infections III

Question 1

What are the characteristics of C. tetani?

Answer 1

Spore forming
Gram + rod
Strict anaerobe
Causative agent of tetanus

Question 2

C. tetani primarily occurs in __________

Answer 2

Unvaccinated or under vaccinated people

Question 3

Predisposing factors to C. tetani include no or inadequate vaccination with deep ______ injury (spore inoculation) with/without foreign body, localized _______ and/or devitalized tissue.

Answer 3

penetrating

ischemia

Question 4

What is the pathogenesis of tetanus toxin aka tetanospasmin produced at local site of infection?

Answer 4

AB toxin metalloprotease

Cleaves SNARE proteins inside inhibitory interneurons –> prevents exocytosis of inhibitory neurotransmitters (GABA/glycine) so motor neurons not inhibited

Leads to spastic, prolonged contraction

Question 5

Toxin action of tetanus lasts ______

Answer 5

weeks to months

Question 6

What is the presentation of C. tetani?

Answer 6

Generalized

Abrupt, intense, extended duration, painful muscle contractions - starts in face/masseter muscle –> lockjaw –> risus sardonicus

Opisthotonos

Question 7

How is C. tetani diagnosed?

Answer 7

Signs and symptoms
Higher clinical suspicious with tetanus-prone injury and no or inadequate tetanus vaccination history

Question 8

Culture is _______ with C. tetani

Answer 8

not useful

Question 9

________ is treated with immediate hospitalization. With bacterial, tx is done with wound debridement and antibiotics to stop toxin production, IV human tetanus immunoglobulin to neutralize free toxin, and vaccination to confer immunity

Answer 9

C. tetani

Question 10

How do we prevent C. tetani?

Answer 10

TdaP or other tetanus toxoid containing vaccine

Question 11

What are the characteristics of mycobacteria?

Answer 11

Acid fast rods
Lipid rich cell wall

Question 12

_______ aka tuberculosis spondylitis, tuberculosis vertebral osteomyelitis, spinal TB. Most common form of skeletal TB and slow onset destruction of thoracic and/or lumbar vertebrae

Answer 12

Pott’s Disease

Question 13

What causes Pott’s disease?

Answer 13

Mycobacterium infection of vertebrae

Question 14

What causes Pott’s Disease?

Answer 14

Hematogenous spread to bone during primary TB lung infection

Extrapulmonary TB spread during active/reactivation infection

Question 15

What is the presentation of Pott’s Disease?

Answer 15

Slow onset back pain

Lower thoracic, upper lumbar spinal tenderness to palpation, visual spinal deformity, neurological deficits at level of deformity

Question 16

How do we diagnose Pott’s Disease?

Answer 16

Presentation and exam
Radiographic evidence of vertebral involvement - X ray , MRI (best
Evidence of Mtb in aspirate or biopsies of spinal lesions - NAAT

Question 17

How do you treat Pott’s Disease?

Answer 17

Multiple anti-TB drugs for 6-9 months

Question 18

What are the characteristics of Mycobacterium leprae?

Answer 18

acid fast bacilli
Culture not possible
Causes Leprosy

Question 19

What is the pathogenesis of Mycobacterium leprae?

Answer 19

Targets marcophages and Schwann cells
Proinflammatory cell wall components

Question 20

What are the 2 disease manifestations of M. leprae?

Answer 20

Tuberculoid Leprosy

Lepromatous Leprosy

Question 21

Tuberculoid Leprosy presents with ______, very few containing few bacilli, if any, observed in biopsies.

Answer 21

Paucibacillary

Question 22

Lepromatous Leprosy presents with _______(containing many bacilli)

Answer 22

Multibacillary

Question 23

What are the skin lesions, histo, infectivity, and immune response of Tuberculoid Leprosy?

Answer 23

Few erythematous plaques, peripheral N damage

Few or no acid fast rods

Low infectivity

DTH reaction to lepromin (Th1)

Question 24

What are the skin lesions, histo, infectivity, and immune response of Lepromatous Leprosy?

Answer 24

Many erthematous macules, extensive tissue destruction

Numerous acid fast rods in skin lesions

High infectivity

No reactivity to lepromin (Th2)

Question 25

How do you diagnose M. leprae?

Answer 25

1. Clinical observation 2. Skin biopsy of leading edge of most active plaque with histo staining, acid fast staining, NAAT

Question 26

What 2 tests may be negative in tuberculoid leprosy?

Answer 26

Acid fast staining NAAT

Question 27

How do you treat M. leprae?

Answer 27

Antibiotics

Question 28

What are Nocardia and Actinomyces?

Answer 28

Gram + filamentous bacteria in branches

Question 29

What are the characteristics of Nocardia?

Answer 29

Aerobic gram + rod Weakly acid fast - cell wall contains mycolic acid Appear as branched filaments Slow growing (colonies in 3-5 days)

Question 30

What is the clinically relevant Nocardia?

Answer 30

N. brasiliensis

Question 31

What cutaneous infection does Nocardia cause?

Answer 31

Primary Cutaneous Nocardiosis (PCN) - usually in immunocompetent hosts

Question 32

_________ is a chronic, slowly progressive (>6 months) skin and subcutaneous tissue infection. Develops after cut/abrasion and contamination with soil and/or vegetation. Discharging sinuses are filled with organism and it is painless.

Answer 32

Mycetoma

Question 33

What bacteria cause Mycetoma?

Answer 33

Nocardia, Actinomyces

Question 34

What are the characteristics of Actinomyces israelii?

Answer 34

Gram + filamentous bacteria Anaerobes Catalase and urease negative Opportunistic - breach in barrier with dental work

Question 35

Actinomyces israelii leads to abscesses containing ________ and the most common presentation is ________

Answer 35

Sulfur granules Cervicofacial actinomycosis

Question 36

How do you diagnose Actinomycosis?

Answer 36

Filamentous gram +, non-acid fast bacteria Lack of staining with modified acid fast stain separates Actinomyces from Nocardia

Question 37

What is the clinical pattern, site, source, and agent of Actinomycosis?

Answer 37

Lump with draining sinuses Cervicofacial, thorax, abdomen, pelvic Endogenous microbiota Actinomyces israelii

Question 38

What is the clinical pattern, site, source, and agent of Nocardiosis?

Answer 38

Sporotrichoid, cellulitis, mycetoma Extremities Environment Nocardia brasiliensis

Question 39

What is a key element of acne vulgaris?

Answer 39

Inflammation due to presence/activity of Cutibacterium acnes

Question 40

What are the characteristics of Cutibacterium acnes?

Answer 40

Small Microaerophilic to anaerobic Gram positive rod Normal microbiota - inhabits sebaceous glands Stimulates inflammatory response

Question 41

A dental plaque is a _______

Answer 41

Bacterial biofilm

Question 42

What bacterial agent causes dental caries?

Answer 42

Streptococcus mutans

Question 43

How does S. mutans cause dental caries?

Answer 43

Acid produced via sugar metabolism by bacteria Acid induced demineralization

Question 44

What is gingivitis?

Answer 44

Reversible inflammation of gingiva

Question 45

What is periodontitis?

Answer 45

Chronic inflammatory disease that includes gingivitis along with irreversible loss of CT and bone support for the teeth

Question 46

Gingivitis and periodontitis is associated with __________ x2

Answer 46

Coronary heart disease Chronic kidney disease

Question 47

Periodontal diseases are caused by __________

Answer 47

Bacteria in dental plaque