micro skin intro

Question 1

skin normal flora:

skin pathogens:

Answer 1

Propionibacterium acnes.
diphtheroids.
coagulase-negative staphylococci.

P. aeruginosa in axilla, perineum

Question 2

Nail or nail bed lesions

Answer 2

Distal subungual onychomycosis.
White superficial onychomycosis (Leukonychia mycotica).
Proximal subungual onychomycosis found in patients with

Question 3

Agents of Nail or nail bed infections

Answer 3

Half caused by fungi.
Tinea unguium (Onychomycosis) Ringworm of the nails: Trichophyton rubrum and
T. metagrophytes account for 90% of dermatophytic nail infections, Epidermophyton
no hair the remainder

Paronychial or onychomycotic candidosis/ Candidal onychomycosis (NOT a
dermatophytic manifestation) Candida sp./C. albicans.

GNR (esp. P. aeruginosa).

Question 4

agents of Stratum Cornium (color change) infection

Answer 4

Pityriasis versicolor/Tinea versicolor:
Malassezia furfur
Hortaea (Exophiala) werneckii

Question 5

agents of Keratin Layer infections

Answer 5

(Highly variable; papulosquamous to vesicular):
Ringworm/Dermatophyte fungi:
Microsporum, Epidermophyton, Trichophyton

Question 6

Agents of Epidermis Including Hair and Sebaceous Gland infections

Answer 6

Maculopapular which may become  vesicular:

• Erythema infectiosum: Parvovirus B19,
• Exanthem subitum: HHV6, HHV7,
• Measles/Rubeola: rubeola/measles virus
• 3-day Measles/Rubella: rubella virus
• Enteroviral infections: ECHOvirus (enteric cytopathic human orphan virus – many [31] serotypes);Coxsackie viruses (A and B - many [30] serotypes;) Enteroviruses 68- 71
• Karposi sarcoma: HHV-8,
• Chicken pox-Shingles: Varicella zoster virus (HHV3)

Question 7

MORE Agents of Epidermis Including Hair and Sebaceous Gland infections

Answer 7

• Cold Sores: HSV-1 and 2
• Scarlet fever: Streptococcus pyogenes,
• Bullous impetigo: Staphylococcus aureus
• Epidemic impetigo: (Staphylococcus aureus, Streptococcus pyogenes)
• Dermatomycosis: Cutaneous Candidiasis

Question 8

Agents of Hair Endothrix or Ectothrix infections

Answer 8

• White Piedra: Trichosporon biegelii resembles nits and lice- Ectothrix
• Tinea capitis: Microsporum and Trichophyton spp.- Ectothrix
• Black Piedra: Piedra hortai (resembles endothrix of Trichophyton)
• Tinea favosa: Trichophyton – endothrix.

Question 9

agents of Hair and face (bearded areas of face) infections

Answer 9

Tinea barbae (Barber’ s itch): anthropophilic strains of Trichophyton rubrum and zoophilic strains of T. mentagrophytes or T. verrucosum
Microsporum, Epidermophyton

Question 10

agents of Hair and scalp infections

Answer 10

Tinea capitis (Ringworm of the scalp and hair): Microsporum or Trichophyton species. M. audouinii and M. canis are responsible for most infections in US.

Question 11

agents of Hair and scalp or Hair and glabrous skin infections

Answer 11

Tinea favosa (Honeycomb ringworm) T. schoenleinii.

Question 12

Dermis: Lymphatic infections

Answer 12

Cervicofacial lymphadenitis in children (Mycobacterium haemophilum).
Erysipelas (Streptococcus pyogenes)
Sporotrichosis (Sporothrix schenckii)
Onchocerciasis, or River Blindness (Onchocerca volvulus)

Question 13

agents of Hair follicle and sebaceous gland with surrounding tissue (Pustular lesions) infections

Answer 13

Acne vulgaris - inflammatory: Propionibacterium acnes
Folliculitis (Superficial infection of individual hair follicle and apocrine regions): S. aureus, GNR, M. furfur
Furuncles( boils): S. aureus
Carbuncles: S. aureus
Small Pox: Variola major virus
Tinea barbae: Microsporum, Epidermophyton, Trichophyton

Question 14

agents of Subcutaneous fat and tissue infection

Answer 14

Cellulitis: bacteria, fungi, viruses
Ecthyma: B-hemolytic Streptococcus pyogenes
Erysipelas: B-hemolytic Streptococcus pyogenes
Sporotrichosis: Sporothrix schenckii
Mycetoma: bacteria and fungi [large numbers of various microorganisms are associated
with mycetoma formation including Actinomyces israelii]).
Lobomycosis/Lobo’s Disease: Loboa loboi
Chromoblastomycosis: fungi
Phaeomycotic cysts: over 30 different fungal agents
Onchocerciasis, or River Blindness: Onchocerca volvulus

Question 15

Fascia infections

Answer 15

necrotizing fasciitis: S. pyogenes; mixed anaerobic infection, etc.

Question 16

muscle infections: myonecrosis

Answer 16

-Gas gangrene/clostridial myonecrosis: Clostridium perfringens, etc.
-Pyomyositis: pyogenic infection of striated muscle with abscess formation: S. aureus
-Trichniosis helminthic infection of striated muscle - Trichinella spiralis.
-Rhabdomyolysis infection of striated muscle: Legionella; pneumococcus,
influenzavirus

Question 17

muscle infections: myopathy

Answer 17

Rheumatic fever: an autoimmune disease due to cross-reactive bacterial (GAS) antigens, acute RF can also involve myocardium, not just valves. Second most commonly acquired-heart disease in US children

Kawasaki disease (AKA mucocutaneous lymph node syndrome): an acute vasculitis of infants and young children. Most commonly acquired-heart disease (aortic aneurism) in US children

Infectious Endocarditis

Question 18

Infectious disease of muscle (All are rare): Acute myopathy: viral etiology

Answer 18

Influenza virus A, B;
Coxsackieviruses A, B (esp. type B);
HIV;
Human Parvovirus B19,
Parainfluenzavirus
adenovirus
mumps
echoviruses
polio viruses
herpes simplex virus 2
Epstein Barr virus
CMV
Hepatitis A or C.

Question 19

Infectious disease of muscle (All are rare): Acute myopathy: bacterial etiology

Answer 19

S. aureus.
Streptococcus pyogenes (GAS).
streptococcal &/or polymicrobic infections.
Clostridia perfringens, type A.
actinomycetes.
MTB.
M. leprae.
Lyme disease.
syphilis.
Legionella.
diphtheria (heart).

Question 20

Infectious disease of muscle (All are rare): Acute myopathy: fungal etiology

Answer 20

candidiasis, coccidioidomycosis, sporotrichosis

Question 21

Infectious disease of muscle (All are rare): Acute myopathy: protozoans

Answer 21

toxoplasmosis
schistosomiasis
Trypanosoma cruzi and the inflammatory disease of the heart associated with
Chagas’ disease.

Question 22

Infectious disease of muscle (All are rare): Acute myopathy: Helminths

Answer 22

Trichinosis - Trichinella spiralis - LEARN,
cysticercosis
echinococcosis.

Question 23

Infectious disease of muscle: pyomyositis

Answer 23

abscess formation in striated muscle: S. aureus.

Question 24

Infectious disease of muscle: rhabdomyolysis:

Answer 24

a clinical syndrome characterized by muscle pain, release of creatine kinase and myoglobin from muscle caused by:

infection (bacterial, most commonly Legionella spp.; viral, e.g., influenzavirus).
trauma
hyperthermia
ischemia
drugs
toxin,
electrolyte disorders.

Question 25

infections of muscle: Kawaski disease

Answer 25

vasculitis

Question 26

infections of muscle: myonecrosis- LEARN

Answer 26

monomicrobic:

a. C. perfringens, type A
b. S. aureus
c. GAS

polymicrobic.

Question 27

G- rods (anaerobic bacteria)

Answer 27

Aggregatibacter (AKA Actinobacillus actinomycetemcomitans;(obligate anaerobe).
Bacteroides fragilis, ureolyticus, forsythus (obligate anaerobe).
Bilophila wadsworthia (obligate anaerobe).
Fusobacterium spp. (obligate anaerobe long rods with tapered ends).
Pasteurella multocida, pestis.
Porphyromonas gingivalis (obligate anaerobe).
Prevotella intermedia (obligate anaerobe).

Question 28

G- Cell Wall Architecture (anaerobic bacteria)

Answer 28

Spirochetes ( internal flagella):

Treponema denticola, T. vincentii (obligate anaerobes)

Question 29

G+ cocci (anaerobic)

Answer 29

Enterococcus faecalis, faecium. (cocci in pairs and chains -
aerotolerant anaerobes).

Peptostreptococcus spp. (obligate anaerobic, cocci in chains) Taxonomic validity of
grouping agents anaerobic, cocci in chains in this genus is in doubt.

Streptococci (cocci in chains - aerotolerant anaerobes):

• Streptococcus agalactiae – Group B strep (GBS),  hemolytic.
• Streptococcus bovis (GIT streptococci),  hemolytic.
• Streptococcus mutans, sanguis, salivarius, mitis (oral streptococci).
• Streptococcus pneumoniae – (lancet shaped diplococci,  hemolytic)
• Streptococcus pyogenes – Group A strep (GAS),  hemolytic

Question 30

G+ rods

Answer 30

Bifidobacterium spp. (obligate anaerobe).
Clostridium species (short rod, anaerobic, spore former[endosores])
a. C. perfringens, type A
b. C. septicum
c. C. noveyi
-Lactobacillus spp. (box-car shaped, aerotolerant anaerobe).
-Gram-positive, thin, branching filaments with clubbed ends (Actinomycetes):
-Clubbed-shaped rod – Propionibacterium acnes (anaerobe).

Question 31

Gram-positive cell wall structure but stain Gram-variableGram-negative:

Answer 31

Rods/pleomorphic shapes: Gardnerella vaginalis (obligate anaerobe).

Curved rods: Mobiluncus morphotypes/spp. (obligate anaerobe).

Question 32

risk: Recurrent hospital admissions

Answer 32

MRSA

Question 33

risk: Contact sports, recurrent boils/abscesses, visiting certain states in the USA

Answer 33

MRSA; MSSA producing Panton-Valentine leukocidin

Question 34

risk: DM

Answer 34

MRSA; MSSA; group B streptococci; anaerobes; Gram- negative bacilli

Question 35

risk: neutropenia

Answer 35

Gram-negative bacilli; Pseudomonas aeruginosa

Question 36

risk: bite wounds

Answer 36

human: Human oral flora (Ekinella)
cat: Pasteurella multocida
dog: Capnocytophaga canimorsus
rat: Streptobacillus moniliformis (also consider tetanus and rabies)

Question 37

risk: animal contact

Answer 37

Campylobacter spp.; dermatophyte infection; Bartonella henselae; Francisella tularensis; Bacillus anthracis; Yersinia pestis

Question 38

risk: water exposure

Answer 38

Vibrio spp.; Aeromonas hydrophila; Mycobacterium marinum; Ps. aeruginosa

Question 39

risk: reptile contact

Answer 39

Salmonella spp.

Question 40

risk: IVDU

Answer 40

MRSA; Clostridium botulinum; Clostridium tetani

Question 41

risk: Travel to tropical regions of Africa or America

Answer 41

Leishmaniasis; cutaneous larva migrans; myiasis;

Cordylobia anthropophaga; Dermatobia hominis