Bacterial Infx in Papules, Plaques

Question 1

Mycobacterium leprae

Answer 1

• Acid-fast rods ’Gr+’
• Nonmotile, nonsporeforming
• Aerobe
• *Obligate intracellular parasite
• Natural hosts: humans, armadillos; has also been found in chimpanzees, certain monkeys
o Endemic in armadillos Texas, Louisiana
• Optimum temp. 27-33°C
• M. leprae affects mostly skin, superficial peripheral nerves, anterior chamber of eyes, testes
• Waxy lipid coat’ responsible for:
o Extremely hydrophobic nature
o Acid-fastness (Ziehl-Neelsen)
• *auramine O, more sensitive- binds mycolic acid
o Clumping = *cord factor
• Granuloma formation
o *Epithelioid cells
o *Multinucleate giant cells
DISEASE
Leprosy= Hansen disease
o *Cardinal signs skin lesions w/ altered sensation, thickened peripheral nerves, acid-fast bacilli in skin biopsies
• 2 Types of Hansen disease
o *Tuberculoid leprosy= paucibacillary Hansen disease
o *Lepromatous leprosy= multibacillary Hansen disease

Question 2

Mycobacterium marinum

Answer 2

• Acid fast rod
• Fresh, salt water
• Cutaneous infect. humans
• Slow-growing
• 30°C
• *Photochromogen (bright yellow pigment induced by light)
• Waxy lipid coat’ responsible for:
   o Extremely hydrophobic nature
   o Acid-fastness (*Ziehl-Neelsen)
     • *auramine O, more sensitive- binds mycolic acid
   o Clumping = *cord factor
• Granuloma formation 
   o *Epithelioid cells
   o *Multinucleate giant cells
DISEASE
- *‘Swimming pool granuloma’, ‘fish tank granuloma’

Question 3

Neisseria gonorrhoeae

Answer 3

• Small Gr- diplococcus, ‘the gonococcus’
   o ‘Kidney bean’ 
• Obligate human pathogen
    o	Rapidly killed by drying, sunlight, moist heat, many disinfectants
• Facultative intracellular
• Aerobe to facultative anaerobe
• Oxidase +
• Catalase +
• *Oxidizes glucose
LABS
• Fastidious
• Chocolate or Thayer-Martin
• CO2, humidity
VIRULENCE** (ALL)
• Adhesins
• Opa  
• Pili
• IgA1 protease
• Facultative intracellular	- Antigenic and phase variation Opa’s, pili, LOS
• Bind host sialic acid to their LOS
• Outer-membrane blebbing
DISEASE
- Disseminated gonococcal infection (DGI)

Question 4

Neisseria meningitides

Answer 4

• Gr- diplococcus
o *Normal microbiota nasopharynx ~10%
• Facultative intracellular
• Aerobe to facultative anaerobe
• Oxidase positive
• Catalase positive
• *Oxidizes glucose and maltose
LAB
• Blood, chocolate, Thayer-Martin 
VIRULENCE** ALL
• LOS
• **Capsule (compared to N. gonorrhoeae)
• IgA1 protease
• Facultative intracellular
 - Bind host sialic acid to LOS
• Outer-membrane blebbing
DISEASE
• The leading cause bacterial meningitis children, young adults U.S.
• A leading cause sepsis
- **Meningococcemia