Chapter 19 - Bacterial Infections of Humans

Question 1

Acne

Answer 1

Cause: Propionibacterium sp.

Question 2

Anthrax

Answer 2

Cause: Bacillus anthracis
Reservoirs: anthrax infected animals, spores in soil, animal hair, wool, animal skins and hides
Other: Can affect the skin, lung inhalation, GI tract - inhalation and GI tract can be fatal

Question 3

Gas gangrene

Answer 3

Cause: Clostridium sp.
Reservoirs: soil
Other: spores enter and germinate in wounds-produces necrotizing enzymes and toxins. Rapid tissue destruction.

Question 4

Leprosy (Hansen disease)

Answer 4

Cause: Mycobacterium leprae
Reservoirs: infected humans, armadillos
Other: Two types - lepromatous (nodules on the skin) and tuberculoid (few skin lesions, not contagious). Both have peripheral nerve involvement. Can become severe - loss of sensation.

Question 5

Staphylococcal skin infections (all hair follicle infections)

Answer 5

Cause: usually S. aureus, S. pyogenes (impetigo)
Reservoirs: infected humans, people with draining lesions or discharges

Question 6

Streptococcal skin infections (impetigo, scarlet fever, necrotizing fasciitis, erysipelas)

Answer 6

Cause: Streptococcus pyogenes
Reservoirs: infected humans (respiratory droplets)

Question 7

Otitis externa

Answer 7

Cause: E. coli (lakes and bird poop), Pseudomonas aeruginosa, Proteus vulgaris, S. aureus
Reservoirs: lakes and contaminated swimming pools
Other: Outer ear canal infection –itching, redness, swelling, impaired hearing

Question 8

Otitis media

Answer 8

Cause: bacteria or virus
Other: Persistent and severe earache, pressure on middle ear, bulging of eardrum

Question 9

Bacterial conjunctivitis

Answer 9

Cause: H. influenzae, S. pneumoniae
Reservoirs: infected humans
Other: irritation and reddening of conjunctiva, discharge. Highly contagious.

Question 10

Chlamydial conjunctivitis

Answer 10

Cause: Chlamydia trachomatis
Reservoirs: infected humans
Other: same as bacterial conjunctivitis, but in babies can cause conjunctiva and cornea scarring.

Question 11

Trachoma (chlamydia keratoconjunctivitis)

Answer 11

Cause: Chlamydia trachomatis
Reservoirs: infected humans via direct contact with infectious nasal or ocular secretions
Other: Results in scarring of cornea and conjunctiva, deformed eyelids and blindness. Found in poverty stricken areas of hot, dry Mediterranean countries and the Far East.

Question 12

Gonococcal conjunctivitis

Answer 12

Cause: Neisseria gonorrhoeae
Reservoir: infected humans, infected maternal birth canal

Question 13

Virulence factors

Answer 13

Adherence 
Factors that disable complement
Factors that allow organisms to escape
Phagocytosis
Factors that suppress immune host systems
Endotoxins 
Exotoxins
Necrotizing enzymes

Question 14

Wound infections

Answer 14

Opportunistic indigenous microbes and environmental microbes can cause infection. Can cause a local or deep tissue infection. Can become systemic