21. Principles of Disease

Diseases that are naturally spread from their usual animal hosts to humans are called ___________ .

Nonliving reservoirs of disease, such as a toothbrush, drinking glass, and needle, are called __________ .

__________ infections are those acquired by patients or staff while in health care facilities.

The total number of cases of a disease in a given area is its __________.

An animal that carries a pathogen and also serves as host for the pathogen is a ___________ vector.

List three conditions that create opportunities for pathogens to become harmful in a human.

List three portals through which pathogens enter the body.

How does Staphylococcus aureus affect the matrix between cells in the human body?

a. S. aureus triggers blood clotting, which coats the matrix and inhibits cellular

communication.

b. S. aureus produces an enzyme that dissolves hyaluronic acid and thus enables it to pass between the cells.

c. S. aureus possesses a hyaluronic acid capsule that causes leukocytes to ignore the bacterium as if it were camouflaged.

d. S. aureus does not affect the matrix but instead produces a necrotizing agent that dissolves body cells.

Which of the following conditions is a systemic disease caused by Staphylococcus?

a. impetigo

b. folliculitis

c. carbuncle

d. toxic shock syndrome

Pathogenic strains that have become resistant to antimicrobial drugs are found in which of the following genera?

a. Staphylococcus

b. Mycobacterium

c. Enterococcus

d. all of the above

The bacterium causing pseudomembranous colitis is

a. Clostridium difficile

b. Streptococcus pyogenes

c. Mycobacterium avium-intracellulare

d. Corynebacterium diphtheriae

Which of the following is not characteristic of mycoplasmas?

a. Cytochromes

b. Sterols in cytoplasmic membranes

c. Use of UGA codon for tryptophan

d. rRNA nucleotide sequences similar to those of Gram-positive bacteria

For each of the following diseases or conditions, indicate the genus (or genera) of bacterium that causes it.

___ Scalded skin syndrome

___ Osteomyelitis

___ Pharyngitis

___ Scarlet fever

___ Pyoderma

___ Rheumatic fever

___ Glomerulonephritis

___ Sinusitis

___ Otitis media

___ Anthrax

___ Myonecrosis

___ Diphtheria

___ Leprosy

___ Dental caries

___ Acne

A. Staphylococcus

B. Streptococcus

C. Mycobacterium

D. Listeria

E. Propionibacterium

F. Corynebacterium

G. Bacillus

H. Clostridium

I. Actinomyces

Why are mycoplasmas able to survive a relatively wide range of osmotic conditions, even though these bacteria lack cell walls?

Mycobacterium avium-intracellulare was considered relatively harmless until the late 20th century, when it became common in certain infections. Explain how this bacterium’s pathogenicity changed.