06 - Bacteriology Review

Question 1

Describe and discuss the features of gram negative rods (bacilli)

Answer 1

Elongated.
Enteric rods: Facultative anaerobes, found in GI tract (normal flora or infectious), soil, and water (eg Escheria coli).
Nonenteric rods: Aerobes, common cause of respiratory tract penetration.

Question 2

Describe and discuss the features of gram negative cocci

Answer 2

Spherical. Can be aerobes or facultative anaerobes. Cytoplasmic (inner) cell membrane and outer membrane with periplasmic space in between containing the thin peptidoglycan layer. Outer membrane contains embedded lipopolysaccharides which act as antigens and are used to ID strains/species (eg Neisseria gonorrhoeae).

Question 3

Describe and discuss the features of gram positive rods (bacilli) and cocci

Answer 3

Both can be aerobes or facultative anaerobes. Cytoplasmic cell membrane and exterior thick, multilayered, peptidoglycan cell wall. Teicholic acids are surface antigens covalently linked to peptidoglycan wall (eg Staphylococcus aureus and Streptococcus pyogenes

Question 4

Describe and discuss the features of bacteria without cell walls

Answer 4

Mycoplasma classification. No peptidoglycan cell walls. Enclosed in trilaminar plasma membrane (lipid bilayer) - pleomorphic (can alter shape). Extremely small, found in nature and mouth/GU tract of mammals (eg Mycoplasma pneumoniae and Mycoplasma hominis).

Question 5

Describe and discuss the features of acid fast bacteria

Answer 5

Stains are used to ID organisms with waxy materials in their cell walls. Most bacteria can be decolorized with alcohol but acid fast bacteria retain stain. Free living. Used clinically to identify certain infections to Mycobacterium. Intracellular infections which leads to tissue destruction (eg Mycobacterium tuberculus and Mycobacterium leprae).

Question 6

Describe and discuss the features of obligate intracellular parasites

Answer 6

Bacteria that can only grow within host cells.