Microbiology

Question 1

What are mechanisms of bacterial resistance to Penicillin?

Answer 1

Beta-lactamase production
Alteration of PBPs
Prevention of access

Question 2

Mechanism of bacterial resistance to Vancomycin?

Answer 2

Alteration of terminal D-alanine to D-lactate such that Vanco can’t recognize and exert its anti-crosslinking effect.

Question 3

Serum-resistent vs serum-sensitive?

Answer 3

Serum-Resistant = If Gram (-) have long O chain then protect against complement-mediated lysis. (But susceptible to clearance d/t antibodies formed after repeated exposure to the bacteria)
Serum-Sensitive = Gram (-) bacteria w/o Chain can't be targeted by clearance but are targeted by complement mediated lysis

Question 4

How does toxic shock syndrome result from high LPS concentrations?

Answer 4

In the blood, LPS binds to a plasma protein (LPS-binding protein; LBP) and this complex interacts with CD14 receptors on monocytes and macrophages. The LBP-CD14 complex activates a membrane protein called Toll- like receptor-4 (TLR-4), resulting in the production of cytokines. These are primarily the proinflammatory cytokines IL-1 and TNF, which act synergistically to induce fever, alter endothelial cells leading to increased adherence of leukocytes to endothelial surfaces, stimulate the production of leukotrienes and prostaglandins and produce a secondary wave of cytokine production with concomitant effects on a number of physiologic targets resulting in the septic shock syndrome.