Nosocomial infections

Question 1

Which diseases are caused by group A Streptococci (GAS) or streptococcus pyogenes.

Answer 1

PURULENT

1. Angina
2. Necrotizing fascitis
3. puerperal sepsis (childbed fever)
4. wound infections and abscesses

TOXIN DERIVED

1. scarlet fever
2. streptococcal toxic shock syndrome

IMMUNO PATHOLOGICAL

1. Reumatic fever
2. Endocarditis
3. Acute glumerulonephritis

Question 2

What are the major pathomechanisms involved with GAS

Answer 2

1. Production of toxins like (Erythrogenic toxin and superantigens)
2. immunological crossreations with and distruction of cardiac myosin
3. deposition of immunocomplexes in kidney and joints
4. secreted factors like streptokinase and streptolysin which leads to local infection.
5. M- proteins, Fimbrae and secreted factors which cause inflammation

Question 3

How can S. pneumoniae infections be prevented

Answer 3

Vaccination.

Pneumococcal polysaccaride vaccine or Pneumococcal conjugate vaccine

Question 4

Define the term health care associated infections

Answer 4

localized or systemic infecetion caused by adverse reaction to the prescence of an infectious agent or its toxin which was contracted in a hospital (considering its abscence before admission or incubating at time of admission)

Question 5

What are the most common bacteria causing HCAI

Answer 5

1. Staphylococcus (MRSA and coagulase negative staph)
2. E. coil, Klebsiella sp. and other enterobacteria
3. Pseudomonas areuinosa
4. Vancomycin- resistant entorcocci

Question 6

How does S. aureus cause disease

Answer 6

1. production of toxins and extracellular enzymes
2. Interation with host proteins and cells
3. inhibition of host immune system
4. Acquisition of resistance genes (mec-A)

Question 7

Describe the impact of biofilms on staphilococcal HCAI

Answer 7

1. simple diffusion barrier
2. binding to positively charged antibiotic molecules rendering them inactive
3. antenuation of host response
4. retention of host nutrients

Question 8

What is the genetic and functional mechanism of methicilin resistance in Staph.

Answer 8

Development of resistane to B-lactam antibiotics because of the development of the mec-A gene which endodes the penicillin binding protein 2a (Pbp2a) which has lower affinity for the beta lactam ring.

Question 9

Discuss the recent trends in antibiotic resistance development

Answer 9

a