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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 10 year old girl presents with sore throat and fever. She denies any cough or rhinorrhea. A throat culture grows bacitracin-sensitive bacterial colonies. The infecting organism would be protected from the lytic action of detergents by its?
assistant
The correct answer is  This girl has streptococcal pharyngitis. The infecting organism is group A beta-hemolytic streptococcus (S. pyogenes); its growth is inhibited by the placement of a bacitracin disk on the throat culture plate. (Beta-hemolysis occurs as the result of the bacterial hemolysin streptolysin S). This is a gram-positive bacterium and therefore possesses a very thick peptidoglycan layer that would protect it from lysis by detergents. (Note that gram-positives also contain teichoic acid.) In contrast, gram-negatives have a thin peptidoglycan layer. Keratin-like proteins in the spore coat and calcium ion chelators (dipicolinic acid) are found in spores formed by species of Bacillus and Clostridium. These protect the spores from the elements: dehydration, heat, chemicals, radiation, etc. Lipopolysaccharide in the outer membrane and a periplasmic space are found in gram-negative organisms. The lipopolysaccharide is an endotoxin and the periplasmic space contains beta-lactamase in some species. Ref: Ray C.G., Ryan K.J. (2010). Chapter 25. Streptococci and Enterococci. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.