<prompt> 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?Keratin-like proteins in the spore coatLipopolysaccharide in the outer membranePeptidoglycan layerPeriplasmic space  <response>: 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. 