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Suggested Answers for Insight Questions, Foundations in Microbiology, 7th Edition, listed by chapter, number, and page location. A note to the users of these answers: These answers discuss some of the possible ways to approach the questions. They are not meant to be exhaustive in depth, but can offer information, suggestions, and points of view that will be helpful in understanding some of the concepts covered in the Insight and the chapter. Furthermore, they are not the final word--you may have thought of some other explanations that are just as valid. It is hoped they will serve to stimulate class discussion and inspire further research. 20.1, pg. 597 – Gram-Negative Sepsis and Endotoxic Shock One of the problems with a diabetic patient is that they have reduced circulation in their skin, and this often leads to diabetic ulcers and sores on extremities and surfaces that are exposed to pressure. Such ulcers will compromise the epithelial barrier, and this provides a route of infection for even commonplace microbes, whether true pathogens or opportunists. Gram negative rods are widely distributed in the environment, in the normal flora, and on fomites, so the likelihood of them becoming inoculated into an ulcer is high. They could readily enter the body and move via lymphatics into the bloodstream. Their presence in the blood stream means that have freedom to grow, increase in numbers, cause sepsis, and the cells will give off endotoxins into the bloodstream as their cell walls break down. Treating the infection with a drug that lyses the cells will actually make the problem even worse. The final assault will be the effect that endotoxemia has on organ function, leading to shock. 20.2, pg. 603 – Diarrheal Disease Microbes can cause damage by destroying cells and tissues of the gut (invasive) or they can alter the function of intestinal cells and tissues by releasing toxins locally (toxigenic). The first case may be accompanied by severe ulceration and bloody diarrhea and can be very dangerous if the intestine perforates into the peritoneal cavity. Toxigenic disease is more insidious and just as dangerous because the toxins released by the infectious agents disrupt the natural activity of the intestinal cells and induce them to pump out large quantities of electrolytes and water into the GI tract. This dehydration and electrolyte loss is not just local in its effects. It can pull water from fluid compartments, lowering blood pressure and shutting down organ function. The loss of critical Na+ and Cl- affects muscle and nerve function and may cause heart failure, coma, and death if the fluids are not replaced. 20.3, pg. 611 – Avoiding Gastrointestinal Infections In countries where the water supply is not purified, experts recommend soaking all fruits and vegetables in water with dissolved iodine tablets. Scrubbing the outside surface of some fruits (apples, tomatoes) and vegetables (peppers, carrots) with detergent and then peeling them could greatly reduce exposure. The choice of fruits can make a difference. Bananas, oranges, and other peeled fruit are less likely to be contaminated than are berries that are not peeled. The most difficult foods to control would be fine greens and sprouts that have many nooks and crannies to trap microbes. Kitchen practices are also important. Fresh fruits and vegetables should always be cut with disinfected tools on clean dry surfaces that have not been used for meats. Such foods should be covered to protect them from mechanical vectors and refrigerated to slow growth of any microbes that they will no doubt have picked up from soil and water that cannot be washed away.