A、Cats have a variety of microbes living in their fur. B、For cat bites, the real danger comes from Pasteurella multocida. C、One

"A cat bite is nothing to trivialize," said Nancy Peterson, cat programs manager at the Humane Society of the United States.(19)Up to 50 percent of cat bites become infected, said Princy N. Kumar, head of the infectious-diseases division at MedStar Georgetown University Hospital. But many people don’t take the injury seriously enough. People underestimate the danger, Kumar said, and don’t realize they should get a bite looked at right away. "They don’t realize, being bitten by a cat, you’ve got a 1-in-2 chance of getting infected. "(20)"If you got a really bad bite, you should get prophylactic antibiotics(预防性抗生素)," Kumar said. A light nip is not a problem, she said, but seek help if the cat has really sunk its teeth in—"if you see a puncture wound and blood coming out of it. " Unlike dogs, which tend to deliver superficial, crushing bites that don’t penetrate far into tissue, cats inflict puncture wounds with their long teeth, which inject bacteria from the cat’s mouth and the environment deep into tissue. And, Peterson said, "Cats have pretty potent bacteria. "(21)While cats have a variety of microbes living in their mouths, the real trouble comes from Pasteurella multocida(多杀性巴氏杆菌), a bacterium that can cause bad infections. One study found that 90 percent of domestic cats are carriers. Dogs also carry these bacteria, first isolated by Louis Pasteur and named after him, but the infection rate from their bites doesn’t come close to cats’ 50 percent.
19. According to the passage, how many of the cat bites become infected?
20. What does Kumar say about cat bites?
21. What can we know about bacteria from cats’ mouths?