At present, hospital and nonhospital settings worldwide are facing unprecedented crises from the rapid emergence and distribution of microbes resistant to one or more antimicrobial agents. Strains of Staphylococcus aureus resistant to methicillin and other antibiotics are endemic in hospitals. Unfortunately, the number of useful drugs against these infections is limited. S. aureus strains with reduced susceptibility to vancomycin have emerged recently in Japan and the U.S., and this is a serious problem for patients and medical care workers. Currently, ca. 30% of Streptococcus pneumoniae isolates are resistant to penicillin, the primary drug used to treat this infection. Many penicillin-resistant strains are also resistant to other antimicrobial drugs. S. pneumonia is responsible for thousands of cases of meningitis and pneumonia, and several million cases of ear infection in the U.S. every year. For sexually transmitted disease clinics that monitor outbreaks of drug-resistant infections, doctors have found that more than 30% of gonorrhea isolates are resistant to penicillin or tetracycline, or combinations of both.
About a half-billion people worldwide are infected with the parasites that cause malaria. Resistance to chloroquine, the drug of choice for preventing and treating malaria, has emerged worldwide. Also, resistance to other antimalarial drugs is widespread and growing.
Strains of multidrug-resistant tuberculosis have emerged over the last decade and pose a particular threat to vulnerable people, e.g., those infected with HIV. Drug resistant strains are as contagious as drug-susceptible ones. Multidrug-resistant tuberculosis is more difficult and more expensive to treat, and patients may remain infectious longer because of inadequate treatment.