The 1990s has become known as the era of multidrug resistance. Bacteria causing several kinds of human infectious diseases have become resistant to multiple antibiotics and the different types continue to increase. Infections challenge and impede the treatment of some patients in hospitals and the community. In hospitals, organisms found include Staphylococcus aureus, Escherichia coli, Pseudomonas, and Acinetobacter. In the community, multidrug-resistant bacteria causing acquiredinfections include pneumococci, gonococci, streptococci, E. coli, and Mycobacterium tuberculosis. There is ample evidence that the antibiotic-resistance problem is global, confronting many communities worldwide. Also, it is known that resistant organisms are spreading from one country to another. Resistant organisms are making it difficult to treat sinusitis, urinary tract infections, pneumonia, septicemias, and meningitis. Two disease-causing organisms — enterococci in hospitals and Mycobacterium tuberculosis in the community and the hospital — have been linked to death because of their resistance to antibiotics.
The costs of antibiotic resistance continue to rise. Mortality and length of hospital stay are at least doubled for resistant strains of some organisms compared with susceptible ones. Treating resistant infections often requires the use of more expensive drugs or more drugs with significant side effects, resulting in longer hospital stays for infected patients. The Institute of Medicine, a part of the National Academy of Sciences, has estimated that the annual cost of treating antibiotic-resistant infections in the U.S. may be as high as $30 billion.
Besides the hospitalized and immunocompromised persons, children attending day-care centers and elderly patients in nursing homes are susceptible risk groups. To make the situation worse, about half of the pharmaceutical companies in the U.S. abandoned the once lucrative antimicrobial field in the mid-1980s. A key reason for the development of antimicrobial resistance is the ability of infectious organisms to adapt quickly to new environmental conditions. Microbes are, in essence, single-celled organisms that have a small number of genes. Subsequently, even a single arbitrary gene mutation can have a large impact on their disease causing properties. Because of the high replication rates of microbes, mutations can evolve rapidly. Many mutations essentially help a microbe survive in the presence of an antibiotic drug, which could quickly predominate throughout the microbial population. Microbes commonly acquire genes, including those encoding for resistance, by direct transfer from organisms of their own species or from unrelated microorganisms. This inborn adaptability of microbes has been complicated by the widespread and inappropriate use of antimicrobials. Ideal conditions exist for the emergence of drug-resistant microbes when antibiotics are prescribed for the common cold and other conditions for which they are not required or when individuals do not complete or forget to take their prescribed treatment regimen. Hospitals can also provide a fertile environment for drug-resistant pathogens because of the close contact between sick patients and extensive use of antimicrobial force pathogens to develop resistance.