New mechanisms of bacterial resistance to antimicrobial agents

Article Abstract:

The discovery of penicillin prompted some early enthusiasm that the end was near for infectious bacteria. Bacteria, however, can develop resistance to antibiotics, and soon resistance to penicillin turned up in some strains. Now it seems evident that, given time, bacteria will develop resistance to virtually any antibiotic, and the fight against bacterial infections has become a constant battle between the genetic variability of bacteria and the ability of man to design and synthesize new pharmaceuticals. The authors provide an in-depth review of bacterial drug resistance which covers a broad variety of organisms and antibiotic compounds. There are both old and novel methods for the development of drug resistance. The first recognized method of developing antibiotic resistance is the expression of beta-lactamases. The molecular structure of penicillin, and many of the antibiotics to follow, is based on the beta-lactam ring. Beta-lactamases are enzymes which cleave this ring. Over 30 different varieties of beta-lactamases have been identified which are genetically coded for by plasmids, that is by loops of DNA outside of the bacterial chromosome. These plasmids may be promiscuously shared among bacteria in recombinant DNA experiments sanctioned only by nature. Once man has placed selective pressure on bacteria through the use of antibiotics, those with the right plasmid are able to survive, grow, and multiply. However, beta-lactamases are far from the only mechanisms of antibiotic resistance. Antibiotics generally bind to a particular site in or on a bacterium; the bacteria may simply alter the structure of this site. Enzymes like aminotransferase and nucleotidyltransferase can inactivate antibiotics such as gentamicin and chloramphenicol. Furthermore, some bacteria have invented entirely new methods for ejecting from within offending molecules such as erythromycin and tetracycline. The pharmaceutical industry works constantly to develop new molecules designed with a knowledge of the resistance strategies in current vogue with the bacteria. Perhaps even newer techniques of genetic engineering will help; the alternative may be a world in which antibiotics are lost as a tool against infection and the only solution is the return of the isolation ward. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Antibiotics, Physiological aspects, Drug resistance in microorganisms, Microbial drug resistance, R factors

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Staphylococcus aureus bacteremia -- consider the source

Article Abstract:

All patients who are admitted to a hospital should be tested to see if they have Staphylococcus aureus in their nasal passages. Hopefully, a rapid diagnostic test will be designed for this purpose. A study of hospital patients with Staphylococcus aureus blood infections found that in most cases, the bacterium came from their own nasal passages, not from another person.

Editorial, Staphylococcus aureus, Bacteremia

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The new beta-lactamases

Article Abstract:

The new beta-lactamases that include extended-spectrum beta-lactamases (ESBLs), plasmid-mediated AmpC enzymes, and carbapenem-hydrolyzing beta-lactamases confer resistance to the beta-lactam antibiotics. The properties of these new beta-lactamases, the ways in which they can be detected, their origins and options for treating the associated infections are discussed.

United Kingdom, Science & research, Research, Beta lactam antibiotics

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