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Antibiotics: what are they and how do they work?
#20
It is important not to become confused between bacteriophages, which are viruses that infect bacteria rather than eukaryotes, and the multiple types of viruses that directly infect eukaryotes including humans, and cause illnesses such as influenza, measles, chicken pox, AIDS and rubella. Antibiotics are antibacterial drugs that kill bacteria and are useless in terms of killing the types of viruses that directly infect humans; as another reply in this discussion thread points out this would require therapy with specific anti-viral medications or can be prevented by vaccinations such as the MMR against measles, mumps and rubella. However, they can be useful if the viral infection then leaves the patient susceptible to secondary bacterial infections, as mentioned by another poster.

Bacteriophages, which infect bacteria are found as part of our gastrointestinal microbiota, for example, as they infect the bacteria in our gut. These bacteriophages express antibiotic resistance genes which are thought to be protective in maintenance of gut health as they help protect the ‘good’ bacteria against the harmful effects of naturally occurring antibiotics. This expression of antibiotic-resistance genes has been a feature of bacteriophages since long before antibiotics were used therapeutically. For example, antibiotic-resistance genes have been identified in bacteriophages found in fossilised faecal samples dating from the 14th century; the presence of these bacteriophages in coprolites (fossilised faecal samples) is indicative that they would have been present in the gastrointestinal tract. Many of the bacteriophage sequences identified were related to phages that we know currently infect bacteria commonly identified in stools, including both harmless, helpful and pathogenic bacteria. They differ taxonomically from bacteriophages identified in modern faecal samples but functionally their role in antibiotic resistance has been conserved. This interesting study has been considered before in a news article on this website (http://www.biotechnologyforums.com/thread-3141.html).

However, such bacteriophages with antibiotic resistance genes also infect pathogenic bacteria, which would contribute to their resistance to antibiotics, as well as these bacteria evolving their own direct antibiotic resistance mechanisms faster than scientists can develop new antibiotics. Over-prescription of antibiotics over time, for example in cases of viral infections, has contributed to the growing public health crisis of multidrug resistant ‘superbugs’. Multi-drug resistant bacteria, such as extended-spectrum β-lactamase (ESBL)–producing Enterobacteriaceae, third-generation cephalosporin-resistant (G3CR) Enterobacteriaceae and methicillin resistant Staphylococcus aureus are now a serious international public health threat. In response to the international nature of this threat, a joint programme initiative, namely the Joint Programme on Antimicrobial Resistance (JPIAMR), has been launched to aims to gather research funders from nineteen European countries, Canada and Israel, as well as having support from other countries ranging from Australia to South Africa (http://www.biotechnologyforums.com/thread-3373.html).

Various research avenues are being explored in an effort to win the battle of antibiotic resistance, for example developing use of uncultured bacteria, which comprise approximately 99% of all bacterial species in external environments, as a source of antibiotics. An example of this was published last week in the journal Nature, in which a new antibiotic called teixobactin, derived from growth of uncultured bacteria, is described. Teixobactin inhibits bacterial cell wall synthesis and when tested on mutant Staphylococcus aureus or Mycobacterium tuberculosis strains, no resistant mutants were identified. This study is the subject of a recent news article on this website (http://www.biotechnologyforums.com/thread-6748.html).

References:

APPELT, S., FANCELLO, L., LE BAILLY, M., RAOULT, D., DRANCOURT, M. and DESNUES, C., 2014. Viruses in a 14th-century coprolite. Appl. Environ. Microbiol. (2014) doi:10.1128/AEM.03242-13

LING LL et al. A new antibiotic kills pathogens without detectable resistance. Nature (2015); doi:10.1038/nature14098
 
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RE: Antibiotics: what are they and how do they work? - by mtwalsh01 - 01-12-2015, 10:05 PM
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Antibiotics: what are they and how do they work?00