Tarheel Health Portal/Phage Therapy

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Today, 23,000 people die annually due to infections from antibiotic-resistant bacteria[1]. To address the pressing problem of antibiotic resistance, many scientists are proposing the use of bacteriophages through phage therapy. Phage therapy is the “use of viruses to infect bacteria as antimicrobials”[2]. Bacteriophages have the ability to clear and kill bacteria, and are highly effective when combined into a phage cocktail. A phage cocktail contains many different types of phages that infect the same species of bacteria and make the emergence of resistant bacteria extremely unlikely[3].

Antibiotic resistance is a growing public health problem. Since antibiotic resistance is a “public” health issue, it is relevant people of any gender, race, age, or life situation, and especially UNC students. Because students have the potential to contract foodborne pathogens that may be antibiotic resistant cause potentially fatal illnesses, it is of interest to my audience. Whether it is in the dining hall or at home, UNC students may be exposed to harmful food pathogens that have detrimental effects in their lives or their loved ones’ lives. For example, feeling ill for long periods of time may cause students to miss class and lag far behind in their schoolwork. Ultimately, phage therapy should be preferred over antibiotic therapy in order to prevent foodborne diseases. Its' application is relevant to both the student population and people across the globe.

Brief History of Antibiotics in Agriculture Industry[edit]

Antibiotic resistance tests; the bacteria in the culture on the left are sensitive to the antibiotics contained in the white paper discs. The bacteria on the right are resistant to most of the antibiotics.

In response to increasing bacteria resistance to antibiotics, the agriculture industry raised antibiotic dosages, invested in new drugs, and implemented antibiotic cocktails. For example, between 1985 and 2001, the U.S. increased antibiotic use by 50%, with 7.5 billion chickens and 300 million turkeys treated by as many as ten different antibiotics each year [1](Gerber et al. 2007); however, many scientists believe the ability to develop new antibiotics is nearing exhaustion. In fact, no new treatments for Gram-negative bacilli have been discovered for over four decades[4]. Gram-negative bacilli, otherwise called Gram-negative bacteria, are responsible for numerous diseases.

Phage Therapy[edit]

The growing concerns over the possibility of foodborne pathogens completely resisting any application of antibiotics has brought phage therapy to the forefront as a new, viable, and effective form of pathogen treatment. Researchers have turned toward the use of bacteriophages to kill bacteria and reduce colony populations in animal populations. Furthermore, there are multiple benefits to bacteriophage use as compared to the application of antibiotics. For instance, bacteriophages are naturally occurring and thus, already present in much of the food and water humans consume[5]. Additionally, bacteriophages specifically target host bacteria, so the isolation of phages capable of infecting specific pathogens, such as Campylobacter and Salmonella, yields a targeted approach toward eliminating harmful pathogens in food sources[5]. This is in contrast to the application of antibiotics, which carry the potential to eliminate bacteria beneficial to livestock and poultry. Finally, several different bacteriophages can be combined into a single “phage cocktail,” eliminating almost any possibility of resistant bacteria[3].  Phage cocktails can be administered through the coarse spraying of animal habitat, or simply added to drinking water.

Diagram of how some bacteriophages infect cells: this is not drawn to scale, bacteriophages are about 100 x smaller than bacteria.

Possibility of Phage Resistance[edit]

Many scientists in the field of microbiology that are investigating the potential effects of phage therapy seek to discover whether or not, after decades of phage use, a number of bacterial pathogens will become resistant to phage cocktails in a similar manner in which they have become resistant to chemical antibiotics. In general, bacteria may evolve resistance to phages. There is evidence that the evolution of phage resistance may occur more slowly in regards to phage cocktails rather than individual phages; nevertheless, employing phage cocktails could select precisely for such hypothetically broadly phage-resistant bacteria that develop into highly resistant bacterial superbugs [6]. Despite the concern about the hypothetical situations about bacterial evolution previously mentioned, there is very strong evidence that proposes bacterial resistance to phage cocktail usage is highly improbable and unlikely. Several studies suggest that the evolution of phage resistant superbugs is not going to occur [6]. For example, phage resistance tends to be disadvantageous for bacterium; it is not beneficial for bacteria to stay resistant to bacteriophages that are no longer in their environment [7].

Furthermore, “even if continuous use of phages forced a bacterial population to become permanently resistant to specific phage-cocktails, biogeography studies of phage infection patterns suggest that new infectious phages will nevertheless be available” [6]. Analyses of studies that examined host-phage interactions concluded that phages could often infect many different host strains from different origins[8]. Other studies have shown that a single bacteriophage “can remain infective to bacteria around the world and that a single bacterium can serve as a host for bacteriophages derived from multiple distant geographical locations” [6]; thus, there is a remarkably small chance that a new infectious phage for pathogenic bacteria will not be found somewhere in the world. There will be a continuous supply of environmental phages that are available indefinitely to use against bacterial targets [6].

Electron micrograph of Bacteriophages

Further Readings[edit]

The National Institute of Health and Center of Disease Control are both useful and easy-to-understand resources for students to consult. Also, Pub Med is a helpful resource for finding recent studies regarding phage therapy. Campus Health Services is another valuable resource that may have some prevention tips, facts, and helpful ways that UNC students could deal with any foodborne illness.

[NIH: Environmental Health Perspectives]

[PubMed: Phage Therapy]

[Center for Disease Control and Prevention: Foodborne Illness and Antibiotic Resistance]

[UNC Online Nurse Advice]

[UNC Nutrition Services]

References[edit]

  1. 1.0 1.1 http://link.springer.com/article/10.1007/s11274-014-1655-7?sa_campaign=email/event/articleAuthor/onlineFirst Jassim and Limoges 2014 Natural solution to antibiotic resistance: bacteriophages 'The Living Drugs'
  2. http://www.tandfonline.com/doi/abs/10.4161/bact.24219#.VTVhVmRViko Örmälä and Jalasvuori 2013 Phage therapy: Should bacterial resistance to phages be a concern, even in the long run?
  3. 3.0 3.1 http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0031698#pone-0031698-g006 Gu et al. 2012 A method for generation phage cocktail with great therapeutic potential
  4. http://www.tufts.edu/med/apua/news/news-newsletter-vol-30-no-1-2.shtml Spellberg 2012 New Antibiotic Development: Barriers and Opportunities in 2012
  5. 5.0 5.1 http://www.sciencedirect.com/science/article/pii/S0958166910001965 Mahony et al. 2011 Bacteriophages as biocontrol agents of food pathogens
  6. 6.0 6.1 6.2 6.3 6.4 http://www.tandfonline.com/doi/abs/10.4161/bact.24219#.VTZzc2TBzGc Örmälä and Jalasvuori 2013 Should bacterial resistance to phages be a concern, even in the long run?
  7. http://www.sciencemag.org/content/332/6025/106.short Gómez and Buckling 2011 Bacteria-Phage Antagonistic Coevolution in Soil
  8. http://www.pnas.org/content/108/28/E288.short Flores et al. 2011 Statistical structure of host–phage interactions