Can We Resist the Antibacterical Lifestyle?

 

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Can We Resist the Antibacterical Lifestyle?   Antibacterial Products and their Effects on Microbial Resistance Introduction Are Antibacterials Even Effective? Mechanisms and Effects of Triclosan (and other common antibacterials) on Microbial Resistance Allergies Increase in Antibiotic Prescriptions and other Antibiotic Uses How Can We Prevent Microbial Resistance? References Drafts

 

Antibacterial Products and their Effects on Microbial Resistance

Introduction

    The recent increase in the everyday use of antibacterial products has raised concerns about the efficacy of these items and their effects in the rise of microbial resistance. Meetings by the FDA and other health organizations have brought many important issues to the attention of researchers. These questions include: Are there any significant health benefits to using antibacterial products on a regular basis? Are these products a major concern in regard to the proliferation of bacterial resistance? Is the repeated use of triclosan and triclocarban, two widespread antimicrobial agents, creating a possibility of environmental contamination and resistant bacteria? And should physicians adopt a more strict policy in prescribing antibiotics?

 

Are Antibacterials Even Effective?

    An FDA advisory panel concluded that the popular, and more expensive, antibacterial soaps and cleansers have not been shown to be more effective at preventing illnesses than plain soap and water.  The committee made only one exception, the use of evaporating alcohol-based hand cleansers (like Purell), which they said could be beneficial in areas without easy and quick access to soap and water (such as daycares or in cases when travelers are visiting regions with no clean water supplies).  These cleansers are efficient in temporarily killing bacteria and there is evidence that they can reduce patient-to-pateint infections in hospitals (see Wiki on Hospital-Acquired Infections) (Zwillich, 2005). A study conducted by Larson and colleagues supported the claims made by the FDA panel. The study aimed to determine the effect of using household antibacterial products on the frequency of infectious disease symptoms. Households told to consistently use the antibacterials over one year did not have a significant difference in the occurrence of infectious disease symptoms from the group that used cleaning supplies without antibacterials. The authors concluded that consumers should be better educated on the limitations and proper use of antibacterial products, since the products did not provide any significant reduction in disease symptoms (Larson et al., 2004). The FDA committee also argued that waste runoff can create an accumulation of triclosan and triclocarbon, frequently used antibacterial agents, in groundwater and soil. This buildup could be contributory to water contamination and the increase in microbial resistance to antibiotics (Zwillich, 2005).

 

Mechanisms and Effects of Triclosan (and other common antibacterials) on Microbial Resistance

    At in-use concentrations triclosan acts as a biocide, with multiple cytoplasmic and membrane targets. At lower concentrations, however, triclosan appears bacteriostatic and is seen to target bacteria mainly by inhibiting fatty acid synthesis. Triclosan binds to bacterial enoyl-acyl carrier protein reductase enzyme (ENR), which is encoded by the gene FabI. This binding increases the enzyme's affinity for nicotinamide adenine dinucleotide (NAD⁺). This results in the formation of a stable ternary complex of ENR-NAD⁺-triclosan, which is unable to participate in fatty acid synthesis. Fatty acid is necessary for reproducing and building cell membranes. Humans do not have an ENR enzyme, and thus are not affected. Some bacterial species can develop low-level resistance to triclosan due to FabI mutations which decrease triclosan's effect on ENR-NAD⁺ binding, as shown in Escherichia coli and Staphylococcus aureus. Another way for these bacteria to gain low-level resistance to triclosan is to overexpress FabI. Some bacteria have innate resistance to triclosan, such as Pseudomonas aeruginosa, which possesses multi-drug efflux pumps that 'pump' triclosan out of the cell. Other bacteria, such as some of the Bacillus genus, have alternative FabI genes (FabK) to which triclosan does not bind and hence are less susceptible.

     Triclosan and triclocarbon have been found in sewage due to incomplete elimination during wastewater treatment processes. The hydrophobic structure of these substances allows them to reside as sludge layers, contaminating wastewater streams. Research has shown that both compounds degrade very slowly in the environment, especially in anaerobic soil conditions (Ying et al., 2007). The lasting presence of these substances in the soil could be contributing to the increasing amount of antibiotic-resistant bacteria. 

 

Allergies

According to the American Academy of Allergy Asthma Immunology (AAAAI), a study by P.J. Gergen et al found that about 50 million Americans suffer from allergies.  This high prevalence level is not only a nuisance to the afflicted individuals, but it is also a costly burden. D. A. Stempel (1997) attempted to measure this burden and estimated it to cost about $7.9 billion in 1997 in both direct and indirect costs. The past forty years have also seen a dramatic increase in the number of individuals who have been diagnosed with allergies in Western countries (Noverr et al 2004). Many studies are also finding that asthma rates are also increasing.  The emergence of these trends has prompted researchers to investigate the “hygiene hypothesis”-that we are simply too clean, which in turn weakens our immune systems allowing for normal bacteria, mold, etc to cause health problems.

 

Two researchers from the University of Michigan, Gary Huffnagle and Mairi Noverr, have teamed up to tackle this problem and deduced that the problem stems from what they call the “microflora hypothesis.” Their theory basically states that the ingestion of antibiotics weakens the gastrointestinal system by removing the natural gut flora made up of various helpful bacteria. With these bacteria removed fungi is able to flourish in this environment. This scenario alone does not cause allergies, however, when coupled with Huffnagle’s earlier research on fungal oxylipins, the “microflora hypothesis” begins to make a lot more sense. Essentially, while the fungi inhibit the gut, they secrete oxylipins which Huffnagle finds disrupt T cell production. With T cells not present to fight off ordinary things such as mold spores (that enter the body every time you breathe), the body in turn becomes sensitive to them (Noverr et al).

 

When Mairi Noverr tested this hypothesis on lab mice she found that the mice that ingested antibiotics developed allergies to the mold whereas those that did not were able to fight off the mold spores (Noverr et al).

 

 

Increase in Antibiotic Prescriptions and other Antibiotic Uses

 

    Acquired resistance was absent in bacteria before the “age of antibiotics,” giving evidence that the increased use of antibiotics has played a major role in the proliferation of microbial resistance. The widespread prescription of antibiotics has made many “once good—and cheap—treatments for infection” ineffective, creating a need for new antibiotics, such as alternatives for previously valuable penicillin, ampicillin, oxacillins, and fluoroquinolones.  The unnecessary prescription of antibiotics for viral infections is a large contributor to this trend, as well as prolonged therapy with common antibiotics (such as ampicillin and penicillin) (Livermore, 2005).

    The use of antibiotics as an additive in animal feed is also widespread, and commonly known as antibiotics for growth promotion (AGMP), and is intended to support growth and prevent disease in the livestock. However, these substances are usually added without prescription, supplied over long periods of time, and are given in massive quantities (millions of pounds!) (Wierup, 2001). Though some countries have banned the use of specific antibiotics in animal feed (Norway, Finland, and Denmark), this use of antibiotics is still utilized in other countries across the globe. 

 

How Can We Prevent Microbial Resistance?

 

    Health officials have provided many suggestions to help fight the spread of microbial resistance (“Antibiotic Resistance,” 2005):

1)      Eliminate the prescription of antibiotics for viral infections

2)      Patients should complete the entire course of the treatment and should not share their prescriptions with others

3)      Patients should never flush their unused/expired medication down the toilet or throw it in the garbage – this only increases the amount of antibiotics in environmental waste (look for drug recycling programs instead)

4)      Avoid frequent use of “antibacterial” soaps, cleansers, etc.

5)      Wash hands on a regular basis for at least 20 seconds with soap and water

6)      Encourage farmers to give only prescribed and necessary antibiotics to their livestock

 

    If patients and farmers follow these guidelines, microorganisms should receive less exposure to antibiotics, hopefully reducing future microbial resistance.

 

 

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References

 Antibiotic resistance. Health Canada. October 2005. Retrieved February 13, 2008 from <http://www.hc-sc.gc.ca/iyh-vsv/med/antibio_e.html>

 

 

Gergen, P.J., Turkeltaub, P.C., Kaovar, M.G.: The Prevalence of Allergic Skin Reactivity to Eight Common Allergens in the US Population: Results from the Second National Health and Nutrition Examination Survey; J. Allergy Clinical Immunol.: 800:669-79, 1987

 

Larson EL, et al. Effect of antibacterial home cleaning and handwashing products on infectious disease symptoms: a randomized, double-blind trial. Annals of Internal Medicine 2004, 140 (5):      321-329.

 

Livermore DM: Minimising antibiotic resistance. The Lancet Infectious Diseases 2005,  5 (7): 450-459.

 

 

Noverr, M and Huffnagle G. (2005) The ‘microflora hypothesis’ of allergic diseases. Clinical and Experimental Allergy. 35: 1511-1520.

 

Noverr, M, Noggle, R, Toews, G, and Huffnagle, G. (2004) Role of Antibiotics and Fungal Microbiota in Driving Pulmonary Allergic Responses. Infection and Immunity. 72 (9): 4996-5003.

 

 

Stempel DA. The health and economic impact of rhinitis. A roundtable discussion. Am J Manag Care. 1997;3:S8-S18.

 

Wierup M: The experience of reducing antibiotics used in animal production in the Nordic countries. International Journal of Antimicrobial Agents 2001, 18: 287-290.

 

 Ying G, et al. Biological degradation of triclocarban and triclosan in a soil under aerobic and anaerobic conditions and comparison with environmental fate modelling. Environmental Pollution        2007, 150: 300-305.

 

Zwillich T. FDA panel: no advantage to antibacterial soap. WebMD Medical News. 20 October 2005. Retrieved February 13, 2008 from                                                                                                <http://www.webmd.com/news/20051020/fda-panel-no-advantage-to-antibacterial-soap>

 

 

http://www.aaaai.org/media/resources/media_kit/allergy_statistics.stm

 

Drafts

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