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Antibiotic Use in Animal Husbandry cause Emergence and Dissemination of Resistant Bacteria

Antimicrobials entail agents whose purpose is to kill microorganism or diminish their growth. Examples of the antimicrobials are antibiotics; they have been in use for over the last seven decades as a form of treatment. An increased reliance on these drugs has led to the infectious bacteria being treated against their adaptation to the antimicrobials and, thus, compromised effectiveness. The use of antibiotics by humans leads to the death of the target bacteria, but also results in the rise of resistant germs that often grow. These bacteria develop resistance in different ways, including neutralization and flushing out the antibiotics. Bacteria that escape the impacts of the antibiotics multiply, thus replacing the dead bacteria. Prokaryotic microorganisms that survive often become more resistant, meaning they are unlikely to be affected by the antibiotic previously used. 

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The above-mentioned type of resistance is an example of the process of natural selection. Increased resistance has led to a global increase in the rate of resistance. For instance, according to the report by the World Health Organization, 480,000 people evolved multidrug-resistant tuberculosis (MDR-TB) in 2013. In 2014, the World Health Organization (WHO) indicated that drug resistance has made it difficult to control the treatment outcomes in the society. There has been confirmed cases of resistance to treatment of such conditions as malaria and influenza. The primary use of antibiotics was in agriculture, especially in animal husbandry for different purposes. As numerous studies found, the increased use of antibiotics in agricultural has led to the development of resistant bacteria. The fact that the bacteria can spread from animals to human beings translates into an instant health risk for people. As a result, the increased use of antibiotics in the agricultural sector works against the efforts to reduce bacterial resistance. 

Use of Antibiotics in Animal Husbandry

In the 20th century, the use of antibiotics in agriculture has expanded to serve many purposes. Essentially, there are three primary uses. The first one is the prophylactic use to prevent diseases. In this scenario, if there is a disease outbreak in a few animals, farmers often treat the whole flock with antibiotics as a preventive measure. The process is commonly referred to as metaphylaxis. It entails using small doses of antibiotics. The antibiotics can be fed to the animals using drinking water and animal feed. The treatment period depends on the extent of the infection and ranges from a few weeks to couple of months. In the modern developed world, food and animal production industries have overly relied on prophylactic use of antibiotics to the extent that almost all animal feed is supplemented with antimicrobials to different levels. According to estimations, all antimicrobials used for treating humans have been also applied in the agricultural sector. Examples of such drugs include fluoroquinolones and streptogramins. Apart from the disease prevention purpose, antibiotics can also be used for treatment. The difference between treatment and prevention is that when treating animals a higher dose of antibiotics is used for a shorter period.

Another agricultural usage of antimicrobials is promoting growth. The process entails the administration of sub-therapeutic doses of the antimicrobials to the animals. Some of the common recipients are poultry and pigs. The purpose is to improve their rate of growth and enhance their productivity. The treatment procedure often lasts for the major part of an animal’s life. According to numerous studies, especially on pigs, small doses of antibiotics often promote growth, diminish the rate of mortality, and enhance the reproductive capabilities of the animals. The appealing outcomes of their usage act as incentives for the farmers to use them continuously.

Transfer of Resistant Bacteria to Humans from Animals

The transmission of resistant bacteria from animals to human beings entails complex systems of varying routes that dictate the possible impacts of the transmission. One of the transmission modes is the food-borne method. The method is the most common due to the numerous number of pathogens that are transmitted through the route. Examples of these pathogens include Salmonella enterica and Yersinia enterocolitica. The pathogens are often common in the developed countries. The transmission process occurs when human beings consume food contaminated with the resistant bacteria. For instance, affected animal parts often interact with the meat during the slaughtering process. Specifically, the evisceration process that entails the removal of guts is a major cause of transmission. 

Another route is through direct contact between people and animals. An example of such pathogens is MRSA CC398. For instance, when handling animals such as pigs and poultry, people can directly pick up the bacteria from waste or skins of animals. For instance, the E. coli bacteria easily transmits from turkeys and chicken to humans. The environment also plays a significant role in the spread of bacteria through manure, as the primary agent. Other agents include soil, water, and air. The route is usually effective because animals often spread the bacteria through excretion. For instance, the United States has recorded the presence of tetracycline-resistance genes in ground water near pig farms. It is estimated that people living near poultry and livestock have a higher probability of contracting the resistant bacteria. A study in the Netherlands also showed that more than 14% of people living near turkey farms acted as hosts for avoparcin, which was a carrier of the enterococcal bacteria. Scientific examination showed that the bacteria were resistant to treatment drugs such as vancomycin. 

Three major phases occur during development of resistance. The first one entails the antibiotics killing the non-resistant pathogens. The next phase is the resistant pathogens surviving and reproducing. The last stage is the spread of the pathogens. Resistance is a result of bacterial modification to reduce or completely diminish the effect of antibiotics. Some of the tactics that bacteria use include neutralization, pumping the antibiotics out, or altering the site of attack.

The development of resistance is an evolutionary mechanism that occurs through the process of natural selection. An example of natural selection phenomenon is mutation. The process entails the application of evolutionary stress on many pathogens. Once these processes generate a resistant gene, the bacteria then transmit new genetic formation among different pathogens in a horizontal manner through plasmid exchange. Bacteria that carry a variety of resistant genes are commonly referred to as multiresistant. The introduction of new antimicrobials acts as an external environmental pressure. It allows the mutative bacteria to survive, thus gives them a chance to reproduce. In effect, the bacteria pass on these traits to the offspring that attain full resistance. 

Numerous studies point to the fact that the mode of the antibiotic usage determines the quantity of the resistant bacteria that arise. For instance, the increased usage of cephalosporins that fall in the third or second generation increases the rate of the development of methicillin resistance. Other factors that may lead to the increased resistance include wrong diagnosis, unwanted prescriptions, and wrongful usage of antibiotics. An example of a resistant pathogen is Staphylococcus aureus. The pathogens habit around the mucous membranes and skins of numerous people. The pathogens develop resistance due to its adaptability to external pressure. In 1947, the pathogens were found to be penicillin resistant. 

An example of an evolving pathogen is the Methicillin-resistant Staphylococcus aureus (MRSA). According the Centers for Disease Control and Prevention (CDC), about one-third of the global population carries the pathogen. In 2004 in the Netherlands, a girl and her parents, who were pig farmers, were found to be positive for MRSA. The situation prompted extensive studies to find whether there was a link. A significant development occurred in 2004 when the link between pigs and humans in terms of transmission was confirmed. The study proved that pigs were the carriers of the pathogen and that the strain could be spread to people from animals. In the study, the pigs in the Netherlands carried a previously unknown MRSA ST398.

In 2005, around 23% of pig farmers in the region of Netherlands had the MRSA ST398 pathogen. The susceptibility puts farmers at a higher risk of being colonized by the MRSA bacteria. Another study in 2008 found that around 5.8% of pig keepers in the country carried the MRSA pathogen associated with the livestock. Despite the Netherlands being a major contributor of global livestock, the country has previously experienced only a few cases of MRSA infections. However, since 2007, the rate of the infections has risen to 20% of the population being infected. Since 2009, more than 30% of the patient population has contracted the infection. The scaring aspect of the MRSA 398 is that it can also be transmitted from one individual to another. Projections by the CDC indicate that a larger proportion of the global population will be infected in the future. There are also scientific predictions that the ST398 will evolve in the future to become even more resistant. The prediction is based on the fact that the virus does not have virulence genes found in MRSA that can be targeted for treatment. 

Medical Consequences of Using Resistant Bacteria to Treatment Antibiotics

The third and fourth generation cephalosporins antibiotics are the modern antimicrobials used to replace the treatment resisted by the bacteria. The main effect of resistant bacteria on such antimicrobials is ineffectiveness of the treatment. For instance, when it comes to these generations, resistant bacteria such as salmonella carry enzymes, including Extended Spectrum Beta-Lactamases (ESBLs). The enzyme makes the bacteria resistant to the cephalosporinsxl. One of the most popular bacteria used in human treatment is Beta-lactams. Horizontal transfer of the enzyme can occur and, thus, facilitate its spread around the globe. 

A major consequence of the increased ineffectiveness of antimicrobials is that it leads to the lack of treatment for numerous infections. The situation arises because the antibiotics available cannot treat the infections adequately. Another consequence is that the reduction of viable cures often delays the treatment, which may cause mortality. Another effect is that the situation leads to the patients needing alternative treatment methods. The alternatives may be expensive or inappropriate due to serious side effects. Other alternative treatments include invasive medication including intravenous injections. A recent report by the WHO cited the rampant increase in resistant bacteria on a global scale. For instance, according to the report, Europe is at risk of infection increases due to the rise of resistant bacteria such as Escherichia coli. It is popular for causing urinary tract infections among others. The World Health Organization also reports that one of the predictors of the mortality rates caused by the E. coli is the lack of adequate antimicrobial therapy. Another arising resistant bacterium is the Staphylococcus aureus, especially in livestock producing countries such as Germany and the Netherlands. 


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According to WHO, a significant consequence of resistance is that modern medical field, which relies heavily on antibiotics for the treatment of numerous infections, can crumble. An example of an infection that could be on the rise is pneumonia whose response to medications such as penicillin may not be adequate to treat the patients. Another infection is cystitis that mostly affects women. In this case, due to its resistance, women might opt to use the costly injection treatments. Other antibiotics that might be at risk include medications used to treat infections related to surgery. In effect, the patients under intensive care may be at risk of not recovering. Another frightening observation by WHO is that very few antibiotics have been developed since 1985, meaning that the antibiotic replacements are almost non-existent.  

Increase in resistance also may result in inappropriate therapy. Inappropriate therapy occurs when a diagnosis leads to wrongful treatment procedure. The primary effect is prolonged stay in the health facilities and eventually death. Such situation is also a recipe for the breakout and spreading of diseases. For example, the spread of diseases such as typhoid fever and pneumonia is closely related to inappropriate therapy. Another related risk is colonization, when a human being becomes a carrier. 

As shown, the medical effects of resistant bacteria increase are the rise of morbidity and mortality rates. Moreover, there is an increased risk that the infections will spread if the antibiotics used for treatment are not effective. The medical repercussions also lead to increased costs for patients and medical facilities. The fact that the infections are on the rise and the rate of the development of treatment is disproportionate translates into increased risks for the society. The risk increases due to the confirmed ability of animals to transmit the resistant bacteria to human beings.