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Firstly, what is post-antibiotic era. According to Margaret Chan, the Director-General of the World Health Organization, post-antibiotic era means the end of modern medicine. Common diseases such as a child's scratch could kill because of bacterial infection (World Health Organization, 2012).  In other words, entering post-antibiotic era means returning to pre-antibiotic era, where there are no effective drugs against pathogenic bacteria. In the pre-20th century, syphilis, which was caused by Treponema pallidum, was one of the deadliest infectious diseases among the sexually-active people. People at that time, due to the lack of knowledge on the disease, took extreme measures to treat syphilis. They would apply mercury on the patients' skin and put them into a hot hut, believing that the mercury and heat would kill the disease-causing agent. However, due to the toxicity of mercury and extreme heat, few managed to survive through the therapy (Salyers and Whitt, 2005).  In 1940's, due to the use of penicillin in the treatment, the spread of syphilis was controlled (Salyers and Whitt, 2005). 
Due to the 'miraculous effects' of antibiotics, many people, even up until now, still believe that antibiotics would cure all diseases, including common cold which is caused by viruses. What is antibiotic actually? Antibiotic is a type of chemotherapy agent that is able to kill or slow down the growth of bacteria. Most of the antibiotics are derived from fungi or bacteria, but there are semi-synthetic antibiotics which are chemically modified from natural substances (Salyers and Whitt 2005, p. 2).  The first antibiotic, which was being discovered by Sir Alexander Fleming, was derived from a fungus called Penicillium notatum. Antibiotics are being classified into two: broad-spectrum which act against both Gram-negative as well as Gram-positive bacteria and narrow-spectrum which is only effective on a specific family of bacteria (Abedon, 1998).  There are several mechanisms of actions of antibiotics on the bacteria: inhibition of bacterial cell wall, inhibition of protein synthesis, interference with bacterial DNA synthesis and interference of metabolic activity in the bacteria (Tenover, 2006). 
In most cases, initially, a newly discovered antibiotic would be able to annihilate a certain strain of bacteria completely. However, through nature selection and mutation, antibiotic-resistant strain would be developed. The bacteria would change the binding site of the antibiotic, produce enzymes to destroy the antibiotic, reduce the permeability of the cell wall towards the antibiotics and enhance efflux to expel the antibiotics out of the cell. Moreover, the bacteria are able to transfer their plasmids among the same species or across the species through horizontal gene transfer. Thus, the antibiotic-resistant genes would be spread to other species (Zhang, 2007). 
Although antibiotic resistance is not a new issue, there had not been a wide coverage on antibiotic resistance before 1990's. People did not aware the severity of this issue as there was new antibiotics being discovered to replace the old one in which the bacteria had developed resistance towards it (Dougherty and Pucci, 2012). For instance, methicillin was introduced in 1960's when penicillin-resistant Staphylococcus aureus was prevalent.  However, similar to penicillin, Staphylococcus aureus strain managed to develop resistance to methicillin (Wax et al. 2008, p. 292). 
In a survey being carried out in A. Salyers' laboratory, the presence of antibiotic resistance genes in Bacteroides species in the human colon was studied (Salyers and Whitt 2005, pp. 104-108).  From the date collected, the antibiotic (tetracycline) resistance gene carried by Bacteroides had increased tremendously in post-1980. The percentage of tetracycline-resistant Bacteroides in healthy people (community isolates) also increased significantly even though there were no recent use of antibiotics on them. This showed that the antibiotic resistance gene acquired by the bacteria was long-lasting.  Antibiotic-resistant Bacteroides might cause post-surgical infection by entering into the bloodstream although the strains are harmless most of the time (Salyers and Whitt 2005, p. 104).
Besides increasing in risks of post-surgical infections, antibiotic resistance from different strains of bacteria would lead to consequences such as: increase in treatment failure due to reduced susceptibility of antibiotics towards bacteria, increase in cost of treatment course due to the use of more expensive drugs and prolonged hospitalization, and increase in mortality rate of patients infected with antibiotic-resistant strains (Tenover, 2006).
Tuberculosis (TB) is an airborne infectious disease caused by Mycobacterium tuberculosis. Today, tuberculosis is still deadly especially in third world countries where the treatment is not properly conducted. These improper uses of treatment, including use of unsuitable drugs and patients' failure to complete the treatment would contribute to the emergence of multidrug-resistant tuberculosis (MDR-TB) as well as extensively drug-resistant tuberculosis (XDR-TB).  If Mycobacterium tuberculosis shows resistance towards first-line anti-TB drugs, at least towards isoniazid and rifampicin, then MDR-TB has developed. Consequently, second-line drugs which are more vigorous with a two-year-long course of treatment are being used. However, if the bacteria is also resistant to the second-line drugs, it is called as XDR-TB, where there is yet to have drugs that are effective against XDR-TB.  In 2011, there were an estimated number of 310 000 MDR-TB cases among the notified TB patients worldwide whereas to date, 84 countries have reported the occurrence of XDR-TB.  20
According to Global Tuberculosis Report 2012, about $100 000 000 is needed for tuberculosis care and control in third world countries from 2013 to 2015. The amount of fund required has doubled comparatively due to the escalating number of MDR-TB and XDR-TB cases.  On top of that, the emergence of drug-resistant Mycobacterium tuberculosis also increases the rate of mortality among TB patients as MDR-TB would cause at least 150 000 deaths per year.  If the condition is not controlled effectively, it might worsen in the near future.
Speaking of antibiotic resistance, it is inevitable to discuss about methicillin-resistant Staphylococcus aureus (MRSA). MRSA is a strain of Staphylococcus aureus that is resistant to Î²-lactam antibiotics, which include common antibiotics such as methicillin.  Generally, MRSA can be classified into two: hospital-acquired MRSA (HA-MRSA) where the patients have just recently received medical procedures such as surgeries and community-associated MRSA (CA-MRSA) that occurs among healthy people who recently do not undergo any medical procedures or hospitalization.  In 1961, which is shortly after the methicillin was put into wide use, the first case of MRSA was reported in United Kingdom.  Since then, there were cases of MRSA reported from all over the world.
Staphylococcus aureus is a bacterium that was responsible to infections such as bloodstream infection which might be lethal and skin infection.  During the pre-antibiotic era, it was cause of amputation among the soldiers who had serious wound infections in wars.  Currently, MRSA strains which are multi-drug resistance can only be treated with intravenous administration of vancomycin or oral administration of linezolid.  However, ever since the first isolation of vancomycin-resistant Staphylococcus aureus (VRSA) in Japan, the number of VRSA cases reported is increasing. Thus, the more effective linezolid, which costs $100 to $1000 more per treatment, might be the only option in the near future.  Thus, preventive measures such as proper use of antibiotics and monitoring system ensuring patients to finish their prescribed antibiotics should be strictly taken.
To conclude, despite the emergence of antibiotic-resistant strains and declining susceptibility of antibiotics on pathogenic bacteria, we still have hope in slowing down the progress to the end of the era of antibiotics. Control and surveillance over the emergence of antibiotic resistance on a global scale while promoting researches on the discovery of new antibiotics are the key players. However, in the long run, it is inevitable for the bacteria to develop resistance to antibioticsbk2148. Thus, alternatives of antibiotics should be discovered as soon as possible. "No action today, no cure tomorrow". Based on the slogan by World Health Organization from World Health Day 2011 "Combat Antimicrobial Resistance", it is crucial for everyone in the human society to realize the severity of antibiotic resistance and to take action immediately, before it is too late.