Infectious diseases caused by microbes have been treated with antimicrobials or antibiotics for long. These antimicrobials significantly lessen the sickness and death caused by infections such as tuberculosis, malaria etc. Antimicrobial resistance (AMR) develops when microbes such as bacteria, fungi, viruses or parasites propagate, or survive in the presence of drugs, created to destroy them. As a result, the antimicrobials treatment for the removal of AMR microbes becomes less or no longer effective. Multidrug resistant (MDR) or sometimes known as superbugs are those microbes which are resistant to more than single antimicrobial. Such as in MDR-TB the bacteria become resistant to both rifampicin and isoniazid (first line drugs).

Resistant microbes are more difficult to treat, requiring alternative drugs or higher doses, both of which may be more expensive or more toxic. There are some antimicrobial resistant infections like Staphylococcus aureus, Streptococcus pneumoniae, Mycobacterium tuberculosis, Enterobacteriaceae, and Pseudomonas aeruginosa etc. which are serious threats to public health globally and about 700,000 people around the world die annually due to drug-resistant infections. It is estimated that by 2050 approximately 10 million people would die due to AMR, which will be highest among other common causes, including road accidents, cancer, diabetes, diarrhoea, measles, cholera, tetanus (Fig. 1).

Reasons of AMR

When microorganisms encounter various antibiotic drugs, it is possible that they might develop AMR. This process is accelerated if antimicrobials are over consumed unnecessarily. Not only the overuse but also the improper use such as consumption of antibiotics during viral infections like cold and flu, increases the threat of AMR to these drugs.  Also the antibiotics are widely used as growth supplements in livestock which are then ingested by humans when they consume

Figure 1. Estimated deaths from most common causes by 2050.

livestock as food. Around more than 35 years ago, it was first noted that the resistant bacteria was transferred to humans by farm animals, when high rates of antibiotic resistance were found in the intestinal flora of both farm animals and farmers. The common factors behind the development and spread of these antimicrobial resistant microbes are the release of huge amount of antibiotics into the environment during pharmaceutical manufacturing and wastewater treatment, poor infection control, inadequate sanitary conditions and inappropriate food-handling.

Problems due to AMR

Most of the available or known antimicrobials are not effective against resistant microbes, which make it more problematic and costly to treat common infectious diseases; therefore resulting in prolonged illness, extra appointments with doctor, prolonged stays in hospital, requirement of more costly drugs to substitute the older ineffective ones, and sometimes death. Microbes are single celled organisms and for their survival within the host, they are constantly evolving to develop new resistance mechanisms. Therefore without effective antimicrobials, medical processes such as organ transplantation, cancer chemotherapy etc. become very risky. About 80-90% of the antibiotics are not metabolized completely when consumed by humans or animals, which in turn passes through the body and enters the environment as waste. After entering the environment as waste product, they still affect the bacteria outside the body and promote resistance. Antibiotics resistance can pass from one bacterium to another and resistant bacterial infections can pass from person to person. Hence, the entire community will further get affected due to the high antibiotic use and antibiotic resistance.

Co-infections with other disease

Co-infections occur when a person is infected with more than one infection at a time. HIV-infected persons are at higher risk of developing other infections such as tuberculosis, hepatitis B and hepatitis C than HIV negative persons. HIV is human immunodeficiency virus which spreads through certain body fluids that weakens our immune system so that it is not able to fight against other opportunistic infections and diseases. Common hepatitis viruses are hepatitis A, hepatitis B and hepatitis C which mainly affects the liver. These viruses are different from each other as they transmit through different ways, cause different symptoms, and require different treatments. Liver is an important organ which gets affected by hepatitis C virus, initial stage of which is termed as fibrosis and the later stage is cirrhosis. Sometimes in critical cases, liver failure and/or liver cancer can occur during later stage of liver infection. Although human body can fight the hepatitis C virus via various treatments, but no efficient vaccines have been developed till date in order to prevent infection by this virus. Hence, there is always a possibility of developing infection again and again. Both HIV and hepatitis C are slow-acting viruses which are able to persist inside the host body for years without developing any signs or symptoms of illness. Therefore, a person can be unaware of getting co-infected by both the viruses. As both the viruses are spread mainly through blood, the major risk for co-infection is sharing of needles or other equipments to infect drugs. According to WHO, approximately 2.3 million people with HIV also have HCV globally. Among these, about 50-90% of HIV/HCV infected people are those who inject drugs.

Another common co-infection is the TB-HIV. It is estimated that a person with HIV positive infection has 26 to 31 times greater risk of developing active TB than the person with healthy immune system. TB is an infectious disease which mainly affects the lungs but can also affect other parts of the body. Mycobacterium tuberculosis is the bacterium which is responsible for causing tuberculosis. It spreads through air when an infected person with lung TB coughs, speak or sneeze, releasing TB germs into the air and another person inhale them to become infected. Again, if a person has chronic disease like diabetes, he is at high risk (two to three times) of getting TB infection due to weak immune system. Large number of people remains undiagnosed in TB, HIV and diabetes cases for long which will increase complications due to TB-diabetes and TB-HIV co-infections, which will further lead to high cost and more side effects in treatment. Sputum culture conversion time can be increased if a person has diabetes too. During TB treatment, the person is at higher risk of death if he is co-infected with diabetes or HIV. TB-associated deaths can be controlled if the infection is detected early and treated effectively. This can be done if both TB and HIV patients are subjected to HIV and TB diagnostic tests respectively.

Preventions

By using some preventive actions we can reduce the development and spread of AMR and these preventions are:

Improving antimicrobial usage

Patients should take antibiotics exactly as prescribed for them by healthcare professional. Antimicrobials should never be preserved for next period of sickness and leftover antimicrobials should never be consumed. Patients should not use antibiotics in viral infections like cold or flu and never use antimicrobials prescribed to another person. They should complete their proper duration of antibiotic treatment even if they feel better and never skip a single dose of their drugs. Healthcare professionals should prescribe accurate medication and dose with respect to infection and avoid unreasonable prescription. Patients should be encouraged by doctors to use antimicrobials as instructed. Doctors should isolate patients who are infected with a resistant pathogen and treated as fast as possible to control the spread of infection.

Research and developments

With the emergence of AMR, it has now become important for scientists/researchers to search new potential drug targets and develop new antibiotics with novel mechanism of action. They should also develop different diagnostic methods for preventing the spread of antibiotic resistance.

Public awareness

Immunization can help prevent AMR. Therefore, government should organize some awareness programs on vaccination and suitable drug usage, so that normal people become aware of the problems emerging due to antimicrobial resistance and its causes. Government should also organize some hygiene programs for public awareness so that they prevent spread of resistant strains between persons. A specific law should be implemented to limit sale of unprescribed drugs.

Conclusion

AMR in recent years have become a rising obstacle before efficient therapeutics. Hence there is urgent need from academicians, clinicians and researchers to act in consortium and unite to end AMR.