Advisor at Japan Food Research Laboratories
We human beings live together with microorganisms some of which infect and disease us. Antibiotics are used to treat these diseases. “Antibiotic” is a generic term for “agents, produced by microorganisms, that inhibit the growth or function of other microorganisms”. In the broad sense, antibiotics include antiviral drugs, antifungal drugs, and anticancer drugs.
Since 1940, antibiotics such as penicillin have been developed and brought significant benefits to humans. Along with the use of antibiotics, bacteria that are resistant to them have been coming into existence as shown in Figure1 making treatment of infection difficult. Penicillin-resistant Staphylococcus aureus was reported to be found in 1960s. Accordingly, new types of antibiotics were developed by altering the molecular structure of penicillin whose representative example is methicillin. In due time, methicillin-resistant Staphylococcus aureus, MRSA, emerged and vancomycin began to be used to cope with this microorganism. However, MRSA that is resistant to vancomycin has emerged, which casts dark clouds over medical front. Microorganisms that are resistant to multiple antibiotics have been born and they are called multiply resistant organisms.
Some food-poisoning bacteria have gained drug resistance. In 2011, a mass food-poisoning case caused by enterohemorrhagic Escherichia coli O104:H4 broke out mainly in Germany. In this case, drug-resistant DNA was found in the causative microorganism. It resulted in a horrific tragedy of more than 4000 patients, 908 complication cases of hemolytic-uremic syndrome, and 50 deaths.
The mechanism that microorganisms gain antibiotic resistance is divided into the following 4 broad categories: 1) Inactivation of antibiotics by an activity of such substances as enzymes, 2) change of actions of antibiotics, 3) enhancement of antibiotics elimination, and 4) inhibition of uptake of antibiotics. Genetic information about drug resistance will be vertically transferred in an intergenerational manner as shown in Figure 2-4. Also the information will be horizontally transferred through bacterial conjugation or mediation of viruses (bacteriophage).
There are three types of places where resistant bacteria emerge. The first is medical facilities where antibiotics are used and nosocomial infection is a significant problem. The second is communities where prescribed antibiotics become a problem. The third is livestock and fisheries production facilities. Antibiotics are given to animals and fishery products not only as a cure for diseases but also for the purpose of preventing diseases or promoting growth. In EU, use of antibiotics for growth promotion is prohibited out of concerns about the future of the relation of antibiotics to humans.
The threat of drug resistance is internationally recognized, and U.N. agencies such as WHO and FAO develop and recommend measures for preventing abuse of antibiotics. WHO has specified five of the most important areas for the control of antibiotic resistance as follows:
1) Surveillance of antimicrobial resistance and use, 2) Rational antimicrobial use and regulation, 3) Antimicrobial use in animal husbandry, 4) Infection prevention and control, 5) Fostering innovations.
There is a possibility that we will be infected with a pathogen which is resistant to all antibiotics and become irremediable. We have to make a lot of effort to prevent drug-resistant organisms from casting dark clouds over food supply chain.
1) IZUMIYA, H., “Global Spreading of Antimicrobial Resistance through Contaminated Foods “, Japanese Journal of Food Microbiology, 31, 57-62 (2014)
2)WHO, The Evolving Threat of Antimicrobial Resistance: Options for Action. Geneva, Switzerland (2012).