Authors: Drs. Ben Enyetornye, Alfred Adjiri-Awere
Antibiotic resistance is a situation in which bacteria adapts and change thereby making it to become insensitive to antibiotics it was previously sensitive to. The bacteria develop ability to survive when treated with antibiotics, designed, specifically, to kill them or halt their growth.
This makes it harder to eliminate bacterial infections as existing drugs become less effective. Antibiotic resistance is now discussed globally, as a threat to both animal and human health; however, practical solutions to the problem are normally left out.
The mechanisms and current situation of antibiotic resistance will be presented in part one of this article where part two provides possible substitutes which are applicable in veterinary medicine and animal production.
HOW ANTIBIOTIC RESISTANCE OCCURS
1. Ridding off of antibiotics by bacteria
Many antibiotics including penicillin, work by targeting the cell wall of bacteria by preventing the synthesis of peptidoglycan that is responsible for fortifying the bacterial cell wall to survive in a biological system. Some bacterial organisms have the ability to get rid of antibiotics by using efflux pump, located in their cell walls.
These pumps extrude the antibiotics from the cell wall as fast as it can enter. This makes it impossible for the antibiotics to work since it is regularly pumped out from its target site.
2. Neutralization of the effects of antibiotics Production of enzymes, having the ability to neutralize the effects of some antibiotics. A classic example is the production of beta lactamase which destroys the beta-lactam rings in penicillin to render it ineffective.
3. Preventing access to antibiotics
Antibiotics usually require access to the cell wall to reach their targets where they interfere with the normal functions of the bacteria. Channels known as porins are the gateways by which antibacterial compounds normally cross the bacterial membrane.
Some bacteria protect themselves by prohibiting the entry of antibiotics past the cell wall by modifying the cell wall membrane porin frequency, size and selectivity.
4. Modification of antibiotic targets
Some bacteria evade antimicrobials by camouflaging critical target sites to avoid recognition. Therefore, in spite of the presence of an intact and active antimicrobial compound, no subsequent binding or inhibition will take place.
MOLECULAR MECHANISMS OF ANTIBIOTIC RESISTANCE
Intrinsic resistance
Intrinsic resistance is the inherent ability of a bacterial species to resist activity of an antimicrobial agent through its inherent structural or functional characteristics, which allow tolerance of a particular antimicrobial class.
This can also be called “insensitivity” since it occurs in organisms that have never been susceptible to that particular drug.
Acquired resistance
Acquired resistance occurs when a microorganism obtains the ability to resist the activity of an antimicrobial agent to which it was previously susceptible. This can result from the mutation of genes involved in normal physiological processes and cellular structure of bacteria or the horizontal transfer of bacterial resistant genes to neighboring bacteria.
FACTORS CONTRIBUTING TO ANTIBIOTIC RESISTANCE IN VETERINARY MEDICINE AND ANIMAL PRODUCTION
The cause of antibiotic resistance is multifaceted and thus has many factors which are at play. These includes but not limited to:
1. Inadequate regulations and usage imprecisions, i.e., dose of antibiotic that is higher than (supratherapeutic dose) or lower than (subtherapeutic dose) the concentration needed to inhibit or kill susceptible bacteria.
2. The use of antibiotics as a poultry and livestock growth promoters rather than to control infection.
3. Easy access to antibiotics by farmers from various veterinary shops.
4. Awareness deficiency in best practices which steers undue or inept use of antibiotics to “cover up”
5. Online marketing which makes the unrestricted availability of low-grade antibiotics very accessible.
6. Spread of antibiotic-resistant bacteria by direct contact (e.g., between animal and human) or via indirect means (e.g., the food chain or drinking water).
7. Global spread of antibiotic-resistant bacteria by movement of the hosts (animals or humans) or contaminated products (e.g., food, water) from one location to another, or even across country borders or between continents.
CURRENT WORLD SITUATION
The global use of antibiotics in livestock production and agriculture (estimated at 63 000–240 000 metric tons per year) is expected to increase by 67% from 2010 to 2030, especially in emerging economies.
With meat production set to increase from 200 million tons to 470 million tons by 2050, it is likely that farmers will rely even more on antibiotics to prophylactically prevent disease in their livestock to meet this expected demand.
In 2015, the United States Food and Drug Administration approved 41 antibiotics for use in livestock and 31 (76%) of those were deemed to be medically important. Estimations suggest that livestock fed antibiotics excrete 75–90% of those antibiotics un-metabolized and these drugs may end up in the environment in groundwater.
The impact on the environment would be to promote more resistant bacteria. Unfortunately, in Africa, there are inadequate systems to track the yearly amount of antibiotic used in animal production.
Antimicrobial resistance has the potential to affect almost all sustainable development goals, particularly those targeting poverty, hunger, health and economic growth. Yearly, the death toll due to antimicrobial resistance is around 700 000 people, and this number is expected to rise to an estimated 10 million deaths annually by 2050.
THE SITUATION IN GHANA
Poultry
In Ghana, antibiotic resistance is a very big deal in animal production, and veterinary and human medicine. The situation in our opinion is increasingly alarming, especially, in poultry production, due to recent consistent findings from bacterial culture and sensitivity results.
Commonly encountered bacteria such as Escherichia coli and Salmonella spp have proven to be resistant to either all or 90% of antibiotics used in the sensitivity test. This finding cuts across for most poultry farms within Accra that sought veterinary medical services.
Surprisingly, these resistant bacteria turn to succumb to antibiotics that are not readily available in veterinary medicine. In an attempt to solve the problem on their farms, poultry farmers resort to the use of readily available human formulations for their birds. The implications of this practice in humans cannot be underestimated.
Unfortunately, there are no structured systems aimed at regulating farmers access to veterinary drugs and biologicals; this makes veterinary personnel get trapped in a vicious cycle.
A case study in Ghana indicated the presence of resistant strains of Escherichia coli and Klebsiella pneumonia in chicken meat.
Aquaculture
Interviews with farmers in the aquaculture industry indicated that antibiotics are added to feed for growth promotion, either directly to the ponds or cages, for the purpose of disease prevention or control. The indication for use of antibiotics and the choice of a particular one to use is normally done without consultation with qualified animal health professionals. Approximately, 80 % of antibiotics used in aquaculture end up in the environment with their activity intact.
A study conducted in the Greater Accra Region of Ghana on healthy human subjects indicated that 74.2% of the study subjects demonstrated the presence of antibiotic residues in their urine; although, all the study participants had not knowingly consumed antibiotics. This implies that about 75% of the study participants were taking antibiotics unknowingly from their food and water.
