Why Antibiotics are Failing

Overview about AMR

Well, I suppose you have been sick at one point in time and you decided to go direct to the chemist or pharmacy to buy medications. You wanted quick relief. And may be you got it, or not. But, what if I tell you that sometimes, self-diagnosis is a danger to your own health and even the entire general public? Stay with me. In this article we are going to tackle facts about anti-microbial resistance.

Anti-microbial resistance alias AMR is an emerging threat to our healthcare within the global region. It due to various reasons. Generally, misuse of drugs targeted at bacterial microbes drives the development of this resistance. Examples include self-medication, and easy access especially through over-the-counter (OTC) access. Additionally, incomplete courses (dosages) can result in AMR.

 

Facts & Figures

What are the statistics that surround AMR ?

• 1.14 million deaths were directly caused by bacterial AMR globally in 2021.
• 4.71 million deaths were associated with bacterial AMR globally in 2021.
• 1 in 6 bacterial infections globally were resistant to antibiotics in 2023.
• AMR could directly cause 39.1 million deaths between 2025 and 2050.
• 169 million deaths could be associated with AMR between 2025 and 2050.
• US$ 412 billion annually could be spent treating resistant bacterial infections by 2035.
• Bacterial AMR could cause US$ 443 billion in annual productivity losses by 2035.
• Sub-Saharan Africa has the highest AMR death rate, estimated at 99 deaths per 100,000 people.
• AMR could reduce global GDP by US$3.4 trillion annually if left unchecked.
• More than 1 million children under five died from infections linked to AMR in 2019

 Risk Factors

What are the risk factors for AMR?

Antibiotic use in people

1. Overuse of antibiotics: Antibiotics are often taken for viral illnesses such as colds and flu, where they do nothing. Each unnecessary dose lets resistant bacteria survive and multiply.
2. Incomplete courses and wrong dosing: Stopping early, skipping doses, or taking too little leaves partially treated bacteria that adapt. Underdosing is a strong driver of resistance.
3. Self-medication and leftover antibiotics: People take antibiotics without a prescription or reuse old supplies. This often means the wrong drug, dose, or duration.
4. Over-the-counter sales: Where antibiotics can be bought without a prescription, use is poorly controlled. This is common in many low- and middle-income countries.
5. Inappropriate prescribing: Clinicians may prescribe antibiotics “just in case,” without a diagnosis, or use broad-spectrum drugs when a narrow one would work. Patient pressure and time constraints contribute.
6. Lack of diagnostic testing: Without culture and sensitivity tests, treatment is guesswork. Broad-spectrum drugs then get used more often than needed.

Health system and hospital factors

1. Poor infection prevention and control: Weak hand hygiene, unsterile equipment, and crowded wards help resistant bacteria spread between patients. Hospitals are hotspots for resistant strains such as MRSA.
2. Invasive devices and procedures: Catheters, ventilators, and surgical wounds give bacteria a way into the body. Biofilms on devices also protect them from antibiotics.
3. Prolonged hospital stay and ICU admission: Longer stays mean more exposure to resistant organisms and more antibiotic courses. Critically ill patients are especially vulnerable.
4. Weak stewardship and surveillance: Without antibiotic stewardship programmes and resistance monitoring, problems go undetected. Treatment guidelines are also less likely to be followed.
5. Substandard and falsified medicines: Poor-quality antibiotics contain too little active ingredient. This exposes bacteria to sub-lethal doses and encourages resistance.

Agriculture, animals, and environment

1. Antibiotics in livestock and farming: Antibiotics are used in animals for growth promotion and disease prevention, not only treatment. Resistant bacteria can reach people through food, direct contact, and manure.
2. Antibiotic pollution of the environment: Waste from pharmaceutical factories, hospitals, and farms contaminates water and soil. This selects for resistance genes in environmental bacteria.
3. Use of antimicrobials on crops: Some antibiotics and antifungals are sprayed on plants. This can promote resistance in environmental microbes, including fungi.

Social and economic factors

1. Poor sanitation, hygiene, and unsafe water: Without clean water and sewage control, infections spread more and are treated more often. Resistant bacteria then circulate in the community.
2. Poverty and limited access to healthcare: People who cannot afford or reach proper care turn to informal providers or cheaper, incomplete treatment. Delayed care also leads to more severe infections.
3. Overcrowding and malnutrition: Crowded housing and poor nutrition raise infection rates and weaken immunity. This increases both the spread of infection and antibiotic use.
4. Travel and trade: People, food, and animals carry resistant bacteria across borders. Resistance anywhere can become a problem everywhere.
5. Weak regulation and policy: Poor enforcement of prescription rules and weak national action plans allow misuse to continue. Limited funding for new drug development makes it worse.

Patient-related factors

1. Extremes of age and weakened immunity: Infants, older adults, and people with HIV, cancer, diabetes, or on immunosuppressants get more infections. They also receive more antibiotics, so they are more likely to carry resistant bacteria.
2. Previous antibiotic exposure: A recent antibiotic course changes the body’s normal bacteria and selects for resistant ones. The risk is highest in the months after treatment.
3. Prior hospitalisation or long-term care: People discharged from hospitals or living in care homes are more likely to carry resistant organisms. They can bring them into the community.

Pathogen factors

1. Genetic mutation and horizontal gene transfer: Bacteria can mutate or swap resistance genes through plasmids. This allows resistance to spread quickly between species.
2. Slow pipeline of new antibiotics: Few new antibiotics are being developed, so treatment options shrink as resistance grows. Pharmaceutical companies have limited financial incentive to invest.

 

Mechanisms of Antimicrobial Resistance (AMR)

A. Classification by origin

1. Intrinsic (natural) resistance

This resistance is built into a species and is present in every member, so the drug was never effective against it.

Impermeable outer membrane. The outer membrane of Gram-negative bacteria stops large molecules from entering. Vancomycin, for example, cannot reach its target in Escherichia coli.

Naturally produced enzymes. Some species carry a chromosomal gene for a drug-destroying enzyme. Klebsiella pneumoniae naturally makes the SHV-1 β-lactamase, so it resists ampicillin.

Low-affinity targets. The drug’s target binds it only weakly from the start. Enterococcus faecalis has penicillin-binding proteins that bind cephalosporins poorly, so these drugs fail.

 

2. Acquired resistance

A previously susceptible bacterium gains resistance, either by mutation or by taking in genes.

Mutation. A chromosomal change alters a drug target or a pump. A gyrA mutation in E. coli, for instance, makes ciprofloxacin ineffective.

Conjugation. Plasmids pass between bacteria through direct contact. The plasmid-borne blaCTX-M gene spreads ceftriaxone resistance among E. coli strains.

Transformation. Bacteria take up free DNA from their surroundings. Streptococcus pneumoniae picks up DNA that creates mosaic penicillin-binding proteins, which lowers its susceptibility to penicillin.

Transduction. Bacteriophages carry resistance genes from one cell to another. Penicillinase plasmids spread among Staphylococcus aureus this way, giving resistance to penicillin.

 

B. Classification by biochemical mechanism

1. Enzymatic inactivation of the drug

Hydrolysis by penicillinase. The enzyme breaks the β-lactam ring. Staphylococcus aureus uses it to destroy benzylpenicillin.

Hydrolysis by extended-spectrum β-lactamases (ESBLs). These enzymes break down third-generation cephalosporins. They allow K. pneumoniae and E. coli to survive ceftriaxone.

Hydrolysis by carbapenemases. These enzymes destroy carbapenems, which are last-line β-lactams. K. pneumoniae producing KPC survives meropenem.

Chemical modification by aminoglycoside-modifying enzymes. They add acetyl, phosphate, or adenyl groups, so the drug can no longer bind the ribosome. Enterococcus faecalis resists gentamicin by this route.

Modification by acetyltransferase. Chloramphenicol acetyltransferase acetylates the drug and inactivates it. Salmonella Typhi strains carrying it survive chloramphenicol.

 

2. Alteration of the drug target

Altered penicillin-binding proteins (PBPs). Mosaic PBPs bind β-lactams weakly. S. pneumoniae uses these to resist penicillin.

Altered cell-wall precursor. The vanA gene changes D-Ala-D-Ala to D-Ala-D-Lac, so vancomycin cannot bind. Enterococcus faecium (VRE) escapes vancomycin this way.

Ribosomal methylation. erm genes methylate 23S rRNA, which blocks macrolide binding. Streptococcus pyogenes then resists erythromycin.

Altered DNA gyrase or topoisomerase IV. Point mutations in gyrA or parC reduce fluoroquinolone binding. E. coli and Neisseria gonorrhoeae survive ciprofloxacin through this.

Altered RNA polymerase. Mutations in rpoB stop rifampicin from binding. Mycobacterium tuberculosis becomes rifampicin-resistant this way.

 

3. Target protection or bypass

Ribosomal protection proteins. Tet(M) pulls tetracycline off the ribosome. S. pneumoniae with this protein survives tetracycline.

Qnr proteins. They shield DNA gyrase from quinolones. K. pneumoniae carrying qnr genes tolerates ciprofloxacin.

Alternative target (bypass). The mecA gene encodes PBP2a, which β-lactams cannot inhibit. This makes MRSA (S. aureus) resistant to oxacillin and methicillin.

Drug-insensitive replacement enzyme. dfr genes produce a dihydrofolate reductase that trimethoprim cannot block. E. coli carrying them survives trimethoprim.

 

4. Reduced drug accumulation

Porin loss. The bacterium reduces or loses the channel the drug uses to enter. Pseudomonas aeruginosa that loses the OprD porin resists imipenem.

Efflux of tetracycline. The TetA pump expels the drug before it reaches the ribosome. E. coli with TetA resists tetracycline.

Multidrug efflux. Pumps such as MexAB-OprM expel several drug classes at once. P. aeruginosa uses this to resist ciprofloxacin and other agents.

Efflux of macrolides. The Mef(A) pump removes macrolides from the cell. S. pneumoniae with it survives erythromycin.

 

5. Community-level protection (biofilm and persistence)

Biofilm formation. A slime matrix blocks drug entry, and slow-growing cells survive inside it. P. aeruginosa in the lungs of people with cystic fibrosis resists tobramycin this way.

Biofilm on medical devices. Cells attached to catheters and implants resist killing. Staphylococcus epidermidis on these devices survives vancomycin.

Summary

AMR is either intrinsic or acquired (through mutation, conjugation, transformation, or transduction). It works through five main routes: destroying the drug, altering the target, protecting or bypassing the target, keeping the drug out, and shielding cells in biofilms.