UPSC Prelims 2022 Q37: Biofilms and Antibiotic Resistance — Explained
Consider the following statements:
1. Biofilms can form on medical implants within human tissues.
2. Biofilms can form on food and food processing surfaces.
3. Biofilms can exhibit antibiotic resistance.
Which of the statements given above are correct?
- 1 and 2 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Answer: (d) 1, 2 and 3
Statement-wise explanation
- 1: correct — A biofilm is a community of microbes stuck to a surface and wrapped in a slimy matrix that the microbes make themselves, called extracellular polymeric substances (EPS). The surface can be living tissue or a non-living object. Implanted devices such as indwelling catheters are typical sites, and *Staphylococcus aureus* and *S. epidermidis* biofilms on them cause bloodstream and urinary tract infections that are hard to treat. Microbiology reviews describe biofilm as a critical medical problem precisely because it forms on medical implants within human tissue.
- 2: correct — Biofilms persist in food processing plants and become a source of cross-contamination and foodborne disease. Bacteria such as *Listeria monocytogenes*, *Salmonella*, *E. coli* O157:H7 and *S. aureus* lodge in grooves and scratches on stainless steel. They also stick to glass, PVC, polycarbonate and latex, to dairy equipment, and to the surfaces of food itself, such as meat.
- 3: correct — Bacteria inside a biofilm can survive antibiotic levels 10 to 1,000 times higher than the dose that kills the same bacteria living freely (planktonic). The EPS matrix slows how far a drug can penetrate and binds it. Slow-growing and dormant 'persister' cells are not hit by drugs that act on active growth. Enzymes such as β-lactamase, efflux pumps and gene transfer between the packed cells add further resistance.
How to eliminate
This question is solved by knowing the concept, not by tricks. None of the statements uses an absolute word such as 'only', 'always' or 'never'. Each says biofilms 'can' do something, and a statement about possibility is hard to make false. One basic fact covers all three: a biofilm forms on almost any wet surface, living or non-living, and its slime protects the microbes inside. Dental plaque proves the medical side, the slime in drains and on kitchen equipment proves the food side, and the slime-as-shield idea proves resistance. If a test asks whether a broad microbiology behaviour 'can' happen, a single real example is enough to make the statement true, so 'all of the above' is often the safe choice. Remember: biofilm means attachment plus an EPS matrix plus protection from antibiotics and disinfectants.
Know more
What a biofilm is. A biofilm is a structured community of microorganisms (bacteria, fungi or both) attached to a surface and enclosed in a matrix the microbes produce themselves, called extracellular polymeric substances (EPS). EPS is made of polysaccharides, proteins, extracellular DNA and lipids, and acts as a 'biological superglue'. Most bacteria in nature live this way rather than as free-floating (planktonic) cells.
How it forms (five stages)
| Stage | What happens |
|---|---|
| 1. Reversible attachment | Weak forces hold cells to the surface. Pili, fimbriae and flagella help. |
| 2. Irreversible attachment | Cells start making EPS and stop moving. |
| 3. Microcolonies | Cells divide and cluster together. |
| 4. Maturation | A 3-D structure forms, with water channels that carry nutrients. |
| 5. Dispersal | Some cells break away to colonise new surfaces. |
Quorum sensing. Bacteria release signal molecules to sense how many of them are present and to act together once their numbers are high enough. Gram-negative bacteria use acyl homoserine lactones (AHLs), Gram-positive bacteria use autoinducing peptides (AIPs), and both use autoinducer-2. Quorum sensing controls biofilm build-up, virulence and dispersal, so blocking it ('quorum quenching') is studied as an anti-biofilm strategy.
Where biofilms matter
| Setting | Examples |
|---|---|
| Medicine | Catheters, artificial joints, heart valves, contact lenses, dental plaque, chronic wounds, cystic fibrosis lungs (Pseudomonas aeruginosa) |
| Food industry | Stainless steel lines, dairy equipment, meat-contact surfaces (Listeria, Salmonella, E. coli O157:H7) |
| Environment/industry | Pipe corrosion, ship hulls, water pipelines. Beneficial biofilms in wastewater treatment and bioremediation |
Why they resist drugs. The matrix limits how far drugs penetrate and binds them, cells grow slowly, persister cells survive, and resistance genes pass between the packed cells by horizontal gene transfer. This makes biofilms a major contributor to antimicrobial resistance (AMR) and to infections that keep coming back. Newer approaches include phage therapy, matrix-degrading enzymes and quorum-sensing inhibitors.