Important Drug-Resistant Bacteria and Associated Diseases

Antimicrobial resistance (AMR) makes infections harder to treat and can limit the medicines available to patients. Drug-resistant bacteria cause illnesses ranging from skin and urinary infections to pneumonia and bloodstream infections. Understanding major resistant pathogens, how resistance develops and how health systems respond is important for public health and examination preparation.

AMR and Important Resistant Bacteria

AMR occurs when microorganisms become resistant to medicines such as antibiotics, antifungals, antivirals and antimalarials. Misuse and overuse of antimicrobials in humans, animals and agriculture accelerate this process. The World Health Organization (WHO) identifies AMR as one of the top ten global public health threats.

• Methicillin-resistant Staphylococcus aureus (MRSA): Resistant to methicillin and several common antibiotics, including penicillin, amoxicillin and oxacillin. It commonly causes skin infections and can also cause pneumonia, bloodstream infections and surgical-site infections.
• Vancomycin-resistant Enterococci (VRE): Enterococci normally occur in the gastrointestinal tract and female genital tract. VRE can cause bloodstream, urinary-tract and surgical-wound infections.
• Carbapenem-resistant Enterobacteriaceae (CRE): This group includes Klebsiella pneumoniae and Escherichia coli. Carbapenems are broad-spectrum beta-lactam antibiotics used for serious infections; CRE may produce carbapenemase enzymes that break them down. Infections can include pneumonia, bloodstream, urinary-tract and wound infections, and may be life-threatening, particularly in hospitalised patients.
• Drug-resistant tuberculosis: Multidrug-resistant TB (MDR-TB) is resistant to at least isoniazid and rifampicin. Extensively drug-resistant TB (XDR-TB) is resistant to those medicines, any fluoroquinolone and at least one of three injectable second-line drugs. Treatment is generally longer and more complex than for drug-susceptible TB.
• Pseudomonas aeruginosa: A cause of healthcare-associated pneumonia, bloodstream and surgical-site infections. Its resistance to multiple antibiotic classes, including carbapenems, can make treatment difficult.
• Acinetobacter baumannii: Often found in healthcare settings and frequently multidrug-resistant, it can cause pneumonia, urinary-tract, bloodstream and wound infections, particularly in critically ill patients.
• Neisseria gonorrhoeae: The bacterium that causes gonorrhoea has developed resistance to nearly all antibiotics used to treat it, creating a significant public-health concern.

How Bacteria Resist Antibiotics

Resistance may arise through bacterial adaptation and can spread between bacteria. Common mechanisms include:

• Enzymatic inactivation: Enzymes such as beta-lactamases modify or break down an antibiotic before it reaches its target.
• Target modification: Changes to the antibiotic’s binding site reduce or prevent its action.
• Efflux pumps: Protein channels pump antibiotics out of bacterial cells, limiting their concentration inside.
• Reduced permeability: Changes to the bacterial outer membrane restrict antibiotic entry.
• Bypass pathways and gene transfer: Bacteria may use alternative metabolic pathways or acquire resistance genes from other bacteria through mobile genetic elements such as plasmids or transposons.

Global and Indian Responses

AMR control requires coordinated action across human health, animal health and agriculture. Public-health planning also depends on disease surveillance, infection control and health-system preparedness to detect resistant infections and support appropriate treatment.

• WHO Global Action Plan on AMR (2015): Endorsed by WHO member states, it sets five strategic objectives: raising awareness; strengthening surveillance and research; reducing infections; optimising antimicrobial use; and ensuring sustainable investment.
• India’s National Action Plan on Antimicrobial Resistance (NAP-AMR), 2017–2021: Aligned with the WHO plan, it adopted a One Health approach and focused on surveillance, infection prevention and control, rational antibiotic use, and research and development.
• Indian Council of Medical Research (ICMR): Plays a key role in AMR surveillance and research in India.
• Red Line Campaign and DCGI: The Red Line Campaign discourages use of prescription-only antibiotics without a doctor’s prescription; these medicines are marked with a red line on their packaging. The Drug Controller General of India (DCGI) regulates the approval, manufacture, sale and distribution of drugs, including antibiotics.
• WHO GLASS: The Global Antimicrobial Resistance and Use Surveillance System supports standardised, comparable country data on AMR and antimicrobial use.

Phage Therapy

Bacteriophages, or phages, are viruses that infect and replicate within bacteria. Many target particular bacterial species or strains. Lytic phages multiply inside bacterial cells and cause them to rupture. This specificity may reduce harm to beneficial bacteria compared with broad-spectrum antibiotics. Phages can replicate at the infection site and may act against antibiotic-resistant bacteria and penetrate biofilms. Their use requires identifying the bacterium and a suitable phage; potential immune responses and regulatory pathways are also considerations. Phage therapy is an emerging approach, not a general replacement for antibiotics.

Key Prelims Takeaways

• AMR affects microorganisms; misuse and overuse of antimicrobials accelerate it.
• MRSA resists methicillin; VRE resists vancomycin.
• CRE includes resistant Klebsiella pneumoniae and E. coli; carbapenems are broad-spectrum beta-lactams.
• MDR-TB resists isoniazid and rifampicin; XDR-TB has additional specified resistance.
• Resistance mechanisms include drug inactivation, target modification, efflux and reduced permeability.
• Phages are bacteria-infecting viruses; lytic phages rupture bacterial cells.

Recent Context

Samishta Hospital (SHRI), Guntur, used a three-phage cocktail developed by SRM University researchers to treat a carbapenem-resistant Pseudomonas aeruginosa artificial-knee infection. The case was published on October 22, 2026, and is reported as India’s first successful use of phage therapy for a carbapenem-resistant artificial-joint infection.