MRSA, or methicillin-resistant Staphylococcus aureus, is any strain of S. aureus that has developed resistance to beta-lactam antibiotics through natural selection. It was first identified in 1963 and an outbreak was investigated by the CDC in 2001. MRSA commonly colonizes the nose, respiratory tract, skin wounds, and IV catheters. Resistance is conferred by the mecA gene and SCCmec genomic island acquired via mobile genetic elements. MRSA infections can range from superficial skin infections to life-threatening conditions like sepsis, pneumonia, or necrotizing fasciitis. Diagnosis involves culture, PCR, or latex agglutination tests. Treatment depends on the strain but may include van

1. MRSA
Syn ORSA / CRSA

2. Introduction
• Any strain of S. Aureus that has developed resistance to Beta-
Lactam Antibiotics
• Natural Selection
• No change in Virulence ; ‘Difficult-to-treat’
• HA vs CA
• Known since 1963 ; Outbreak investigation by CDC in LA County
Prison in 2001
• Commonly colonizes Ant Nares, Respiratory Tract, Urinary Tract,
open wounds, IV catheters

3. Genetic Basis for Resistance
Acquisition of Extrachromosomal Genetic Elements
via Plasmids, TGEs in MSSA of :
– mecA (Resistance Genes for Transpeptidases)
– SCCmec (Genomic Island / Staphylococcal Cassette
Chromosome)
– ACME (Virulence factor / Arginine Catabolic Mobile
Element)
– Strains : EMRSA15/16 & ST5/250 MRSA I-IV

4. Predisposition
• Hospitals (Nosocomial)
– Open wounds
– Invasive devices
– Immunocompromised indls
– Diabetics
– Institutionalization
• Prisons
• Old-age homes / Orphanages
• Children
• Contact & Team Sports (‘Turf Burns’ / Shared Eq)
• IVDUs
• Unregulated Antibiotic usage (esp Quinolones)
• Veterinarians, livestock handlers (CC398 var), and pet owners

5. Clinical Features
• Preceding Prodromal / Constitutional symptoms
• Small Papules / Superficial Folliculitis / Impetigo resembling
IBR  painful , deeper lesions viz Carbunculosis, Abscess,
Cellulitis
• 75% CA-MRSA + HA-MRSA - skin and soft tissue
• 25% highly virulent strains predominantly can cause
Septicemia, TSS, Necrotizing Fasciitis, Pyomyositis,
Necrotizing Pneumonia, IE, Osteomyelitis, Septic Arthritis
• Toxin-mediated (Panton-Van Leukocidin PVL, Hemolysin
Gamma Hig, Phenol Soluble Modulin PSM)

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9. Diagnosis
• Clinical (High index of suspicion)
• Culture (Blood / Sputum / Pus )
• NAATs (PCRs / LCRs / TMA / bDNA)
• Latex Agglutination Test for PBP2a  imparts
the ability of S. aureus to be resistant to
oxacillin

10. Treatment
CA-MRSA > HA-MRSA (S)
• SULPHA DRUGS (SEPTRAN)
• TETRACYCLINES (DOXYCYCLINES)
• LINCOSAMIDES (CLINDAMYCIN)
• GLYCOPEPTIDES (VANCOMYCIN / TEICOPLANIN)  VISA
• OXAZOLIDINONES (LINEZOLID)
• PRISTINAMYCINS (QUINPRISTIN+DALFOPRISTIN)
• LIPOPEPTIDES (DAPTOMYCIN)
• GLYCYLCLINES (TIGICYCLINE)

11. RESEARCH / EXPERIMENTAL
• Antibiotics under trial :
TELAVANCIN, DALBAVANCIN,
CEFTAROLENE, CEFTABAPROLENE,
TOREZOLID, NEMONOXACIN
• PLATENSIMYCIN , a natural antibiotic, under
investigation 2006 ; from Streptomyces)
• Medical grade Honey viz ULMO 90 / MANUKA 25
tried in 2010 (activity of hydrogen peroxide,
methylglyoxal, and a novel compound named Bee
Defensin-1)

12. • Ocean-dwelling living sponges produce compounds 
make MRSA more susceptible to antibiotics
• Semi-toxic fungi/mushrooms excrete broad spectrum
antibiotics
– The psychedelic mushroom Psilocybe Semilanteacae has
been shown to strongly inhibit the growth of
Staphylococcus aureus
• Cannabinoids
– Cannabidiol (CBD) Tetrahydrocannabinol (THC)
– Cannabinol (CBN), Cannabichromene (CBC)
• Phage therapy
• MDT

13. Prevention
• Screening (Nasal Cultures)
• Hand-Washing / Good hygiene
• Surface Sanitization
• Copper Coating (C11000 / C19700 / C4400)
• Biomedical Waste Management
• Restricted Antibiotic Usage
• Decolonization (04-Point-Technique)

14. THANK YOU