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)

6. • a

7. • aa

8. • aa

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