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  1. 1.MRSA stands for?
  2. 2.identify and interpret the given picture.
  3. 3.What is ICR?
  4. 4.What are the clinical indications of clindamycin ?
  5. 5.What are the drugs that can be used in MRSA infections.
  6. 6.what drugs have to to be avoided in MRSA infections.

1. MRSA stands for Methicillin resistant Staphylococcus aureus. It is the most common multidrug resistant organism causing HAI. The resistance is mediated by a chromosomally coded mec A gene which alters penicillin binding protein (PBP) on S.aureus cell membrane to PBP 2a. As PBP is essential protein needed for cell wall synthesis of bacteria . lactam drugs bind and inhibit this protein,there by inhibiting the cell wall synthesis. This altered PBP 2a of MRSA has less affinity for β lactam antibiotics; hence MRSA are resistant to all lactam antibiotics including Penicillins, Cephalosporins (except Fifth generation cephalosporins like – ceftaroline, ceftobiprole only β lactam which is effective against MRSA), Carbapenems and Aztreonam.

2. Identify and interpret the given picture?
The given pictures is showing Antibiotic Susceptibility Testing (AST) performed by Kirby Bauer’s Disc diffusion method. In this a lawn culture of MRSA (Methicillin Resistant Staphylococcus aureus) was done on Muller Hinton Agar and incubated at 37oC for 18-24hrs. The above isolate is resistant to Penicillin, Clindamycin(P), Ciprofloxacin(CIP), Erythromycin and Cefixime (CXM) and cefoxitin. MRSA isolates are resistant to all the beta lactam antibiotics and cefoxitin. Indicating Erythromycin has induced and allowed expression of clindamycin resistance. Thus the isolate is resistant to both Erythromycin and Clindamycin. Thus clindamycin is not useful in this patient with MRSA infection as it can result in treatment failure. Cefoxitin is used to detect MRSA isolates

3. What is ICR? Clindamycin is an alternative antibiotic in the treatment of Staphylococcus aureus infections, both in infections by methicillin susceptible and resistant (MSSA and MRSA) strains. The major problem of use of clindamycin for staphylococcal infections is the presence of inducible clindamycin resistance that can lead to treatment failure in such infections(1). Inducible clindamycin resistance. (i MLSB phenotype)Erythromycin is an inducer of clindamycin resistance (IMLSB), which induces production of erythromycin ribosomal methylase (erm) that allows expression of clindamycin resistance. Double disc diffusion (D test) is recommended by CLSI for detection of inducible clindamycin resistance [2]. A negative result for inducible clindamycin resistance (ICR) by D test confirms clindamycin susceptibility and provides a good therapeutic option, thus necessitates the detection of inducible clindamycin resistance [3]. A positive Dtest indicates the drug cannot be used. (Erythromycin resistant, Clindamycin sensitive) Thus a D test should be performed on all isolates of MRSA and the inducible clindamycin resistance must be taken into consideration by the clinicians while treating MRSA to avoid treatment failure.

4. What are the clinical indications of clindamycin ? A. Clindamycin is an alternative to the penicillins and cephalosporins for the treatment of skin and soft tissue infections. Clindamycin is the drug of choice, combined with penicillin, for severe group A streptococcal infection and possibly C perfringens infections. Clindamycin is the drug of choice for moderate to severe diabetic foot infections, usually combined with a quinolone, although cephalexin is equally effective for mild to moderate infections.

Clindamycin is an alternative to penicillins and cephalosporins for the treatment of septic arthritis and osteomyelitis, but is the drug of choice in diabetic osteomyelitis, combined with a quinolone. Clindamycin is an alternative to penicillins for dental infections and endocarditis prophylaxis and is the treatment of choice for recurrent streptococcal pharyngitis/tonsillitis. Clindamycin is the treatment of choice for anaerobic lung infections, including anaerobic lung abscess and necrotizing pneumonia. Clindamycin may be employed as an alternative for treatment of intra-abdominal and pelvic infections , in the treatment of C trachomatis in pregnancy and as an alternative to metronidazole for the treatment of bacterial vaginosis. Clindamycin is an alternative to trimethoprim/ sulfamethoxazole for the treatment of P carinii pneumonia. It should be used sparingly in in-patients because of its association with C difficile colonization and diarrhea.

5. What are the drugs that can be used in MRSA infections? Clindamycin, Cotrimoxazole, Ceftaroline, Dalbavancin, Daptomycin, Dicloxacillin, Doxyxycline, Linezolid, Quinupristin/Dalfopristin, Telavancin, Oritavancin, Tigecycline, Nafcillin,Vancomycin Emperical therapy( IF MRSA STATUS IS NOT YET KNOWN). Vancomycin with or without an aminoglycoside. Vancomycin is indicated only if MRS risk is high as in hospitalised patients with serious invasive infections. Antibiotics should be cautiously chosen.

6. Drugs to be avoided in MRSA infections?Erythromycin, Cephalexin, Ciprofloxaicn,

  1. Current indications for the use of clindamycin: A critical review. Marek Smieja, MD FRCPC DTM&H. Can J Infect Dis. 1998 Jan-Feb; 9(1): 22–28.
  2. Clinical Laboratory Standards Institute (CLSI) guidelines. Performance standards for antimicrobial susceptibility testing: twenty second informational supplement. CLSI document M100-S22. Clinical and Laboratory Standards Institute. Pennsylvania; Wayne; 2012.
  3. Rodrigues Perez LR, Caierao J, Souza Antunes AL, Alves d’Azevedo P. Use of D test method to detect inducible clindamycin resistance in coagulase negative staphylococci (CoNS). Braz J Infect Dis. 2007;11:186-88.
  4. Methicillin-Resistant Staphylococcus aureus:A growing risk in the hospital and in the community.JoseL.Raygada, P.Levine. American health and drug benefits,vol 2,No.2,feb-March 2009.
  5. Inducible Clindamycin Resistance among Clinical Isolates of Staphylococcus aureus from Sub Himalayan Region of India. Kiran K. MoKta1, Santwana VerMa2, DiVya Chauhan3, Sunite a. Ganju4, DiGVijay SinGh5, anil KanGa6, anita KuMari7, VinoD Mehta8. Journal of Clinical and Diagnostic Research. 2015 Aug, Vol-9(8): DC20-DC2