IN VITRO ACTIVITY OF LINEZOLID AGAINST CLINICAL ISOLATES OF METHICILLIN RESISTANT STAPHYLOCOCCUS
AbstractBackground: Staphylococcus is responsible for a variety of medical problems, including skin and softtissue infections (SSTIs), surgical site infections (SSIs), endocarditis and hospital acquired bacteraemia.Methicillin resistance in staphylococcus has become a global problem limiting the treatment modalitiesto a large extent. Methods: The aim of this study was to evaluate the in vitro activity of linezolid andother antibiotics against clinical isolates of methicillin resistant staphylococcus (n=163); including 105methicillin resistant Staphylococcus aureus and 58 methicillin resistant coagulase negativestaphylococci. Antibiogram of these isolates was determined by the Kirby-Bauer disc diffusion methodand minimum inhibitory concentration of linezolid was determined by standard agar dilution method.Results: Overall methicillin resistant S. aureus showed high multi-drug resistance. ATCC 25923Staphylococcus aureus and ATCC 29213 Staphylococcus aureus were used as the standard controlstrains. MIC90 of linezolid was comparable for methicillin resistant coagulase negative staphylococciand methicillin resistant S. Aureus (4.0 mg/L); however at MIC50 linezolid was two fold more activeagainst methicillin resistant coagulase negative staphylococci (1mg/L) than methicillin resistant S.aureus (2mg/L). Conclusion: It is concluded that linezolid has excellent activity against methicillinresistant staphylococci including multidrug resistant strains.Keywords: Linezolid, MIC, MRSA, MRCoNS
Casey AL, Lambert PA, Elliott TSJ. Staphylococci. Int J
Antimicrob Agents 2007;29(Suppl.3):23–32.
Livermore DM. Antibiotic resistance in staphylococci. Int J
Antimicrob Agents 2000;16:3–10.
Raad I, Alrahwan A, Rolston K. Staphylococcus epidermidis:
emerging resistance and need for alternative agents. Clin
Infect Dis 1998;26:1182−7.
Mehdinejad M, Sheikh AF, Jolodar A. Study of methicillin
resistance in staphylococcus aureus and species of coagulase
negative staphylococci isolated from various clinical
specimens. Pak J Med Sci 2008;24:719–24.
Appelbaum PC. Reduced glycopeptide susceptibility in
methicillin-resistant Staphylococcus aureus (MRSA). Int J
Antimicrob Agents 2007;30:398–408.
Perez F, Salata RA, Bonomo RA. Current and novel
antibiotics against resistant Gram-positive bacteria. Infect
Drug Resist 2008;1:27–44.
Zhanel GG, Schroeder C, Vercaigne L , Gin AS, Embil J,
Hoban DJ. A critical review of oxazolidinones: An
alternative or replacement for glycopeptides and
streptogramins?. Can J Infect Dis. 2001;12:379–90.
Clinical and Laboratory Standards Institute.. Performance
standards for antimicrobial susceptibility testing, 17th
informational supplement M100-S17. Clinical and
Laboratory Standards Institute, Wayne, PA. 2007.
CIP SXT AZM AK
MRSA (105) MRCoNS (58)
J Ayub Med Coll Abbottabad 2009;21(1)
Hanlon A, Taylor M, Dick D. Agar dilution susceptibility
testing. In: Schwalbe R, Moore LS, Good win AC, editors.
Antimicrobial Susceptibility Protocols. Newyork: Taylor
And Francis Group; 2007. p.91–103.
Turnidge JD, Bell JM. Antimicrobial susceptibility on solid
media. In: Lorian V, ed. Antibiotics in laboratory medicine.
th ed. Baltimore: Lippincott Williams & Wilkins; 2005. p. 8-
Manfredi R. Update on the appropriate use of linezolid in
clinical practice. Ther Clin Risk Manag 2006:2(4):455–64.
Tiwari HK, Sapkota D, Sen MR. High prevalence of
multidrug-resistant MRSA in a tertiary care hospital of
northern India. Infect Drug Resist 2008;1:57–61.
Pakistan antimicrobial resistance network [homepage on the
Internet]. Available from: http://parn.org.pk/index_files/
Antimicrobial%20data.html. Last accessed at 15th Jan 2009.
Qureshi AH, Rafi S, Qureshi SM, Ali AM. The current
susceptibility patterns of methicillin resistant Staphylococcus
aureus to conventional anti staphylococcus antimicrobials at
Rawalpindi. Pak J Med Sci 2004;20:361–4.
Tunger A. Ayedemir S,Uluer S and Cilli F. In vitro activity
of linezolid and quinipristin/dalfopristin against Gram
positive cocci. Indian J Med Res 2004;120:546–52.
Karlowsky JA, Kelly LJ, Critchley IA, Jones ME,
Thornsberry C, Sahm DF. Determining Linezolid’s Baseline
In Vitro Activity in Canada Using Gram-Positive Clinical
Isolates Collected prior to Its National Release. Antimicrob
Agents Chemother 2002;46:1989–92.