In-vitro susceptibility of linezolid against methicillin resistant Staphylococcus aureus at a tertiary care hospital in Pakistan

Abstract

Objective: Methicillin resistant Staphylococcus aureus is a major nosocomial pathogen causing significant morbidity and mortality. The aim of this study was to evaluate the in vitro activity of linezolid against methicillin-resistant S. aureus. Methods: This was a descriptive study carried out at the Department of Microbiology, Army Medical College Rawalpindi from January to July 2010. The in vitro minimum inhibitory concentration of linezolid was determined against 74 strains of methicillin-resistant S. aureus by using the Epsilon- test (E-test) method (AB Biodisk, Sweden). Methicillin-resistant S. aureus was isolated from routine clinical specimens using standard microbiological procedures. Cefoxitin (30 μg) disk was used for detection of methicillin-resistant strains of Staphylococcus aureus. Results: Seventy-four isolates of methicillin-resistant S. aureus were obtained from various clinical samples. The majority of samples were from the pus followed by nasobronchial lavage, urine and vaginal swabs. All the isolates were highly susceptible to linezolid with minimum inhibitory concentration range of 0.023 - 0.75 mg/dL having MIC50 0.25 and MIC90 0.5 mg/dL respectively. Conclusion: Linezolid shows good in vitro activity against methicillin-resistant Staphylococcus aureus.

Keywords

• Linezolid, methicillin resistance, minimum inhibitory concentration, Staphylococcus aureus, vancomycin

In-vitro susceptibility of linezolid against methicillin resistant Staphylococcus aureus at a tertiary care hospital in Pakistan

Öz

Amaç: Metisilin dirençli Staphylococcus aureus belirgin morbidite ve mortaliteye neden olan önemli bir nozokomiyal patojendir. Bu çalışmanın amacı, metisilin dirençli S. aureus’a karşı linezolidin in vitro etkinliğini değerlendirmektir.Yöntemler: Army Medical College Rawalpindi Mikrobiyoloji Anabilim Dalında, Temmuz-Ocak 2010’da yürütülen tanımlayıcı bir çalışmadır. Linezolid için in vitro minimum inhibe edici konsantrasyon, metisiline dirençli 74 S. aureus türü için Epsilon- test (E-test) metodu (AB Biodisk, İsveç) kullanılarak belirlendi. Metisiline dirençli S. aureus standart mikrobiyolojik yöntemler kullanılarak rutin klinik örneklerden izole edilmiştir. Metisilin dirençli S. aureus suşlarının saptanması için sefoksitin (30 µg) disk kullanılmıştır. Bulgular: Metisilin dirençli 74 S. aureus izolatı çeşitli klinik örneklerden elde edilmiştir. Numunelerin çoğunluğu nasobronchial lavaj, idrar ve vajinal sürüntülerden alınan püydü. Tüm izolatların 0.023-0.75 mg/dL minimum inhibitör konsantrasyon aralığında sırasıyla MIC50 0.25 ve MIC90 0.5 mg/dL ile linezoilde son derece duyarlı idi.Sonuç: Linezolid metisiline dirençli S. aureus karşı i in vitro iyi aktivite gösterir

Anahtar Kelimeler

• Linezolid, metisilin direnci, minimum inhibitör konsantrasyon, Staphylococcus aureus, vankomisin

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