E F F E C T S O F L Y S O Z Y M E AND NISIN ON G R O W T H AND B I O F I L M F O R M A T I O N O F F O O D B O R N E S T A P H Y L O C O C C U S A U R E U S STRAINS Staphylococcus aureus is one of the most important pathogenic bacteria in food producing toxins and causing food poisoning. In this study, the effects of biopreservatives lysozyme and nisin on growth and biofilm formation of S. aureus strains (n=14) isolated from different foods were examined by quantitative microplate method. On the basis of obtained data, 1, 2, 3, 4, and 5 mg/ml o f lysozyme concentrations did not inhibit the growth of strains and all strains were determined as resistant to lysozyme. On the other hand, nisin at 12,5 mg/ml concentration showed 100% inhibition on most o f the strains, except S. aureus SE-22C strain at 37,5 mg nisin/ml concentration, the growth of strain was obtained after a long incubation time. As a result of biofilm tests, in four strains increasing concentrations of lysozyme were found to activate biofilm formation. In SE-22C strain, with compared to medium without lysozyme, firstly biofilm formation was decreased then with increasing lysozyme concentrations the increased biofilm formation was obtained. In addition, in two strains biofilm formation was decreased with increased lysozyme concentrations. Nisin reduced biofilm formation o f four strains with increasing concentrations, but there was no effect o f nisin on biofilm formation o f the other strains. As a result of this study, lysozyme was determined as an ineffective biopreservative against S. aureus strains, but it can activate biofilm formation o f the strains. Conversely, high concentrations of nisin had an inhibitory effect on bacterial growth, whereas the presence o f nisin resistant S. aureus strains could exist
ÖZET
Staphylococcus aureus gıdalarda gelişebilen ve ürettiği toksinlerle gıda zehirlenmesine yol açan en önemli patojen bakterilerdendir. Bu çalışmada, besin maddelerinde sıklıkla biyokoruyucu olarak kullanılan lizozim ve nisinin, değişik gıdalardan izole edilen 14 adet S. aureus suşunun gelişme ve biyofilm oluşturması üzerindeki etkileri kantitatif mikroplaka yöntemi ile araştırılmıştır. Elde edilen veriler doğrultusunda 1, 2, 3, 4 ve 5 mg/ml konsantrasyonlardaki lizozimin, bakteri gelişmesini engelleme yönünde hiçbir etkisinin olmadığı ve tüm suşların lizozime karşı dirençli oldukları tespit edilmiştir. Diğer yandan, 12,5 μg/ml konsantrasyonda nisinin bazı suşlarda % 100 inhibisyon gösterdiği saptanmış, sadece bir suşta ise (S. aureus SE-22C) 37,5 μg/ml konsantrasyonda uzun inkübasyon sonrasında gelişme görülmüştür. Biyofilm testleri sonucunda, lizozimin artan konsantrasyonlarının dört suşta biyofilm yapımını aktive ettiği, bir suşta ise lizozim içermeyen besiyerine göre önce azalttığı, artan lizozim konsantrasyonlarında ise biyofilm oluşumunu arttırdığı tespit edilmiştir. Diğer yandan lizozimin artan konsantrasyonlarının iki suşta biyofilm oluşumunu azalttığı görülmüştür. Nisinin artan konsantrasyonlarının dört suşta bakterilerin biyofilm oluşumunu azalttığı, diğer suşlarda ise bir değişikliğe yol açmadığı bulunmuştur. Çalışmamız neticesinde lizozimin S. aureus suşlarına karşı etkisiz bir biyokoruyucu olduğu, fakat biyofilm yapımını aktive edebildiği; buna karşın nisinin yüksek konsantrasyonlarda bakteri gelişmesi üzerine inhibisyon etkisinin olduğu, ancak nisine dirençli S. aureus suşlarının bulunabileceği sonucuna varılmıştır.
Anahtar Kelimeler: Staphylococcus aureus, lizozim, nisin, biyofilm, gıda
ABSTRACT
EFFECTS OF LYSOZYME AND NISIN ON GROWTH AND BIOFILM FORMATION OF FOODBORNE STAPHYLOCOCCUS AUREUS STRAINS
Staphylococcus aureus is one of the most important pathogenic bacteria in food producing toxins and causing food poisoning. In this study, the effects of biopreservatives lysozyme and nisin on growth and biofilm formation of S. aureus strains (n=14) isolated from different foods were examined by quantitative microplate method. On the basis of obtained data, 1, 2, 3, 4, and 5 mg/ml of lysozyme concentrations did not inhibit the growth of strains and all strains were determined as resistant to lysozyme. On the other hand, nisin at 12,5 mg/ml concentration showed 100% inhibition on most of the strains, except S. aureus SE-22C strain at 37,5 mg nisin/ml concentration, the growth of strain was obtained after a long incubation time. As a result of biofilm tests, in four strains increasing concentrations of lysozyme were found to activate biofilm formation. In SE-22C strain, with compared to medium without lysozyme, firstly biofilm formation was decreased then with increasing lysozyme concentrations the increased biofilm formation was obtained. In addition, in two strains biofilm formation was decreased with increased lysozyme concentrations. Nisin reduced biofilm formation of four strains with increasing concentrations, but there was no effect of nisin on biofilm formation of the other strains. As a result of this study, lysozyme was determined as an ineffective biopreservative against S. aureus strains, but it can activate biofilm formation of the strains. Conversely, high concentrations of nisin had an inhibitory effect on bacterial growth, whereas the presence of nisin resistant S. aureus strains could exist.
Key Words: Staphylococcus aureus, lysozyme, nisin, biofilm, food
Primary Language | Turkish |
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Journal Section | Research Article |
Authors | |
Publication Date | March 10, 2013 |
Published in Issue | Year 2013 Volume: 39 Issue: 2 |