Çeşitli dezenfektanların minimum bakterisidal konsantrasyonlarının pseudomonas aerugınosa’nın biyofilm kültürlerine karşı araştırılması

Pseudomonas aeruginosa su sistemlerinde, kaynaklarında veya suyla ilgili her ortamda genellikle biyofilmler içerisinde gömülü mikrokoloniler halinde üreme eğilimindedir. Biyofilmler planktonik hücrelere göre dezenfektanlara karşı çok daha dirençli olduğundan, başarılı bir dezenfeksiyon işleminin gerçekleşebilmesi için dezenfektanların biyofilmlere karşı bakterisidal konsantrasyonlarının belirlenmesi gerekmektedir. Bu amaçla, P.aeruginosa ATCC 15442 standart suşunun planktonik ve biyofilm hücre kültürlerine karşı sodyum hipoklorit ve benzalkonyum klorürün minimum bakterisidal konsantrasyonları (MBK) temiz ve kirli olmak üzere iki farklı deney koşulu altında mikrodilüsyon yöntemiyle belirlenmiştir. Temas sürelerinin 5, 10, 15, 30, 60 dakika ve 24 saat uygulandığı deneylerde temiz koşullarda sodyum hipoklorit ve benzalkonyum klorürün planktonik hücrelere karşı MBK değerleri sırasıyla 0.06 mg/ml ve 0.016 mg/ml olarak saptanırken, kirli koşullarda bu değerler, sırasıyla dört ve iki kat artış göstermiştir. Sodyum hipokroritin biyofilmdeki bakteriye karşı MBK değerinin ise, 10 dakikalık temas süresinin sonunda 6 mg/ml olduğu, bu sürenin 30, 60 dakika ve 24 saate uzatıldığında sırasıyla 4, 2 ve 0.5 mg/ml’ye indiği tespit edilmiştir. Benzalkonyum klorürün ise biyofilmdeki bakteriye karşı belirgin bir bakterisidal aktivite gösteremediği saptanmıştır. Sonuç olarak, bulgularımız biyofilm şüphesi bulunan bir su sisteminde dezenfeksiyon işlemi yapılırken kullanılacak dezenfektan maddenin tipini, miktarını ve temas süresini seçerken dezenfektanın biyofilm üzerinde oluşturduğu bakterisidal aktivitenin göz önünde bulundurulması gerektiğini göstermektedir

Evaluation of the minimum bactericidal concentrations of various disinfectants against pseudomonas aeruginosa in biofilm cultures

In water systems, sources or any aqueus environment Pseudomonas aeruginosa tend to grow as microcolonies embeded in biofilms. Since biofilms are much more resistant to disinfectants than planktonic cells, it is necessary to determine the bac- tericidal activity of disinfectants against biofilms, in order to achieve a successful procedure of disinfection. For this purpose, under two different experimental conditions, clean and dirty, the minimum bactericidal concentrations (MBC) of sodium hypochlorite and benzalkonium chloride were assessed against planktonic and biofilm cell cultures of P.aeruginosa ATCC 15442 standard strain using microdilution method. By applying 5, 10, 15, 30, 60 minutes and 24 hours contact time, under clean conditions the MBC values of sodium hypochlorite and benzalkonium chloride against planktonik cells were obtained as 0.06 mg/ml and 0.016 mg/ml, respectively, whereas under dirty conditons these values were increased four and two fold, respectively. The MBC values of sodium hypochlorite against cells in biofilms was 6 mg/ml after an exposure time of 10 minu- tes and decreased to 4, 2 and 0.5 mg/ml after contact time of 30, 60 minutes and 24 hours, respectively. Benzalkonium chlo- ride didn’t show any significant bactericidal activity against biofilms. Consequently, the findings of our study show that when a disinfection procedure is carried out in a water system where biofilms are expected, it is necessary to take the bactericidal activity of the disinfectant into consideration while the type and amount of the disinfectant and exposure time have been choosen.

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