Evaluation of Biofilm Formation in Coagulase Negative Staphylococci on Various Congo Red Agar Medium

Abstract

Objectives: In this study, it was aimed to evaluate the performance of different Congo red agar (CRA) media and its modifications in comparison with the microplate method in the demonstration of biofilm formation in coagulase negative staphylococcus (CoNS) isolates. Materials and Methods: A total of 80 CoNS isolates, including 24 (30%) catheter colonizers, 13 (16.3%) bloodstream infection (BSI) agents, 20 (25%) catheter-related bloodstream infection (CR-BSI) agents and 23 (28.8%) obtained from the nasal cavities of hospital staff, were evaluated in the study. In the determination of biofilm formation, CRA mediums (CRA G (2% glucose added), CRA GN (2% glucose and 1.5% NaCl added), CRA GNV (2% glucose, 1.5% NaCl 0.5 μg/mL vancomycin added) and microplate method were used. Sensitivity, specificity, positiveN predictive and negative predictive values were calculated by comparing with the microplate method. Results: Staphylococcus hominis was the most frequently detected species (36.25%), followed by Staphylococcus epidermidis (35%), Staphylococcus haemolyticus (13.75%), Staphylococcus capitis (11.25%), Staphylococcus saprophyticus (2.5%), and Staphylococcus warneri (1.25%). Thirty-four (42.5%) isolates were detected by CRA method, 57 (71.25%) [18 (22.5%) weak, 24 (30%) medium strength, 15 (18.75%) strong biofilm] isolates were detected by microplate method. Six (7.5%) of CoNS agents of BSI, 20 (25%) of CoNS agents of CRBSI, 18 (22.5%) of those with catheter colonization, 13 (16.3%) of those isolated from nasal cavities formed a biofilm of varying strengths. The sensitivities of the CRA, CRA G, CRA GN and CRA GNV methods were 59.6%, 59.6%, 59.6% and 58.2%, and their specificities were 100%, respectively. Conclusion: Biofilm formation in staphylococcal species is affected by various environmental conditions and media content. To assess biofilm formation in all staphylococcal isolates, no superiority of modified CRA media was found over the original CRA. Microplate method can be recommended as a general screening method for the detection of biofilm-producing bacteria, compared to CRA and its modified forms.

Keywords

• Biofilm
• Coagulase Negative Staphylococci
• Congo Red Agar and Modified Forms
• Microplate Method

Koagülaz Negatif Stafilokoklarda Biyofilm Oluşumunun Çeşitli Kongo Kırmızısı Besiyerlerinde Değerlendirimi

Abstract

Amaç: Bu çalışmada koagülaz negatif stafilokok (KNS) izolatlarının biyofilm oluşturma özelliklerinin saptanmasında kullanılan Kongo kırmızısı agar (KKA) besiyeri ve modifikasyonlarının performanslarının mikroplak yöntemi ile karşılaştırılarak değerlendirilmesi amaçlanmıştır. Gereç ve Yöntem: Çalışmada 24’ü (%30) kateter kolonizanı, 13’ü (%16,25) kan dolaşım enfeksiyonu (KDE) etkeni, 20’si (%25) kateter ilişkili kan dolaşım enfeksiyonu (KİKDE) etkeni ve 23’ü (%28,75) hastane çalışanlarının burun boşluklarından elde edilen olmak üzere toplam 80 KNS izolatıdeğerlendirilmiştir. Biyofilm özelliklerinin incelenmesinde KKA besiyerleri [KKA G (%2 glukoz ilaveli), KKA GN (%2 glukoz ve %1,5 NaCl ilaveli), KKAGNV (%2 glukoz, %1,5 NaCl 0,5 μg/mL vankomisin ilaveli)] ve mikroplak yöntemi kullanılmıştır. Mikroplak yöntemi ile kıyaslanarak KKA besiyerleriiçin duyarlılık, özgüllük, pozitif ve negatif prediktif değerleri hesaplanmıştır. Bulgular: İzolatların %36,25’i Staphylococcus hominis, %35’i Staphylococcus epidermidis, %13,75’i Staphylococcus haemolyticus, %11,25’iStaphylococcus capitis, %2,5’i Staphylococcus saprophyticus ve %1,25’i Staphylococcus warnerii olarak tiplendirilmiştir. KKA yöntemi ile 34’ü(%42,5), mikroplak yöntemi ile 57’si (%71,25) [18’i (%22,5) zayıf, 24’ü (%30) orta kuvvette ve 15’i (%18,75) kuvvetli], biyofilm pozitif olarak saptanmıştır. KDE etkeni olan KNS’lerin 6’sı (%7,5), KİKDE etkeni olan KNS’lerin 20’si (%25),kateter kolonizanı olanların 18’i (%22,5), burun boşluklarından izole edilenlerin 13’ü (%16,25) çeşitli kuvvetlerde biyofilm oluşturmuştur. KKA, KKA G ve KKA GN ve KKA GNV yöntemlerinin duyarlılıkları sırasıyla %59,6, %59,6, %59,6 ve %58,2, özgüllükleri ise %100’dür. Sonuç: Stafilokok türlerinde biyofilm oluşumu çeşitli çevresel koşullardan ve besiyeri içeriğinden etkilenmektedir. Çalışmamızda stafilokok izolatlarında biyofilm oluşumunu değerlendirmek için, modifiye KKA besiyerlerinin orijinal KKA besiyerine göre üstünlüğü saptanmamıştır. Biyofilm üreten bakterilerin saptanmasında KKA ve modifiye formlarına kıyasla, mikroplak yönteminin kullanılması daha uygundur

Keywords

• Biyofilm
• Koagülaz Negatif Stafilokok
• Kongo Kırmızısı Agar ve Modifikasyonları
• Mikroplak Yöntemi

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