Klinik Örneklerden İzole Edilen Çoklu İlaç Dirençli Gram Negatif İzolatların Kolistin Direncinin Sıvı Mikrodilüsyon ve Otomatize Sistem ile Karşılaştırılması

Abstract

Çoklu ilaca dirençli (ÇİD) Gram-negatif bakteriler, özellikle hastane enfeksiyonlarında tedavi seçeneklerini kısıtlayan önemli bir sağlık sorunudur. Kolistin, Acinetobacter baumannii, Klebsiella pneumoniae ve Pseudomonas aeruginosa gibi patojenlere karşı son çare antibiyotiklerden biri olarak kullanılmaktadır. Ancak kolistin duyarlılığının doğru belirlenmesi, uygun tedavi yönetimi açısından kritik öneme sahiptir. Bu çalışmada kolistin duyarlılığının belirlenmesinde BD Phoenix™ 100 sistemi ile sıvı mikrodilüsyon (SMD) yöntemi karşılaştırılmıştır. Toplam 758 Gram-negatif izolat değerlendirilmiştir. SMD yöntemine göre izolatların 541’i (%71,4) duyarlı, 217’si (%28,6) dirençli bulunurken; Phoenix™ 100 sistemi ile 647 (%85,4) izolat duyarlı, 111’i (%14,6) dirençli olarak raporlanmıştır. Tanı testi performans analizinde BD Phoenix™ 100 sisteminin genel kategorik uyumu (KU) %81,0, büyük hata (BH) oranı %3,5 ve çok büyük hata (ÇBH) oranı %57,6 olarak hesaplanmıştır. Tür bazında değerlendirildiğinde A. baumannii için KU %81,3, BH %2,4, ÇBH %65,0; K. pneumoniae için KU %80,8, BH %4,9, ÇBH %50,5; P. aeruginosa için ise KU %79,5, BH %3,3, ÇBH %57,1 bulunmuştur. Özellikle yüksek ÇBH oranı, dirençli izolatların yanlışlıkla duyarlı olarak raporlanabileceğini göstermekte ve tedavi başarısızlığı açısından ciddi risk oluşturmaktadır. Sonuç olarak, kolistin duyarlılığının değerlendirilmesinde SMD yönteminin altın standart olarak kullanılması ve Phoenix™ 100 sonuçlarının doğrulanması gerektiği düşünülmüştür.

Keywords

• Acinetobacter baumannii
• BD Phoenix otomatize sistem
• Klebsiella pneumoniae
• Kolistin
• Pseudomonas aeruginosa
• Sıvı mikrodilüsyon

Comparison of Colistin Resistance in Multidrug-Resistant Gram-Negative Clinical Isolates Using Broth Microdilution and Automated Systems

Abstract

Multidrug-resistant (MDR) Gram-negative bacteria have become a major healthcare problem, particularly in hospital-acquired infections. Colistin remains one of the last-resort antibiotics against pathogens such as Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Accurate determination of colistin susceptibility is therefore critical for appropriate patient management. In this study, the BD Phoenix™ 100 automated system was compared with the broth microdilution (BMD) method for colistin susceptibility testing. A total of 758 Gram-negative isolates were evaluated. According to the BMD method, 541 (71.4%) isolates were susceptible and 217 (28.6%) were resistant, whereas the Phoenix™ 100 system reported 647 (85.4%) isolates as susceptible and 111 (14.6%) as resistant. Performance analysis of the BD Phoenix™ 100 system demonstrated an overall categorical agreement (CA) of 81.0%, a major error (ME) rate of 3.5%, and a very major error (VME) rate of 57.6%. Species-based analysis revealed CA, ME, and VME rates of 81.3%, 2.4%, and 65.0% for A. baumannii; 80.8%, 4.9%, and 50.5% for K. pneumoniae; and 79.5%, 3.3%, and 57.1% for P. aeruginosa, respectively. The high VME rates indicate that a substantial proportion of resistant isolates may be falsely reported as susceptible, posing a serious risk for treatment failure. In conclusion, the broth microdilution method should remain the gold standard for colistin susceptibility testing, and Phoenix™ 100 results should be confirmed by BMD, particularly for critical isolates.

Keywords

• Acinetobacter baumannii
• BD Phoenix automated system
• Klebsiella pneumoniae
• Colistin
• Pseudomonas aeruginosa
• Broth microdilution

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