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Volume 38, Issue 2

Original Article

Investigation of Biofilm Formation and Antibacterial Susceptibility in Klebsiella and Acinetobacter Strains Isolated from Hospital-Acquired Pneumonia

İlkay Nur Can
Affiliations
  • Kanuni Sultan Süleyman Eğitim ve Araştırma Hastanesi, İnfeksiyon Hastalıkları ve Klinik Mikrobiyoloji Kliniği, İstanbul, Türkiye
https://orcid.org/0000-0002-3307-4837
,
Sema Alp
Affiliations
  • Dokuz Eylül Üniversitesi Tıp Fakültesi Hastanesi, İnfeksiyon Hastalıkları ve Klinik Mikrobiyoloji Anabilim Dalı, İzmir, Türkiye
https://orcid.org/0000-0003-2807-8769
,
Nur Yapar
Affiliations
  • Dokuz Eylül Üniversitesi Tıp Fakültesi Hastanesi, İnfeksiyon Hastalıkları ve Klinik Mikrobiyoloji Anabilim Dalı, İzmir, Türkiye
https://orcid.org/0000-0002-7759-5992
  • antibiotic susceptibility test
  • Biofilm
  • disc diffusion
  • E test
  • microdilution

Abstract

Objective: This study aimed to evaluate the biofilm formation and susceptibility of Klebsiella pneumoniae and Acinetobacter baumannii strains, isolated as causative agents of ventilator-associated pneumonia (VAP), to meropenem and amikacin using various antimicrobial susceptibility testing methods. Additionally, the study investigated the potential impact of biofilm formation on the outcomes of agar-based antibiotic susceptibility tests.

Methods: K. pneumoniae and A. baumannii strains were isolated from tracheal aspirate samples of patients diagnosed with VAP between October 2019 and June 2021 in the intensive care unit. Biofilm production was tested using the tissue culture plate method. Broth microdilution, E-test, and disk diffusion methods were used to assess susceptibility to meropenem and amikacin. The agreement between these methods was evaluated using the Kappa test.

Results: Among 98 isolates, 67 were identified as A. baumannii and 31 as K. pneumoniae. Biofilm production was detected in all K. pneumoniae isolates and 83.6% of A. baumannii isolates. Biofilm formation was significantly more frequent in K. pneumoniae (p=0.015). Resistance rates determined by the microdilution method were significantly higher in A. baumannii isolates for both meropenem (p=0.003) and amikacin (p=0.042) compared to those of K. pneumoniae. In biofilm-producing K. pneumoniae, agreement among test methods was stronger for meropenem (kappa=0.71) than for amikacin (kappa=0.32).

Conclusion: Although the number of tested isolates in our study was limited, concordance was observed between disk diffusion, E-test, and microdilution methods for meropenem in biofilm-producing K. pneumoniae strains. However, the same level of agreement was not observed for amikacin. It is considered that the formation of biofilm-like structures on the agar surface by microorganisms, combined with the hydrophilic nature of amikacin limiting its penetration into these structures, may significantly affect the test results.

A Correction to this article was published on 24 October 2025.

Show References

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  • 103-11
  • İlkay Nur Can
  • [email protected]
  • 10.36519/kd.2025.5108
  • October 20, 2024
  • March 29, 2025
  • June 28, 2025

  • Can İN, Alp S, Yapar N. [Investigation of biofilm formation and antibacterial susceptibility in Klebsiella and Acinetobacter strains isolated from hospital-acquired pneumonia]. Klimik Derg. 2025;38(2):103-11. Turkish.
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