Original Research
Tuesday, October 15, 2024
08:30 AM–10:00 AM
Abstract
Introduction:
Increasing incidence of antimicrobial resistance limits therapeutic options and worsens patient outcomes. Cefiderocol is a siderophore conjugated antibiotic utilizing iron metabolism pathways for cell entry, whose resistance mechanisms are not fully elucidated.
Research Question or Hypothesis:
To examine possible mechanisms of cefiderocol resistance in Klebsiella pneumoniae.
Study Design:
Methods:
KP ATCC 13883(wild type),KP MK8(cefiderocol sensitive) and KP 550(cefiderocol resistant) were tested for biofilm formation in cation-adjusted Mueller Hinton broth(CAMHB) and iron-depleted Mueller Hinton broth(ID-MHB). Absorbance at ?600 was measured to quantitate biofilm density and normalized to bacterial growth. Cellular iron content was measured by streptonigrin resistance assay, siderophores production was measured by chrome azurol test. Bacterial cultures ware incubated with sub-inhibitory concentrations of cefiderocol then assayed by LC/MS and compared to control to detect the presence degrading enzymes. All testing was performed on six biological duplicates for statistical robustness.
Results:
The normalized absorbance(mean ±SD) in CAMHB(KP ATCC13883; 0.20±0.07,KP MK8; 0.27±0.09,KP 550; 0.49±0.09), in ID-MHB(KP ATCC 13883;0.046±0.002,KP MK8; 0.049±0.003,KP 550;0.128±0.009). Calculated siderophore units were 2.94, 3.10, 3.15 in CAMHB and 4.10, 4.33, 4.45 in ID-MHB for KP ATCC 13883,KP MK8 and KP 550 respectively. As low cellular iron content mediates streptonigrin resistance, analysis of survival showed mean growth(CFU/mL) 1.9x102, 1.7x102, 1.9x102 in CAMHB and 2.6x104, 2.1 x104, 2.4x104 in ID-MHB for KP ATCC 13883, KP MK8 and KP 550 respectively. Mean cefiderocol concentrations at the end of 2-hour incubation period were 83% in control 78% in KP ATCC 13883 and 44% in KP 550 of the initial 0-hour concentration.
Conclusion:
Cefiderocol resistant KP did not produce significantly higher biofilm density, higher amount of siderophore nor store more iron relative to the wild type and sensitive isolate. Degradation of cefiderocol was faster in the resistant isolate indicating possible production of hydrolyzing enzymes. These observations will be confirmed by whole genome sequencing to examine corresponding genes.
Presenting Author
Islam Ghazi PharmDArnold and Marie Schwartz College of Pharmacy
Authors
Diaa Alrahmany BSc Pharm
3- Pharmaceutical Care Department, Directorate General of Medical Supplies, Ministry of Health, Muscat 3110, Oman
Wasim Elnekidy PharmD, BCPS, BCACP
Cleveland Clinic Abu Dhabi
Gehan Harb B.Sc. Phamr
Harb Statisitics