Thesis (M.Sc.) -Cairo University, 2024.

Bibliography: pages 73-98.

Background: Multidrug-resistant (MDR) Klebsiella pneumoniae represents a growing threat to human health, causing infections associated with high morbidity and mortality. Since colistin is one of the few treatment options for treating these infections, colistin resistance represents a challenge due to the limited range of potentially available effective antibiotics. Antibiotic combination therapy has proven to be superior to monotherapy increasing the efficacy of the drugs and reducing toxicity and resistance.

Objectives: The study aimed to evaluate the in vitro antibacterial activity of colistin-meropenem and colistin-amikacin combinations on MDR colistin- resistant Klebsiella pneumoniae.

Methods: A total number of thirty colistin-resistant Klebsiella pneumoniae isolates were collected. Klebsiella pneumoniae isolates were identified by their colony morphology on MacConkey ’s agar and standard biochemical reactions. All isolates were tested for their susceptibility to antibiotics using the Kirby- Bauer disk diffusion method and proven to be multidrug -resistant. The colistin broth disk elution method confirmed colistin resistance in all isolates. The checkerboard method to test the antibiotic combinations was used.

Results: The results revealed that colistin-meropenem combination had a better synergistic effect (73.3%) on MDR colistin -resistant Klebsiella pneumoniae isolates compared to colistin-amikacin combination (40%) with a statistically significant difference between them (P-value= 0.015).

Conclusion: Antibiotic combination therapy is a promising option for treating

MDR colistin-resistant Klebsiella pneumoniae.

النشاط المختبري لمزيج الكوليستين مع مضادات حيوية أخرى ضد الكلبسيلا الرئوية المقاومة للكوليستين /

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