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العنوان
Fluoroquinolones Resistance and its Potential Underlying Mechanisms in some Gram Negative Bacterial Isolates Recovered from Infected Cancer Patients /
المؤلف
Atwa, Samira Mohamed Hamed.
هيئة الاعداد
باحث / Samira Mohamed Hamed Atwa, M.Sc.
مشرف / Mohamed Seif El-din Ashour
مشرف / Walid Faisal Ahmed Elkhatib
مناقش / Hadir Ahmed El-Mahallawy
تاريخ النشر
2018.
عدد الصفحات
173 P. :
اللغة
الإنجليزية
الدرجة
الدكتوراه
التخصص
العلوم الصيدلية
تاريخ الإجازة
1/1/2018
مكان الإجازة
جامعة عين شمس - كلية الصيدلة - قسم الميكروبيولوجيا والمناعة
الفهرس
Only 14 pages are availabe for public view

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from 173

Abstract

Fluoroquinolones (FQs) are the drugs of choice for prophylaxis of bacterial infections in immunocompromised cancer patients. FQs prophylaxis has been long questioned for favoring the emergence of FQ resistance. The current study aimed to investigate FQs resistance and the underlying resistance mechanisms in Gram negative pathogens causing infections to cancer patients. A total of 239 Gram negative isolates were recovered from various clinical specimens collected at the national cancer institute (NCI), Cairo, Egypt. The recovered isolates were identified as Escherichia coli (95; 39.7%), Klebsiella pneumoniae (82; 34.3%), Acinetobacter baumannii (24; 10%), Pseudomonas aeruginosa (19; 7.9%) and other Gram negative species (19; 7.9%) comprising Enterobacter cloacae (8; 3.3%), E. aerogenes (5; 2.1%), K. oxytoca (3; 1.3%), Proteus mirabilis (2; 0.8%) and Citrobacter freundii (1; 0.4%). Disc diffusion and broth microdilution tests showed that 70.7% of the isolates were non-susceptible to ciprofloxacin (CIP) (MIC50= 64 mg/l). Polymerase chain reaction (PCR) showed that 53.6% of the isolates carried at least one plasmid-mediated quinolone resistance (PMQR) determinant. Of the PMQR-positive isolates, 23.4% were susceptible to CIP. The most prevalent gene was aac(6′)-Ib-cr that was identified in 36.8% of the isolates, while qnr genes were harbored by 31.0% (qnrS, 24.3%; qnrB, 7.1%, and qnrA, 0.4%). The oqxAB genes were only detected in Klebsiella spp. isolates (92.5%). PMQR-determinants were more likely detectable among isolates recovered from pediatric patients than adults (59.3% versus 43.8%) and were significantly associated with ceftriaxone (CRO) and gentamicin (GEN) resistance. A combined genetic analysis using random amplified polymorphic DNA (RAPD)-PCR and enterobacterial repetitive intergenic consensus (ERIC)-PCR showed that most of the qnr-positive isolates were not clonal. Target site mutations were analyzed using PCR and DNA sequencing in 15 selected CIP-resistant isolates. Of which, all had gyrA mutations (codons 83 and 87) with parC mutations (codons 80 and 84) in 93.3%. CIP MIC reduction by combining carbonyl-cyanide-m-chlorophenylhydrazone (CCCP), an efflux pump inhibitor, was tested among the CIP-resistant isolates. Using a cut off value of a four fold reduction, the contribution of efflux activity to FQ resistance was suspected in 18.3% of the isolates more frequently among non-fermenters (50.0%).
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The effect of combining CIP with various antimicrobial agents was tested in eight isolates of different species using the checkerboard assay. Indifferent effect on CIP activity was found in most combinations (52.5%), additive effect in 42.5% of them. Synergism was evident in only two (5.0%) where CIP was combined with either of amikacin (AMK) and CRO. Combining CIP with silver oxide nanoparticles (NPs) was also tested by the broth microdilution method and showed variable effect on CIP MIC. Four fold CIP MIC reduction was achieved in two isolates (25.0%) while 37.5% showed two fold CIP MIC reduction. Silver oxide NPs did not make any difference in CIP MIC of two isolates (25.0%) and caused four fold increase in CIP MIC in one isolate.
FQs resistance among Gram negative isolates causing infections in cancer patients was found to be the result of a complex interplay between most of the known FQs resistance mechanisms each demonstrated in a high prevalence. Additional evidence that chromosomal target site mutations play an essential role in FQs resistance was provided. Dissemination of PMQR genes, with a high prevalence, was demonstrated in clonally unrelated isolates. Reduced antibiotic accumulation arising from the over expression of efflux pump systems was also evident but with low impact on CIP MIC. An association of CIP resistance and PMQR genes with non-susceptibility to other antimicrobial agents was demonstrated. Accordingly, failure of empirical treatments of Gram negative infections in cancer patients following CIP prophylaxis is a possible scenario.
Findings emerging from several aspects of our study also raised concerns about the efficacy of FQs use for prophylaxis of bacterial infections in cancer patients in our region. Detection of PMQR genes in CIP-susceptible bacteria sheds light onto the urgent need to reconsider the existing FQs breakpoints defined by the clinical and laboratory standards institute (CLSI). Synergism between CIP and each of AMK and CRO was demonstrated in only two isolates while silver oxide NPs had variable effects on the antimicrobial activity of CIP. Further investigation of CIP combinations with other antimicrobial and non-antimicrobial agents are required.