Abstract
Colistin is considered as the last resort for treatment of bacterial infections caused by carbapenem-resistant Gram-negative bacilli (GNB). Colistin resistance can increase due to the spread of plasmid-borne mcr-1 gene. This study aimed to determine colistin susceptibility and to detect the presence of mcr-1 gene in the clinical isolates of GNB recovered from different clinical samples collected from Ain Shams University Hospital, Cairo, Egypt. About thirty-five GNB isolates were recovered from the different clinical samples that were collected during the period from February-April, 2019. These isolates were subjected to antibiotic susceptibility testing using disc diffusion assay, and Colistin susceptibility through the E-test. In addition, conventional Polymerase chain reaction (PCR) was carried out for detection of mcr-1 gene among the colistin GNB resistant isolates. Most of the GNB isolates (60 %) were recovered from blood samples. Klebsiella pneumoniae (K. pneumoniae) was the most common isolated bacterium; that was represented by 24 isolates (68%). Out of the 35 GNB, only five isolates (14.3 %) were resistant to colistin by E-test, with MIC >256 𝜇g/ ml. The mcr-1 gene was detected only in one Pseudomonas aeruginosa (P. aeruginosa) isolate. This study concluded the low frequency of mcr-1 gene among the current GNB isolates. However, a large scale study is recommended to detect colistin resistance among GNB.
Highlights
Colistin, was first recognized as a narrow spectrum antibiotic with potent activity against multidrug resistant (MDR) Gram-negative bacteria (GNB) in the 1940s, but its use as systemic antibiotic was reduced as being nephrotoxic and neurotoxic (Falagas et al, 2005)
A previous study conducted by Baron et al, (2016) reported that the chromosomally-mediated or intrinsic colistin resistance is mediated by different complex mechanisms that lead to the loss or modification in the production of lipopolysaccharide in GNB, and this type of resistance may develop during treatment by colistin drug
This study was conducted on 35 clinical isolates of GNB isolated from different clinical samples from patients admitted to the Intensive care unit (ICU) of Ain Shams University Hospital, during the period from February to April, 2019
Summary
Colistin, was first recognized as a narrow spectrum antibiotic with potent activity against multidrug resistant (MDR) Gram-negative bacteria (GNB) in the 1940s, but its use as systemic antibiotic was reduced as being nephrotoxic and neurotoxic (Falagas et al, 2005). The emergence of resistance against colistin has been detected in different countries worldwide in recent years (Poirel et al, 2017). A previous study conducted by Baron et al, (2016) reported that the chromosomally-mediated or intrinsic colistin resistance is mediated by different complex mechanisms that lead to the loss or modification in the production of lipopolysaccharide in GNB, and this type of resistance may develop during treatment by colistin drug. The plasmid-mediated colistin resistance is due to mcr-1 gene that was discovered in southern China in 2015, and was recorded in 20% of animal strains and 1% of human strains (Liu et al, 2016). Dalmolin et al, (2018) revealed the detection of mcr-1 gene among MDR Gram-negative species in different countries since its discovery. In Egypt, mcr-1 gene was firstly detected in an E. coli isolate in 2016 from patient with bacteremia (Elnahriry et al, 2016)
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