Distribution of Colistin Resistance Genes Among Clinical Isolate of Gram-Negative Bacteria

Abstract

This study focuses on the identification and the distribution of Colistin resistance genes among Gram-negative bacteria isolated from clinical samples at the National Ribat Teaching hospital, in Khartoum, Sudan. A total of 165 Gram-negative isolated pathogens were as follow Klebsiella pneumoniae (73/44.2%), E. coli (53/32.1%), Pseudomonas aeruginosa (33/20%), Proteus vulgaris (6/3.6%), and Citrobacter freundii (2/1.2%), isolated between December 2019 and February 2020 from clinical samples at the National Ribat Teaching hospital in Khartoum, Sudan. Stock of all isolates were stored in 20% Glycerol-broth at -80°C for further subculture for antimicrobial susceptibility profile and resistance genes associated with Colistin resistance were identified. Colistin resistance associated genes (mcr-1, mcr-2, mcr-3, mcr-4, mcr-5) of Gram-negative isolates were determined by polymerase chain reaction (PCR) using appropriate primer sets. Out of 165; 11 isolates (7%) were resistance to Colistin antibiotic with MIC ≥ 9-10 μg/Ml. The majority 67% (4/6) of K. pneumoniae Colistin resistant strains were considered MDR. Three out of the 6 (50%) clinical Colistin-resistant K. pneumoniae isolates were resistant to carbapenems (meropenem ≤ 2 μg/ml). One of these 3 strains was resistant to all tested antibiotics. The remaining K. pneumoniae strains were susceptible to most tested antibiotics (Supplementary material Table A1). The two Colistin resistant P. vulgaris isolates were resistant to all antibiotics including the carbapenems (meropenem ≤ 2 μg/ ml) and were only susceptible to amikacin and ciprofloxacin. One Colistin resistant C. freundii isolate was only susceptible to amikacin, cotrimoxazole, and carbapenems. The Antibiotic resistant patterns were very low among P. aeruginosa isolates, as the majority of the isolates were shown more sensitive to most of the antibiotics. Only one Colistin resistant E. coli isolate was resistant to aminoglycoside and beta-lactam antibiotics. The gene detection by PCR revealed positive mcr-1 gene in 11/165 (7%) of the isolates; 6/73 (8%) were K. pneumoniae with highest mcr-1 gene among Colistin resistant K. pneumoniae 60% (6/10). 2/6 (33%) P. vulgaris, 1/53 E. coli, 1/33 (3%) P. aeruginosa, and 1/2 (50%) C. freundii. While only one (0.6%) K. pneumoniae isolate was found