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Plasmid-mediated mcr-1 gene in Acinetobacter baumannii and Pseudomonas aeruginosa: first report from Pakistan
Fareeha Hameed1, Muhammad Asif Khan1, Hafsah Muhammad1
1Khyber Medical University, Institute of Basic Medical Sciences, Department of Medical Microbiology, Peshawar, Khyber Pakhtunkhuwa, Pakistan.
Introduction:
The increased use of colistin against infections caused by Acinetobacter baumannii and Pseudomonas aeruginosa has resulted in colistin resistance. The purpose of this study was to detect plasmid-mediated mcr-1 gene in colistin-resistant A. baumannii and P. aeruginosa isolates.
Methods:
A total of 146 clinical isolates of A. baumannii (n = 62) and P. aeruginosa (n = 84) were collected from the four largest tertiary care hospitals in Peshawar, Pakistan. All bacterial isolates were phenotypically screened for multidrug resistance using the Kirby-Baur disc diffusion method. The minimum inhibitory concentration (MIC) of colistin in all isolates was phenotypically performed using dilution methods. mcr-1 gene was detected through polymerase chain reaction and the nucleotide sequence of amplicon was determined using Sanger sequencing.
Results:
Approximately 96.7% A. baumannii and 83.3% P. aeruginosa isolates were resistant to multiple antibiotics. Colistin resistance was found in 9.6% (6/62) of A. baumannii and 11.9% (10/84) of P. aeruginosa isolates. Among 16 colistin resistant isolates, the mcr-1 gene was detected in one A. baumannii (1.61% of total isolates; 16.6% of colistin resistant isolates) and one P. aeruginosa strain (1.19% of total isolates; 10% of colistin resistant isolates). Nucleotide BLAST showed 98-99% sequence similarity to sequences of the mcr-1 gene in GenBank.
Conclusions:
Our study reports, for the first time, the emergence of plasmid-mediated mcr-1-encoded colistin resistance in multidrug resistant strains of A. baumannii and P. aeruginosa. Further large scales studies are recommended to investigate the prevalence of this mode of resistance in these highly pathogenic bacteria.
Insights
Colistin resistance is rising in Acinetobacter baumannii and Pseudomonas aeruginosa. This study detected the plasmid-mediated mcr-1 gene, a key factor in colistin resistance, in these bacteria for the first time in Pakistan.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Increasing colistin use has led to resistance in Acinetobacter baumannii and Pseudomonas aeruginosa.
- Colistin resistance poses a significant threat in treating infections caused by these Gram-negative bacteria.
Purpose of the Study:
- To detect the presence of the plasmid-mediated mcr-1 gene in colistin-resistant A. baumannii and P. aeruginosa isolates.
- To investigate the emergence of colistin resistance mechanisms in clinical isolates from Pakistan.
Main Methods:
- Phenotypic screening for multidrug resistance using Kirby-Baur disc diffusion.
- Colistin minimum inhibitory concentration (MIC) determination via dilution methods.
- Detection of the mcr-1 gene using polymerase chain reaction (PCR) and Sanger sequencing.
Main Results:
- High rates of multidrug resistance were observed in A. baumannii (96.7%) and P. aeruginosa (83.3%).
- Colistin resistance was identified in 9.6% of A. baumannii and 11.9% of P. aeruginosa isolates.
- The mcr-1 gene was detected in one isolate of each species, confirming plasmid-mediated colistin resistance.
Conclusions:
- This study reports the first emergence of plasmid-mediated mcr-1-encoded colistin resistance in A. baumannii and P. aeruginosa.
- Further large-scale studies are recommended to understand the prevalence of this resistance mechanism.
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