Detection of PhoP-mediated colistin resistance in Gram-negative bacteria without mcr genes in human population in the Ho Municipality, Ghana

Introduction: Antimicrobial resistance (AMR) has become a global public health threat, with colistin emerging as a last-resort treatment option for multidrug-resistant Gram-negative infections. However, the emergence of colistin resistance, mediated by mechanisms like mutations in the PhoP gene, raises concerns about the future utility of this antibiotic. This study aimed to determine the prevalence of PhoP-mediated colistin resistance in Gram-negative bacteria isolated from the stool of residents in the Ho Municipality, Ghana.

Methods: In this cross-sectional study, 110 stool samples were collected from June 2021 to December 2022. Gram-negative bacteria were isolated, and colistin susceptibility was determined by broth microdilution. Genomic DNA from resistant isolates was extracted and sequenced using the Nanopore platform to detect the presence of the PhoP gene.

Results: Of the 107 Gram-negative isolates, 57 % were resistant to colistin. The PhoP gene was detected in 61.4 % of the colistin-resistant isolates, with the highest prevalence observed in Proteus mirabilis, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae.

Conclusion: The study reveals a high prevalence of PhoP-mediated colistin resistance among Gram-negative bacteria colonizing residents in the Ho Municipality, highlighting the role of the gut microbiota as a reservoir for antibiotic resistance. Continued surveillance and a collaborative One Health approach are crucial to address this growing threat.