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Review
. 2025;25(4):298-311.
doi: 10.22099/ijvr.2024.50497.7453.

Mechanisms in colistin-resistant superbugs transmissible from veterinary, livestock and animal food products to humans

N Satarzadeh  1 , A Saraee  2 , Z Hatif Mahdi  3 , A Sadeghi Dousari  4 , M Armanpour  5 , M Taati Moghadam  6
Affiliations
Review

Mechanisms in colistin-resistant superbugs transmissible from veterinary, livestock and animal food products to humans

N Satarzadeh et al. Iran J Vet Res. 2025.

Abstract

In the era of antibiotic resistance, where multidrug-resistant (MDR), extensively drug resistant (XDR), and pan-drug resistant (PDR) Gram-negative infections are prevalent, it is crucial to identify the primary sources of antibiotic resistance, understand resistant mechanisms, and develop strategies to combat these mechanisms. The emergence of resistance to last-resort antibiotics like colistin has sparked a war between humanity and resistant bacteria, leaving humanity struggling to find effective countermeasures. Although colistin is used as a highly toxic antibiotic in infections that are not treated with routine antibiotics, its widespread use in animal breeding and veterinary medicine has contributed to the spread of colistin-resistant bacteria, plasmid-borne colistin resistance genes (mcr), and antibiotic residues in livestock and animal-derived foods. These sources can potentially transmit colistin resistance to humans through various routes. Therefore, managing the use of colistin in livestock and animal foods, implementing strict monitoring, and establishing guidelines for its proper use are essential to prevent the escalation of colistin resistance. This review article discusses the latest mechanisms of colistin antibiotic resistance, particularly biofilm production as a public health threat, the livestock and animal food sources of this resistance, and the routes of transmission to humans.

Keywords: Animal foods; Colistin resistance; Multidrug-resistant; Veterinary medicine; mcr.

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Conflict of interest statement

The authors have no conflicts of interest to declare.

Figures

Fig. 1
Fig. 1
The primary mechanisms of action of colistin collectively serve as a foundation for eliminating Gram-negative infectious bacteria in hospital settings
Fig. 2
Fig. 2
A comprehensive overview of the latest mechanisms of resistance to colistin in Gram-negative bacteria reveals that the mcr mechanism is particularly significant in the dissemination of resistance and the transfer of this resistance from animals to humans
Fig. 3
Fig. 3
When colistin administration is increased in veterinary medicine and food as an additive, it can lead to selective pressure on the gut microbiota of animals. Thus, colistin resistance bacteria, unprocessed colistin and mcr-carrying plasmids in the feces of these animals are released into the sewage and contaminate the aquatic environment. Humans can obtain colistin-resistant bacteria or mcr carriers when contamination reaches carcasses and meat during production, by handling, eating raw or undercooked meat, as well as on the farm. In this case, humans can develop clinical infections, and mcr can be transmitted from colistin-resistant bacteria to common bacteria in the gut microbiota, and then again, these resistant bacteria contaminate the aquatic environment through human feces. If water contaminated with colistin resistant bacteria and mcr genes is used in agriculture, contaminated vegetables are likely to reach consumers, as well as livestock drinking this contaminated fresh water and eating contaminated products
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