Prevalence of Antimicrobial and Colistin Resistance in Enterobacterales in Healthy Pigs in Ghana Before and After Farmer Education

Abstract

High levels of antimicrobial resistance (AMR) were found in healthy pigs in the Greater Accra region of Ghana in 2022; this led to awareness creation and education of pig farmers about how to improve antimicrobial practices and biosecurity. To assess changes in AMR after the intervention, we compared AMR, multi-drug resistance (MDR), and determined colistin resistance levels in healthy pigs in the region before (2022) and after (2024) the education of farmers. Rectal swabs (n = 140) from pigs in 14 farms were cultured for isolation of Enterobacterales (Escherichia coli and Enterobacter spp.) and subjected to antimicrobial susceptibility testing. A selective culture method was employed to isolate colistin-resistant Enterobacterales, which were further screened for the mcr-1 gene. AMR and MDR findings were compared with those from 140 pigs from the same farms in 2022. Enterobacterales were found in 137 (2022) and 138 (2024) rectal swabs, with Escherichia coli predominating. There was a marked increase in AMR prevalence for eight of the nine tested antibiotics in 2024. Notable increases in resistance were for tetracycline (58–82%), ampicillin (33–49%), and ciprofloxacin (3–33%). MDR prevalence was highest in Escherichia coli, increasing from 20% to 44%. Phenotypic colistin resistance was found in 44% of Escherichia coli isolates in 2024 (in 2022, using different methodology, phenotypic colistin resistance was 8%)—in 2024, the mcr-1 gene was found in 51% of these isolates. There were no relevant associations between farm and pig characteristics and prevalence of MDR and phenotypic colistin resistance. Although education is an important aspect of AMR control, the findings highlight that education alone cannot curb the rise of AMR. Further interventions including continuous surveillance, stronger regulatory policy on antimicrobial use, and behavioral interventions will be needed to mitigate the situation.