Carriage of colistin-resistant Gram-negative bacteria in children from communities in Cape Town (Tuberculosis child multidrug-resistant preventive therapy trial sub-study)

CITATION: Snyman, Y., et al. 2021. Carriage of colistin-resistant Gram-negative bacteria in children from communities in Cape Town (Tuberculosis child multidrug-resistant preventive therapy trial sub-study). Southern African Journal of Infectious Diseases, 36(1):a241, doi:10.4102/sajid.v36i1.241.The original publication is available at https://sajid.co.zaPublication of this article was funded by the Stellenbosch University Open Access FundENGLISH ABSTRACT: Colistin is a last-resort antibiotic against multidrug-resistant, Gram-negative bacteria. Colistin resistance has been described in the clinical settings in South Africa. However, information on carriage of these bacteria in communities is limited. This study investigated gastrointestinal carriage of colistin-resistant Escherichia coli and Klebsiella spp. and mcr genes in children from communities in Cape Town. Colistin-resistant E. coli was isolated from two participants (4%, 2/50), and mcr-1-mcr-9 genes were not detected. Gastrointestinal carriage of colistin-resistant Enterobacterales was rare; however, continuous extensive surveillance is necessary to determine the extent of carriage and its contribution to resistance observed in clinical settings.https://sajid.co.za/index.php/sajid/article/view/241Publisher's versio

Characterisation of mobile colistin resistance genes (mcr‑3 and mcr‑5) in river and storm water in regions of the Western Cape of South Africa

CITATION: Snyman, Y., et al. 2021. Characterisation of mobile colistin resistance genes (mcr‑3 and mcr‑5) in river and storm water in regions of the Western Cape of South Africa. Antimicrobial Resistance and Infection Control, 10:96, doi:10.1186/s13756-021-00963-2.The original publication is available at https://aricjournal.biomedcentral.comPublication of this article was funded by the Stellenbosch University Open Access FundBackground: Colistin is regarded as a last-resort antimicrobial against multi-drug resistant Gram-negative bacteria (GNB), therefore the dissemination of colistin resistance in the environment is of great concern. Horizontal transfer of mobile colistin resistance (mcr) genes to potential pathogens poses a serious problem. This study aimed to describe the presence of colistin resistant GNB and mcr genes in river and storm water in regions of the Western Cape. Methods: Water samples were collected from three rivers during May 2019 and January 2020 and two storm water samples were collected in November 2019. Colistin resistant GNB were cultured on MacConkey agar containing colistin and identified by MALDI-TOF. Colistin resistance was confirmed using broth microdilution (BMD). mcr-1-5 genes were detected by PCR performed directly on the water samples and on the colistin resistant isolates. mcr functionality was assessed by BMD after cloning the mcr genes into pET-48b(+) and expression in SHuffle T7 E. coli. Results: mcr-5.1 and various mcr-3 gene variants were detected in the Plankenburg-, Eerste- and Berg rivers and in storm water from Muizenberg, and only mcr-5.1 was detected in storm water from Fish Hoek. Colistin resistant GNB were isolated from all of the water sources. Aeromonas spp. were the most common colistin resistant organisms detected in the water sources; 25% (6/24) of colistin resistant Aeromonas spp. isolated from the Berg river contained novel mcr-3 variants; mcr-3.33 (n = 1), mcr-3.34 (n = 1) mcr-3.35 (n = 1) mcr-3.36 (n = 2) and mcr-3.37 (n = 1), which were confirmed to confer colistin resistance. Conclusions: The mcr-5.1 and mcr-3 colistin resistance gene variants were present in widely dispersed water sources in regions of the Western Cape. The mcr genes were only detected in water sampled downstream of and alongside communities, suggesting that their presence is driven by human influence/contamination. This is the first documentation of mcr-3 and mcr-5 gene variants in any setting in South Africa. Spill-over of these genes to communities could result in horizontal gene transfer to pathogenic bacteria, exacerbating the challenge of controlling multidrug resistant GNB infections.https://aricjournal.biomedcentral.com/articles/10.1186/s13756-021-00963-2Publisher's versio