Environmental Dissemination of Multidrug-Resistant Gram-Negative Pathogens in Djibouti's Wastewaters

The occurrence of multidrug-resistant (MDR) Enterobacteriaceae-producing extended-spectrum β-lactamases (ESBLs) and/or carbapenemases is increasingly reported in clinical and environmental settings. Here, we aimed to investigate the resistance profile of gram-negative bacterial isolates from urban and environmental wastewater in Djibouti.

Twenty-five wastewater samples were collected from eight different locations of Djibouti. After bacterial culture on selective media for gram-negative bacteria (GNB), obtained isolates were identified using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Antibiotic susceptibility testing was performed by disk diffusion and E-test methods. Standard PCR and Sanger sequencing were used to investigate antibiotic resistance genes, including β-lactamases, carbapenemases, and colistin resistance genes.

Eleven MDR gram-negative isolates were identified from the 25 water samples collected, including six Escherichia coli, one Enterobacter cloacae, and four Klebsiella pneumoniae isolates. Interestingly, the pandemic ESBL gene bla _CTX-M-15 was detected in 9 of the 11 (81.8%) from both urban and environmental water samples. In addition, the carbapenemase gene bla _OXA-48 was identified in 4 of the 11 strains (36.4%), including two E. coli, one K. pneumoniae, and one E. cloacae, all from urban wastewater, particularly hospital water samples.

For the first time, we describe here MDR-GNB bacterial isolates from urban and environmental wastewater in Djibouti. To date, carbapenem-resistant isolates have only been present in hospital wastewater. Regular surveillance policies, consistent with the "One Health" approach, are recommended to prevent the spread and monitor the evolution of antibiotic resistance in the environment and within the Djiboutian community.