Microbial Resistance in Saharan Dust: Identification of Antibiotic-Resistant Bacteria in Aerosol Samples Collected at Puerto Rico

DYLAN TRISTANI-RODRIGUEZ, Travis Santana, Francees Barreto, Janet K. Hatt, Claribel Luciano-Montalvo, Borja Riquelme, Konstantinos T. Konstantinidis, Natasha DeLeon-Rodriguez, Interamerican University of Puerto Rico, Metropolitan Campus

     Abstract Number: 214
     Working Group: Bioaerosols

Abstract
The Sahara Desert is a significant source of atmospheric mineral dust that, carried by winds across the North Atlantic Ocean, impacts the North America, Caribbean, and Mexico. Although it has been shown that particles transported during these events affect air quality and human health by promoting respiratory and skin allergies, few studies have explored the microbial communities present in these dust clouds and their potential impact on human health. This study aimed to identify organisms in Saharan dust capable of resisting antibiotics, as well as to characterize the antibiotic resistance genes (ARGs) they carry and their similarity to clinically relevant ARGs and those found in human-populated environments. Samples were collected during Saharan dust events in Puerto Rico using passive deposition methods and were subsequently exposed to six antibiotics: levofloxacin, tetracycline, penicillin, ciprofloxacin, vancomycin, and kanamycin. DNA was then extracted from the surviving enrichment cultures and analyzed metagenomically. Gram-positive bacteria were identified in all samples, despite the expectation that they would not grow under the selective pressure imposed by the antibiotics. Among the MAGs (metagenome-assembled genomes), Bacillus toyonensis and Bacillus thuringiensis were the two most abundant bacterial species. Both species carried ARG associated with mechanisms such as antibiotic target alteration and target protection, which help them withstand growth inhibition. Although B. toyonensis harbored a higher number of unique resistance genes, B. thuringiensis exhibited greater relative abundance, contributing more significantly to the total ARG load detected. B. toyonensis is commonly used in the formulation of probiotics and B. thuringiensis is an insecticide due to its pathogenicity to insects. Finally, we observed that these species are common in urban environments, suggesting that their ability to carry ARGs could make them environmental vectors of antibiotic resistance genes to bacteria that pose a risk to public health.