Molecular characterization of serotype and virulence genes of Pseudomonas aeruginosa isolated from patients admitted at two hospitals in Addis Ababa, Ethiopia

<b>Introduction.</b> <i>Pseudomonas aeruginosa</i> contains a wide range of extracellular and cell-associated virulence factors that support its pathogenesis. The most variable portion of lipopolysaccharide, O-polysaccharide, confers serogrouping and is crucial for virulence.<b>Gap Statement.</b> Despite their importance, <i>P. aeruginosa</i> serotypes and associated virulence factors are not well described at the level of strains obtained from Ethiopian clinical samples.<b>Aim.</b> To characterize the serotypes and virulence factors of <i>P. aeruginosa</i> isolates from patients admitted to two hospitals in Addis Ababa, Ethiopia.<b>Methodology.</b> Whole-genome sequencing was performed to characterize genes responsible for serotypes and virulence factors.<b>Results.</b> Eight distinct serotypes were identified, with O6 (50%) and O11 (14.1%) being the most common and O9 (1.6%) being the least common. Serotype O6 was the most frequent serotype in all infections, and the percentage of O11 (38.5%) was high in burn wound isolates. The percentage of multidrug resistance was 56.6%. High levels of resistance to ciprofloxacin (51.8%) and ceftazidime (50.6%) and low levels of resistance to ceftazidime-avibactam (4.8%) were observed. Multidrug-resistant phenotypes were more common for the O11 (88.9%) and O5 (66.7%) serotypes. There were four (6.3%) <i>exoU+</i> strains and one (1.6%) <i>exoU+exoS</i>+ multidrug-resistant strain, all of which were O11 serotypes. The frequencies of <i>toxA</i>, <i>exoY</i>, <i>pilA</i> and <i>exoT</i> were 93.8%, 96.9%, 17.2% and 96.9 %, respectively.<b>Conclusion.</b> This study showed the presence of highly virulent multidrug-resistant <i>P. aeruginosa</i> strains in Ethiopia, and continuous molecular surveillance is essential for monitoring the spread of these strains and creating efficient management strategies.