Understanding the colonization of Pseudomonas aeruginosa (P. aeruginosa) in healthy humans is useful for future prevention and treatment of P. aeruginosa infection. This study aimed to investigate the prevalence and risk factors of of P. aeruginosa colonization in healthy humans. At the same time, the virulence of the isolated P. aeruginosa was also studied. In the study, 609 Vietnamese volunteers (310 females and 299 males, age range of 2 to 73 years), who had no acute infection or disease symptoms participated at the time of sample collection. Samples were taken from the throat, nostrils, and outer ears. P. aeruginosa was found in 19 participants (3.12%, 95% CI: 0.017–0.045), mainly from the throat (11/19, 57.89%). Participants with a history of sinusitis were 11.57 times more likely to be colonized with P. aeruginosa than participants without a history of sinusitis (OR: 11.57, 95% CI: 4.08–32.76, p-value < 0.0001, Fisher’s Exact test). Age and sex were not significantly associated with P. aeruginosa colonization. Among 16 P. aeruginosa isolates used in virulence tests, 100% (16/16) were positive for the synthesis of biofilm, pyocyanin, and siderophores; 93.75% (15/16) isolates were positive for the synthesis of gelatinase and protease; and 50% (8/16) isolates were positive for lipase. There were no differences in the pattern and range of virulence factors of P. aeruginosa isolates taken from participants with and without sinusitis history. P. aeruginosa colonized 3.12% of participants, and its presence was associated with sinusitis history.

Pseudomonas aeruginosa (P. aeruginosa) is one of the most concerning pathogens due to its multidrug resistance. P. aeruginosa can be a part of the normal commensal flora of humans but can also cause a wide range of infections. In this study, we investigated the prevalence of commensal P. aeruginosa in 609 Vietnamese participants (310 females and 299 males, age range of 2 to 73 years) who had no acute infection or disease symptoms at the time of sample collection. Samples were taken from the throat, naris and outer ears. As a result, 19 were positive with P. aeruginosa (3.12%, 95% CI: 0.017-0.045) which came mostly from throat (11/19, 57.89%). Participants with a history of sinusitis were 11.57 times more likely to be colonized with P. aeruginosa than participants without a history of sinusitis (OR: 11.57, 95% CI: 4.08-32.76, p-value< 0.0001). Age and gender were not significantly associated with P. aeruginosa colonization. The commensal P. aeruginosa isolates were tested for biofilm formation, pyocyanin, siderophore, lipase, protease and gelatinase production. Among 16 P. aeruginosa isolates used for these tests, 100% (16/16) were positive for biofilm, pyocyanin and siderophores; 93.75% (15/16) isolates were positive for gelatinase and protease; and 50% (8/16) isolates were positive for lipase. There were no differences in the pattern and range of virulence factors of P. aeruginosa isolates taken from participants with and without sinusitis history. In summary, P. aeruginosa colonized 3.12% of participants, and its presence was clearly associated with sinusitis history. Most commensal P. aeruginosa isolates can produce biofilm, pyocyanin, siderophores, gelatinase and protease.Author summaryP. aeruginosa is both a common opportunistic pathogen which causes various infections in humans, such as blood, lung, and skin infections and a commensal bacterium which can be found normal human flora. In this study, we showed that the P. aeruginosa colonized 3.12% participants and resided mostly in human throat. Interestingly, we found that people with sinusitis history were more likely to be P. aeruginosa carriers. On the other hand, age and gender did not significantly affect P. aeruginosa colonization. Most tested P. aeruginosa isolates expressed various virulence factors, including biofilm, siderophores, pyocyanin, gelatinase, protease, and lipase.