P. aeruginosa is associated as a versatile opportunistic human pathogen and its ultimate infection is reported to complete by attachment, colonization, local invasion and dissemination as a systemic disease (21–22).
In this study, the prevalence of P. aeruginosa isolates was 4.29%, in which the distribution in male patients 56 (64.36%) was higher than in female patients 31 (35.63%). The possible reasons might be types of studied populations, different geographical locations, type of hospitals. In addition, other reasons may be the male have a routine outdoor work and they are frequently in the risk of infection from the infected environments (16). The prevalence rate of infections was higher in outpatients 63 (72.41%) compared to the hospital admitted patients 24 (27.58%) which may be due to frequent exposure to infected environment. In addition, the occurrence of P. aeruginosa isolates to be greater in the age group 60–79 (41.37%), infection caused by P. aeruginosa is more common in patients of old age group. This could be described as because of decrease immune system, prolonged duration of hospitalization (23–25).
In our study, the difference between gender of patients and P. aeruginosa isolation from different clinical specimens was found to be statistically significant (p = 0.016). Likewise, the difference between type of patients and P. aeruginosa isolated from different clinical specimens was found to be statistically significant (p = 0.009). There was no statistical significance between the different age groups and occurrence of P. aeruginosa in male and female patients (p = 0.071) at 5% level of significance.
In this study, the most effective drug for P. aeruginosa isolates was found to be polymyxin B 73 (83.90%), also called last resort antibiotic for Pseudomonadecae family in the hospitals and less effective antibiotic was cefixime 87 (100%). Out of 87 P. aeruginosa isolates, 20 (22.98%) were identified to be MDRPA. The development of antibiotic resistant towards P. aeruginosa might be due random use of antibiotics, production of different types of enzyme like carbapenamase, AmpC-lactamases, quorum sensing modification of different target side etc (26, 13). Furthermore, one of the major cause of the emergence of P. aeruginosa is prescribing the antibiotics without performing susceptibility test due to lack of laboratory facilities in most of the healthcare centers in Nepal (16, 24, 27–28).
The PCR results showed that 87 (100%) of 87 P. aerugiosa isolates were positive for oprL genes. Similarly in this study 83 (95.40%) of 87 P. aeruginosa were positive for toxA gene. Almost comparable study was carried out by Ibraheem at 2018 which showed 100% of toxA and 98.8% oprL genes. According to the Khattab et al in (2015), 100% of oprL gene, and 63.33% toxA gene were reported among the P. aeruginosa. The divergences in the distribution of virulence factor genes in the different populations might be due to the probability that some P. aeruginosa strains are better adopted to the particular conditions found in infectious sites that may returned to the diverse geographical and environmental sources. The prevalence of P. aeruginosa and its virulence genes depends on various causes consisting nature of places, degree of contamination and type, immune status of individual patients and virulence of strains (29).
Exotoxins A are either actively secreted through the type 1 secretion system (T1SS), the type 2 secretion system (T2SS), and the type 3 secretion system (T3SS) or passively secreted via the cell (27). The exotoxin A is encoded by gene called exoA which is involved in the tissue necrosis and resistant to antibiotics (28). The L, and I are two outer membrane lipoproteins of P. aeuginosa are found only in this organism, so that they could be a suitable factors for rapid identification of P. aeruginosa in clinical specimens. This bacterium is also answerable for inherent resistance to antiseptics and antibiotics (29).
In this study, detection of P. aeruginosa by multiplex PCR for amplification of oprL gene, present study showed that of 87 tested P. aruginosa isolates 87 (100%) contained the oprL gene (sensitivity = 100%), where as other species of bacteria did not produce any positive result (specificity = 100%). While amplification of the toxA gene showed that of 87 tested P. aeruginosa isolates 83 (95.40%) contained the toxA gene (sensitivity = 95%), where as other species of bacteria did not yield any positive result (specificity = 100%). This study revealed that the multiplex PCR may be one of the rapid diagnostic tool for the identification of P. aeruginosa infections.