Discussion
Pseudomonas aeruginosa is a major cause of opportunistic nosocomial infections that are often severe, with a high mortality rate
(12, 13). In the present study, the frequency of drug-resistant
P. aeruginosa isolates was 34.2%, which is higher than the frequency reported in the same area in 2017
(12). In addition to sample type and time of study, factors such as infection control policies (prevention with biocides), the amount and method of antibiotic administration, study population, type of predominant strain and laboratory diagnosis methods could affect identification of drug-resistant strains
(14).
Factors influencing the selection of disinfectant include effectiveness of, non-toxicity, skin compatibility, cost-effectiveness, odor, availability and ease of use. Chlorhexidine is an antiseptic that acts against a wide range of gram-positive and gram-negative bacteria, as well as some fungi and viruses. An advantage of this anti-septic compound is that it can bind to the surface of many substrates without losing its disinfecting activity and then released slowly, which results in long-term maintenance of its effectiveness in the environment
(15, 16). It has been demonstrated that chlorhexidine gluconate has favorable antimicrobial activity against oral bacteria
(17). Moreover, MIC concentrations of chlorhexidine gluconate could prevent biofilm formation in bacteria causing nosocomial infections, while sub-MIC concentrations of this compound can stimulate biofilm production
(18).
A previous study reported that both chlorhexidine and chamomile extract had good inhibitory activity against
Staphylococcus aureus and
Streptococcus pneumoniae isolates from patients in intensive care unit, but the antimicrobial effect of chlorhexidine was generally greater than that of the chamomile extract
(19). In this study,
P. harmala had a much better antibacterial effect compared to the chlorhexidine gluconate. Given the results obtained from our study, the aqueous extract of
P. harmala has favorable antimicrobial activity against
MDR P. aeruginosa isolates.
A previous study also demonstrated the favorable antimicrobial activity of this extract against various species of bacteria, particularly drug-resistant bacteria
(20).
In our study, more than 90% of MDR
P. aeruginosa isolates were susceptible to the aqueous extract of
P. harmala, researchers stated that the aqueous extract of
P. harmala is significantly more effective against
Lactobacillus and
Candida spp. compared to the aqueous extract
(21).
Our results also show that the type of solvent has a significant impact on the extraction of active compounds from the plant. Polar solvents such as ethanol and water are thought to be more suitable for extraction of bioactive secondary metabolites of plants. The antibacterial activity of the ethanolic extract
of P. harmala can be attributed to the presence of alkaloids i.e. harmine and harmaline. The abundance of these compounds in the aqueous extract may also explain the higher antimicrobial activity
(22). Researchers in Iran demonstrated that the antibacterial effect of aqueous extract of
P. harmala was about 1.23 times higher than that of the ethanolic extract on
A.
baumannii clinical isolates
(10).
In this study, the antibacterial activity of the aqueous extract increased in a dose-dependent manner in a way that 1000 μg/mL of the extract was able to inhibit the growth of almost all MDR
P. aeruginosa isolates. Since the present study was conducted during the COVID-19 pandemic, the beauty clinics and local kitchens were either closed, or working part-time, which justifies the relatively low frequency of isolates.
Conclusion
We observed that the prevalence of MDR
P. aeruginosa isolates is high in environment. Fortunately, the aqueous extract of
P. harmala had favorable antimicrobial activity against these isolates in comparison of chlorhexidine. This extract has low toxicity and great antimicrobial activity, which makes it a cost-effective alternative to chemical antibiotics for the treatment of infections caused by drug-resistant
P. aeruginosa strains.