Antibacterial effects of chitosan-based hydrogels containing Trachyspermum ammi essential oil on pathogens isolated from dogs with otitis externa.

BACKGROUND: Growing antibiotic resistance has made treating otitis externa (OE) increasingly challenging. On the other hand, local antimicrobial treatments, especially those that combine essential oils (EOs) with nanoparticles, tend to be preferred over systemic ones. It was investigated whether Ajwain (Trachyspermum ammi) EO, combined with chitosan nanoparticles modified by cholesterol, could inhibit the growth of bacterial pathogens isolated from OE cases in dogs. In total, 57 dogs with clinical signs of OE were examined and bacteriologically tested. Hydrogels of Chitosan were synthesized by self-assembly and investigated. EO was extracted (Clevenger machine), and its ingredients were checked (GC-MS analysis) and encapsulated in chitosan-cholesterol nanoparticles. Disc-diffusion and broth Micro-dilution (MIC and MBC) examined its antimicrobial and therapeutic properties. RESULTS: Staphylococcus pseudintermedius (49.3%) was the most common bacteria isolated from OE cases, followed by Pseudomonas aeruginosa (14.7%), Escherichia coli (13.3%), Streptococcus canis (9.3%), Corynebacterium auriscanis (6.7%), Klebsiella pneumoniae (2.7%), Proteus mirabilis (2.7%), and Bacillus cereus (1.3%). The investigation into the antimicrobial properties of Ajwain EO encapsulated in chitosan nanoparticles revealed that it exhibited a more pronounced antimicrobial effect against the pathogens responsible for OE. CONCLUSIONS: Using chitosan nanoparticles encapsulated with EO presents an effective treatment approach for dogs with OE that conventional antimicrobial treatments have not cured. This approach not only enhances antibacterial effects but also reduces the required dosage of antimicrobials, potentially preventing the emergence of antimicrobial resistance.

Antimicrobial and antibiofilm effects of Satureja hortensis essential oil against Escherichia coli and Salmonella isolated from poultry.

BACKGROUND AND OBJECTIVES: Escherichia coli and some Salmonella serovars cause various disease manifestations in poultry leading to significant economic losses. The widespread and imprudent use of antibacterial agents in poultry flocks have increased resistant to many antibacterial agents which has become a major public health concern. Some medicinal plants may be alternative to antibacterial agents. The purpose of this study was to investigate the antibacterial and anti-biofilm activity of summer savory essential oil against E. coli and Salmonella isolated from poultry. MATERIALS AND METHODS: The essential oil was extracted using a Clevenger apparatus and subsequently its compounds were determined using GC-MS. Antibacterial properties of essential oil were determined by disc diffusion method, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). To evaluate the anti-biofilm properties the Microtiter plate test was used. Herbal essential oil was extracted and its compounds were identified correctly. RESULTS: The major components of Satureja hortensis essential oil were thymol (41.28%), γ-terpinene (37.63%), p-cymene (12.2%) and α-terpinene (3.52%). The inhibition zone diameter in the disc diffusion test for E. coli and Salmonella were 32 ± 3 and 38 ± 4 mm, respectively, which was confirmed by MIC and MBC values. Regarding anti-biofilm activity, the MIC/2 concentration of S. hortensis significantly inhibited biofilm formation of E. coli. However, inhibition of biofilm formation of Salmonella was shown at concentration of MIC/2 and MIC/4. CONCLUSION: Based on our results, S. hortensis essential oil showed the growth inhibition and bactericidal activity against E. coli and Salmonella. Moreover, this study demonstrated anti-biofilm activity of S. hortensis essential against both tested bacteria.

Assessment of immunity against avian colibacillosis induced by an aroA mutant containing increased serum survival gene in broilers

Colibacillosis is an important disease in the poultry industry which causes serious economic damages. As it is suggested that vaccination is one of the means to control colibacillosis, we tried to investigate the vaccine potential of a ÃaroA derivative of an O78:K80 avian pathogenic Escherichia coli containing increased serum survival gene. 490 chicks were selected as follows: For assessment of virulence of ÃaroA mutant, 30 chicks were divided into three groups and injected with 0.5ml of PBS or bacterial suspension containing either10(7)colony forming units (CFU) of mutant or parent strains via subcutaneous route. Macroscopic lesions and mortality rate were recorded in different groups during the week after challenge. For assessment of safety and immunogenicity of the ÃaroA mutant, three groups of 20 chicks were vaccinated by aerosol administration of 250 ml of suspension containing 10(8) CFU of mutant strain at days 1 and 14, while the two other groups received PBS or wild type strain. Macroscopic lesions and mortality rate were recorded in different groups until day 21. To determine whether the vaccination is protective against challenges or not, the chickens were vaccinated at days 1 and 14 and challenged intramuscularly with either a homologous or heterologous strains at day 21. Macroscopic lesions and mortality rate were recorded in different groups during the week after challenge. The results revealed that the ÃaroA mutant was slightly virulent, however it was safe and did not cause mortality, lesions or weight loss after vaccination. Antibody responses were similar in the control and mutant groups and vaccination did not induce a significant humoral immunity. The mutant could not protect chickens against both homologous and heterologous challenges. This could be due to several factors such as the high amount of maternal antibodies in the first two weeks of life, and the vaccination procedure.