Ashraf M. O. Abdelwahab

Plasmid-mediated antimicrobial resistance is a major contributor to infections associated with high morbidity and mortality. Given the urgent demand for effective and safe elimination of plasmids from multidrug-resistant (MDR), this study is the first to examine the potential of Nigella sativa essential oil (NSO) and thymoquinone (TQ) in eliminating antimicrobial resistance plasmid from Staphylococcus aureus . Plasmid profiles of resistant variants derived from the original MDR strains following exposure to sublethal concentrations of NSO and TQ were analyzed and compared with those of the untreated parent strains using agar gel electrophoresis. Computational analyses were performed to evaluate the interactions between eleven phytoconstituents of Nigella sativa constituents and cytidylyltransferase (CTP) and glutamine amidotransferase (Gat-D) enzymes, which are involved in cell wall biosynthesis. NSO and TQ exhibited plasmid- curing and MDR reversal effects comparable to SDS. Remarkably, their combination with antimicrobials or SDS resulted in superior plasmid elimination efficiency. The eleven NSO constituents demonstrated moderate to strong binding affinities with CTP and Gat-D enzymes, thereby impairing their catalytic function by obstructing substrate interaction. The plasmid curing property offers a novel therapeutic strategy for combating antibiotic resistance by eliminating resistance genes from infectious S. aureus .

Background: Thermophilic Campylobacter species are among the main culprits behind bacterial gastroenteritis globally and have grown progressively resistant to clinically important antimicrobials. Many studies have been carried out to explore innovative and alternative strategies to control antibiotic-resistant campylobacters in animal reservoirs and human hosts; however, limited studies have been performed to develop efficient control schemes against Campylobacter biofilms. Methods: This study investigated the antimicrobial and antibiofilm activities of some herbal extracts against multidrug-resistant (MDR) Campylobacter species recovered from different sources using phenotypic and molecular techniques. Results: The overall Campylobacter species prevalence was 21.5%, representing 15.25% and 6.25% for C. jejuni and C. coli, respectively. Regarding C. jejuni, the highest resistance rate was observed for amoxicillin–clavulanic acid and colistin (85.25% each), followed by cefotaxime (83.61%) and tetracycline (81.97%), whereas C. coli isolates showed absolute resistance to cefotaxime followed by erythromycin (92%) and colistin (88%). Remarkably, all Campylobacter isolates were MDR with elevated multiple antimicrobial resistance (MAR) indices (0.54–1). The antimicrobial potentials of green tea (Camellia sinensis), rosemary (Rosmarinus officinalis) and ginger (Zingiber officinale) extracts against MDR Campylobacter isolates were assessed by the disk diffusion assay and broth microdilution technique. Green tea extract showed a marked inhibitory effect against tested isolates, exhibiting growth inhibition zone diameters of 8 to 38 mm and a minimum inhibitory concentration (MIC) range of 1.56–3.12 mg/mL, unlike the rosemary and ginger extracts. Our findings reveal a respectable antibiofilm activity (>50% biofilm formation inhibition) of green tea against the preformed biofilms of Campylobacter isolates. Furthermore, real-time quantitative polymerase chain reaction (RT-qPCR) results showed a significant decrease (p < 0.05) in the expression levels of biofilm biosynthesis gene and its regulator (FlaA and LuxS, respectively) in Campylobacter isolates treated with the green tea extract in comparison with untreated ones. Conclusion: This is the first in vitro approach that has documented the inhibitory activity of green tea extract against MDR-biofilm-producing Campylobacter species isolated from different sources. Further in vivo studies in animals’ models should be performed to provide evidence of concept for the implementation of this alternative candidate for the mitigation of MDR Campylobacter infections in the future.