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Polyhydroxybutyrate (PHB) is a biopolymer formed by some microbes in response to excess carbon sources or essential nutrient depletion. PHBs are entirely biodegradable into CO2 and H2O under aerobic and anaerobic conditions. It has several applications in various fields such as medicine, pharmacy, agriculture, and food packaging due to its biocompatibility and nontoxicity nature.
In the present study, PHB-producing bacterium was isolated from the Dirout channel at Assiut Governorate. This isolate was characterized phenotypically and genetically as Bacillus cereus SH-02 (OM992297). According to one-way ANOVA test, the maximum PHB content was observed after 72 h of incubation at 35 °C using glucose and peptone as carbon and nitrogen source. Response surface methodology (RSM) was used to study the interactive effects of glucose concentration, peptone concentration, and pH on PHB production. This result proved that all variables have a significant effect on PHB production either independently or in the interaction with each other. The optimized medium conditions with the constraint to maximize PHB content and concentration were 22.315 g/L glucose, and 15.625 g/L peptone at pH 7.048. The maximum PHB content and concentration were 3100.799 mg/L and 28.799% which was close to the actual value (3051 mg/l and 28.7%). The polymer was identified as PHB using FTIR, NMR, and mass spectrometry. FT-IR analysis showed a strong band at 1724 cm− 1 which attributed to the ester group’s carbonyl while NMR analysis has different peaks at 169.15, 67.6, 40.77, and 19.75 ppm that were corresponding to carbonyl, methine, methylene, and methyl resonance. Mass spectroscopy exhibited molecular weight for methyl 3- hydroxybutyric acid.
PHB–producing strain was identified as Bacillus cereus SH-02 (OM992297). Under optimum conditions from RSM analysis, the maximum PHB content and concentration of this strain can reach (3100.799 mg/L and 28.799%); respectively. FTIR, NMR, and Mass spectrometry were used to confirm the polymer as PHB. Our results demonstrated that optimization using RSM is one of the strategies used for reducing the production cost. RSM can determine the optimal factors to produce the polymer in a better way and in a larger quantity without consuming time.
In the present study, Zingiber officinale is used for the synthesis of Zingiber officinale capped silver nanoparticles (ZOE-AgNPs) and compares the antimicrobial efficacy and compressive strength of conventional glass ionomer cement (GIC) combined with ZOE-AgNPs, lyophilized miswak, and chlorhexidine diacetate (CHX) against oral microbes. Five groups of the disc-shaped GIC specimens were prepared. Group A: lyophilized miswak and GIC combination, Group B: ZOE-AgNPs and GIC combinations, Group C: CHX and GIC combination, Group D: ZOE-AgNPs + CHX + GIC; Group E: Conventional GIC. Results confirmed the successful formation of ZOE-AgNPs that was monitored by UV-Vis sharp absorption spectra at 415 nm. The X-ray diffractometer (XRD) and transmission electron microscope (TEM) results revealed the formation of ZOE-AgNPs with a mean size 10.5–14.12 nm. The peaks of the Fourier transform infrared spectroscopy (FTIR) were appearing the involvement of ZOE components onto the surface of ZOE-AgNPs which played as bioreducing, and stabilizing agents. At a 24-h, one-week and three-week intervals, Group D showed the significantly highest mean inhibitory zones compared to Group A, Group B, and Group C. At microbe-level comparison, Streptococcus mutans and Staphylococcus aureus were inhibited significantly by all the specimens tested except group E when compared to Candida albicans. Group D specimens showed slightly higher (45.8 ± 5.4) mean compressive strength in comparison with other groups. The combination of GIC with ZOE-AgNPs and chlorhexidine together enhanced its antimicrobial efficacy and compressive strength compared to GIC with ZOE-AgNPs or lyophilized miswak or chlorhexidine combination alone. The present study revealed that The combination of GIC with active components of ZOE-AgNPs and chlorhexidine paves the way to lead its effective nano-dental materials applications.
Staphylococcus aureus is a cause of high mortality in humans and therefore it is necessary to prevent its transmission and reduce infections. Our goals in this research were to investigate the frequency of methicillin-resistant S. aureus (MRSA) in Taif, Saudi Arabia, and assess the relationship between the phenotypic antimicrobial sensitivity patterns and the genes responsible for resistance. In addition, we examined the antimicrobial efficiency and application of silver nanoparticles (AgNPs) against MRSA isolates. Seventy-two nasal swabs were taken from patients; MRSA was cultivated on Mannitol Salt Agar supplemented with methicillin, and 16S rRNA sequencing was conducted in addition to morphological and biochemical identification. Specific resistance genes such as ermAC, aacA-aphD, tetKM, vatABC and mecA were PCR-amplified and resistance plasmids were also investigated. The MRSA incidence was ~49 % among the 72 S. aureus isolates and all MRSA strains were resistant to oxacillin, penicillin, and cefoxitin. However, vancomycin, linezolid, teicoplanin, mupirocin, and rifampicin were effective against 100% of MRSA strains. About 61% of MRSA strains exhibited multidrug resistance and were resistant to 3-12 antimicrobial medications (MDR). Methicillin resistance gene mecA was presented in all MDR-MRSA strains. Most MDR-MRSA contained a plasmid of > 10 kb. To overcome bacterial resistance, AgNPs were applied and displayed high antimicrobial activity and synergistic effect with penicillin. Our findings may help establish programs to control bacterial spread in communities as AgNPs appeared to exert a synergistic effect with penicillin to control bacterial resistance.
Extended-spectrum β-lactamase (ESβL) producing E. coli pose a significant medical challenge. It has spread worldwide, making it as the source of a variety of urinary tract and wound infections. Recently, nanosilver has been widely utilized in the medicinal applications. We aimed at fabricating silver nanoparticles (AgNPs) and observing how they affected the ESβL-producing E. coli isolated from different human anatomical regions. Under optimal circumstances, AgNPs were biosynthesized using Bacillus thuringiensis isolated from raw milk and they were wholly characterized. The AgNPs were occurred to be crystalline and have a stable structure. AgNPs are hexagonal and spherical in form with no considerable agglomeration, according to TEM-results. The particle diameters varied between 13.2 and 36.8 nm. AgNPs and AgNPs-cotton clothing for wound treatment and self-sterilizing coats were displayed to have an antimicrobial action versus ESβL-producing E. coli. AgNPs, and their application i.e., AgNPs-wound dressing, shown a considerable antibacterial efficiency against ESL-producing E. coli. The minimum inhibitory concentrations (MIC) of AgNPs against ESβL-producing E. coli ranged from 7 to 9 μg mL−1, while the MIC of AgNPs with ampicillin was 1.25–4 g mL−1. This is mostly due to the AgNPs plus ampicillin have a synergistic efficiency, increasing the antibacterial effectiveness of AgNPs by 2–4 times. Our findings implied that the generated AgNPs might be applied as a nano-drug individually or combined with ampicillin against ESβL-producing E. coli.
Caries lesions during cement repairs are a severe issue, and developing a unique antimicrobial restorative biomaterial can help to reduce necrotic lesion recurrence. As a result, Thymus vulgaris extract was used to biosynthesize copper nanoparticles (TVE-CuNPs) exhibiting different characteristics (TVE). Along with TVE-CuNPs, commercial silver nanoparticles (AgNPs) and metronidazole were combined with glass ionomer cement (GIC) to test its antibacterial efficacy and compressive strength. FTIR, XRD, UV-Vis spectrophotometry, and TEM were applied to characterize the TVE-CuNPs. Additionally, AgNPs and TVE-CuNPs were also combined with metronidazole and GIC. The modified GIC samples were divided into six groups, where groups 1 and 2 included conventional GIC and GIC with 1.5% metromidazole, respectively; group 3 had GIC with 0.5% TVE-CuNPs, while group 4 had 0.5% TVE-CuNPs with metronidazole in 1.5%; group 5 had GIC with 0.5% AgNPs, and group 6 had 0.5% AgNPs with metronidazole at 1.5%. An antimicrobial test was performed against Staphylococcus aureus (S. aureus) and Streptococcus mutans (S. mutans) by the disc diffusion method and the modified direct contact test (MDCT). GIC groups 4 and 6 demonstrated a greater antimicrobial efficiency against the two tested strains than the other groups. In GIC groups 4 and 6, the combination of GIC with two antimicrobial agents, 1.5% metronidazole and 0.5% TVE-CuNPs or AgNPs, enhanced the antimicrobial efficiency when compared to that of the other groups with or without a single agent. GIC group specimens combined with nanosilver and nanocopper had similar mean compressive strengths when compared to the other GIC groups. Finally, the better antimicrobial efficacy of GIC boosted by metronidazole and the tested nanoparticles against the tested strains may be relevant for the future creation of more efficient and modified restorations to reduce dental caries lesions.
Dental infections cause chronic diseases, such as periodontitis and dental caries, thereby leading to the tooth loss. Antibacterial and antibiofilm efficiencies of silver and zinc oxide nanoparticles combined with chitosan and erythromycin against several bacterial oral diseases have been, therefore, demonstrated. Silver nanoparticles (TVE-AgNPs) were compared with a commercial ZnONPs that conjugated with chitosan to form TVE-AgNPs-CS and ZnONPs-CS. The synergistic efficiency of TVE-AgNPs-CS or ZnONPs-CS combined with erythromycin against Streptococcus mutans (S. mutans), Bacillus subtilis (B. subtilis) and Pseudomonas aeruginosa (P. aeruginosa) was estimated by broth micro-dilution assays, agar diffusion and biofilm formation. Herein, TVE-AgNPs were produced using Thymus vulgaris extract (TVE) and the peak obtained of TVE-AgNPs at 450 nm indicated the formation of TVE-AgNPs. Furthermore, results displayed the creation of spherical TVE-AgNPs with diameters a ranging from 10 to 24 nm. The FTIR analysis suggested that TVE contains reducing agents that consequently had a function in silver ions reduction and TVE-AgNPs formation. The minimum Inhibitory Concentration (MIC) value of TVE-AgNPs-CS and ZnONPs-CS with erythromycin exhibited an MIC value of 4–8 and 8–16 μg mL−1, respectively. The inhibition ratio versus biofilm was evaluated to be 75, 77.7, and 65.5% for S. mutans, B. subtilis and P. aeruginosa, respectively at TVE-AgNPs-CS/erythromycin concentration of 4 μg mL−1, while it was 91.6, 83.3, and 79.3% at ZnONPs-CS/erythromycin concentration of 8 μg mL−1. Our results provided an evidence of TVE-AgNPs-CS and ZnONPs-CS with erythromycin being antibacterial and antibiofilm agents against the tested bacteria. Also, they caused cell membrane damage of bacterial cells. Thus, ZnONPs-CS/erythromycin could be used in dental applications due to its non-toxicity profile and may be an important in the future development of more effective therapies for control of dental diseases.