Multiple action sites of ultrasound on Escherichia coli and Staphylococcus aureus

Ultrasound,is thought to a potential non-thermal sterilization technology in food industry.However,the exact mechanisms underlying microbial inactivation by ultrasound still remain obscure.In this study,the action modes of ultrasound on both Gram-negative and Gram-positive microorganisms were estimated.From colony results,ultrasound acted as an irreversible effect on both Eshcerichia coli and Staphylococcus aureus without sublethal injury.The result in this study also showed that a proportion of bacteria subpopulation suffered from serious damage of intracellular components(e.g.DNA and enzymes)but with intact cell envelopes.We speculated that the inactivated effects of ultrasound on microbes might more than simply completed disruption of cell exteriors.Those microbial cells who had not enter the valid area of ultrasonic cavitation might be injected with free radicals produced by ultrasound and experienced interior injury with intact exterior structure,and others who were in close proximity to the ultrasonic wave field would be immediately and completely disrupted into debris by high power mechanic forces.These findings here try to provide extension for the inactivation mechanisms of ultrasound on microorganisms.

Susceptibility breakpoint for cefquinome against Escherichia coli and Staphylococcus aureus from pigs

Cefquinome is the only fourth-generation cephalosporin used solely for veterinary applications.In this study,we established the wild-type cut-off(CO_(WT))and pharmacokinetic/pharmacodynamic cut-off(CO_(PD))of cefquinome against Escherichia coli and Staphylococcus aureus.A total of 210 E.coli and 160 S.aureus isolates were collected from pigs in Guangdong Province between 2014 and 2018.The minimum inhibitory concentrations(MICs)were determined using a microdilution broth method.MIC_(50)and MIC_(90)were 0.06 and 0.25μg m L^(–1)for E.coli and 0.5 and 1μg m L^(–1)for S.aureus,respectively.Statistical analysis and the ECOFFinder Program showed that the CO_(WT)for cefquinome against E.coli and S.aureus were0.125 and 2μg m L^(–1),respectively.The resistance rates were 11.9%for E.coli and 6.25%for S.aureus.Based on a5000-subject Monte Carlo simulation,the CO_(PD)value for cefquinome against E.coil and S.aureus was 0.25μg m L^(–1)under the recommended dose(2 mg kg^(–1),twice a day for 3 days),confirming that infections caused by strains with MIC≤0.25μg m L^(–1)could be effectively treated.Following adjustment of the dosing regimen to 4.5 mg kg^(–1),effective treatment(>90)was achieved for S.aureus infections with MIC_(90)1μg m L^(–1).This susceptibility breakpoint determination is significant for resistant surveillance and cefquinome dosage guidance against E.coli and S.aureus in pigs.

The growth of Staphylococcus aureus and Escherichia coli in low-direct current electric fields

Electrical potentials up to 800 mV can be observed between different metallic dental restorations. These potentials produce fields in the mouth that may interfere with microbial communities. The present study focuses on the impact of different electric field strengths （EFS） on the growth of Staphylococcus aureus （ATCC 25923） and Escherichia coil （ATCC 25922） in vitro. Cultures of S. aureus and E. coil in fluid and gel medium were exposed to different EFS. Effects were determined by calculation of viable counts and measurement of inhibition zones. In gel medium, anodic inhibition zones for S. aureuswere larger than those for E. coliat all field strength levels. In fluid medium, the maximum decrease in the viable count of S. aureus cells was at 10 V.m-1. Field-treated S. aureus cells presented ruptured cell walls and disintegrated cytoplasm. Conclusively, S. aureus is more sensitive to increasing electric field strength than E. coll.

Investigation of effect of antibacterial,antioxidant,and phytochemical factors of Ocimum basilicum extract on Escherichia coli and Staphylococcus aureus

The use of natural antibacterial compounds in tcontroling and eliminating pathogenic microorganisms including bacteria and fungi has been extensively evaluated.Plant extracts have been studied in the past years as antibacterial agents in medicine,plant pathology,and canned food,and unlike antibiotics,they do not cause drug resistance in pathogens.BHA(Beta-hydroxy acid)is a synthetic antioxidant with good fat solubility.Most of the extracted materials have antifungal,antiviral,and antibacterial properties.Different mechanisms of these act on bacteria and prevent their growth and multiplying.Many plants’extraction has phenolic active groups in their structures.Due to the importance and antimicrobial effects of essential oil and basil extract,the present study was performed to investigate the effect of different concentrations of basil extract on the growth of two bacterial pathogens Escherichia coli and Staphylococcus aureus.Also,the chemical composition of this plant extract and its antioxidant properties have been studied.The results of this study showed that basil extract,especially in 100 and 70%concentration,had antibacterial properties against Staphylococcus aureus but it does not show sufficient antimicrobial effect against Escherichia coli in the same dose.Analysis of chemical compounds in the extraction of this plant showed a total of 15 chemical compounds,most of which are related to the compounds neofitidine with concentration(41.44%),dimethylamino pentane with concentration(14.81%)and cyclohexane with concentration(91.9%).We also compared the antioxidant properties of basil extract with BHA and showed a significant difference in comparison with the inhibition of DPPH(2,2-Diphenyl-1-Picrylhydrazyl)formation by the extract and the standard BHA,so that the inhibition of DPPH by the standard BHA sample was significantly higher than the BHA.But basil extract showed good antioxidant properties equivalent to 400 mg/mL in 800 mg/mL BHA.

Investigation of effect of antibacterial, antioxidant, and phytochemical factors of Ocimum basilicum extract on Escherichia coli and Staphylococcus aureus

The use of natural antibacterial compounds in tcontroling and eliminating pathogenic microorganisms including bacteria and fungi has been extensively evaluated.Plant extracts have been studied in the past years as antibacterial agents in medicine,plant pathology,and canned food,and unlike antibiotics,they do not cause drug resistance in pathogens.BHA(Beta-hydroxy acid)is a synthetic antioxidant with good fat solubility.Most of the extracted materials have antifungal,antiviral,and antibacterial properties.Different mechanisms of these act on bacteria and prevent their growth and multiplying.Many plants’extraction has phenolic active groups in their structures.Due to the importance and antimicrobial effects of essential oil and basil extract,the present study was performed to investigate the effect of different concentrations of basil extract on the growth of two bacterial pathogens Escherichia coli and Staphylococcus aureus.Also,the chemical composition of this plant extract and its antioxidant properties have been studied.The results of this study showed that basil extract,especially in 100 and 70%concentration,had antibacterial properties against Staphylococcus aureus but it does not show sufficient antimicrobial effect against Escherichia coli in the same dose.Analysis of chemical compounds in the extraction of this plant showed a total of 15 chemical compounds,most of which are related to the compounds neofitidine with concentration(41.44%),dimethylamino pentane with concentration(14.81%)and cyclohexane with concentration(91.9%).We also compared the antioxidant properties of basil extract with BHA and showed a significant difference in comparison with the inhibition of DPPH(2,2-Diphenyl-1-Picrylhydrazyl)formation by the extract and the standard BHA,so that the inhibition of DPPH by the standard BHA sample was significantly higher than the BHA.But basil extract showed good antioxidant properties equivalent to 400 mg/mL in 800 mg/mL BHA.

Antibacterial activity of the essential oils from the leaves of Eucalyptus globulus against Escherichia coli and Staphylococcus aureus

Objective:To examine the in vitro antimicrobial activities of essential oil of the leaves of Eucalyptus globulus(E.globulus).Methods:The essential oils of this plant were obtained by the hydrodistillation method.The inhibitory effects of this essential oil were tested against Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)by using agar disc diffusion and dilution broth methods.Results:The results obtained showed that essential oil of the leaves of E.globulus has antimicrobial activity against gram negative bacteria(E.coli)as well as gram positive bacteria(S.aureus).Conclusion:The encouraging results indicate the essential oil of E.globulus leaves might be exploited as natural antibiotic for the treatment of several infectious diseases caused by these two germs,and could be useful in understanding the relations between traditional cures and current medicines.

In vitro control of Staphylococcus aureus (NCTC 6571) and Escherichia coli (ATCC 25922) by Ricinus communis L.

Objective:To evaluate antibacterial activity of hot and cold ethanol and methanol leaf extracts of Ricinus communis L(R.communis)against Staphylococcus aureus(S.aureus)(NCTC 6571)and Escherichia coli(E.coli)(ATCC 25922).Methods:Leaf powder of R.communis L.was extracted with hot(in Soxhlet)and cold ethanol and methanol,separately.The antibacterial activity of the extracts was determined by agar well diffusion and macro broth dilution methods.The extracts were also subjected to phytochemical analysis.Results:All the four test extracts showed inhibition on both S.aureus and E.coli.Hot and cold ethanol extracts revealed significantly(P<0.05)higher inhibition on S.aureus than methanol extracts,and the hot ethanol extract had the lowest minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC)values(5 mg/mL and 10 mg/mL,respectively).E.coli was highly inhibited by hot extracts of both ethanol and methanol with the MIC and MBC of 40 mg/mL and 80 mg/mL,respectively.Phytochemical analysis revealed the presence of saponins,cardiac glycosides,tannins,flavonoids and terpenoids in all test extracts.Conclusions:This study demonstrates that the hot and cold methanol and ethanol extracts are potential sources for control of S.aureus and E.coli.Especially,the hot and cold extracts of ethanol are more inhibitive against 5.aureus even at lower concentration.Further study is needed to identify the specific bioactive compounds,their mode of action and their nontoxic nature in vivo condition.

Development of a Multiplex PCR for Diagnosis of Staphylococcus aureus, Escherichia coli and Bacillus cereus from Cows with Endometritis

Staphylococcus aureus, Escherichia coli and Bacillus cereus are the major agents of cow endometritis in dairy cows. A multiplex PCR （SEB-mPCR） was established based on the conserved genes of S. aureus, E. coli and B. cereus, and the detection limits were 103, 102 and 103 CFU mL-1, respectively. SEB-mPCR could not amplify genomic DNA of pathogenic bacteria of other common bovine diseases. A total of 309 vaginal discharge samples from cows with endometritis were tested by SEB-mPCR. Of the samples, 23.95% had the three kinds of bacteria detected, 17.15% had S. aureu and E. coli, 9.39% had E. coli and B. cereus, and 9.71% had S. aureus and B. cereus. The rates of infections with S. aureus, E. coli and B. cereus were 11.35, 16.18 and 9.06%, respectively. Therefore, SEB-mPCR has a potential as a diagnosis tool for endometritis in dairy cows.

Ultrastructural Analysis of Chitosan Antibacterial Activity against Clinical Isolates of <i>Staphylococcus aureus</i>and <i>Escherichia coli</i>

The continuous search for an antimicrobial agent led to the identification of potential antimicrobial biomaterials based on polymers naturals, such as chitosan (CS). However, the mechanism of action of antibacterial activity of CS for gram-positive and gram-negative bacteria was not completely elucidated. The aim of this work is to report the antibacterial activity of CS through ultrastructural analyses of the clinical isolates Staphylococcus aureus and Escherichia coli by Transmission Electron Microscopy. The CS has a bactericidal action against S. aureus and E. coli which alters its cellular ultrastructure, such as with collapsed cell walls, condensed chromatin and the increase of intracellulares structures like vacuoles and cell debris. In this way, the CS represents a potential model for the future design of antibacterial in order to control bacterial resistance of patients in hospital settings.

Establishment and evaluation of diabetic ulcer model in rats infected with Staphylococcus aureus and Escherichia coli

Objective:To establish a rat model of diabetic ulcer infected by Staphylococcus aureus and Escherichia coli, and provide a suitable animal model for experimental research of diabetic ulcer. Methods: Forty male SD rats were randomly divided into five groups: general ulcer group, diabetic ulcer group, diabetic ulcer treatment group, model group, and model treatment group. After modeling, take local skin tissue for HE staining.Detection of high-sensitivity C-reactive protein, fibroblast growth factor, tumor necrosis factor-α, advanced glycosylation products, interleukin-1β, interleukin-6, and nitric oxide in rat serum by enzyme-linked immunosorbent Level, and record the wound healing time, and evaluate the stability and practicability of the model. Results:The healing time of ulcer in the model group was significantly delayed compared with other groups (p <0.001). The serum H-CRP levels in the model group and the model treatment group were higher than those in the common ulcer group, the diabetic ulcer group, and the diabetic ulcer treatment group (p <0.05). After healing, the levels of H-CRP, bFGF, AGEs, TNF-α, IL-1β, IL-6, and NO in the serum of the diabetic ulcer group were higher than those in the common ulcer group (all p <0.05);The levels of TNF-α, IL-1β, IL-6, and NO were higher than those in other groups (all p <0.05);HCRP, AGEs, TNF-α, IL-1β, IL-6, and NO levels in the serum of the model treatment group They were all higher than those in diabetic ulcer treatment group (all p <0.05). Conclusion: This model is in line with the local environment of infectious diabetic ulcers and provides a reliable tool for the study of diabetic infections.

Antibacterial potential of essential oils of the needles of Pinus halepensis against Staphylococcus aureus and Escherichia coli

Objective:To examine the in vitro antimicrobial activities of essential oil of the needles of Pinus halepensis(P.halepensis).Methods:The antibacterial activity of essential oil of the needles of P.halepensis was determined using the agar well diffusion technique and disc diffusion method against Staphylococcus aureus ATCC 25923,and Escherichia coli ATCC 25922.Results:The diameter of zones of inhibition exhibited by the essential oil was between 6 and 17 mm.The essential oils was compared favorably with gentamycin used as a standard control.The minimum inhibitory concentration determined by the agar well diffusion method was 0.52 mg/mL for Staphylococcus aureus and 2.15 mg/mL for Escherichia coli.The minimum bactericidal concentration of the oils against the two microorganisms was 4.17 mg/mL.Conclusions:The results obtained from this study reveal that P.halepensis essential oils possess antibacterial activities and can be used as antimicrobial agents in the search for new drugs.

Antibacterial behavior and related mechanisms of martensitic Cu-bearing stainless steel evaluated by a mixed infection model of Escherichia coli and Staphylococcus aureus in vitro

Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)are the most typical pathogenic bacteria with a significantly high risk of bio-contamination,widely existing in hospital and public places.Recent studies on antibacterial materials and the related mechanisms have attracted more interests of researchers.However,the antibacterial behavior of materials is usually evaluated separately on the single bacterial strain,which is far from the practical condition.Actually,the interaction between the polymicrobial communities can promote the growing profile of bacteria,which may weaken the antibacterial effect of materials.In this work,a 420 copper-bearing martensitic stainless steel(420 CuSS)was studied with respect to its antibacterial activity and the underlying mechanism in a co-culturing infection model using both E.coli and S.au reus.Observed via plating and counting colony forming units(CFU),Cu releasing,and material characterization,420 CuSS was proved to present excellent antibacterial performance against the mixed bacteria with an approximately 99.4%of antibacterial rate.In addition,420 CuSS could effectively inhibit the biofilm formation on its surfaces,resulting from a synergistic antibacterial effect of Cu ions,Fe ions,reactive oxygen species(ROS),and proton consumption of bacteria.

Effect of Ciprofloxacin on S.aureus and E.coli Growth in Presence of Vitamin C Using Cup Cut Diffusion Method

Ciprofloxacin is a second-generation of fluoroquinolone,broad-spectrum antibiotic with bactericidal activity against Gram-positive and Gram-negative organisms.It is one of the most widely used antibiotics,because of its efficacy,safety,and relatively low cost.Ascorbic acid(vitamin C)is water-soluble monosaccharide antioxidant;it is essentially required by the body for its various biochemical and physiological processes.S.aureus is Gram-positive cocci;widely distributed in the environment,it is a member of the normal flora of the body.S.aureus is not always pathogenic;it is a common cause of skin infections including abscesses,respiratory infections such as sinusitis,and food poisoning.E.coli is Gram-negative bacteria,found in the environment,foods,and intestines.Most E.coli strains are harmless;it is part of the normal microbiota of the gut.However,some serotypes of E.coli cause serious food poisoning in their hosts;it can cause diarrhea,while others cause urinary tract infections,respiratory illness and pneumonia,and other illnesses.Method:Cup cut diffusion method was applied.Experiment I:is carried out to choose the concentration of vitamin C to be used in experiment II.The negative control is normal saline,added in cup in each plate,vitamin C(100 mg/mL,200 mg/mL,400 mg/mL)was added,the volume in each cup was 100μL.Experiment II:Eight groups of treatments were applied.The first is the negative control(1%normal saline),the second group is the positive control of vitamin C(200 mg/mL).The third,fourth and fifth groups are ciprofloxacin with different concentrations(10 mg/mL,20 mg/mL,40 mg/mL);the sixth,seventh and eighth are the combination of vitamin C with each concentration of ciprofloxacin(10 mg/mL,20 mg/mL,40 mg/mL).Each group includes six petri dishes.Bacterial plates were incubated at 37 oC for 24 h and 48 h.Zone of inhibition is measured in mm.Results and conclusion:Ciprofloxacin produces dose dependent increase in zone of inhibition of S.aureus and E.coli growth,after 24 and 48 hours incubation.While vitamin C in the concentration used produced inhibitory effect on the growth of S.aureus and E.coli,after 24 hours incubation,vitamin C effect was not changed after 48 hours incubation.After 24 hours incubation,vitamin C potentiated the effect of ciprofloxacin at low concentration(10 mg/mL);while vitamin C antagonized the effect of ciprofloxacin at higher concentrations(20 and 40 mg/mL)on S.aureus growth.In the same time,ciprofloxacin antagonized the inhibitory effect of vitamin C on S.aureus growth.After 48 hours incubation,S.aureus produced resistance against ciprofloxacin alone,and that combined with vitamin C compared to zone of inhibition after 24 hours.Ciprofloxacin produced dose dependent inhibition of E.coli growth after incubation for 24 and 48 hours.Vitamin C potentiated the inhibitory effect induced by ciprofloxacin(additive effect).The inhibitory effect of ciprofloxacin,vitamin C and the combination was not changed after 48 hours compared to 24 hours.

Monitoring of Escherichia coli, Salmonella spp. and Staphylococci in Poultry Meat-Based Fast Food in Saudi Arabia

An investigation was made to survey the possible presence of Staphylococcus aureus, Escherichia coli and Salmonella spp. from fast-food shops in Al-Ahsa Province, Kingdom of Saudi Arabia (KSA), as potential reservoir of human infection and antimicrobial resistance. A total of 100 samples of shawarma poultry meat were collected from different localities of the province. Conventional, commercial VITEK 2 and molecular techniques were used for isolates’ identification and antibiogram detection. Staph aureus was isolated at a rate of 14% and CNS as Staph. sciuri and Staph. xylosus at 2%. E. coli was identified at a rate of 12% and antibiogram analysis showed 41.67% of isolates to be extended-spectrum β-lactamases (ESBL) with evidence of multi-drug resistance (MDR). Molecular analysis of E. coli revealed presence of sero-groups O1 and O2, entero-toxigenic (ETEC), shiga-toxigenic, ST540 and the prototypical ETEC strain H10407 which are potential public health hazard. Salmonella enterica serovar Enteritidis showed 19% prevalence while S. Typhimurium with 8% prevalence. Anti-microbial sensitivity of 15 strains of S. Enteritidis and 5 strains of S. Typhimurium showed multi-drug resistance (MDR).

Punch‑excised explants of bovine mammary gland to model early immune response to infection

Background Mammary gland(MG)infections(mastitis)are frequent diseases of dairy cows that affect milk quality,animal welfare and farming profitability.These infections are commonly associated with the bacteria Escherichia coli and Staphylococcus aureus.Different in vitro models have been used to investigate the early response of the MG to bacteria,but the role of the teat in mastitis pathogenesis has received less attention.In this study,we used punch-excised teat tissue as an ex vivo model to study the immune mechanisms that arise early during infection when bacteria have entered the MG.Results Cytotoxicity and microscopic analyses showed that bovine teat sinus explants have their morphology and viability preserved after 24 h of culture and respond to ex vivo stimulation with TLR-agonists and bacteria.LPS and E.coli trigger stronger inflammatory response in teat when compared to LTA and S.aureus,leading to a higher produc-tion of IL-6 and IL-8,as well as to an up-regulation of proinflammatory genes.We also demonstrated that our ex vivo model can be applied to frozen-stored explants.Conclusions In compliance with the 3Rs principle(replacement,reduction and refinement)in animal experimenta-tion,ex vivo explant analyses proved to be a simple and affordable approach to study MG immune response to infec-tion.This model,which better reproduces organ complexity than epithelial cell cultures or tissue slices,lends itself particularly well to studying the early phases of the MG immune response to infection.

Prevalence and Disinfection of Bacteria Associated with Various Types of Wristbands

The potential role of personal items in the transmission of pathogens is poorly understood. In this study, we cultured bacteria of public health importance found on wristbands, determined whether there is a correlation between wristband material and prevalence, and tested three household disinfectants for efficacy in reducing bacteria on wristbands made of plastic, rubber, metal, and cloth, using standard microbiological assays. Total cultivable bacteria, Staphylococci, Enterobacteria (Escherichia coli), and Pseudomonas on 20 smartwatch wristbands were cultured from randomly recruited subjects. Nearly all wristbands (95%) were contaminated, with the highest average numbers of 3.46E+4 cfu/cm2 and 1.52E+4 cfu/cm2 on rubber and plastic bands respectively. Metallic gold and silver wristbands had zero to 18 cfu/cm2. While the high prevalence of Staphylococcus spp (85% of wristbands)—skin microbiota;was not unexpected, the occurrence of Pseudomonas spp (30%), and enteric bacteria (60%), even at relatively low numbers is of public health significance. Bacterial load on individual subjects varied remarkably with males and females harboring average total bacteria of 4.045 and 3.42 log10cfu/cm2 of wristband, respectively. The most important predictor of wristband bacteria load was the texture of wristband material and activity (hygiene) of the subject at sampling time. Potential pathogens—Staphylococcus aureus (8143 cfu/cm2) and Pseudomonas spp. (1126 cfu/cm2) were most abundant on cloth and rubber wristbands, respectively, while the presence of the E. coli group was associated with animal handling activity by a veterinarian. Lysol Disinfectant Spray and 70% Ethanol were highly effective regardless of wristband material with >99.99% kill rate and a log cfu/cm2 reduction of 3 - 4.0 and 3 - 4.5 respectively within 30 seconds. Apple Cider Vinegar (ACV) was not as potent. Only 2 - 3.5 log cfu/cm2 drop was obtained after 120 seconds of exposure. Further susceptibility assays with standard reference bacteria showed that Lysol and 70% alcohol effectively killed > 99.99% (>8 log CFU drop) of Escherichia coli strain 7001, Staphylococcus aureus strain 6538, and Pseudomonas aeruginosa strain 10662 within 30 seconds of contact. Vinegar had a similar efficacy on the gram negatives but little or no effect on Staph aureus (only a 2-log CFU/ml reduction in 5 minutes!) The high prevalence of potential pathogens, some of which could be reservoirs of antibiotic resistance reveals a weak link in infection control and underscores the need for regular cleaning of personal and hand-held accessories with adequate considerations of their texture.

Prevalence and Antimicrobial Susceptibility Status of Gram-Negative and Gram-Positive Bacteria on Handheld Shopping Trolleys and Baskets in Supermarkets in Ndola, Zambia

Background: Supermarkets are a place visited by individuals with different health conditions daily where microbiological contaminants through touch onto fomites such as trolleys and baskets can be passed on to other people hence potentially spreading infectious diseases. This study aimed to investigate the presence of Gram-negative and Gram-positive bacteria on handheld shopping trolleys and baskets and their antimicrobial susceptibility status against commonly used antibiotics in Zambia. Methods: A cross-sectional study was conducted. Trolleys and basket handles were swabbed and standard microbiological methods were used to identify the bacteria and disc diffusion to determine their antimicrobial susceptibility status. Data was collected from December 2021 to April 2022. Data was analysed using IBM Statistical Package for Social Sciences (SPSS) Version 22. Results: Twenty-eight percent of the 200 total samples were found to be culture-positive and predominant isolates were Staphylococcus aureus (17.3%), Pseudomonas species (4.5%), Escherichia coli (2%), Corynebacterium species (2%), Staphylococcus species (1.5%) and Enterobacter aerogenes (0.5%). Staphylococcus aureus showed the most resistance to azithromycin (17%) followed by ciprofloxacin (2.8%), nitrofurantoin (2.8%) and chloramphenicol (2.8%). Escherichia coli showed 100% resistance to amoxicillin, cloxacillin and ampicillin, 75% resistance to ciprofloxacin and the least resistance to azithromycin (25%) while it was susceptible to nitrofurantoin. Staphylococcus species, Corynebacterium species, Enterobacter aerogenes and Pseudomonas species showed no resistance to any antibiotics. Conclusion: The study showed the presence of microorganisms with considerable antimicrobial resistance to antibiotics in Zambia on trolley and basket handles indicating the need for more initiatives to address proper hygiene in public environmental sites for better infection prevention and control.

三叶片抑制金黄色葡萄球菌和大肠埃希菌作用的关键组分挖掘

目的 挖掘三叶片发挥抑制金黄色葡萄球菌(Staphylococcus aureus,S.aureus)和大肠埃希菌(Escherichia coli,E.coli)作用的关键组分。方法 采用16S rRNA测序技术,在高脂饮食小鼠模型上评价三叶片对肠道菌群的调节作用及对肠道中致病菌S.aureus、E.coli的抑制作用。采用牛津杯法测定三叶片、不同药物组合及其单味药对S.aureus和E.coli的体外抑菌活性,挖掘三叶片中发挥抑菌作用的关键组分,并采用琼脂稀释法研究三叶片及其关键组分对两种致病菌株的最小抑菌浓度(MIC)。结果 菌群测序结果显示,三叶片可以上调高脂饮食小鼠肠道菌群物种丰富度和多样性,降低菌群中包括S.aureus、E.coli等致病菌的丰度。体外抑菌结果显示,三叶片、丹参赤芍组合以及丹参、赤芍组分对上述细菌均有显著的抑制作用。其中三叶片对S.aureus的MIC为0.781 25 mg·mL^(-1),对E.coli的MIC为3.125 mg·mL^(-1)。丹参赤芍组合对S.aureus的MIC为0.25 mg·mL^(-1),对E.coli的MIC为3.125 mg·mL^(-1)。三叶片中丹参组分可显著抑制S.aureus,其MIC为0.125 mg·mL^(-1);赤芍组分对E.coli的抑制作用优于其他组分,其MIC为3.125 mg·mL^(-1)。结论 三叶片能够抑制常见的肠道致病菌如S.aureus和E.coli,该方中丹参为抑制S.aureus的关键组分,赤芍为抑制E.coli的关键组分。

三种致病性细菌的SERS光谱研究

用便携式拉曼光谱仪获得了金黄色葡萄球菌、变形杆菌、大肠杆菌在微波法制备的纳米银溶胶上的表面增强拉曼光谱。金黄色葡萄球菌在725,1 330,1 450cm-1有明显的拉曼振动峰,变形杆菌在650,725,950,1 325,1 463cm-1有明显的拉曼振动峰,大肠杆菌在650,950,1 125,1 242,1 320,1 457cm-1有明显的拉曼振动峰,对各个峰进行了初步归属。三种细菌的拉曼振动峰的位置和强度区别明显,因此SERS技术可以用于大肠杆菌、金黄色葡萄球菌和变形杆菌的快速鉴别。

硫掺杂氮化碳纳米微球的制备及光催化杀菌性能研究

目的 制备硫掺杂氮化碳纳米微球,并对其光催化杀菌性能进行研究。方法 采用一步法制备常规石墨烯相氮化碳(graphite phase carbon nitride, GCN),并采用超分子自组装法制成具有微球结构的GCN,并在高温条件下进行硫掺杂(记为S-GCN)。通过X射线衍射,X射线光电子能谱以及傅里叶红外光谱等方法对制备的纳米微球材料进行表征,通过平板计数法来验证该材料对大肠杆菌和金黄色葡萄球菌的光催化杀菌效果,并采用扫描电镜和透射电镜观察杀菌前后的细菌形态和细胞膜完整性。结果 与常规块状石墨烯相氮化碳相比,在微观层面,硫掺杂氮化碳纳米微球呈圆形,此结构使光催化剂的比表面积增加,在分子层面,S原子取代GCN中部分N原子,形成C-S键,降低了光催化材料的光生电子-空穴复合速率。在抗菌活性方面,常规GCN在60min内对大肠杆菌和金黄色葡萄球菌灭菌率是73.2%和76.3%,而S-GCN灭菌率则达到98.8%和99.9%,提高了光催化剂的杀菌性能。扫描电镜和透射电镜的结果证明,光催化剂能够改变细菌形态以及破坏细胞膜的完整性。结论 S-GCN纳米微球对食源性致病菌有较好的灭活能力,有望成为新型食品安全控制技术。