2016—2020年辽宁省沙门菌耐药性及分子分型研究

目的 分析辽宁省2016—2020年食源性疾病监测中沙门菌分离株的耐药情况及分子分型特征,为沙门菌引起感染性腹泻的防控、临床抗生素使用提供可靠科学依据。方法 对辽宁省2016—2020年临床腹泻病例分离的90株沙门菌进行血清学鉴定,应用脉冲场凝胶电泳（PFGE）进行分子分型,采用BioNumeries 7.6软件对菌株间的相似度进行聚类分析,采用微量肉汤稀释法进行药物敏感性检测。结果 90株沙门菌分为13种血清型,以肠炎沙门菌和鼠伤寒沙门菌为主。PFGE聚类分析得到54种带型,各带型间相似度为51.4%～100%,每种带型包含1～10株菌,同一血清型菌株的PFGE带型相似度较高,且存在多次聚集现象。药敏结果显示90株沙门菌呈现36种耐药谱,氨苄西林耐药率最高（66.7%,60/90）,其次为萘啶酸（62.2%,56/90）,头孢西丁全部敏感。多重耐药率达48.9%（44/90）,其中鼠伤寒沙门菌和肠炎沙门菌多重耐药率分别为87.5%和45.8%。结论 辽宁省沙门菌引起腹泻病例呈散发态势,菌株多重耐药趋势明显,且耐药率较高,耐药谱广泛,应进一步加强分子溯源及耐药性监测。     

2021年贵州省食源性疾病主动监测分离沙门菌耐药及分型特征

目的 了解2021年贵州省食源性疾病主动监测分离沙门菌的血清型、耐药和分子分型特征。方法 对全省2021年食源性疾病主动监测腹泻病例中分离的164株沙门菌采用玻片凝集法进行血清学分型，采用微量肉汤稀释法测定菌株对14种抗生素的最小抑菌浓度（MIC）值，采用脉冲场凝胶电泳（PFGE）进行分子分型。结果 164株沙门菌可分为25种血清型，优势血清型为鼠伤寒沙门菌（76，46.34%）、肠炎沙门菌（25，15.24%）和爪哇安纳沙门菌（15，9.15%）。164株沙门菌耐药率为100%，多重耐药率达86.59%；其中对氨苄西林、四环素和萘啶酸耐药率较高，分别为95.12%（156/164）、78.05%（128/164）和63.41%（104/164）。72株鼠伤寒沙门菌PFGE聚类分析后共分为58种指纹图谱，24株肠炎沙门菌有12种指纹图谱，15株爪哇安纳沙门菌有3种指纹图谱。结论 贵州省腹泻患者沙门菌血清型种类较多，多重耐药现象严重，PFGE指纹图谱表现出遗传多样性。应加强对沙门菌的耐药监测，尤其是优势血清型鼠伤寒沙门菌的临床用药。     

中山市540株腹泻病例沙门菌血清型分布和耐药分析

目的研究2016—2017年中山市腹泻病例沙门菌血清型分布和耐药性。方法对2016—2017年中山市腹泻病例沙门菌监测分离的540株菌株进行血清学分型,并采用微量肉汤稀释法进行药敏试验。结果 540株沙门菌涵盖59种血清型,两年有22种共同血清型,优势血清型为鼠伤寒沙门菌单相变体(41.9%,226/540)、肠炎沙门菌(13.1%,71/540)、鼠伤寒沙门菌(9.3%,50/540)和斯坦利沙门菌(9.3%,50/540),共占菌株总数的73.5%(397/540)。药敏结果显示沙门菌对氨苄西林、氨苄西林/舒巴坦和四环素的耐药率均50.0%,对头孢类抗生素的耐药性差异较大,头孢唑啉、头孢噻肟、头孢他啶和头孢西丁的耐药率分别为34.1%(184/540)、25.7%(139/540)、12.2%(66/540)和1.5%(8/540);所有菌株均对亚胺培南敏感,斯坦利沙门菌对6种抗生素敏感;菌株多重耐药率达65.4%(353/540),4种优势血清型中鼠伤寒沙门菌单相变体、肠炎沙门菌、鼠伤寒沙门菌、斯坦利沙门菌的多重耐药率分别为82.7%(187/226)、56.3%(40/71)、72.0%(36/50)、16.0%(8/50)。结论中山市腹泻病例沙门菌血清型呈生物多样性,菌株多重耐药率较高,其中鼠伤寒沙门菌单相变体耐药情况最严重,应引起重视。     

2021年广西腹泻病人来源的鼠伤寒沙门菌及其单相变种比较分析

目的 通过研究比较2021年广西壮族自治区腹泻病人来源的鼠伤寒沙门菌及其单相变体1，4，［5］，12∶i∶-（S.1，4，［5］，12∶i∶-）流行特征与耐药情况，更好地了解鼠伤寒沙门菌及其单相变体多重耐药克隆的流行病学及其在传播的潜力。方法 对来自病例监测分离的276株鼠伤寒沙门菌用血清凝集方法进行第一次分型，当第二项鞭毛抗原诱导三次后依然不凝集，再用多重PCR的方法进行第二次分型，用微量肉汤稀释法进行药敏试验。结果 经多重PCR确认为鼠伤寒沙门菌单相变体的有201株（72.8%），鼠伤寒沙门菌75株。鼠伤寒沙门菌对磺胺类药物、氯霉素的耐药率显著高于鼠伤寒沙门菌单相变体（P<0.05）。鼠伤寒沙门菌单相变体对氨苄西林、头孢噻肟、萘啶酸、庆大霉素、四环素5种抗生素的耐药率显著高于鼠伤寒沙门菌（P<0.05）。两种沙门菌对3类及以上抗生素耐药率达到79%以上，共同多重优势耐药谱为耐氨苄西林、氯霉素、甲氧苄啶/磺胺甲唑和四环素。结论 鼠伤寒沙门菌单相变体已经超过鼠伤寒沙门菌成为广西壮族自治区腹泻病人中最优势的血清型。两种沙门菌耐药情况不容乐观，特别是多重耐药菌株的快速增加。需要有针对性地加强对食源性鼠伤寒沙门菌和鼠伤寒沙门菌单相变体进行耐药监测，揭示其耐药性的潜在决定因素，并展开有效的干预措施。     

预包装熟肉制品生产加工过程沙门菌污染状况及病原学特征研究

目的 了解预包装熟肉制品生产加工过程各环节中沙门菌污染状况,并分析分离株的分子特征及耐药性。方法 按照国家《熟肉制品（预包装）生产加工过程监测工作手册》采样要求,2015—2017年在德州某预包装熟肉制品厂采集环境样品和熟肉样品共460份,依据现行有效的GB 4789.4—2016进行沙门菌分离鉴定;用血清凝集法对沙门菌进行血清分型;用脉冲场凝胶电泳（PFGE）和多位点序列分型（MLST）法对沙门菌进行分子分型分析;采用微量肉汤稀释法对15种抗生素进行耐药性检测。结果 460份样品中沙门菌检出率为5.65%（26/460）,2016年沙门菌的检出率最高（7.65%,14/183）,不同年份沙门菌检出率差异无统计学意义（χ²=2.82,P>0.05）;中间产品中沙门菌的检出率最高,不同样品属性沙门菌检出率差异有统计学意义（χ²=64.16,P<0.05）;仅在生制品加工车间检出沙门菌,不同车间沙门菌检出率差异有统计学意义（χ²=78.08,P<0.05）。26株沙门菌共分为6个血清型,肠炎沙门菌最多,占53.85%（14/26）。26株沙门菌经PFGE分型后获得12种带型,以S4型为主;经MLST分型共获得5种ST型,ST11为优势型别。26株分离株中有22株对不同的抗生素有耐药性,耐药率最高的是氨苄西林,为73.08%（19/26）,多重耐药率（耐3种及以上抗生素）为73.08%。结论 熟肉制品加工过程中沙门菌污染主要集中在加工过程的原辅料和中间产品环节,产品蒸煮后污染状况可被有效控制。     

腹泻患儿粪便中沙门菌的血清型、药敏分析及脉冲场凝胶电泳分子分型研究

目的 研究2019年北京市朝阳区0-10岁腹泻患儿粪便中分离出的沙门菌的血清型、PFGE分子分型研究及耐药特点。方法 对分离自腹泻患儿病例的47株沙门菌进行血清分型,采用微量肉汤稀释法进行27种抗生素的药敏实验;采用PFGE脉冲场凝胶电泳进行指纹图谱分型研究。结果 47株沙门分为9种血清型,优势血清型两种,分别为肠炎沙门菌23株占48.94%,鼠伤寒沙门菌14株占29.79%。47株沙门菌对磺胺异恶唑耐药率(57.45%)最高,其次为氨苄西林(48.94%)和链霉素(48.94%)。23株肠炎沙门菌可分成8个PFGE指纹图谱,15株鼠伤寒沙门菌可分成14个PFGE指纹图谱。结论 北京市朝阳区0-10岁儿童食源性沙门菌血清主要为肠炎沙门菌和鼠伤寒沙门菌,各血清型的耐药性有所不同,PFGE指纹图谱呈多样性。     

2015—2020年安徽省腹泻病人沙门菌血清型分布及耐药性研究

目的 了解安徽省近年来沙门菌(Salmonella)的血清型分布及耐药特性,为本省沙门菌引起腹泻病的诊断和治疗提供科学依据。方法 对2015—2020年来自安徽省16个地市食源性疾病主动监测腹泻病例中分离出的980株沙门菌进行血清分型,采用微量肉汤稀释法进行药物敏感性实验。结果 980株沙门菌分为82种血清型,优势血清型为肠炎沙门菌[31.43%(308/980)]、鼠伤寒沙门菌[26.22%(257/980)]、阿贡纳沙门菌[7.35%(72/980)]、汤卜逊沙门菌[6.63%(65/980)]和伦敦沙门菌[3.37%(33/980)]。沙门菌对氨苄西林(AMP)、萘啶酸(NAL)、四环素(TET)、氨苄西林/舒巴坦(AMS)耐药率较高,分别为62.35%、47.96%、47.86%、43.16%;对AMP、AMS、NAL、头孢西丁(CFX)、阿奇霉素(AZM)耐药率呈现明显上升趋势(P＜0.05)。沙门菌耐药性呈现区域性特点,皖北地区耐药情况较皖中、皖南更加严重。多重耐药率达40.41%,鼠伤寒沙门菌、伦敦沙门菌多重耐药严重。结论 2015—2020年安徽省腹泻病人沙门菌血清型主要为肠炎沙门菌、鼠伤寒沙门菌、阿贡纳沙门菌、汤卜逊沙门菌和伦敦沙门菌。菌株耐药情况较严重,且对多数抗生素耐药率呈上升趋势,多重耐药水平较高。需密切关注并持续对本地区沙门菌的耐药情况进行监测。     

2017—2019年绍兴市沙门菌病人分离株的耐药性与分子分型分析

目的 了解绍兴市2017—2019年沙门菌病人分离株的分子分型特征及耐药情况。方法 收集245株分离自绍兴市食源性腹泻病例中的沙门菌,进行血清学分型,采用微量肉汤稀释法进行药敏检测,使用脉冲场凝胶电泳(PFGE)对分离株进行分子分型,利用BioNumerics V7.1软件进行聚类分析。结果 245株沙门菌可分为60种血清型,优势血清型为鼠伤寒沙门菌(32.24%)、肠炎沙门菌(10.20%)和伦敦沙门菌(6.94%)。225株分离株对25种抗生素存在不同程度的耐药,其中氨苄西林(77.14%)、四环素(73.88%)和链霉素(66.53%)的耐药率较高,且多重耐药率达76.33%。Xba Ⅰ酶切后的鼠伤寒沙门菌、肠炎沙门菌和伦敦沙门菌分别含48种、11种和12种不同PFGE指纹图谱。结论 绍兴市沙门菌血清型种类繁多,PFGE指纹图谱呈多样性,抗生素耐药呈现较集中且主要为氨苄西林-四环素-链霉素(AMP-TET-STR)。     

青岛市屠宰场整鸡中沙门菌污染水平定量检测及耐药性分析

目的调查青岛市规模化肉鸡屠宰场屠宰后整鸡样品中沙门菌的污染及抗生素耐药谱分布状况。方法2014年10~12月在青岛市选择2家规模化肉鸡屠宰场,采用胴体漂洗法定量检测3次共采集的141份屠宰后整鸡样品中沙门菌,根据Kauffmann-White表对沙门菌菌株进行血清学鉴定,应用微量肉汤稀释法检测菌株对11种抗生素的耐药性。结果整鸡样品沙门菌总体污染率为74.5%(105/141),污染水平3.6~1 100 MPN/100 g,中位数为43 MPN/100 g;共分离355株沙门菌,血清型分布为肠炎沙门菌220株,印第安纳沙门菌88株和阿贡纳沙门菌19株,以及其他型28株。355株沙门菌分离株的总体耐药率为90.4%(321/355),萘啶酸(NAL)耐药率最高(88.7%,315/355)。220株肠炎沙门菌中219株(99.5%)耐药,6株(2.7%)为多重耐药株,优势耐药谱为奈啶酸(156株)。88株印第安纳沙门菌均耐药,85株为多重耐药株,优势耐药谱为庆大霉素-氯霉素-环丙沙星-萘啶酸-氨苄西林-青霉烷砜/氨苄西林-头孢他啶-头孢噻肟-复方新诺明。19株阿贡纳沙门菌除1株对奈啶酸耐药外,其余18株对所测试11种抗生素均敏感。结论青岛市肉鸡屠宰场沙门菌污染率较高,血清型以肠炎沙门菌、印第安纳沙门菌和阿贡纳沙门菌为主。沙门菌总体耐药率较高,并呈现多重耐药性趋势。     

2014—2018年江西省食源性疾病患者沙门菌分离株MLST分型及流行特征研究

目的 掌握江西省食源性疾病患者沙门菌分离株优势ST（MLST）型及其时空分布特征、流行趋势，分析血清型与ST型的对应关系。方法 以分离自2014—2018年江西省食源性疾病患者的313株沙门菌为研究对象，采用多位点序列分型（MLST）技术对菌株进行基因分型，探讨ST型别的时空分布特征及其与血清型的对应关系。结果 313株沙门菌共分为39种ST型，占比最高的是ST34（32.59%），其次是ST11（15.97%）、ST19（11.50%）。每年的优势ST型基本为ST34、ST11、ST19，地区间ST型分布存在差异：上饶市ST型种类最多（20种），其次是抚州市（15种）、景德镇市（14种）；南昌市优势ST型别为ST11、新余和鹰潭市优势ST型为ST19，而其他地市的优势ST型均为ST34。313株沙门菌共分为30个血清型，优势血清型为4，［5］，12：i：-（30.35%）、肠炎沙门菌（15.97%）、鼠伤寒沙门菌（14.06%）。结论 江西省食源性疾病患者沙门菌分离株的ST型别较多，年度流行ST型以ST34、ST11、ST19为主。这三种优势ST型在江西省不同地区间均有分布，但ST型在时空分布上也存在地区差异。     

Arsenic content of some edible mushroom species

The arsenic contents of 162 fruit body samples of 37 common edible mushroom taxa were analyzed. The samples were gathered from different habitats of Hungary (mainly from mountains) between 1984 and 1999. The arsenic content of the samples was measured by the inductively coupled plasma spectrometry method. Very low [lower than 0.05 mg/kg dry matter (DM)] concentrations were found in the samples of 13 taxa, while higher (or very high) contents were quantified in other common taxa (the highest arsenic content was recorded in the fruit body of Laccaria amethysthea at 146.9 mg/kg DM). The species of eight genera (Agaricus, Calvatia, Collybia, Laccaria, Langermannia, Lepista, Lycoperdon, Macrolepiota) belong to the so-called accumulating taxa, and this tendency is evident on all habitats. This arsenic accumulation capability is found in two orders of Basidiomycetes (Agaricales and Gasteromycetales), which is to say this phenomenon occurs in the families Agaricaceae, Tricholomataceae and Gasteromycetaceae. The accumulating taxa found all have a saprotrophic type of nutrition; arsenic accumulation is not detectable in xilophagous or in mycorrhizal species. The consumption of the accumulating species found has only a low toxicological risk for three reasons: the consumed fresh fruit bodies contain about a tenfold lower arsenic level than the dried ones, the majority of arsenic occurs not in poisonous inorganic, but in less dangerous (or not poisonous) organic forms, and the frequency of consumption is low.     

Organization and localization of the dnaA and dnaK gene regions on the multichromosomal genome of Burkholderia multivorans ATCC 17616

The Burkholderia multivorans strain ATCC 17616 carries three circular chromosomes with sizes of 3.4, 2.5, and 0.9 Mb. To reveal the distribution and organization of the genes for fundamental cell functions on the genome of this bacterium, the dnaA and dnaK gene regions of ATCC 17616 were cloned and characterized. The gene organization of the dnaA region was rnpA-rmpH-dnaA-dnaN-gyrB with a single consensus DnaA-binding box (TTATCCACA) between the rmpH and dnaA genes. This intergenic region, however, did not work as an autonomously replicating sequence in ATCC 17616. On the other hand, the gene organization of the dnaK region was grpE-orf1 (gene for thioredoxin homologue)-dnaK-dnaJ-pabB (gene for p-aminobenzoate synthetase component homologue). A putative heat-shock promoter that showed good homology to the sigma32-dependent promoter consensus sequence in Escherichia coli was found upstream of the grpE gene, suggesting that these five genes constitute an operon. In M9 succinate minimal medium the dnaJ mutant grew more slowly than the wild-type strain, indicating that this operon is functional. Pulsed-field gel electrophoresis and Southern blot analyses indicated that both the dnaA and dnaK gene regions exist as single copies on the 3.4 Mb chromosome.     

Susceptibility of stored product insects to high concentrations of ozone at different exposure intervals

Ozone is a highly reactive gas with insecticidal activity. Past studies have indicated that ozone technology has potential as a management tool to control insect pests in bulk grain storage facilities. The objective of this study was to determine the efficacy of short periods of exposure to high ozone concentrations to kill all life stages of red flour beetle (Tribolium castaneum (Herbst)) (Coleoptera: Tenebrionidae), and Indianmeal moth (Plodia interpunctella (Hübner)) (Lepidoptera: Pyralidae), adult maize weevil (Sitophilus zeamais (Motsch.)) (Coleoptera: Curculionidae) and adult rice weevil (S. oryzae (L)) (Coleoptera: Curculionidae). Insects were treated with six ozone concentrations between 50 and 1800 ppm. The specific objective was to determine minimal time needed to attain 100% mortality. The most ozone-tolerant stages of T. castaneum were pupae and eggs, which required a treatment of 180 min at 1800 ppm ozone to reach 100% mortality. Eggs of P. interpunctella also required 180 min at 1800 ppm ozone to reach 100% mortality. Ozone treatments of 1800 ppm for 120 min and 1800 ppm for 60 min were required to kill all adult S. zeamais and adult S. oryzae, respectively. The results indicate that high ozone concentrations reduce the treatment times significantly over previously described results. Our results also provide new baseline information about insect tolerance to ozone treatment.     

Contamination with storage fungi of human food from Cameroon

In a mycological study, a total of 95 human food samples were investigated to evaluate the incidence of fungal contamination in Cameroon by conventional identification method and partly confirmed by DNA sequencing. The isolated fungal spp. were further studied to determine their toxigenic potentials. The investigation revealed the predominance of Aspergillus and Penicillium with 96% of samples contaminated with at least one species of these fungi, whereas the incidence of co-contamination of samples was 85%. Aspergillus flavus and Aspergillus parasiticus (Flavi section) were the most predominant species contaminating mainly maize and peanuts. In addition, P. crustosum and P. polonicum were the most common contaminants belonging to the genus Penicillium. On the other hand, A. ochraceus (Circumdati section) registered a low incidence rate of 5%, including other members of the Aspergillus group. Other members of the genera Rhizopus and Alternaria spp. were also registered in the study. A majority of fungal strains of A. ochraceus, A. parasiticus, P. crustosum and P. polonicum isolated were toxigenic, producing the mycotoxins tested for, while none was detected in cultures of A. fumigatus. The high incidence rate of fungi contamination coupled with their potentials in producing mycotoxins gives a strong indication that the samples tested may likely be contaminated with various mycotoxins. There is need for further study to assess the incidence of mycotoxins contamination in similar food samples.     

Formation of cereulide and enterotoxins by Bacillus cereus in fermented African locust beans

Afitin, iru and sonru are three spontaneously fermented African locust bean Benin condiments. The fermentation processes are exothermic, with temperatures mostly being above 40 °C. A total of 19 predominant Bacillus cereus isolates from afitin, iru and sonru, were investigated. The enterotoxin genes nhe (A, B, C) were present in all 19 isolates, the hbl (A, C, D) in one (afitin), and the cytK gene in three isolates (afitin). Levels of cytotoxicity to Vero cells and NheA production in BHI-broth was within the range of known diarrheal outbreak strains. Autoclaved cooked African locust beans inoculated with emetic (cereulide producing) B. cereus Ba18H2/RIF supported growth at 25, 30 and 40 °C with highly different maximum cereulide productions of 6 ± 5, 97 ± 3 and 0.04 ± 0.02 μg/g beans, respectively (48 h). For non-autoclaved cooked beans inoculated with 2, 4 and 6 log₁₀B. cereus Ba18H2/RIF spores/g beans, cereulide production was 5 ± 4, 64 ± 8 and 69 ± 34 μg/g beans, respectively at 24 h, while it was 70 ± 43, 92 ± 53 and 99 ± 31 μg/g at 48 h of fermentation at 30 °C. Even though high toxin levels were observed, to date there are no known reports on diarrhea or vomiting due to the consumption or afitin, iru and sonru in Benin, which also according to the present study is likely to be expected from the low levels of cereulide produced at 40 °C.     

Microbial profiles of frozen trimmings and silver sides prepared at Indian buffalo meat packing plants

To assess microbiological quality of buffalo meat trimmings (TT = 114) and silver sides (SS = 41), samples were collected from four different Indian meat packing plants. The aim of this study was: (i) to evaluate standard plate count (SPC), psychrotrophic count (PTC), Enterococcus feacalis count (EFC), Staphylococcus aureus count (SAC) and Escherichia coli count (ECC) and the presence of Salmonella spp. and Listeria monocytogenes; and (ii) also to determine vero toxic E. coli (VTEC) by polymerase chain reaction (PCR). TT samples had significantly higher (P < 0.001) SPC, PTC, EFC, and SAC than SS, while across the meat types there was no difference (P > 0.05) in ECC. E. coli was recovered from 32.4% TT and 19.5% SS samples. The prevalence rate of Salmonella spp. and L. monocytogenes in TT was 1.75% and 0.87%, respectively. But no SS sample was found to be positive for any of these two pathogens. VTEC was found in 2.58% of all the tested samples. This finding suggests that TT contain higher microbes but only small numbers of pathogens of latent zoonotic importance. The present study confirmed the importance of maintaining good process hygiene at meat plants for microbiological status of buffalo meat.     

Feeding deterrent activity of terpenoid lactones with a p-menthane system against stored-product pests

Feeding deterrent activity of eight enantiomeric pairs and one optically inactive terpenoid lactone with a p-menthane system against three storage pests was determined. The lactones were tested on adults of Sitophilus granarius, adults and larvae of Tribolium confusum and larvae of Trogoderma granarium. The isomeric starting natural compounds, (+) and (−) pulegones and (+) and (−) isopulegols, were also tested. The results showed that the introduction of the lactone moiety into the p-menthane system produced antifeedant activity in the lactones obtained. The lactones with a spiro arrangement of lactone and cyclohexane rings were more active than those with condensed rings. The configuration of chiral centres present in the molecule significantly influenced the activity of the compounds studied. In most cases, lactones obtained from R-(+)-pulegone were more active antifeedants than those obtained from S-(−)-pulegone.     

Effect of Zataria multiflora Boiss. essential oil and nisin on Salmonella typhimurium and Staphylococcus aureus in a food model system and on the bacterial cell membranes

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO: 0, 5, 15 and 30 μl 100 ml⁻¹) and nisin (N: 0, 0.25 and 0.5 μg ml⁻¹), temperatures (T: 25 and 8 °C), and storage times (up to 21 days) on growth of Salmonella typhimurium and Staphylococcus aureus in a commercial barley soup were evaluated in a factorial design study. The growth of S. typhimurium was significantly (P < 0.05) decreased by EO concentrations and their combinations with N concentrations at 8 °C. For S. aureus, the viable count was significantly (P < 0.05) inhibited by EO and N concentrations and their combinations, incubated at both storage temperatures. The mechanism of the antimicrobial action of EO, N, and their combinations against cell membranes of the tested organisms were also studied by measurement of the release of cell constituents and by the electronic microscopy observations of the cells. The significant increase of the cell constituents’ release of both organisms was observed as a result of treatments with EO and EO in combination with N. Electronic microscopy observations revealed that the cell membranes of S. typhimurium treated by EO and EO in combination with N were significantly damaged, while cells treated with only N looked similar to untreated cells. The electron micrographs of treated cells of S. aureus with EO, N, and their combination also showed important morphological damages and disrupted membranes.