Growth response and modelling of the effects of Zataria multiflora Boiss. essential oil, pH and temperature on Salmonella Typhimurium and Staphylococcus aureus

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO: 0.0, 0.015, 0.03 and 0.06%), pH values (7.3 and 6.0) and storage temperatures (T: 15, 25 and 35 °C) on some growth kinetics, time-to-detection (TTD, time to the nearest visible detection) and log₁₀ probability percentage (log P%) of growth initiation of Salmonella Typhimurium and Staphylococcus aureus in Brain Heart Infusion broth were evaluated in a factorial design study. For the log P%, the effects of another variable, storage time (D, up to 43 days) was also assessed as an additional factor. The TTD and log P% of both organisms were significantly affected (P<0.01) by the values of EO, pH, T and D (just for log P%). The combinations of pH=7.3, and EO?0.015 could not obviously affect the growth kinetics of the organisms in this study. Whereas, strong inhibitory action was observed by increasing of EO concentration to 0.06% at the considered pH (7.3) and T (?35 °C). The growth of both organisms was completely inhibited at the combinations of EO=0.06%, pH=6.0 and up to 43 days of storage. Regression equations were derived relating TTDs to EO, pH and T and log P% of both organisms to EO, pH, T and D. From these models the values of predicted TTD and log P% of S. Typhimurium and St. aureus can be calculated by any combinations of EO, pH, T and D (for log P%) within the limits studied. However, between the two TTD and log P% models obtained for both organisms in this study, the TTD models of S. Typhimurium and St. aureus showed better prediction (R²=0.951 and 0.978, respectively) than the log P% models of them (R²=0.852 and 0.804, respectively).     

The effect of nisin and garlic (Allium sativum L.) essential oil separately and in combination on the growth of Listeria monocytogenes

In the present study, the anti-listerial activity of the nisin and garlic (Allium sativum L.) essential oils (GO) alone and in combination was investigated at different temperatures (20 and 30 °C), pH (6.8, 5.6 and 4.8) and NaCl concentrations (0, 0.5, 2.5 and 4.5 g/100 mL). Minimum inhibitory concentrations (MICs) against Listeria monocytogenes were assessed for the nisin and essential oil. Furthermore, for combinations of the antimicrobials, the Differences in Population (DP) method were used to determine their effect. Both essential oil and nisin possessed considerable antimicrobial effects on the microorganism. The MICs for nisin and GO were 12.5 IU/mL and 100 μg/mL, respectively. Regardless of NaCl concentration and temperature, the anti-listerial activity of both GO and nisin was strongly influenced by pH. Moreover, at the same temperature, and regardless of pH value, the growth of the organism was also affected by increasing NaCl concentration. In combination, the DP was related strongly to the agent’s concentration and media pH. Meanwhile, among all combined systems, the effect of the combination (EC) of nisin with GO at 30 °C, pH 5.6 and 0 g/100 mL NaCl, showed significant anti-listerial activity (P ≤ 0.05).     

一起金黄色葡萄球菌食物中毒事件的病原检测和溯源分析

目的 对上海市浦东新区一起食物中毒事件进行病原检测和溯源分析,为此类事件的处置和判定提供依据。方法 对病例和从业人员肛拭子以及留样食品样品进行病原分离和鉴定;对分离株进行肠毒素检测、药物敏感性试验、脉冲场凝胶电泳(PFGE)和多位点序列分型(MLST)分子分型和溯源。结果 从9份病例肛拭子、1份从业人员肛拭子及3份留样食品样品中分离到13株金黄色葡萄球菌。10株人源分离株产A型和E型肠毒素,3株食源分离株产A型、D型和E型肠毒素。13株分离株均对青霉素耐药,PFGE条带相似度为100%,MLST分型均为ST6型。结论 本起事件是由金黄色葡萄球菌污染引起的食物中毒事件,需要进一步加强对食品加工企业、食堂等的宣传教育和管理,防止类似事件的发生。     

我国食源性金黄色葡萄球菌耐药及遗传特征情况研究

目的 探究我国2020年食源性金黄色葡萄球菌的耐药性、毒力因子及分子分型特征。方法 采用微量肉汤稀释法对菌株进行药物敏感性试验,基于全基因序列分析多位点序列分型及重要耐药基因（mecA）和毒力基因。结果 224株食源性金黄色葡萄球菌对12类抗菌药物的整体耐药率为87.9%（197/224）,对青霉素的耐药率最高为82.6%（185/224）。多重耐药率为23.2%（52/224）,多重耐药菌中ST398占比最高为26.9%（14/52）,耐甲氧西林金黄色葡萄球菌检出率为8.0%（18/224）。葡萄球菌肠毒素基因整体携带率为52.2%（117/224）,其中sea的携带率最高为24.6%（55/224）,携带肠毒素基因种类最多的ST型为ST1。共检测到31种ST型,其中ST7最多（12.9%,29/224）,ST398次之（10.7%,24/224）。中毒性休克综合征毒素编码基因（tsst-1）和杀白细胞素编码基因（lukF-PV和lukS-PV）的携带率分别为6.3%（14/224）和4.5%（10/224）。结论 我国食源性金黄色葡萄球菌耐药率和肠毒素携带率均较高,且检出了临床感染中重要的毒力基因,提示食品中金黄色葡萄球菌的潜在危害不容忽视。ST型与食品类别、耐药性和致病性存在一定相关性,可为了解我国食源性金黄色葡萄球菌的流行特征和风险防控提供数据支撑。     

食源性金黄色葡萄球菌的危害及其快速检测方法研究进展

金黄色葡萄球菌是一种常见的食源性致病菌,可通过污染乳制品、肉制品等蛋白质或淀粉含量丰富的食品引起食物中毒,还易引发人体局部化脓性感染、肺炎、心包炎等疾病,严重时甚至会出现败血症。采用准确、高效的金黄色葡萄球菌检测方法,是预防食源性金黄色葡萄球菌及食品安全质量控制的关键。金黄色葡萄球菌检测方法主要有免疫血清学检测技术、聚合酶链式反应检测技术和生物传感器检测技术等。本文总结了各类检测方法的核心技术特征和应用实例,为食源性金黄色葡萄球菌的快速检测方法的研发和使用提供思路。     

沙门菌、金黄色葡萄球菌、副溶血性弧菌的选择性共增菌培养基的研制

目的 研制一种可同时对沙门菌、金黄色葡萄球菌及副溶血性弧菌进行富集的共增菌培养基SSV,达到同时检测3种食品中常见的食源性致病菌的目的。方法 根据3株菌的营养需求,选择不同的培养基组分进行单因素实验,确定选择性共增菌培养基的配方,通过OD600 nm、受损菌复苏、多重聚合酶链式反应(PCR)、培养基选择性4个方面对SSV培养基进行验证。结果 确定增菌培养基的成分为：蛋白胨10.0 g、KH₂PO₄ 1.5 g、NaCl 15.0 g、LiCl 1.0 g,Na₂S₂O₃ 5.0 g、去氧胆酸钠0.05 g、甘露醇1.0 g、丙酮酸钠5.0 g,蒸馏水1 000 mL。SSV培养基能同时富集以上3株菌,37℃培养16 h后,3株菌的菌体浓度均达到107 CFU/mL及以上;SSV培养基对于受损的目标菌有良好的复苏效果,复苏后OD₆₀₀ nm较于复苏前增长了3倍;同时多重PCR、培养基选择性也得到很好的验证。结论共增菌培养基SSV可用于同时培养沙门菌、金黄色葡...     

甘露醇氯化钠琼脂培养基成分对鉴定金黄色葡萄球菌的影响

目的 探究甘露醇氯化钠琼脂培养基成分中氯化钠和胰酪胨对甘露醇氯化钠琼脂培养基质量的影响,同时考察市售5个国产品牌和1个进口品牌的甘露醇氯化钠琼脂培养基的产品质量。方法 采用不同品牌不同浓度的氯化钠和胰酪胨配制成甘露醇氯化钠琼脂培养基,应用平板涂布计数、半定量划线法探究氯化钠和胰酪胨对甘露醇氯化钠琼脂培养基质量的影响;对不同种金黄色葡萄球菌和大肠杆菌在5个国产品牌和1个进口品牌的甘露醇氯化钠琼脂培养基上的生长情况进行定量测定。参照GB 4789.28—2013比较不同品牌培养基对不同菌株的生长率、生长指数和菌落大小的影响,对培养基质量进行评价。结果 实验菌株在使用不同种类、不同浓度的氯化钠或胰酪胨配制的甘露醇氯化钠琼脂培养基上的生长率、生长指数存在较大差异;不同品牌的甘露醇氯化钠琼脂培养基非目标菌生长指数均合格,但目标菌的生长率和菌落生长大小存在显著差异。结论 氯化钠和胰酪胨对于甘露醇氯化钠琼脂培养基质量影响较大,会直接决定培养基的质量是否合格,市售的国内外不同品牌甘露醇氯化钠琼脂培养基质量存在较大差异,国产甘露醇氯化钠琼脂培养基的质量优于进口培养基。     

The occurrence of Staphylococcus aureus in fermented milk products (Fura and Manshanu) in Nigeria

Ninety-three samples of fermented milk cereal (Fura) and 79 of local butter (Manshanu) were collected from four different markets around Zaria. For Fura the mean content of Staphylococci for each of the four markets ranged from 4.5 × 10³ to 4.3 × 10⁴ cfu/ml and the mean aerobic mesophilic plate count from 5.6 × 10⁵ to 2.7 × 10⁶ cfu/ml. For Manshanu the mean staphylococcal count and aerobic mesophilic plate count ranged from 3.4 × 10² to 2.2 × 10³ cfu/ml and 6.7 × 10⁴ to 1.1 × 10⁶ cfu/ml respectively. Significant differences were seen between the different markets.     

四株ST9型耐甲氧西林金黄色葡萄球菌的全基因组序列分析

目的 了解不同来源ST9耐甲氧西林金黄色葡萄球菌（MRSA）的全基因组特征。方法 对收集的4株分离自猪胴体和屠宰工作人员的ST9 MRSA菌株进行全基因组序列测序,分析ST9 MRSA的基因特征、耐药基因和毒力基因携带情况,利用比较基因组学筛选单核苷酸多态性（SNP）,并与NCBI收录的11株不同ST型的MRSA和甲氧西林敏感金黄色葡萄球菌菌株进行核心基因分析,构建系统发育树。结果 4株不同来源ST9 MRSA全基因组序列全长约为2.6 Mbp,共含有2 122~2 494个基因,基因组的平均GC含量为32.8%。不同来源菌株基因组中均含有26~31种耐药基因、44~56种毒力基因。4株ST9 MRSA与欧洲主要流行的ST398代表性菌株比较,核苷酸同源性高,菌株之间SNP数量少于300个。系统进化发育树分析结果显示ST9和ST398 MRSA在分子进化过程中分成了不同独立进化分支,家畜和人来源的MRSA菌株在分子进化中没有明显相关性。结论 本研究获得了不同来源ST9 MRSA全基因组基本特征的背景材料,了解了不同ST型MRSA分子进化溯源关系,为后续ST9 MRSA的分子流行病学和致病性机制研究提供科学指导。     

基于反向传播人工神经网络的酱牛肉中金黄色葡萄球菌的生长模型

探讨了反向传播神经网络模型预测酱牛肉中金黄色葡萄球菌生长情况的准确性。收集不同温度(15、25、36℃)和不同初始接菌量(10~2、10~3、10~4CFU/mL)组合条件下金黄色葡萄球菌在酱牛肉中的生长数据,借助Python和Matlab软件,筛选出拟合效果最佳的网络结构,构建起反向传播神经网络模型,同时建立起修正的Gompertz模型作对比。通过平方根误差、偏差因子和准确因子分别检验两个模型的准确性。结果显示:网络结构为2-35-30的模型拟合效果最佳,反向传播神经网络模型与修正的Gompertz模型误差均在可接受范围内;与修正的Gompertz模型相比,反向传播神经网络误差更小,能更加准确预测金黄色葡萄球菌在酱牛肉中的生长情况。     

Changes in culturability and virulence of Salmonella typhimurium during long-term starvation under desiccating conditions

The survival of Salmonella typhimurium under desiccation and starvation conditions commonly associated with farm buildings was investigated in a desiccation model system: filtration onto polycarbonate membranes placed in a sealed desiccator with 0.0067 g/m³ absolute humidity. Heterogeneities within bacterial populations in relation to time of desiccation were investigated on a single-cell basis by epifluorescence microscopy coupled with an image analysis system in conjunction with fluorescent dyes Chemchrome V6 and DAPI. Changes in cellular states were compared to the results of plate counts (colony forming units, CFU) on selective (modified semi-solid Rappaport Vassiliadis (MSRV)) and non-selective (nutrient agar (NA) and R2A agar) media, and to the measurements of infectivity and virulence using two animal models (chicks and mice). During 9 weeks of experimental desiccation, total cell counts (DAPI) of starved S. typhimurium remained stable, as did esterase activity (Chemchrome V6), but DAPI fluorescence intensity decreased slowly. Bacterial cells entered gradually into non-culturable states (decrease of CFU counts on MSRV, NA and R2A agar media) and the total loss of culturability on NA (defined as probability of presence of 1 CFU on the membrane inferior to 10⁻⁶) was obtained after 9 weeks. Loss of chick infectivity and mice virulence in animal models occurred more rapidly, within three weeks of experimental desiccation.     

Control of food spoiling bacteria in cooked meat products with nisin,lacticin 3147, and a lacticin 3147-producing starter culture

Nisin, in the form of the commercial product Nisaplin, and lacticin 3147 in whey powdered form were added to minced pork-meat in amounts of 0.15% (w/w) and 1.5% (w/w), respectively. The meat was cooked and inoculated with a Staphylococcus aureus strain of meat origin and a Listeria innocua strain at a level of 10⁷ or 10⁵ CFU g^–1. The batches were stored vacuum-packaged for 21 days at 8 °C. Nisin and lacticin 3147 immediately reduced the L. innocua population at the time of inoculation. Nisin showed higher inhibitory activity than lacticin 3147. During the storage period, a slight L. innocua growth was observed in the batches inoculated with the larger inoculum, and a bacteriostatic effect was observed against Listeria in the batches inoculated with 10⁵ CFU g^–1. Nisin maintained a constant S. aureus population in the cooked batch inoculated with 10⁷ CFU g^–1, although the bacteriocin was capable of reducing the amount of S. aureus by 90% in the batch inoculated with 10⁵ CFU g^–1. On the other hand, lacticin 3147 did not show an inhibitory effect against S. aureus in the cooked meat. The starter culture Lactococcus lactis DPC 303-T4 (containing the conjugative plasmid encoding production of lacticin 3147) was inoculated in a portion of a Longissimus dorsi pork muscle with brine. L. lactis DPC 303-T4 performed a good fermentation, but lacticin 3147 production was not found after 7 days at 12 °C of storage.     

金黄色葡萄球菌污染牛奶后的代谢产物研究

为解决食品安全中存在的隐患,作者构建了气相色谱-质谱（GC-MS）结合顶空固相微萃取（HS/SPME）技术用于探究金黄色葡萄球菌的挥发性代谢产物,并结合代谢组学和基因组学分析牛奶中金黄色葡萄球菌的差异性代谢产物及其代谢途径。结果表明,金黄色葡萄球菌的差异性代谢物包括N-甲硫基甲酰胺、1-丁醇、乙酸、乙苯、均三甲苯、辛酸、苯甲酸、正癸酸、十二烷酸、乙醇、苯酚和丙二醇。之后对其进行基因组学分析得到金黄色葡萄球菌主要是以基础的生命代谢为主,明确了代谢网络中参与代谢的物质（乙醇、乙酸、1-丁醇）的代谢途径和相关基因。本研究为金黄色葡萄球菌的生物标志物研究提供了理论基础。     

Inactivation kinetics of a piezotolerant Staphylococcus aureus isolated from high-pressure-treated sliced ham by high pressure in buffer and in a ham model system: Evaluation in selective and non-selective medium

The kinetics of inactivation by high pressure of a pressure-resistant strain of Staphylococcus aureus isolated from pressure-treated packaged sliced ham, in buffer and in a ham model system was studied. Selective (BP agar) and enrichment media (BHI agar) were used for enumeration in order to count healthy and sublethally injured cells of the pathogen. A first-order kinetic inactivation was observed in both suspension media, and a very significant increase in D values was apparent when the microorganism was suspended and pressurized in the model food system compared to buffer. In the case of phosphate buffer as suspension medium, the z_p values obtained were 107.5 and 113.6 MPa for the two recovery media, i.e. BP and BHI agars, respectively. In contrast, in the case of the food model system, a two-phase linear relation was apparent and the PDT (Pressure Death Time) curve can be divided into two linear sections, so that two z_p values could be defined, one for each section. Z_p values of 100 and 79.4 MPa correspond to pressures < 500 MPa for the BP and BHI counts, respectively, while z_p values of 416.7 and 333.3 MPa correspond to higher pressures > 500 MPa for the selective and non-selective medium, respectively. When S. aureus had been pressurized in phosphate buffer, the BHI agar was slightly better in cell recovery, while in the case of the ham model system, the BP agar proved superior and gave significantly higher colony counts.

Industrial relevance

The paper provides significant information for the food processing industry as it deals with the effect of high-pressure technology on a piezotolerant pathogen that may survive in sliced ham. This technology is already applied in ham products and this paper supports the need for the use of real food in pressure studies in order to avoid underestimation of the effect and hence the processing times. It is also shown that different recovery media, i.e. selective and non-selective, should be used to avoid underestimation of the surviving cells.     

Heat-adaptation induced thermotolerance in Staphylococcus aureus: Influence of the alternative factor σ

The role of σ^B in the Staphylococcus aureus heat-shock induced thermotolerance was investigated. Survival curves at 58 °C of S. aureus strain Newman and its isogenic ΔsigB mutant were obtained for native and heat-shocked cells (45 °C for 5–120 min) in exponential and stationary phase of growth. The magnitude of the acquisition of thermotolerance at 58 °C depended on the growth phase and on the duration of the heat shock. Stationary growth phase cells were always more heat tolerant than exponentially growing cells and thermotolerance increased with heat-shock duration up to 120 min. S. aureus cells were able to increase their heat tolerance in the absence of the σ^B factor. In stationary phase, whereas in the parental strain the thermotolerance was increased by a factor of 12 after a heat shock of 120 min at 45 °C (δ values at 58 °C for native and heat-shocked cells were 0.63 and 7.22 min, respectively), in the mutant strain it increased 43 fold (δ values 0.09 and 3.87 min). The addition of chloramphenicol to the adaptation medium resulted in a lower increase in heat tolerance but did not prevent it completely, suggesting that S. aureus can partially increase its thermotolerance without “de novo” protein synthesis. Both the number of non-damaged cells and the proportion of cells able to repair sublethal damage were higher for heat-shocked cells.     

The influence of precultivation parameters on the catabolism of branched-chain amino acids by Staphylococcus xylosus and Staphylococcus carnosus

The influence of precultivation parameters on the ability of Staphylococcus xylosus and Staphylococcus carnosus to convert branched-chain amino acids—leucine, isoleucine and valine—into volatile flavour compounds was investigated using resting cells in a defined reaction medium. The studied precultivation parameters were: growth phase, temperature, NaCl concentration and the concentration of leucine, isoleucine and valine (only for S. xylosus). Flavour compounds were sampled by automatic static headspace collection and separated/quantified using gas chromatography/flame ionization detection (GC/FID).Main catabolic products from degradation of leucine, isoleucine and valine were the flavour intensive branched-chain acids: 2- and 3-methylbutanoic and 2-methylpropanoic acids. The precultivation parameters altered the production of the branched-chain acids significantly, but to various degrees for S. xylosus and S. carnosus.Production of branched-chain acids by S. carnosus was only influenced slightly by the growth phase and not by changing the NaCl concentration between 4.0% and 10.0% (w/w). Lowering the temperature from 28°C to 18°C significantly decreased S. carnosus’ generation of branched-chain acids. In contrast, S. xylosus was significantly influenced by all precultivation parameters, in particular by the growth phase. Cells taken from growing cultures had a much higher production of branched-chain acids compared to cells taken from stationary cultures. Addition of leucine and valine to the precultivation medium enhanced the production of branched-chain acids whereas addition of isoleucine had the opposite effect.     

Interference of Origanum vulgare L. essential oil on the growth and some physiological characteristics of Staphylococcus aureus strains isolated from foods

The aim of this study was to investigate the chemical composition of Origanum vulgare L. essential oil, the inhibitory effect of the oil on the cell viability of Staphylococcus aureus strains isolated from foods, and the influence of sub-inhibitory concentrations of the oil on some physiological attributes of these strains. GC-MS analysis showed that carvacrol (57.71%) was the most prevalent compound in the oil, followed by p-cymene (10.91%), γ-terpinene (7.18%), terpinen-4-ol (6.68%) and thymol (3.83%). The results showed that O. vulgare essential oil at 0.03, 0.6 and 0.12 μL mL⁻¹ inhibited the cell viability of Staph. aureus. At 0.12 μL mL⁻¹ the oil caused cidal effect with decrease ≥3 log cycles of the initial inoculum after 15 min of exposure. Sub-inhibitory concentrations (0.03 and 0.015 μL mL⁻¹) of the oil suppressed some physiological attributes of the Staph. aureus strains such as coagulase, lipase and salt tolerance. The oil interfered on the microbial metabolic activity in a dose-dependent manner. O. vulgare essential oil could be a novel antimicrobial with capability to suppress some physiological characteristics, in addition to inhibit the growth and survival of pathogen bacteria in foods, particularly Staph. aureus.     

The antimicrobial effect of thyme essential oil, nisin, and their combination against Listeria monocytogenes in minced beef during refrigerated storage

The antimicrobial effect of thyme essential oil (EO) at 0.3%, 0.6%, or 0.9%, nisin at 500 or 1000IU/g, and their combination against Listeria monocytogenes was examined in both tryptic soy broth (TSB) and minced beef meat. Thyme EO at 0.3% possessed a weak antibacterial activity against the pathogen in TSB, whereas at 0.9% showed unacceptable organoleptic properties in minced meat. Thus, only the level of 0.6% of EO was further examined against the pathogen in minced meat. Treatment of minced beef meat with nisin at 500 or 1000IU/g showed antibacterial activity against L. monocytogenes, which was dependent on the concentration level of nisin and the strains used. Treatment of minced beef meat with EO at 0.6% showed stronger inhibitory activity against L. monocytogenes than treatment with nisin at 500 or 1000IU/g. All treatments showed stronger inhibitory activity against the pathogens at 10 degrees C than at 4 degrees C. The combined addition of EO at 0.6% and nisin at 500 or 1000IU/g showed a synergistic activity against the pathogen. Most efficient among treatments was the combination of EO at 0.6% with nisin at 1000IU/g, which decreased the population of L. monocytogenes below the official limit of the European Union recently set at 2logcfu/g, during storage at 4 degrees C.     

Comparative efficacy of Zataria multiflora Boiss., Origanum compactum and Eugenia caryophyllus essential oils against E. coli O157:H7, feline calicivirus and endogenous microbiota in commercial baby-leaf salads

Ready-to-eat salads using baby-leaf and multi-leaf mixes are one of the most promising developments in the fresh-cut food industry. There is great interest in developing novel decontamination treatments, which are both safe for consumers and more efficient against foodborne pathogens. In this study, emulsions of essential oils (EOs) from Origanum compactum (oregano), Eugenia caryophyllus (clove), and Zataria multiflora Boiss (zataria) were applied by spray (0.8 ml) after the sanitizing washing step. The aim was to investigate their ability to control the growth of potentially cross-contaminating pathogens and endogenous microbiota in commercial baby leaves, processed in a fresh-cut produce company. Zataria EO emulsions of 3%, 5% and 10% reduced Escherichia coli O157:H7 by 1.7, 2.2 and 3.5 log cfu/g in baby-leaf salads after 5 days of storage at 7 °C. By contrast, reductions in E. coli O157:H7 counts remained the same when clove was applied at concentrations of 5% and 10% (2.5 log cfu/g reduction). Oregano (10%) reduced inoculated E. coli O157:H7 counts in baby-leaf salads by a maximum of 0.5 log cfu/g after 5 days of storage. Zataria showed strong antimicrobial efficacy against E. coli O157:H7 and also against the endogenous microbiota of baby-leaf salads stored for 9 days. Feline calicivirus (FCV), a norovirus surrogate, survived on inoculated baby-leaf salads during refrigerated storage (9 days at 7 °C) regardless of treatment. Refrigeration temperatures completely annulled the effectiveness of the EOs against FCV inoculated in baby-leaf salads as occurred in FCV cultures. This study shows that EOs, and zataria in particular, have great potential use as an additional barrier to reduce contamination-related risks in baby-leaf salads. However, further research should be done into foodborne viruses in order to improve food safety.     

VFDB注释法在食源性金黄色葡萄球菌肠毒素基因分型分析中的应用

目的 应用VFDB注释法对食源性金黄色葡萄球菌肠毒素基因进行分型并评价其准确性。方法 分别使用VFDB注释法和特异引物PCR方法对2009—2016年从北京地区食品中分离的53株金黄色葡萄球菌的18种肠毒素基因（包括传统肠毒素基因sea~see,新型肠毒素基因seg~sej和类肠毒素基因sek~seu）携带情况进行分析。将VFDB注释法所得肠毒素基因序列上传至NCBI,使用BLASTX程序和refseq_protein数据库对注释结果进一步核对。结果 VFDB注释法和PCR方法都检测出53株金黄色葡萄球菌分离株中有45株携带1种或多种肠毒素基因,有8株未携带肠毒素基因,肠毒素基因的总携带率为84.91%（45/53）,经典肠毒素基因的携带率为58.49%（31/53）。45株携带肠毒素基因的分离株中,16株菌（35.56%,16/45）肠毒素基因VFDB分型结果与PCR一致,29株菌（64.44%,29/45）的肠毒素基因VFDB分型结果与PCR不一致。经BLASTX核对,VFDB注释法可能误判的基因型包括sea/sed、sea/sej、sea/sep、sea/ser、seg/ser和sek/sei（VFDB注释/BLASTX核对）。结论 VFDB注释法可对食源性金黄色葡萄球菌肠毒素基因进行分型分析,但是对注释为sea、seg和sek的序列建议采用BLASTX程序和refseq_protein数据库进一步核对,以提高基因分型的准确性。