Role of rodents in transmission of Salmonella and Campylobacter

Salmonella and Campylobacter are generally regarded as the most important food‐borne pathogens in the world. Reduction or elimination of these pathogens in the first part of the food chain (on the farm) is important to prevent disease among consumers of animal products. In organic farming, elimination becomes more difficult, as food animals are allowed outdoors and have easy access to potential sources of hazardous pathogens. Whilst rodents are often associated by organic farmers with infrastructural damage and eating or spoiling of stored feed and products, their zoonotic risks are frequently underestimated. They can amplify the number of pathogens in the environment and transfer them to food animals. Thus organic farmers should be aware of the need for rodent control from a food safety perspective. Preferably, rodent control should form an integral part of a total package of hygiene measures to prevent transfer of food‐borne pathogens. These should also include e.g. control of wild birds and flies and obligatory disinfection of boots/clothes and equipment for farm workers and visitors. Copyright © 2007 Society of Chemical Industry     

Mutagenicity of aminonitrophenol compounds in Salmonella typhimurium: a study of structural-activity relationships

In our studies of structure-activity relationships, four aminonitrophenol isomers and eleven derivatives of 3-amino-4-nitrophenol and 4-amino-3-nitrophenol were tested for their ability to induce mutations in Salmonella typhimurium strains TA1535, TA100, TA1537, TA1538 and TA98. In the presence of an Aroclor-1254-induced rat-liver microsomal activation system (S9mix), 4-N- β -hydroxyethylamino-3-nitroanisole and (4-amino-3-nitro) phenoxyethanol were mutagenic in several of these strains. The compounds 3-amino-4-nitrophenol, 3-N-methylamino-4-nitrophenol, 3-N-β-hydroxyethylamino-4-nitrophenol, 3-amino-4-nitroanisole, 3-N-methylamino-4-nitroanisole, 3-N- β -hydroxyethylamino-4-nitroanisole, (3-amino-4-nitro)phenoxyethanol, (3-methylamino-4-nitro)phenoxyethanol, (3-N- β -hydroxyethylamino-4-nitro)phenoxyethanol, 4-amino-3-nitrophenol and 4-N- β -hydroxyethylamino-3-nitrophenol were inactive, both in the presence and in the absence of S9 mix. In contrast to the results with 3-amino-4-nitrophenol and 4-amino-3-nitrophenol, which were negative, the isomers 2-amino-4-nitrophenol and 2-amino-5-nitrophenol were found to be mutagenic. These results on mutagenic and non-mutagenic aminonitrophenols and their derivatives suggest that the occurrence of mutagenic activity among these compounds depends on the nature of the substituent chemical groups and their position in the molecular structure of the compounds.
Aminonitriphenols: relation structure-activité     

IQ-Check Salmonella II Kit方法对食品中沙门氏菌检测的评价

通过对标准菌株和人工污染沙门氏菌的食品样品进行检测,评价IQ-Check Salmonella Ⅱ试剂盒方法。该研究采用试剂盒方法对50株不同血清型的沙门氏菌和50株非沙门氏菌进行检测,分析该方法的灵敏性和特异性;通过对人工污染沙门氏菌食品样品(包括液体奶、婴幼儿配方乳粉、肉及肉类制品)的检测,评价试剂盒方法与GB 4789.4-2016方法的一致性。实验结果表明:当菌浓度在10³ CFU/mL及以上,试剂盒方法对50株沙门氏菌实现全部检出,其对不同血清型沙门氏菌检出限的平均值为6.98×10² CFU/mL。试剂盒方法对50株非沙门检测结果均为阴性,说明试剂盒特异性较好。试剂盒方法与GB方法对人工污染沙门氏菌的食品样品阳性检出率分别为98.77%(161/163)和96.32%(157/163);相对准确度为:96%、99%、97%,总体准确度为97.33%;相对灵敏度为:96.22%、100%、100%,总体灵敏度为98.73%;相对特异性为:95.74%、98.15%、92.86%,总体特异性为95.80%。参照ISO 16140进行方法一致性分析,结果表明两方法在统计学上无显著性差异。该研究表明该试剂盒方法具有高灵敏性和特异性强的特点,在人工染菌食品样品检测中与GB方法呈高度一致性,值得在食品沙门氏菌快速检测中推广应用。     

Modeling the irradiation followed by heat inactivation of Salmonella inoculated in liquid whole egg

ABSTRACT:  This study presents mathematical models that describe the inactivation of Salmonella Enteritidis, Salmonella Typhimurium, and Salmonella Senftenberg suspended in liquid whole egg (LWE) by irradiation followed by heat treatments (IR-H treatments). These models also enable prediction of cell injury in Salmonella after exposure to IR-H. Salmonella viability decreased exponentially (primary model) with heat treating time for all the radiation doses (0, 0.1, 0.3, 0.5, 1.0, and 1.5 kGy) and temperatures investigated (55, 57, and 60 °C). Two secondary models that related the D_T values (time required to eliminate 90% of viable cells at a given temperature) with radiation dose, heating temperature, and recovery medium after treatments were also developed. The developed final equations enabled to establish the process criterion (combinations of irradiation doses, temperature, and heat treatment times) required to achieve a given reduction ( performance criterion ) in Salmonella spp. suspended in LWE or the cell damage caused by the treatments. Process criteria to obtain the established performance criteria (a 5-log₁₀ reduction) on any of the investigated Salmonella serovars were determined to be, 57.7 °C/3.5 min following 1.5 kGy when treated cells were recovered in tryptic soy agar and 59.3 °C/3.5 min following 0.5 kGy when cells were recovered in tryptic soy agar amended with 3% NaCl. Based on our results, current industrial LWE heat treatments (60 °C/3.5 min) would inactivate 3 log₁₀ cycles of the Salmonella population. The results of this study can be applied to engineering design and for the evaluation and optimization of the IR-H process as a new technique to obtain Salmonella -free LWE.     

Dynamic predictive model for the growth of Salmonella spp. in liquid whole egg

Abstract: A dynamic model for the growth of Salmonella spp. in liquid whole egg (LWE) (approximately pH 7.8) under continuously varying temperature was developed. The model was validated using 2 (5 to 15 °C; 600 h and 10 to 40 °C; 52 h) sinusoidal, continuously varying temperature profiles. LWE adjusted to pH 7.8 was inoculated with approximately 2.5–3.0 log CFU/mL of Salmonella spp., and the growth data at several isothermal conditions (5, 7, 10, 15, 20, 25, 30, 35, 37, 39, 41, 43, 45, and 47 °C) was collected. A primary model (Baranyi model) was fitted for each temperature growth data and corresponding maximum growth rates were estimated. Pseudo‐R² values were greater than 0.97 for primary models. Modified Ratkowsky model was used to fit the secondary model. The pseudo‐R² and root mean square error were 0.99 and 0.06 log CFU/mL, respectively, for the secondary model. A dynamic model for the prediction of Salmonella spp. growth under varying temperature conditions was developed using 4th‐order Runge–Kutta method. The developed dynamic model was validated for 2 sinusoidal temperature profiles, 5 to 15 °C (for 600 h) and 10 to 40 °C (for 52 h) with corresponding root mean squared error values of 0.28 and 0.23 log CFU/mL, respectively, between predicted and observed Salmonella spp. populations. The developed dynamic model can be used to predict the growth of Salmonella spp. in LWE under varying temperature conditions. Practical Application: Liquid egg and egg products are widely used in food processing and in restaurant operations. These products can be contaminated with Salmonella spp. during breaking and other unit operations during processing. The raw, liquid egg products are stored under refrigeration prior to pasteurization. However, process deviations can occur such as refrigeration failure, leading to temperature fluctuations above the required temperatures as specified in the critical limits within hazard analysis and critical control point plans for the operations. The processors are required to evaluate the potential growth of Salmonella spp. in such products before the product can be used, or further processed. Dynamic predictive models are excellent tools for regulators as well as the processing plant personnel to evaluate the microbiological safety of the product under such conditions.     

免疫磁珠法检测食品中的沙门菌及分离菌株的耐药性

为检测沙门菌在本市食品中的污染和耐药情况,采集各类食品样品303件,经增菌后通过特异的免疫磁珠（IMS）吸附并接种XLD平板分离沙门菌.分离的菌株按年度分成2组,分别以改良K-B法测试对28种抗生素的耐药性.在303件样品中检出87件阳性,总阳性率28.71%.分离到的112株沙门菌以德比、肠炎血清型占优势.肉类制品的阳性率40.20%（82/204）明显高于其它食品,共分离出107株沙门菌（107/112,95.54%）.菌株耐药率在2年中有显著改变的抗生素有环丙沙星、复方新诺明、妥布霉素、二甲胺四环素、氯霉素和链霉素.耐10种以上抗生素的多重耐药株有12株（12/112,10.71%）,有4株头孢哌酮耐药株.IMS用于食品中沙门菌的分离效果较好.结果显示耐环丙沙星和多重耐药菌株的增多说明加强食源性沙门菌耐药监测的重要性。     

奶牛场沙门氏菌分离株的流行特征及抗性分析

研究奶牛场沙门氏菌分离株的流行特征及抗性分析。从成都市某规模化奶牛场采集样品,对菌株进行分离鉴定和血清型分析,药敏检测,毒力基因、耐药基因和抗消毒剂基因检测,对常用消毒剂MIC值检测,以及有效巴氏灭菌温度分析。该研究共采集样品700份,分离16株沙门氏菌,得到4种血清型（肠炎沙门氏菌6株、甲型副伤寒沙门氏菌6株、鼠伤寒沙门氏菌3株、婴儿沙门氏菌1株）;菌株对头孢他啶、左氧氟沙星、亚胺培南敏感,携带24种耐药基因,检出率最高是tetB（93.75%）,其次是aaC4（75.00%）;检出12种毒力基因,sipA检测率最高为62.50%;抗消毒剂基因检出率最高为qacEΔ1（56.25%）。16株沙门氏菌对9种不同消毒剂MIC值普遍高于厂家推荐使用浓度的1~3倍;菌株在全脂乳和脱脂乳中100%杀菌温度分别为64.00 ℃和63.50 ℃。该奶牛场沙门氏菌分离菌株对消毒剂抗性较强,但在64.00 ℃能够对其有效杀灭。建议奶牛场加强沙门氏菌防控,规范消毒剂使用。     

Effect of Product Dimensions and Surface Browning Method on Salmonella Contamination in Frozen,Surface‐Browned,Breaded Chicken Products Treated with Antimicrobials

Not‐ready‐to‐eat breaded chicken products formulated with antimicrobial ingredients were tested for the effect of sample dimensions, surface browning method and final internal sample temperature on inoculated Salmonella populations. Fresh chicken breast meat portions (5 × 5 × 5 cm), inoculated with Salmonella (7‐strain mixture; 5 log CFU/g), were mixed with (5% v/w total moisture enhancement) (i) distilled water (control), (ii) caprylic acid (CAA; 0.0625%) and carvacrol (CAR; 0.075%), (iii) CAA (0.25%) and ε‐polylysine (POL; 0.5%), (iv) CAR (0.15%) and POL (0.5%), or (v) CAA (0.0625%), CAR (0.075%) and POL (0.5%). Sodium chloride (1.2%) and sodium tripolyphosphate (0.3%) were added to all treatments. The mixtures were then ground and formed into 9 × 5 × 3 cm (150 g) or 9 × 2.5 × 2 cm (50 g) portions. The products were breaded, browned in (i) an oven (208 °C, 15 min) or (ii) deep fryer (190 °C, 15 s), packaged, and stored at –20 °C (8 d). Overall, maximum internal temperatures of 62.4 ± 4.0 °C (9 × 2.5 × 2 cm) and 46.0 ± 3.0 °C (9 × 5 × 3 cm) were reached in oven‐browned samples, and 35.0 ± 1.1 °C (9 × 2.5 × 2 cm) and 31.7 ± 2.6 °C (9 × 5 × 3 cm) in fryer‐browned samples. Irrespective of formulation treatment, total (after frozen storage) reductions of Salmonella were greater (P < 0.05) for 9 × 2.5 × 2 cm oven‐browned samples (3.8 to at least 4.6 log CFU/g) than for 9 × 5 × 3 cm oven‐browned samples (0.7 to 2.5 log CFU/g). Product dimensions did not (P ≥ 0.05) affect Salmonella reductions (0.6 to 2.8 log CFU/g) in fryer‐browned samples. All antimicrobial treatments reduced Salmonella to undetectable levels (<0.3 log CFU/g) in oven‐browned 9 × 2.5 × 2 cm samples. Overall, the data may be useful for the selection of antimicrobials, product dimensions, and surface browning methods for reducing Salmonella contamination.     

Invasiveness and intracellular growth of multidrug-resistant salmonella and other pathogens in Caco-2 cells

ABSTRACT:  The increase of multidrug-resistant pathogens of human and animal origins is a major public health concern. For a better understanding of the health consequences of multidrug-resistant bacteria transmitted from animal products to humans, the host interaction of zoonotic Salmonella isolates along with other pathogenic and commensal bacteria was evaluated using a human intestinal Caco-2 cell system. Multidrug-resistant S . Agona, S . Heidelberg, and S . Typhimurium possessed plasmid-mediated class 1 integrons. The S . Typhimurium DT104 isolate from ground beef showed the well-known genotypic and phenotypic resistance characteristics of the species, and contained the chromosomally located class 1 integron. Among the multidrug-resistant Salmonella isolates, the S . Heidelberg 219 had the highest invasion number at 1.0 × 10⁴ CFU/mL, followed by the S . Typhimurium DT104 isolate at 7.7 × 10³ CFU/mL. Listeria monocytogenes was the best performer among the tested species in invading the Caco-2 cell. Multidrug-resistant opportunistic pathogens Klebsiella pneumoniae and Pseudomonas aeruginosa were also able to invade the cells. The invasion of S . Heidelberg 219, S . Typhimurium DT104, L. monocytogenes , K. pneumoniae , and P. aeruginosa into the Caco-2 cells was not affected even in the presence of commensal E. coli . During the intracellular growth of S . Heidelberg 219, S . Typhimurium DT104, and L. monocytogenes , the bacterial counts increased 2 log cycles in 9 h in the Caco-2 cells. Therefore, these strains could rapidly proliferate after their invasion into the cells.     

Prevalence and Characterization of Salmonella Isolated from Chicken Meat in Turkey

This study was conducted in a Turkish province to investigate the presence of Salmonella spp. in 150 chicken meat samples using 2 phenotyping techniques: classic culture technique (CCT) and immunomagnetic separation (IMS). For the confirmation of the isolates at molecular levels, invA gene was detected in these isolates. The presence of invA, class 1 (Cls1) integrons, and integrase (Int1) genes was demonstrated by PCR assay; and the resistance of the isolated Salmonella spp. strains to antibiotics was determined by disk diffusion test. All the cultural and PCR results were evaluated together; Salmonella spp. were detected in a total of 64 (42.66%) chicken meat samples. Contamination rate was higher in carcasses (53.33%, n = 75) than in meat pieces (32%, n = 75). When results of standard culture were compared with IMS technique, IMS (n = 54) showed a clear superiority over the CCT (n = 38). A very high resistance rate (≥89.28%) to vancomycin, tetracycline, streptomycin, or nalidixic acid was found. Trimethoprim‐sulfamethoxazole resistance was present in 32.14%. Relatively lower incidence of resistance (≤8.33%) to gentamicin, chloramphenicol, ampicillin, and ceftriaxone was observed. Concurrent resistance to at least 4 antibiotics was detected in 92.85% of the isolates. Cls1 integrons and Int1 were positive in 80.95% and 95.23% of the isolates, respectively. However, Int1 alone was detected in 15.47% (n = 13). In conclusion, the high prevalence of Salmonella spp. in chicken meat may pose a potential public health risk, and the presence of antibiotic‐resistant Salmonella spp. isolate together with Cls1 integron and/or integrase might play an important role in horizontal antibiotic gene transfer.