Listeria monocytogenes population and the expression patterns of three virulence (plcA, hly, and iap) and one stress-related (sigB) genes in dry-cured ham with different water activity (a_w) values (0.92, 0.88, and 0.84) and treated with high pressure processing (HPP, 450 MPa/10 min and 600 MPa/5 min) were monitored throughout 30 days (d) at 4 °C. The antimicrobial effect of HPP at 600 MPa against L. monocytogenes S4-2 (serotype 1/2b) and S12-1 (serotype 1/2c) was greater in dry-cured ham with a_w values of 0.92, with reductions of 2.5 and 2.8 log units, respectively. The efficacy of HPP treatments decreased at lower a_w values. Regarding gene expression, L. monocytogenes strains responded differently to HPP. For strain S4-2, the four target genes were generally overexpressed in dry-cured ham immediately after HPP treatments at the three a_w values investigated, although the extent of this induction was lower in the samples pressurized at 600 MPa and with a_w values of 0.84. For strain S12-1, the expression of all target genes was repressed at the three a_w values investigated. The antimicrobial efficacy of HPP against L. monocytogenes could be compromised by low a_w values in food products. However, no growth of HPP-survival cells was observed during refrigerated storage in low-a_w dry-cured ham, and the overexpression of virulence and stress-related genes decreased.

中文翻译：

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加压冷藏干火腿冷藏过程中水分活度对单核细胞增生李斯特菌灭活和基因表达的影响。

具有不同水分活度（a _w）值（0.92、0.88和0.84）的干腌火腿中单核细胞增生李斯特菌的种群以及三种毒力（plcA，hly和iap）和一种应激相关（sigB）基因的表达模式在4°C的整个30天（d）内，对经过高压处理（HPP，450 MPa / 10分钟和600 MPa / 5分钟）处理的水进行监测。HPP在600 MPa下对单核细胞增生李斯特氏菌S4-2（血清型1 / 2b）和S12-1（血清型1 / 2c）的抗微生物作用在干腌火腿中具有更大的_w值，降低值为2.5和2.5。分别为2.8个日志单位。HPP治疗的功效在较低的_w时降低价值观。关于基因表达，单核细胞增生李斯特菌菌株对HPP的反应不同。对于菌株S4-2，在HPP处理后的三个a _w值下，四个目标基因通常在干腌火腿中立即过表达，尽管在600 MPa和_w值加压的样品中，诱导的程度较低为0.84。对于菌株S12-1，所有靶基因的表达均在所研究的三个a _w值处被抑制。HPP对单核细胞增生李斯特氏菌的抗微生物功效可能会因食品中的低_w值而受损。但是，冷藏储存期间在低一个观察到的HPP-存活细胞不生长_瓦特 干腌火腿，毒力和应激相关基因的过表达减少。