In the summer of 2014, a multistate outbreak of listeriosis associated with contaminated stone fruit (peach and nectarine) was reported. A serotype 4b variant Listeria monocytogenes (Lm) strain of singleton Sequence Type (ST) 382 was isolated from clinical samples and stone fruit associated with the outbreak. A serotype 1/2b Lm strain of ST5, Clonal Complex 5 was isolated only from outbreak-associated stone fruit, not from clinical samples. Here we investigated the fate of the serotype 4b and 1/2b strains, at two inoculation levels (high level at 3.7 logCFU/fruit and low level at 2.7 logCFU/fruit), on the surfaces of white peach, yellow peach and yellow nectarine stored at 4 °C for 26 days. After rinsing the fruits, we determined the Lm levels in the rinsates and on the peels. We enumerated Lm using a direct plating method and compared two chromogenic agars. The Lm populations rapidly declined in the first 3 days and then declined more slowly until Day 19/21. The maximum decline was 1.6 logCFU/fruit on yellow peach inoculated with serotype 4b at high level. For fruits inoculated with high-level Lm, the lowest level of Lm (1.7 logCFU/fruit) was observed on for white peach inoculated with serotype 1/2b, and the highest level of Lm (2.6 logCFU/fruit) on Day 19/21 was observed on yellow peach inoculated with the serotype 1/2b strain. For fruits inoculated with low-level Lm, the lowest level of Lm (1.3 logCFU/fruit) was observed on yellow nectarine inoculated with either the serotype 4b or 1/2b strain, and the highest level of Lm (1.7 logCFU/fruit) on Day 19/21 was observed on yellow peach inoculated with ST382. The D-values ranged from 15 days to 28 days. Lm remained viable until the end of storage (Day 26), but the levels were not significantly different from those on Day 19/21. The types of stone fruit and Lm strain did not significantly affect the survival of Lm. These results demonstrate that contaminated stone fruit can carry a potential risk for causing listeriosis in susceptible populations. Comparison of direct plating results using two chromogenic agars showed that RAPID' L. mono and Agar Listeria Ottavani & Agosti performed equivalently for enumerating Lm on stone fruit. The fruit rinsing recovered 80% to 84% of Lm from fruit surfaces.

2014年夏天，报告了多州爆发的李斯特菌病，与核果（桃子和油桃）污染有关。从临床样本和与暴发相关的核果中分离出单例序列类型（ST）382的血清型4b变异单核细胞增生李斯特菌（Lm）菌株。仅从暴发相关的核果中分离出ST5的血清型1 / 2b Lm ST5克隆复合体，而不从临床样品中分离出。在这里，我们调查了存储在白桃，黄桃和黄色油桃表面上的两种接种水平（3.7 logCFU /水果的高水平和2.7 logCFU /水果的低水平）的血清型4b和1 / 2b菌株的命运。在4°C下放置26天。冲洗水果后，我们确定Lm在冲洗液和果皮上的含量。我们使用直接电镀法对Lm进行了计数，并比较了两种生色琼脂。该Lm的人口迅速下降在第3天，然后下降较缓慢，直到19/21天。在高水平接种4b血清型的黄桃上最大下降为1.6 logCFU /果实。对于接种了高水平Lm的水果，接种了1 / 2b血清型的白桃的Lm最低水平（1.7 logCFU /水果），在第19/21天观察到了最高水平的Lm（2.6 logCFU /水果）。在接种了1 / 2b血清型的黄桃上观察到了这种现象。对于接种低水平Lm的水果，最低水平的Lm在接种4b或1 / 2b血清型的黄色油桃中观察到（1.3 logCFU /水果），在接种ST382的黄桃上，在第19/21天观察到最高水平的Lm（1.7 logCFU /水果）。D值的范围从15天到28天。Lm一直保持存活直到储存结束（第26天），但水平与第19/21天没有明显差异。核果的类型和Lm菌株对Lm的存活没有明显影响。这些结果表明，被污染的核果可能在易感人群中引起李斯特菌病的潜在风险。使用两种生色琼脂直接电镀结果的比较显示，RAPID'L . mono和琼脂李斯特菌（ Lesteria Ottavani）和阿格斯蒂（Agosti）在枚举核果上的Lm方面表现相当。冲洗水果后，从水果表面回收了80％至84％的Lm。