BACKGROUND An outbreak of listeriosis was identified in South Africa in 2017. The source was unknown. METHODS We conducted epidemiologic, trace-back, and environmental investigations and used whole-genome sequencing to type Listeria monocytogenes isolates. A case was defined as laboratory-confirmed L. monocytogenes infection during the period from June 11, 2017, to April 7, 2018. RESULTS A total of 937 cases were identified, of which 465 (50%) were associated with pregnancy; 406 of the pregnancy-associated cases (87%) occurred in neonates. Of the 937 cases, 229 (24%) occurred in patients 15 to 49 years of age (excluding those who were pregnant). Among the patients in whom human immunodeficiency virus (HIV) status was known, 38% of those with pregnancy-associated cases (77 of 204) and 46% of the remaining patients (97 of 211) were infected with HIV. Among 728 patients with a known outcome, 193 (27%) died. Clinical isolates from 609 patients were sequenced, and 567 (93%) were identified as sequence type 6 (ST6). In a case-control analysis, patients with ST6 infections were more likely to have eaten polony (a ready-to-eat processed meat) than those with non-ST6 infections (odds ratio, 8.55; 95% confidence interval, 1.66 to 43.35). Polony and environmental samples also yielded ST6 isolates, which, together with the isolates from the patients, belonged to the same core-genome multilocus sequence typing cluster with no more than 4 allelic differences; these findings showed that polony produced at a single facility was the outbreak source. A recall of ready-to-eat processed meat products from this facility was associated with a rapid decline in the incidence of L. monocytogenes ST6 infections. CONCLUSIONS This investigation showed that in a middle-income country with a high prevalence of HIV infection, L. monocytogenes caused disproportionate illness among pregnant girls and women and HIV-infected persons. Whole-genome sequencing facilitated the detection of the outbreak and guided the trace-back investigations that led to the identification of the source.

中文翻译：

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南非与加工肉相关的李斯特菌病暴发。

背景技术2017年在南非发现了李斯特菌病暴发。来源不明。方法我们进行了流行病学，追溯和环境调查，并使用全基因组测序对单核细胞增生李斯特菌进行了分离。在2017年6月11日至2018年4月7日期间，将一例定义为实验室确诊的单核细胞增生李斯特氏菌感染。结果共鉴定出937例，其中465例（50％）与妊娠有关；406例妊娠相关病例（87％）发生在新生儿中。在这937例病例中，229例（24％）发生在15至49岁的患者中（不包括怀孕者）。在已知人类免疫缺陷病毒（HIV）状况的患者中，妊娠相关病例中有38％（204人中有77人）和其余患者中46％（211人中有97人）感染了HIV。在728例结果已知的患者中，有193例（27％）死亡。对来自609例患者的临床分离株进行了测序，其中567种（93％）被鉴定为序列类型6（ST6）。在病例对照分析中，与非ST6感染的患者相比，ST6感染的患者更容易食用玉米粥（即食加工肉）（优势比为8.55； 95％置信区间为1.66至43.35）。 。polony和环境样品也产生了ST6分离株，这些分离株与患者分离株一起属于同一核心基因组多基因座序列分型群，其等位基因差异不超过4个。这些发现表明，单一场所产生的polony是疫源。从该设施中召回的即食加工肉制品与单核细胞增生李斯特氏菌ST6感染的发生率迅速下降有关。结论这项调查表明，在一个艾滋病毒感染率很高的中等收入国家，单核细胞增生李斯特氏菌在孕妇，妇女和感染艾滋病毒的人中造成了不成比例的疾病。全基因组测序有助于发现疫情，并指导追溯调查，从而鉴定出病源。单核细胞增多症在怀孕的女孩，妇女和艾滋病毒感染者中引起不成比例的疾病。全基因组测序促进了疾病暴发的发现，并指导了追溯调查，从而确定了病源。单核细胞增多症在怀孕的女孩，妇女和艾滋病毒感染者中引起不成比例的疾病。全基因组测序有助于发现疫情，并指导追溯调查，从而鉴定出病源。