Short communication: Long-term -20°C survival of Listeria monocytogenes in artificially and process-contaminated ice cream involved in an outbreak of listeriosis

Survival of Listeria monocytogenes on Frozen Vegetables during Long-term Storage at -18 and -10°C

Two recent listeriosis outbreaks have occurred in the United States and Europe due to contaminated individually quick-frozen (IQF) vegetables. While one of the outbreaks was due to frozen vegetables considered ready-to-eat (RTE), the other was linked to frozen corn whose packaging contained cooking instructions and was considered not-ready-to-eat (NRTE). However, consumers may thaw certain frozen vegetables and consume without cooking. Since no data is available on the survivability of L. monocytogenes on IQF vegetables during frozen storage, this study examined the population of six different strains (comprising lineages 1/2a, 1/2b, and 4b) on IQF vegetables during long-term storage. Individual strains were inoculated onto an IQF vegetable mix at 4 log CFU/g and stored at -18 or -10°C for 360 days. Although fluctuations in populations of all strains were observed on the vegetables during storage, no significant differences based on strain, lineages, or temperature were observed. Overall, L. monocytogenes populations were only reduced by up to 0.47 and 0.59 log CFU/g after 360 days at -18 and -10°C, respectively. Results from this study suggest that L. monocytogenes is able to persist on IQF vegetables for extended time periods with no significant reduction in population. Future studies could evaluate the survival and growth of L. monocytogenes on IQF vegetables during thawing and storage.

Context matters: environmental microbiota from ice cream processing facilities affected the inhibitory performance of two lactic acid bacteria strains against Listeria monocytogenes

IMPORTANCE

Antilisterial LAB strains have been proposed as biological control agents for application in food processing environments. However, the effect of resident food processing environment microbiota on the performance on antilisterial LAB strains is poorly understood. Our study shows that the presence of microbiota collected from ice cream processing facilities' environmental surfaces can affect the attachment and inhibitory effect of LAB strains against L. monocytogenes. Further studies are therefore needed to assess whether individual microbial taxa affect antilisterial properties of LAB strains and to characterize the underlying mechanisms.

Listeriosis during pregnancy: a retrospective cohort study

Background

Pregnancy-associated listeriosis is a severe infectious disease and potentially leads to fetal/neonatal fatal, while limited information on pregnancy-associated listeriosis is available in China. This study aimed to reveal the clinical characteristics and outcomes of pregnancy-associated listeriosis cases and provide references for treating and managing this disease.

Methods

We performed a retrospective study on maternal and neonatal patients with pregnancy-associated listeriosis. The clinical characteristics of pregnancy-associated listeriosis were studied, and the outcome determinants of neonatal listeriosis were explored.

Results

14 cases of pregnancy-associated listeriosis were identified. The incidence of pregnancy-associated listeriosis in our hospital was 16.69/100,000 births. All of the 14 maternal patients eventually recovered after delivery shortly with no sequelae. None of the 12 mothers who delivered in this hospital received antepartum first-line empirical treatment. Among the 14 neonatal cases, 1 was late-onset listeriosis and 13 were early-onset cases; 11 survived and 3 died. Fatality rates were significantly higher in outborn neonates (P = 0.005). Besides, higher mortality rates were observed in neonates with lower birth weight (P = 0.038), gestational age < 28 weeks (P = 0.056), and Apgar score (5th min) < 5 (P = 0.056), with marginally significant differences.

Conclusions

Pregnancy-associated listeriosis would bring disastrous effects to the neonatal cases, especially to the outborn, low birth weight, and low gestational age of neonates. Timely detection and treatment should be taken seriously for the key neonates. How to early detect L. monocytogenes infected cases, especially in the prenatal stage, remains a serious challenge.

Review of the prevalence of foodborne pathogens in milk and dairy products in Ethiopia

Food safety is a significant barrier to social and economic development throughout the world, particularly in developing countries. Here, we reviewed the prevalence of major bacterial foodborne pathogens (Salmonella spp., Listeria monocytogenes, Escherichia coli O157:H7 and Campylobacter spp.) in the rapidly growing Ethiopian dairy supply-chain. We identified 15, 9, 5 and 0 studies that had reported the prevalence of Salmonella spp., L. monocytogenes, E. coli O157:H7, and Campylobacter spp. in dairy foods, respectively. The studies reviewed reported a median prevalence of Salmonella, L. monocytogenes, and E. coli O157:H7 of 6, 9 and 10%, respectively, in raw cow milk in Ethiopia, indicating a concerning occurrence of bacterial foodborne pathogens in raw milk. Implementation of good hygiene and production practices and assessment of interventions targeting the reduction of contamination in the dairy supply chain is needed to inform coordinated efforts focused on improvement of dairy food safety in Ethiopia.