Case report: vertical transmission of Plesiomonas shigelloides. Is it time to strengthen information on safety concerns for raw seafood dietary exposure in pregnancy?

Abstract The consumption of raw seafood, generally considered to be a healthy food, has greatly increased worldwide. Pathogens of fish can cause foodborne illnesses in humans, especially following the consumption of raw seafood from contaminated water. Foodborne illness in pregnant women is seldom the cause of neonatal infection, but, as in the reported cases, it has been associated with a high degree of morbidity and mortality. We present the case of a newborn with septicemia and meningitis caused by Plesiomonas shigelloides acquired via the transplacental route. There was a maternal history of ingestion of raw seafood 1 week prior to delivery. A few similar cases are described in the existing literature, which reports 7 neonatal deaths. Therefore, the primary objective of this paper is to highlight the fact that the popularity of raw seafood such as sushi, sashimi, and oysters, requires an improvement in dietary advice regarding unsafe choices in pregnancy in order to avoid preventable foodborne diseases, sometimes fatal for the newborn.


Introduction
Dietary advice during pregnancy and breastfeeding has become increasingly complex, and incorrect or missing recommendations can result in unsafe choices. Over the past decade, dietary models/behaviors have changed. The purchase of ready-to-eat (RTE) food in supermarkets and hypermarkets, takeaways, and doorto-door deliveries is constantly increasing. The consumption of raw seafood such as sushi and sashimi as well as oysters, shellfish, edible mollusks, carpaccio, tartare, or ceviche has greatly increased worldwide.
The popularity of RTE food and raw seafood draws attention to the possible microbiological and chemical hazards concerning fish safety.
Although sushi and in general raw seafood is considered to be a healthy food there is scarce information regarding the levels of chemical contaminants and potentially toxic elements, since some seafood species can also be an important source of chemical pollutants. The ingestion of shellfish and contact with contaminated freshwater have been reported as sources of infection. Fish-borne diseases are becoming more common with the increasing popularity of raw food: Shigella is a major cause of dysentery worldwide and Anisakis in edible marine fish is well recognized by the seafood industry [1].
ACOG "Update on Seafood Consumption During Pregnancy" in January 2017 and reaffirmed in March 2020, FDA (Food and Drug Administration) and EPA (Environmental Protection Agency) state that a consumption of 2-3 servings a week of a variety of lowmercury seafood can be particularly favorable during pregnancy, with benefits on neurodevelopmental outcomes.
The advice clearly indicates that pregnant women should avoid certain fish with the highest mercury concentrations, all raw and undercooked seafood, eggs, and meat. More than 60 fish types are classified into three categories: "Best Choices," "Good Choices," and "Choices to Avoid" [2,3].
Whilst it is well known that Toxoplasma gondii and Listeria monocytogenes maternal infections are related to an increased risk for the fetus and newborn in cases of transplacental spread, in contrast, knowledge about fish parasites and shigellosis infections in pregnancy is limited.
The main consequences of fish-borne parasitic infections include maternal anemia, immune reaction, preterm delivery, and fetal growth restriction.
Only a few cases of shigellosis infectious during pregnancy have been reported: the complications are potentially severe with progressive damage [4,5].

Case description
In July 2022, at Santo Stefano Hospital, Prato, Italy, a male newborn with septicemia and meningitis was diagnosed with Plesiomonas shigelloides (Aeromonas shigelloides) infection acquired via the transplacental route (developed on the second day of life).
There was a maternal history of ingestion of raw seafood, including oysters, 1 week prior to delivery. This anamnestic data guided a prompt identification of the causative agent, preventing a delay in the treatment. In fact, third-generation cephalosporin was administered to treat newborn infection since P. shigelloides is mostly resistant to penicillin and ampicillin. The neonate survived and to date he is on a follow-up program with brain ultrasound and MRI for a brain abscess.
Plesiomonas shigelloides, an anaerobic gramnegative bacillus, mostly resistant to penicillin and ampicillin, is an important fish pathogen and commonly found in aquatic environments. It can cause enteric disease in humans, especially following the Raw or undercooked Fish/shellfish/seafood (including sushi, sashimi, tartare, oysters, clams, mussels, and scallops, shrimp and crab) Raw or undercooked refrigerated smoked seafood Fish with Highest Mercury levels (such as Tuna bigeye, King mackerel, Marlin, Swordfish, Shark) Raw or undercooked or not cured meet (including tartare, salami, cured raw beef, not seasoned ham) Raw or undercooked eggs (including foods, dressing, cake and ice-cream containing raw eggs) Unpasteurized raw milk or yogurt (including products made with them such as soft cheeses and blue-veined)

Unpasteurized fruit or vegetable juices
Unwashed fresh vegetables and salads (including fruits requiring peeling or cutting such as melons) Ready-to-Eat Foods if not steaming hot (including Hot dogs, deli meats, and luncheon meats) consumption of oysters or raw seafood from contaminated water.
A PubMed search revealed only 12 previous newborns (2 cases in Europe) affected by sepsis and meningitis/meningoencephalitis due to maternal Plesiomonas shigelloides vertical transmission with 7 neonatal deaths [4,5].

Discussion
Foodborne diseases in pregnancy can cause a wide variety of different symptoms, complications, and long-term sequelae. Advice during pregnancy and breastfeeding has become increasingly complex, and incorrect information or lack of recommendations can result in unsafe choices.
To strengthen the information regarding safety concerns about the consumption of raw, undercooked, or cold meats should be part of healthcare in pregnancy; folders, leaflets, or a targeted app on mobiles could be helpful for the patient. To improve prenatal care including good nutrition counseling according to the ACOG and FDA recommendations [2,3] the Authors propose to give women an easy-to-reference guide/reading sheet with updates on fish consumption ( Figure 1). Moreover, it is significant to consider that in case of unexplained complex neonatal infection -including sepsis and meningitis-the history of maternal dietary behavior can guide the diagnosis and then, prompt, effective, and targeted treatment.
In conclusion, the Authors highlight the importance of dietary recommendations in prenatal care; the popularity of raw seafood requires an improvement in the advice given regarding unsafe choices in order to avoid foodborne diseases which are often fatal for the newborn and, moreover, to develop stricter regulations in order to monitor the safety and quality of fish for the interest of public health.

Disclosure statement
No potential conflict of interest was reported by the author(s).

Funding
This research received no external funding.