Listeria monocytogenes is an uncommon but probably underdiagnosed cause of neonatal sepsis (Kylat, 2016). This facultative intracellular gram-positive bacillus can be isolated from the feces of 1 to 5 percent of adults. Nearly all cases oflisteriosis are thought to be foodborne. Outbreaks have been caused by raw vegetables, coleslaw, apple cider, melons, milk, fresh Mexicanstyle cheese, smoked ish, and processed foods such as pate, hummus, wieners, and sliced deli meats (Centers for Disease Control and Prevention, 20 13e).
Listerial infections are more common in pregnant women, immunocompromised patients, and the very old or young. he incidence of such infections in pregnancy is estimated to be up to 100 times that in the general population (Kourtis, 2014; Rouse, 2016). In 1651 cases reported in 2009 to 2011, the CDC found that 14 percent were in pregnant women (Silk, 2013). It is unclear why pregnant women still account for a significant number of these reported cases. One hypothesis is that pregnant women are susceptible because of decreased cellmediated immunity (Baud, 2011).
Listeriosis during pregnancy may be asymptomatic or may cause a febrile illness that is confused with influenza, pyelonephritis, or meningitis (Centers for Disease Control and Prevention, 2013e). he diagnosis usually is not apparent until blood cultures are reported as positive. Occult or clinical infection also may stimulate labor. Discolored, brownish, or meconiumstained amnionic fluid is common with fetal infection, even in preterm gestations. VIaternalrlisteriosis causes fetal infection that characteristically produces disseminated granulomatous lesions with microabscesses (Fig. 64-9). Chorioamnionitis is common, and placental lesions include multiple, well-demarcated macroabscesses. Early-and late-onset neonatal infections are similar to group B streptococcal sepsis. In a review of 222 cases, infection resulted in abortion or stillbirth in 20 percent, and neonatal sepsis developed in 68 percent of surviving newborns (Mylonakis, 2002). In one large, prospective cohort study, 24 percent of mothers experienced fetal loss, but none after 29 weeks' gestation (Charlier, 2017). However, a neonatal-case fatality rate of 21 percent has been reported (Sapuan, 2017).
FIGURE 64-9 The pale placenta (A)and stillborn infant (B) resulted from maternal listeriosis.
Treatment with ampicillin plus gentamicin is usually recommended because of synergism against Listeria species (Rouse, 2016). T rimethoprim-sulfamethoxazole can be given to penicillin-allergic women. Maternal treatment in most cases is also efective for fetal infection (Chan, 2013). No vaccine is available. Prevention is by washing raw vegetables, cooking all raw food, and avoiding the implicated foods listed previously (American College of Obstetricians and Gynecologists, 2016d).