According to Ryan and Ray (2003, p. 53), ‘congenital listeriosis is a bacterial infection caused by Listeria monocytogenes’. The neonatal version of the infection occurs when a newborn is infected immediately after birth. However, recent studies show that Listeria inanovii and Listeria grayi are other causative agents of listeriosis (Alonzo et al. 2011). In most cases, congenital and neonatal listeriosis occurs when the foetus swallows infected amniotic fluid before or during birth. Utero infection can lead to abortion, meningitis, still birth, or neonatal sepsis.
Pregnant women infected with this condition are mostly asymptomatic. In neonates and foetuses, signs and symptoms are subject to the route and time of infection. The common clinical manifestations of the condition include neonatal sepsis, abortion, meningitis, or stillbirth as aforementioned. On the timing aspect, symptoms may be detected within hours, days, or weeks after birth. Infants with early onset of neonatal listeriosis normally have exceptionally low birth weights, complications during birth, and sepsis at birth, which is characterised by respiratory difficulties. On the other side, some neonates have delayed onset (occurring after days or weeks), which is characterised by sepsis and meningitis.
Diagnosis can be done via two ways. First, the mother’s blood or amniotic fluid can be cultured. The second method involves culturing the infected neonate’s blood, infected tissue, stool, or gastric aspirate. Specimens obtained from cervix or blood of pregnant women with fever symptoms should be cultured to detect the presence of Listeria monocytogenes. If a neonate is sick and the mother had L. monocytogenes infection, specimens from blood or infected areas should be cultured for the bacteria.
Alonzo et al. (2011, p. 426) posit that laboratory ‘confirmation of the organism involves biochemical testing and observation of motility using a slide test or showing motility in semisolid media’. According to Alonzo et al. (2011, p. 427), ‘L. monocytogenes exhibits a distinctive end-over-end “tumbling” motility due to the presence of flagella at both ends’.
Given that listeriosis is caused by a bacterium, antibiotics are used for treatment. Ampicillin is the commonly used antibiotic in infants. This antibiotic can be used together with aminoglycosides. The central purpose of aminoglycosides is to prevent bacterial protein synthesis, thus killing the bacterium (Cagno, Pettit & Weiss 2012). Conventionally, the drugs are taken for 14 days or 21 days in case of meningitis. However, this period is not fixed and it can be prolonged depending on the neonate’s response to treatment, which highlights the view that the optimal dosage duration is unknown. Where sepsis is involved, the infected neonates may require supportive therapy like hemodynamic and respiratory management on top of the antibiotics (Cagno, Pettit & Weiss 2012).
L. monocytogenes is a ubiquitous bacterium and thus pregnant women can easily be infected. Listeriosis is mainly food borne and thus general cleanliness is the first measure to prevent infections. The US Food and Drug Administration (FDA) in conjunction with the World Health Organisation (WHO) have embarked on a sensitisation program amongst the pregnant women to create awareness of how to prevent infections. People should clean their hands thoroughly before handling food coupled with observing hygiene all the time. If infections are noted in pregnant women, Cagno, Pettit, and Weiss (2012, p.60) advise that treatment ‘may be given before delivery or intrapartum to prevent vertical transmission’.
Case study question
What is the prevalence of congenital and neonatal listeriosis across the world?
Alonzo, F, Bobo, L, Skiest, D & Freitag, N 2011, ‘Evidence for subpopulations of Listeria monocytogenes with enhanced invasion of cardiac cells’, Journal of Medical Microbiology, vol.60, no.4, pp. 423–434.
Cagno, C, Pettit, J & Weiss, B 2012, ‘Prevention of perinatal group B streptococcal disease: updated CDC guideline’, American Family Physician, vol.86, no.1, pp. 59-65.
Ryan, K & Ray, C 2003, Sherris Medical Microbiology, McGraw Hill, New York.