Congenital and Neonatal Listeriosis: Disease Analysis
According to Okike, Lamont, and Heath (2013, p. 405), ‘congenital and neonatal listeriosis is a bacterial infection caused by a gram positive bacterium called Listeria monocytogenes’. Goulet et al. (2012, p. 655) posit that Listeria monocytogenes ‘is a gram-positive motile bacterium that causes infections mainly at the extreme ends of life (newborns and the elderly) in the immunocompromised and in pregnant women’.
Congenital and neonatal listeriosis is of global importance as the fatality rates stand at 56% of the infected neonates across the world (Okike, Lamont & Heath 2013). Biologically, L. monocytogenes is adapted to living in diverse environments, which increases its survival rates in different ecological zones. Socially and economically, the condition is prevalent amongst the poor due to squalid living conditions.
The pathogen enters the body via food, and thus the gastrointestinal tract (GIT) is the entry site of the causative agent. The pathogen then crosses the intestinal barrier via the epithelial cells. The pathogen is then carried to the liver by blood or lymph. In the liver, the pathogen invades the hepatocytes where it undergoes colonisation. Vazquez-Boland et al. (2001, p. 585) note that to ‘invade, Listeria induces macrophage phagocytic uptake by displaying D-galactose in their teichoic acids that are then bound by the macrophage’s polysaccharide receptors’.
The bacterium afterwards undergoes replication within the host cell’s cytol before moving via cellular mechanisms to infect other cells. From pregnant women, the bacterium moves in the same manner to unborn babies via vertical transmission or via swallowing amniotic fluid during birth.
Immune defences and responses from the host
L. monocytogenes induces both adaptive and innate immune responses. After the pathogens enter the hepatocyte cells, the majority of them are encapsulated and eliminated by resident macrophages (Zenewicz & Shen 2007). Those that escape these macrophages activate T cell responses, which underscore the adaptive immune response. The processes involved in innate immune system include the use of phagocytes (neutrophils and macrophages), inflammatory cytokines, and autophagy, which mainly inhibit bacterial growth and multiplication. Adaptive immune response comes after innate immune response. CD4 and CD8 T cells, regulatory T cells, non-classical MHC T cells, and B cells are all involved in adaptive immune response (Zenewicz & Shen 2007).
According to Okike, Lamont, and Heath (2013, p. 406), the common clinical manifestations of neonatal and congenital listeriosis include ‘bacteraemia, meningitis, pneumonia, and other focal infections’. Diagnosis can be done by culturing either the pregnant mother or neonate’s blood or specimens from the infected areas to determine the presence of the pathogen. Polymerase Chain Reaction (PCR) can also be used for diagnosis.
Neonatal and congenital listeriosis is treated using antibiotics like ampicillin. The prevention and control of this condition is critical, as it is a major cause of meningitis amongst children across the world. In the US, the FDA gives guidelines on how to prevent infection and spread of the causative bacterium via observing hygiene. Across the world, the WHO, in conjunction with different health bodies in different countries, is involved in sensitisation programmes to ensure high hygiene standards, as listeriosis is foodborne, and thus cleanliness is the best way of preventing it.
Goulet, V, Hebert, M, Hedberg, C, Laurent, E, Vaillant, V, De Valk, H & Desenclos, J 2012, ‘Incidence of listeriosis and related mortality among groups at risk of acquiring listeriosis’, Clinical Infectious Diseases, vol. 54, no. 5, pp. 652–660.
Okike, O, Lamont, R & Heath, P 2013, ‘Do we really need to worry about listeria in new born infants’, The Paediatric Infectious Disease Journal, vol.32, no.4, pp. 405-406.
Vazquez-Boland, A, Kuhn, M, Berche, Chakraborty, T, Dominguez-Bernal, G, Goebel, W, González-Zorn, B, Wehland, J & Kreft, J 2001, ‘listeria pathogenesis and molecular virulence determinants’, Clinical Microbiology Review, vol.14, no.3, pp. 584-640.
Zenewicz, L & Shen, H 2007, ‘Innate and adaptive immune responses to Listeria monocytogenes: A short overview’, Microbe Infections, vol. 9, no. 10, pp. 1208-1215.