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Abstract

Neonatal listeriosis: a summer outbreak.

Abstract

An outbreak of neonatal listeriosis affecting 12 newborn infants born in 7 hospitals in Western Australia over a 22-month period from January 1978 to October 1979 is described. Ten of the 12 incidents occurred during the three hottest months of the year (January to March) in contrast to the peak incidence of endemic listeriosis in ewes and lambs which typically exhibit infection in the spring. Infection was apparent in 11 babies within 12 h of birth but presented at one week of age in one who then developed fever and meningitis. Previous maternal obstetric histories were unremarkable and the pregnancies until the onset of labour had appeared normal. Ten of the infants were born preterm (28-38 weeks); maternal fever developed at the onset of labour in 5 instances and meconium-stained liquor was noted in 7. Typically the infants were of low birth weight and developed respiratory distress within hours of birth. Convulsions, skin rashes and abnormalities of the chest X-ray were inconstant features. Samples for culture were collected within 7 h of birth and Listeria was isolated from 8 of 10 blood cultures (but not from the 2 cultures taken from infants of mothers who had already received ampicillin), from 4 of 5 gastric aspirates, from 34 of 42 superficial sites (eye, ear, nose, throat, trachea, umbilicus, rectum) but not from 9 cerebro-spinal fluid samples, 5 of which had been collected after the child had received antibiotics. Treatment with gentamicin, usually with penicillin, was commenced pending the culture result and then ampicillin or amoxycillin was added once the diagnosis was clear. The 2 non-survivors were the only 2 infants who did not receive ampicillin.
The one child with delayed onset of listeriosis responded satisfactorily to antibiotics; Listeria had been isolated from the infant's blood.
Although born in different hospitals in Western Australia, all the infants were cared for in one of two neonatal intensive care units. For such infections the mortality rate was relatively low (17%). During the years 1970 to 1980 no other cases of neonatal listeriosis have been diagnosed in this region; the reason why these infections were confined to a 22-month period is unexplained.
C. A. Morris.