ATLANTA – While the majority of neonatal listeriosis cases are caused by consumption of contaminated food by the pregnant mother, the number of listeriosis cases of nonmaternal origin has grown into a small, but increasingly significant portion of total diagnoses.
This is according to a new study presented by Kelly A. Jackson of the Centers for Disease Control and Prevention’s Enteric Diseases Epidemiology Branch at the International Conference on Emerging Infectious Diseases.
©decade3d/Thinkstock.com
Listeriosis cases associated with pregnancy were analyzed by collecting clinical, demographic, exposure, and microbiologic data from the Listeria Initiative, a CDC surveillance program conducted between 2004 and 2012. Ms. Jackson and her coinvestigators looked at the time from the onset of symptoms in the mother to delivery or recognition of fetal losses among cases of definite maternal origin. For those of potential nonmaternal origin, differences in gestational age at birth and recognition of fetal loss were compared.
Differentiation between definite maternal and possible nonmaternal cases were made by examining data on foodborne outbreak status, maternal symptoms, pregnancy outcome, maternal hospitalization, and neonatal death. In total, 554 pregnancy-associated listeriosis cases were examined, of which 338 (61%) were classified as definite maternal origin, 96 were classified as possible nonmaternal origin (17%), and 120 (22%) were excluded because either the neonatal isolates were collected 2-7 days after birth, pregnancy outcome was unknown, or the mothers were still pregnant at the time reporting occurred.
Seventy-two percent of listeriosis cases that definitely began with the mother showed symptoms within 7 days of fetal loss, with fever (80%) and chills (62%) being the most commonly reported symptoms. Both of those symptoms occurred far less frequently in cases of possible nonmaternal origin, with 38% reporting fevers and only 2% reporting chills.
Nearly 75% of mothers whose neonates had listeriosis developed symptoms less than a week before delivery or recognition of fetal loss, the authors explained; the median number of days from mothers’ onset to delivery was 2 days (range of 0-146 days), compared with a median of 4 days (range 0-151 days) from onset to recognition of fetal loss. The median gestational age of live-born infants with definite maternal origin of listeriosis was lower than in infants of possible nonmaternal origin: 35 weeks (range 24-42 weeks) versus 39 weeks (34-42 weeks) (P < .01).
Dr. Jackson and her colleagues call for further study into possible nonfoodborne sources of late-onset listeriosis in neonates, which would likely reveal the sources of exposure and from which prevention plans can be developed to protect mothers and their children.
Dr. Jackson did not report any relevant financial disclosures.