Analysis of clinical and food-borne isolates of Listeria monocytogenes in the United States by multilocus enzyme electrophoresis and application of the method to epidemiologic investigations

Abstract

To investigate the microbiology and epidemiology of the 1,700 sporadic cases of listeriosis that occur annually in the United States, we developed a multilocus enzyme electrophoresis (MEE) typing system for Listeria monocytogenes. We studied 390 isolates by MEE. Eighty-two electrophoretic types (ETs) were defined. Two distinct clusters of ETs, ET group A (ETGA) and ET group B (ETGB), separated at a genetic distance of 0.440, were identified. Strains of ETGB were associated with perinatal listeriosis (P = 0.03). All strains of H antigen type a were in ETGA, while all strains of H antigen type b were in ETGB. Among 328 clinical isolates from cases of listeriosis, 55 ETs of L. monocytogenes were defined. Thirty-four ETs were identified among 62 isolates from food products. The mean number of strains per ET (5.2) was significantly higher among clinical isolates than among food-borne isolates. Examination of isolates from outbreaks further documented the link between cases and contaminated food products. In one investigation, we found 11 different ETs, ruling out a single common source as a cause of that outbreak. By examining a large number of isolates collected over a specified time in diverse geographic locations in the United States, we have begun to establish a baseline for the study of the epidemiology of listeriosis by MEE.

Interactions between the environmental pathogen Listeria monocytogenes and a free‐living protozoan (Acanthamoeba castellanii)

“…Listeria monocytogenes is relatively ubiquitous in nature where it is most closely associated with decaying vegetation and no animal reservoir has been identified for this organism (Fenlon, 1999). As a species, L. monocytogenes is comprised of 13 serovars and at least two distinct genetic lineages (Piffaretti et al, 1989;Bibb et al, 1990;Ericsson et al, 2000;Call et al, 2003;Zhou et al, 2005). Serovars from one lineage (Division I; serovars 1/2b and 4b) have a greater predilection for causing disease in humans compared with serovars from the other lineage (Division II; serovars 1/2a and 1/2c) (Wiedmann et al, 1997).…”

The incidence, numbers and types of Listeria monocytogenes isolated from farm bulk tank milks

“…monocytogenes is still poorly understood. This is partially due to the sporadic nature of most of the outbreaks (Gellin and Broome 1989) but also because serological typing methods are not sufficiently discriminating and many strains are not phage typeable (Bibb et al 1990). Multilocus enzyme electrophoresis (MEE) has recently been used on a number of bacterial species, including L .…”

“…Multilocus enzyme electrophoresis (MEE) has recently been used on a number of bacterial species, including L . monocytogenes, mainly on clinical isolates (Bibb et al 1990), but also recently on food and dairy isolates (Nsrrung and Skovgaard 1993;Harvey and Gilmour 1994).…”

DETERMINATION AND SIGNIFICANCE OF GENETIC DIVERSITY IN LISTERIA ISOLATED FROM FOOD AND ENVIRONMENT

“…Bibb et al (1989) described 56 electrophoretic types (ETs) from 3 10 strains of L. monocyfogenes. In another investigation Bibb et al (1990) examined 390 isolates of which 328 clinical strains fell into 55 ETs and 62 nonclinical isolates into 34 ETs. MEE has proven useful in epidemiological investigations (Barnes ef al.…”