Heavy-Metal and Benzalkonium Chloride Resistance of Listeria monocytogenes Isolates from the Environment of Turkey-Processing Plants

Abstract

The resistance of Listeria monocytogenes to cadmium and arsenic has been used extensively for strain subtyping. However, limited information is available on the prevalence of such resistance among isolates from the environment of food-processing plants. In addition, it is not known whether the resistance of such isolates to heavy metals may correlate with resistance to quaternary ammonium compounds extensively used as disinfectants in the food-processing industry. In this study, we characterized 192 L. monocytogenes isolates (123 putative strains) from the environment of turkey-processing plants in the United States for resistance to cadmium and arsenic and to the quaternary ammonium disinfectant benzalkonium chloride (BC). Resistance to cadmium was significantly more prevalent among strains of serotypes 1/2a (or 3a) and 1/2b (or 3b) (83% and 74%, respectively) than among strains of the serotype 4b complex (19%). Resistance to BC was encountered among 60% and 51% of the serotype 1/2a (or 3a) and 1/2b (or 3b) strains, respectively, and among 7% of the strains of the serotype 4b complex. All BC-resistant strains were also resistant to cadmium, although the reverse was not always the case. In contrast, no correlation was found between BC resistance and resistance to arsenic, which overall was low (6%). Our findings suggest that the processing environment of turkeyprocessing plants may constitute a reservoir for L. monocytogenes harboring resistance to cadmium and to BC and raise the possibility of common genetic elements or mechanisms mediating resistance to quaternary ammonium disinfectants and to cadmium in L. monocytogenes.Listeria monocytogenes causes listeriosis, a relatively rare but serious food-borne disease with symptoms such as stillbirths or abortions, septicemia, and meningitis or encephalitis. It has a high mortality rate (ca. 20%) for at-risk populations, which include pregnant women and their fetuses, neonates, and those who are elderly and/or immunocompromised (25). Strains of three serotypes (1/2a, 1/2b, and 4b) are associated with most human listeriosis cases. A substantial fraction of sporadic cases and the majority of food-borne outbreaks are due to serotype 4b strains (12,25). However, strains of serotype 4b tend to be underrepresented in foods, and the majority of food isolates are of serotype 1/2a or 1/2b (11,14,27). The environment of food-processing plants is considered to play a key role in contamination of processed ready-to-eat foods, and substantial evidence points to the ability of certain strains to colonize the processing-plant environment and to persist there, frequently over extended periods of time (for reviews, see references 12 and 13).Benzalkonium chloride (BC) and other quaternary ammonium compounds (QACs) are extensively used as disinfectants in the food-processing industry (19,22). Frequent use of BC and other QACs in food-processing plants may constitute a selective pressure for the emergence and establishment of resistance to these compounds among L. monocytogenes isolates...

Respuesta fisiológica de Euglena gracilis al estrés por cobre

“…En este sentido, el uso de microorganismos tolerantes con capacidad de almacenar metales ha demostrado ser una biotecnología con ventajas sobre los métodos físicos-químicos, ya que ofrece un menor impacto ambiental y menor costo económico. 3 En este sentido el protista acuático de vida libre Euglena gracilis representa un modelo biológico idóneo para ser empleado en procesos de biorremediación. Este microorganismo forma parte del plancton de aguas dulces y puede ser cultivado de manera eficiente en condiciones controladas de laboratorio y con diferentes fuentes de carbono.…”

Identification of the mechanisms of resistance and potential cross resistance of Listeria monocytogenes upon adaptation to different antimicrobials

“…All BC-resistant strains were found to be also resistant to cadmium (though the reverse was not the case; ca. 30% of the cadmium-resistant isolates lacked resistance to BC) (154). This led to the speculation that BC resistance determinants (e.g.…”

“…This led to the speculation that BC resistance determinants (e.g. bcrABC) were acquired by plasmids that already harbored cadmium resistance determinants (154,155).…”

“…biofilm-forming potential, ability to grow in the cold, resistance to phage and disinfectants) make L monocytogenes a persistent, highly problematic contaminant of the environment and equipment in food processing plants (14,118,120,154,158). Persistent colonization of the processing plant environment is considered to be a major factor for contamination of processed, ready-to-eat foods with this pathogen, and thus contributes to the burden of human listeriosis (118,120 (182) were also tested.…”

“…susceptibility assessments were done as described (154). Strains were considered resistant to cadmium when they yielded confluent growth in the presence of 35 μg/ml cadmium chloride anhydrous (Sigma) following incubation at 37C for 48 h. and incubation at 37C for 36 h. Experiments were done in duplicate and in at least three independent trials.…”