Characterization of Listeria monocytogenes Originating from the Spanish Meat-Processing Chain

Abstract

Using agglutination techniques, 118 Listeria monocytogenes isolates from red meat and poultry were serotyped. Strains were ascribed to the serotypes 4b/4e (44.1% of the strains), 1/2 (a, b or c; 28.0%), 4c (6.8%), 4d/4e (5.9%) and 3 (a, b or c; 2.5%). Among these are the serotypes most frequently involved in cases of human listeriosis. The susceptibility of 72 strains to 26 antibiotics of clinical importance was determined by disc diffusion (Clinical and Laboratory Standards Institute; CLSI). High levels of resistance were observed to cefoxitin (77.8% of the strains showed resistance), cefotaxime (62.5%), cefepime (73.6%), nalidixic acid (97.2%), nitrofurantoin (51.4%) and oxacillin (93.1%). Less than 3% of the strains showed resistance to the antibiotic classes used in human listeriosis therapy (i.e., ampicillin, gentamicin, rifampicin, chloramphenicol, enrofloxacin, vancomycin, trimethoprim-sulfamethoxazole, erythromycin, and tetracycline). The influence of species and serotype on the growth kinetics (modified Gompertz equation) and on the adhesion ability (crystal violet staining) of nine isolates of L. monocytogenes (serotypes 1/2a, 1/2b, 1/2c, 3a, 3b, 3c, 4a, 4b, and 4d), and one strain of Listeria ivanovii were investigated. The maximum growth rate (ΔOD420-580/h) varied between 0.073 ± 0.018 (L. monocytogenes 1/2a) and 0.396 ± 0.026 (L. monocytogenes 4b). The isolates of L. monocytogenes belonging to serotypes 3a and 4a, as well as L. ivanovii, showed a greater (p < 0.05) biofilm-forming ability than did the remaining strains, including those that belong to the serotypes commonly implied in human listeriosis (1/2a, 1/2b, 1/2c and 4b). The need for training in good hygiene practices during the handling of meat and poultry is highlighted to reduce the risk of human listeriosis.

Antimicrobial Resistance of Listeria monocytogenes Strains Isolated from Humans, Animals, and Food Products in Russia in 1950–1980, 2000–2005, and 2018–2021

“…Levofloxacin was active against all strains but as for other fluoroquinolones besides levofloxacin, 2.5% and 3% of all strains demonstrated resistance to ciprofloxacin and enrofloxacin, respectively. Our data are in line with other studies revealing from 0 to 13% of ciprofloxacin-resistant and less than 3% of enrofloxacin-resistant strains among L. monocytogenes isolated in some European countries [34,35,37]. Nonetheless, in other countries the situation with resistance to fluoroquinolones might be different.…”

“…No ampicillin resistant strains and only one gentamicin-resistant strain were found among 544 strains isolated in Germany [36]. Less than 3% of the strains showed resistance to ampicillin and gentamicin among 118 L. monocytogenes isolates from meat in Spain [37]. Our results demonstrate low occurrence of ampicillin/amoxicillin and aminoglycoside resistant strains in Russia.…”

“…Thirteen of 50 strains isolated in Spain were resistant to ciprofloxacin [34]. Erythromycin is another antibiotic of choice in cases of allergy to β-lactams; 4% of studied strains were resistant to erythromycin which is relatively higher than in works analyzing L. monocytogenes strains isolated in other European countries in recent years [36,37,39].…”

Architecture and Viability of the Biofilms Formed by Nine Listeria Strains on Various Hydrophobic and Hydrophilic Materials

“…Listeria monocytogenes is the one responsible for the vast majority of cases of human listeriosis, although some cases of human disease caused by Listeria ivanovii and Listeria seeligeri have been described [9,10]. L. monocytogenes is divided into thirteen different serotypes based on somatic and flagellar antigens, of which three (1/2a, 1/2b, 4b) are responsible for more than 90% of the cases of human illness worldwide [11,12].…”

Expression of NanoLuc Luciferase in Listeria innocua for Development of Biofilm Assay

“…High-biofilm-forming strains produce a dense, three-dimensional biofilm, whereas low-biofilm-forming strains produce a thin, patchy biofilm ( Borucki et al, 2003 ). Increased biofilm formation was observed in serotypes 1/2a and 1/2c ( Borucki et al, 2003 ), or serotypes 3a and 4a ( Capita et al, 2019 ). The biofilm production correlates with environmental conditions, such as temperature and acidic conditions ( Borucki et al, 2003 ; Nilsson et al, 2011 ; Barbosa et al, 2013 ).…”